Modern Approach to Maintenance in Spinning (Woodhead Publishing India)

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Modern approach to maintenance in spinning

Modern approach to maintenance in spinning

Neeraj Niijjaawan and Rasshmi Niijjaawan

WOODHEAD PUBLISHING INDIA PVT LTD New Delhi

●

Cambridge

●

Oxford

Published by Woodhead Publishing India Pvt. Ltd. Woodhead Publishing India Pvt. Ltd., G-2, Vardaan House, 7/28, Ansari Road Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington Cambridge CB21 6AH, UK www.woodheadpublishing.com First published 2010, Woodhead Publishing India Pvt. Ltd. © Woodhead Publishing India Pvt. Ltd., 2010 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission. Reasonable efforts have been made to publish reliable data and information, but the authors and the publishers cannot assume responsibility for the validity of all materials. Neither the authors nor the publishers, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing India Pvt. Ltd. The consent of Woodhead Publishing India Pvt. Ltd. does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing India Pvt. Ltd. for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Woodhead Publishing India Pvt. Ltd. ISBN: 978-93-80308-02-9 Woodhead Publishing India Pvt. Ltd. EAN: 9789380308029 Woodhead Publishing Ltd. ISBN: 978-0-85709-000-3 Typeset by Sunshine Graphics, New Delhi Printed and bound by Sanat Printers, New Delhi

Contents

Preface

xiii

1

Need of maintenance

1

1.1 1.2 1.3

Introduction Modes of failure Role of maintenance

1 1 8

2

Role of maintenance

10

2.1 2.2 2.3 2.4 2.5 2.6

Introduction Maintenance Planned maintenance Unplanned maintenance Quality-based maintenance Role of maintenance department in spinning mill

10 11 12 17 18 19

3

Proactive maintenance

21

3.1 3.2 3.3 3.4 3.5

Introduction Preventive maintenance Condition-based monitoring Benefits of condition-based monitoring Implementation of condition-based maintenance

21 22 24 34 34

4

Planning and scheduling

37

4.1 4.2 4.3 4.4 4.5 4.6 4.7

Introduction General principles of planning Procedure of planning Scheduling Principle of standardization of frequencies and jobs Principle of cyclic schedule for the maintenance team Principle of interlinking spare part planning with maintenance plan and schedule Operators must act as machine keepers Maintenance schedule

37 37 38 40 40 41

4.8 4.9

41 42 44

vi

Contents

5

Maintenance audit

50

5.1 5.2 5.3 5.4

Introduction Methodology Preparation of maintenance audit report Presenting the report to management

50 50 53 54

6

Role of manpower in maintenance

55

6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8

Introduction Factors affecting manpower planning Manpower norms Maintenance organization structure Concept of common gang Responsibilities at various positions Human error in maintenance Crew size required for various activities in maintenance department

55 55 57 58 59 62 66 68

7

Maintenance repair inventory and its control

71

7.1 7.2 7.3 7.4 7.5 7.6

Inventory Types of inventory Inventory carrying cost Material and repair inventory Different methods for controlling the inventory How to implement the spare parts management?

71 71 72 73 73 83

8

Maintenance information systems

89

8.1 8.2 8.3

Computer-managed maintenance system Benefits of CMMS Components of CMMS

89 90 91

9

Safety while maintenance

133

9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10

Accident Effects of an accident Accidents and its related losses Cause of accidents How to prevent accidents? Electrical safety House keeping Workshop/workplace Machine guarding Methods and procedure

133 134 134 135 136 144 144 147 147 148

Contents

9.11 9.12 9.13 9.14 9.15

Safety in shifting material Safety while unpacking and cleaning Precautions for handling machine under maintenance Precautions during spinning operation Safety tags

10

Lubricants

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9

Types of lubricants Functions of lubricant Liquid lubricants Semisolid lubricants Solid lubricants Lubricant used in spinning mill Lubricants handling and storage Conservation of lubricants Summary

11

Belt drive and its maintenance

11.1 11.2 11.3 11.4 11.5 11.6 11.7

Introduction Flat belt drives Spindle tape Flat pulley V belts V pulleys Timing belts

12

Steel wire and chain

12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 12.10 12.11 12.12 12.13 12.14 12.15

Steel wire rope Construction Design of wire Classification of steel wire ropes Measuring wire rope Wire pulley or sheave Lubrication Reason for failure of wire Chains Construction of chain Designation of chain Chain lubrication Chain installation Maintenance of chains British standard roller chain

vii 151 152 153 154 155

157 157 160 160 166 172 173 175 177 178

183 183 184 192 197 199 211 213

223 223 223 224 225 225 226 226 227 228 229 229 230 231 232 233

viii

Contents

12.16 12.17 12.18

American standard roller chain Leaf chain Silent chain

13

Temporary fasteners

13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 13.9 13.10 13.11 13.12 13.13

Introduction Screwed joint Different types of bolt/screw Washer Nut Locking device Key Tension element Pins Retaining rings Taper lock Universal joint Screw hose clamps

14

Oil seal and gasket

14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9

Introduction Material selection Why garter spring is needed? Shelf life Procedure for installation Reasons for seal failure Gasket Effecting a seal Installation of gasket

15

Gears

15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9

Introduction Spur gear Helical gears Worm gears Bevel gears Gear trains Black lash Lubrication Reasons for the failure of gear teeth

235 237 238

242 242 242 247 251 252 252 254 255 256 256 257 258 259

261 261 262 265 265 266 268 268 269 270

272 272 272 276 279 282 284 287 288 289

Contents

16

Compressed air

16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 16.9 16.10 16.11 16.12 16.13 16.14 16.15 16.16 16.17 16.18 16.19 16.20 16.21 16.22 16.23 16.24 16.25 16.26 16.27 16.28 16.29 16.30 16.31 16.32 16.33 16.34 16.35 16.36 16.37

Introduction Compression of air Free air or atmospheric air Analyzing compressed air needs Production of compressed air How to specify the right compressor type, capacity and pressure? Receiver or tank size for air compressor Moisture Quality of water required for compressor What is oil free compressed air? Air distribution systems Pneumatic cylinder Regulator Lubricator Moisture separator Minimum pressure switch Filters Safety valves Non-return valve Quick release valve Micro valve Speed control device Time delay valve Port flow control valve Silencer Piping Pressure hoses Push-type fitting Threaded connector Barbed-type connectors Solenoid valve Dial indicator Compressed air system leaks Leak detection Pressure drop and controlling system pressure Compressor air system economics Maintenance of pneumatic system

17

Bearing and its maintenance

17.1

Introduction

ix

290 290 291 291 293 294 297 301 302 305 306 306 309 313 314 316 317 318 319 320 320 321 321 322 323 323 323 324 324 325 325 326 326 328 329 330 331 332

333 333

x

Contents

17.2 17.3 17.4 17.5 17.6 17.7 17.8 17.9 17.10 17.11 17.12 17.13

Bearing Types of bearing Roller bearings Bearing designation Internal clearance Withdrawal sleeves with nut and locking washer Bearing characteristics Lubrication of bearing Mounting of different bearings Dismounting method of different bearing Reason for failure of bearings Examinations of bearing in service

18

Tools

18.1 18.2 18.3 18.4 18.5 18.6 18.7 18.8 18.9 18.10 18.11 18.12 18.13 18.14 18.15 18.16 18.17 18.18 18.19 18.20 18.21 18.22 18.23 18.24 18.25 18.26 18.27 18.28

Open-ended spanner Ring spanner Sockets and accessories Torque wrench sockets Allen key Try square Steel rule Feeler gauge Hammers Soft hammers Dial gauge Spirit level Vernier calliper Digital vernier calliper File Chisels Screw driver Vices Punch Hacksaw Taps Die and die stock Grinding wheels Pliers Stud extractor Kit for mounting of bearing Pullers Micrometer

333 337 342 346 348 349 350 351 353 359 361 362

365 365 366 367 367 368 369 370 372 373 375 375 376 378 380 381 384 384 386 387 388 389 391 393 394 395 396 398 400

Contents

18.29 18.30 18.31 18.32 18.33 18.34 18.35 18.36

Drill Step ladder Oil cans Grease gun Chalk line Knife Plumb bob Requirement of tool for erection, installation and maintenance

19

Tips to fine tune the spinning machinery

19.1 19.2 19.3 19.4 19.5 19.6 19.7 19.8 19.9

Introduction Blow room Card Drawframe Comber Speedframe Ringframe Automatic cone winder Two-for-one twister

20

Tips to improve energy saving in spinning mills

20.1 20.2 20.3 20.4 20.5

Energy Textile production process Energy consumption in spinning mill Maximum cost effectiveness in energy use Energy conservation measures

Index

xi 401 402 403 404 404 405 405 406

408 408 408 413 416 417 419 421 426 432

435 435 436 436 438 438 446

Preface

In every spinning mill the performance of the plant depends on the reliability, availability and maintainability of the machines, all of which are of primary importance for ensuring an excellent and affordable product. Maintenance of equipment is still a challenge due to factors such as size, cost, complexity and competition. There is a definite need for effective maintenance practices that will positively influence critical success factors such as safety, product quality, speed of innovation, price, profitability, and reliable delivery. Maintenance cost is the major part of the total operating costs of all manufacturing or production plants. The goal of maintenance is to keep the production system in good working order at minimal cost. It is observed in the industry that maintenance functions are difficult to control due to the following reasons: maintenance work is very diverse, extent of job unknown, workers have different abilities, and job can be dependent on the part availability. The maintenance function of a company run on modern principles, gives major weightage to production availability performance rates, to cost of operations and maintenance. Maintenance of machines includes all efforts directed to keep health of the machine (maintaining at minimum cost), which leads to the smooth and efficient working of an industrial plant, thus helping to improve the productivity and hence the profitability of the company. Effective maintenance is defined as the activity that gives ‘the maximum level of availability as well as performance of plant’. This is achieved through maintenance management, involving planning, organizing control and execution directed at specified objectives that ensure the company achieves its business objectives. The role of maintenance is changing and that means the role of maintenance personnel (managers/ engineers) should also change in order to provide competitive products and services in global economy. Competencies of maintenance personnel (people and processes) must be enhanced in order to meet the new global challenges. The book is written keeping in mind the practical needs of the maintenance engineer in a textile mill. Sufficient theory is included for a proper understanding of the principles involved. This book would help to implement the maintenance management program successfully, which

xiv

Preface

includes activities such as work-order scheduling, preventive maintenance, condition-based maintenance and inventory management. Students doing diploma and degrees in Textile Technology will find that the fundamental principles of the subject are given in a simpler way. This book would help these students as a practical guide when they will join manufacturing concern. Comments and suggestions for the improvement of this book from my wife Dr Rasshmi Nijjaawan are gratefully acknowledged. I am very thankful to, my daughter Kritika, my mother, my both elder sisters, my brother-in-law, my younger brother and his wife for their co-operation in bringing out this book. Neeraj Niijjaawan Rasshmi Niijjaawan

1 Need of maintenance

1.1

Introduction

Most of the equipments and machines fail in the spinning industry due to various types of loads acting in one form or another exceed their limit value in terms of size or time. These forces helps to initiate the deterioration process, which leads to failure of the function of component or complete failure of the component depending upon the intensity of the forces. This process may be quick or it may take relatively long time; it may be predictable or unpredictable. These failures may be due to the deficiencies in the design of the equipment, poor maintenance, negligence’s of the operator and due to over life of the equipment. Component Failure

10–15 due to accident

70–80% due to water

10–15% due to design

1.1 Reasons of component failure.

The only reason for the failure of machine components is wear. Wear is unavoidable and inevitable. The twin task of good management is to keep wear at the lowest permissible level, and also to detect in right time the level of wear which can cause failures and then replace the worn out part before it fails. To do so effectively requires some understanding of the failure mechanism or process of deterioration that leads to failure.

1.2

Modes of failure

The eleven aspects of failure mechanism are briefly outlined to show how condition of machines can be monitored using this knowledge.

1.2.1

Wear

Wear can be defined as the progressive loss of material from the surface of body. The primary cause for wear is a relative motion between two

1

2

Modern approach to maintenance in spinning

surfaces in contact with each other and forces like friction interacting between them. Wear is a phenomenon in which small particles of material get removed from the component, eventually producing in observable decrease in dimensions leading to breakdown or malfunction. Several factors influence the rate of wear in a complex manner, which makes theoretical prediction of the extent of wear almost impossible. These factors are material hardness, material combination, material structure, temperature, load, speed of relative movement, movement duration, surface layer (oxides), lubricant and its properties, surface roughness, contaminants such as particles on surfaces, etc. Stages of wear Under normal operating parameters, the property changes during usage normally occur in three different stages as follows: ●

●

●

Primary or early stage or run-in period, where rate of change can be high. Secondary or mid-age process, where a steady rate of aging process is maintained. Most of the useful or working life of the component is comprised in this stage. Tertiary or old-age stage, where a high rate of aging leads to rapid failure.

Example The primary cause for wear of wire is due to the work done by the vital leading edge of metallic wire tooth point in coping with the opposite forces needed to obtain carding action which separates from fibre to fibre (forces like fibre/fibre friction and fibre /metal friction interacting between the relative motion of two rotating parts at this stage). Wear is a phenomenon in which small particles of material get removed from the component, eventually producing in observable decrease in dimensions leading to round edge of wire. Due to this round edge there is a loss of carding power because the point condition has deteriorated to an extent where they can not hold on the fibre against carding resistance between two revolving parts. This ultimately leads to fibre becoming rolled into nep results into the deteriorating of carding sliver. Several factors influence the rate of wear of wire, which makes theoretical prediction of the extent of wear almost impossible. These factors are metallic wire hardness, material used for making wire, type of fibre, temperature, setting, speed of relative movement, movement duration, production rate surface roughness, contaminants such as dust and trash particles on surfaces, etc.

Need of maintenance

New lickerin wire

3

Worn wire

1.2 Worn wire due to fibre processing.

1.2.2

Adhesive wear

Adhesive is that form of wear, which occurs when metallic surfaces of two components have a relative motion, which may be sliding, rolling or reciprocating type. In a spinning mill friction occurs because of textile materials – fibre, sliver, roving or yarn – coming in contact with metallic or ceramic surfaces. Even the smoothest surfaces have crest and valleys at micro-levels. Relative motion causes crests of mating components to shear and thereby cause loss of material. Example of friction in spinning processes are of two kinds: inter-metallic friction like shaft rotating in a brush in bush bearings or ball bearings, ring with travellers, two gears meshing; and textile material to metal friction such as of cotton with beaters in the blowroom, yarn with the travellers or with thread guides, etc. The amount of friction depends on the coefficient of friction between two surfaces in contact, active load, surface finish of mixing component, lubrication, nature of motion-sliding, rolling, reciprocating, etc.

1.2.3

Abrasive wear

Abrasion occurs due to grinding and rotating action of foreign metal and dust particles on base metal surface. Minute particles dislodged from the component also again act as foreign particles. Abrasion occurs in metallic wire during grinding, i.e. rotating action of grinding roller on the wire points of metallic wire. Minute particles of wire dislodged from the wire thus reduce the height of wire in every grinding. The extent of abrasion depends on the type of abrasives, i.e.

4

Modern approach to maintenance in spinning

hardness, shape of particles, size of particles, speed of impact, direction of flow, pressure at which particles strike, operating conditions (mainly pressure of abrasive material on the component), hardness of wire, and manufacturing material of wire. Figure 1.3 shows the effect of grinding.

New wire

Worn wire

Resharpen wire

1.3 Effect of grinding.

1.2.4

Impact wear

An impact is a high force or shock applied over a short time period. Such a force or acceleration can sometimes have a greater effect than a lower force applied over a proportionally longer time period. These types of wear act mostly when some foreign material comes between the metallic wires of two surfaces along with fibre. The extent of impact wear depends on the amount of load, frequency of blows, hardness of component hitting the base metal, ductility of base metal and duration of impact. The major three reasons for impact wear are sudden very high load, repetitive high load and repetitive low load resulting in chipping, cracking and fatigue, respectively, as shown in the Fig. 1.4.

Damaged tooth of wire

1.4 Result of impact wear.

Need of maintenance

1.2.5

5

Fatigue

Fatigue comes into effect on metal due to repeated cycles of stress. In this type of failure there is no obvious warning but cracks form without appreciable deformation of structure making it difficult to detect the presence of growing cracks. Fractures usually start from small nicks or scratches or fillets which cause a localised concentration of stress. Failure can be influenced by a number of factors including size, shape and design of the component, condition of the surface or operating environment. Fatigue initiates and aggravates cracking and ultimately results in breaking the material leading to breakdown of the machine. The main cause for fatigue failure is dynamically acting loads which cause a normal stress below the plastic flow level of metal. A corrosive atmosphere may accelerate the fatigue process due to interaction with the crack propagation process. Acceleration also may take place at elevated temperatures due to combined effect of crack propagation and plastic flow. Several factors causing fatigue are operation related effects, i.e. vibration and dynamic load; environmental related effects, i.e. corrosive exposure in addition to load; and influence of high temperature; design related effects, i.e. notches in critical cross-section and unfavourable material selection. Factors that affect fatigue life ● Cyclic stress state. Depending on the complexity of the geometry and the loading, one or more properties of the stress state need to be considered, such as stress amplitude, mean stress, biaxiality, in-phase or out-of-phase shear stress, and load sequence. ● Geometry. Notches and variation in cross-section throughout a part lead to stress concentrations where fatigue cracks initiate. ● Surface quality. Surface roughness cause microscopic stress concentrations that lower the fatigue strength. ● Material type. Fatigue life, as well as the behaviour during cyclic loading, varies widely for different materials, e.g. composites and polymers differ markedly from metals. ● Residual stresses. Welding, cutting, casting and other manufacturing processes involving heat or deformation can produce high levels of tensile residual stress, which decreases the fatigue strength. ● Size and distribution of internal defects. Casting defects such as gas porosity, non-metallic inclusions and shrinkage voids can significantly reduce fatigue strength. ● Environment. Environmental conditions can cause erosion, corrosion, or gas-phase embrittlement, which all affect fatigue life. Corrosion fatigue is a problem encountered in many aggressive environments. ● Temperature. Higher temperatures generally decrease fatigue strength

6

Modern approach to maintenance in spinning

1.2.6

Corrosion

Corrosion can be defined as the disintegration of a material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen. Weakening of iron due to oxidation of the iron atoms is a well-known example of electrochemical corrosion. This is commonly known as rusting. This type of damage typically produces oxide(s) and/or salt(s) of the original metal. Corrosion can also refer to other materials than metals, such as ceramics or polymers. Although in this context, the term ‘degradation’ is more common. Corrosion can be concentrated locally to form a pit or crack, or it can extend across a wide area to produce general deterioration. While some efforts to reduce corrosion merely redirect the damage into less visible, less predictable forms, controlled corrosion treatments such as passivation and chromate-conversion will increase a material’s corrosion resistance.

1.5 Pin corroded due to atmospheric condition.

1.2.7

Erosion

Erosion takes place due to fluids which are in the form of colloidal suspension. The resultant abrasive flow at high speed grinds on particles from base metal surface, e.g. in textile mill this process occurs in wet processing such as bleaching and dyeing.

1.2.8

Cavitation

When a liquid flows on a metal surface at high speed, minute bubbles are formed which explode on the surface. This generates shock waves giving rise to fatigue spots and then to removal of the spots causing pits on the base metal surface, e.g. in textile mills such pitting occur in wet processing such as bleaching and dyeing.

Need of maintenance

1.2.9

7

Mechanical over load

The failure or fracture of a product or component in a single event is known as mechanical overload. It is a common failure mode and may be contrasted with fatigue, creep, rupture, or stress relaxation. Failure may occur because either the product is weaker than expected owing to a stress concentration, or the applied load is greater than expected and exceeds the normal tensile strength, shear strength or compressive strength of the product.

1.6 Belt broken due to overload.

1.2.10 Ozone Ozone is a modified version of normal oxygen available in atmosphere. Normally oxygen referred as O 2 contains two oxygen atoms where as ozone contains three atoms O 3. Ozone is highly reactive and has a strong bactericidal action on various substances. Ozone is present everywhere. The atmosphere of the earth has an ozone layer at about 40–50 km which absorbs ultraviolet rays from the sun. Usually the concentration of ozone in the atmospheric air varies from 0 to 7 per hundred million. In the spinning department, repeated air changes are responsible for producing ozone little more than atmospheric concentration. The effect of ozone will be severe on the rubber, especially when it is in stretched condition by over 5%. Ozone has high reactivity. Every ozone molecules react with a chain of polymer molecules and break the chain. Rubber under stress is an easy target for ozone reaction. Aprons used in the spinning mill consist of polymeric chain and they are in the stretched condition on the machine. Hence they are prone to reaction with ozone. Factors that influencing ozone concentration in the department: 1. Modern spinning plants have generally the facility of changing the air as high as 45 per hour. With more air changes, the ozone attack on the apron will be higher. 2. Over-head cleaners increase the volume of air discharge on the drafting zone of ring spinning, this increases the possible reaction by ozone.

8

Modern approach to maintenance in spinning

3. If the apron is coated by some foreign matter like wax, it gets protected from ozone attack. This can always be seen in an apron that has worked for long time. The ozone crack always starts from the corners. In the middle portion of apron, it will be minimum as the traverse area is protected by wax coating from cotton. 4. Cleaner the atmosphere, higher will be the chances for ozone reaction. Generally the dust particles present in the air react with ozone. If the air is clean, more ozone is available for reaction with rubber.

1.2.11 Heat Surfaces exposed to cyclic high temperature get changed in microstructure resulting in thermal fatigue. This results in micro-cracks or scaling, e.g. wearing of rings and travellers and development of cracks in the belt due to high temperature.

1.7 Cracks are developed due to improper ventilation.

1.3

Role of maintenance

Any in-effective management in the spinning industry results to a big loss to the company as poor maintenance directly affects the quality of the products. It affects the reliability of the plant due to high production down time, low production availability, high overtime labour cost and maintenance cost. Effective maintenance management system helps to reduce the cost of spare parts, minimizes the repair time and associated labour cost. Ultimately it helps to attain the goal of company as it reduces the negative impact of expedited shipment and loss of production at the minimum maintenance cost. Good effective maintenance means improving product quality, productivity and overall effectiveness of the manufacturing and production of the spinning plant, hence the profitability of the plant. Good maintenance system is the attitude that uses the actual condition of the actual operating condition of the plant equipment and system to optimize the plant operations. It uses the cost-effective tools to obtain the

Need of maintenance

9

actual operating condition of the critical plant system and based on this actual data scheduled its maintenance activities. Further it helps to identify and quantify the root cause of failure mode and make the system to eliminate and improve the overall equipment effectiveness. Hence good management system helps to improve or eliminate the following six crippling shop floor losses: 1. 2. 3. 4. 5. 6.

Machine breakdown Setup and adjustment slowdown Idling and short-term stoppages Reduced capacity Start-up losses Quality-related losses

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

16. 17. 18. 19.

NIJHAWAN N . (2006) Comprehensive Hand Book of Maintenance in Spinning Part-1, The Textile Association (India). NIJHAWAN N . (2006) Comprehensive Hand Book of Maintenance in Spinning Part-2, The Textile Association (India). NIJHAWAN N . (2006) Comprehensive Hand Book of Maintenance in Spinning Part-3, The Textile Association (India). NSK Roller bearing catalogue and operating manual (Cat no. E1101e). Operating instruction for the high production card C1/3 issued in November 1987. Rieter Card C-61 Instruction manual, year 2002. S.K.F Machine Analyst CD version 1.00. S.K.F Bearing Maintenance Hand Book, year 1992. Industrial Engineering and Management Science by T. R. BANGA, N. K. AGARWAL, S . C . SHARMA , Edition 1993. Maintenance Management in Spinning by South India Textile Research Association, Coimbatore, Edition 1999. A Text Book of Machine Design by DR . P .C . SHARMA and DR. D.K. AGARWAL. Proper Installation and Maintenance Can Prolong the Life of V-Belts, by JOHN C . ROBERTSON, maintenance reliability specialist. Timing belt from Wikipedia, the free encyclopedia. V belt and Timing Belt installation and maintenance, by BANDO . GatesFacts™ Technical Information Library (Gates Compass™ Power Transmission CD-ROM version 1.) The Gates Rubber Company Denver, Colorado USA. Basics of belt drive by JOSEPH L . FOSZCZ , Senior Editor, Plant Engineering Magazine – Plant Engineering. Take the right steps to ensure proper drive belt alignment, by DAN PARSONS, Senior Project Engineer, Gates Corp., Denver – Plant Engineering, 6/1/2006. The Complete Guide to Chain, Tsubakimoto Chain Co. Instruction Manual Connect/Disconnect Instructions for Silent Chain Published by the member companies of the American Chain Association.

10

Modern approach to maintenance in spinning

2 Role of maintenance

2.1

Introduction

In a spinning mill the profitability of plant depends on the reliability, availability and maintainability of the machines. In a spinning mill, the present trend is to use most sophisticated and automated machines with complicated process control systems. All the machines work around the clock in an environment comprising dirt, dust, high relative humidity and high temperature. Hence, it puts an additional responsibility on the maintenance department as good maintenance ‘Patches out’ the work thereby decreasing the number of disruptions leading to the maximization of availability of machines for output. Spinning is a continuous process and failure of one machine can disrupt the production of whole plant. Good maintenance permits maximizing the production rate without causing difficulties or without needing more attention from operators. Maintenance role is changed substantially in the spinning mills since the last two decades. In 1970, management believed in taking action only after the failure of machine or equipment. In this type of mechanism cost is very high. The major expenses involved in this type of maintenance are high spare inventory cost, high overtime labour cost, high machine down time and low production availability, as no body anticipate the maintenance requirements. In 1990 the trend changed to preventive maintenance. This type of maintenance system intended to prevent the unscheduled down time and premature equipment failure. This type of system is a time-driven schedule and involved recurring tasks such as lubrication, cleaning and adjustments that are designed to maintain the acceptable level of reliability and ability of machine. In 2000 the maintenance involved predictive maintenance, in addition to preventive maintenance. In this system, instead of relying on average life statistics to determine the schedule activities, one uses direct monitoring system of the mechanical condition, system efficiency and other indicators to determine maintenance activity of each machine in the spinning plant. Hence, maintenance is changing its role in the spinning mill as it plays a major role in contributing the profitability of plant by supplying consistent quality products and services and thereby adding value.

10

Role of maintenance

11

Techniques

Third Generation

Second Generation

First Generation

Run to life Maintenance

Preventive Maintenance + Unplanned Maintenance + Systems for Planning and Controlling work

1970–80

1990–2000

Preventive Maintenance + Predictive Maintenance + Hybrid (Best of Preventive and Predictive Maintenance) + Failure modes and effect analysis + Expert systems + Multiskill and Teamwork

2000 on ward

2.1 Changing role of maintenance department.

2.2

Maintenance

The maintenance function of a company run on modern principles, i.e. not to attend the problem after the breakdown but to prevent all the problems, in advance, created by the machines and systems. The mission of maintenance department is to optimise availability of machine for production at the best operating condition, to reduce the cost of operations and maintenance by maximum utilization of maintenance resources. Maintenance of machines can be defined as those activities which are required to keep the good health of the machine to have original productive capacity. A sound maintenance policy should have the following objectives in a spinning mill. 1. Optimum availability – to maximize the service life of all assets, i.e. production machinery, ancillary equipments, etc. 2. Optimum operating condition – to permit the highest production rates consistent with good yarn quality. 3. Safety – to ensure full safety of personnel dealing with machinery and equipments. 4. Maximum utilization of maintenance resources – to produce the good

12

Modern approach to maintenance in spinning

quality yarn at the optimum maintenance cost. 5. Optimum equipment life – one way to reduce the maintenance cost is to increase the useful life of plant equipment. 6. Minimum spare inventory – reduction in the major inventor is the major goal of maintenance department. 7. Ability to react quickly – maintenance department must be able to attend the unexpected failure in least time. Hence, maintenance may be defined as the work necessary to maintain and preserve the machines and accessories in a suitable condition. Maintenance

Planned Maintenance Eliminates breakdown and disruptions through a program of lubrication and adjustments in machines hence ensure continous process

Unplanned Maintenance Dealing with problems and breakdown when they occur

Continuous Improvement Modification, Improvement in design

2.2 Structure of maintenance.

2.3

Planned maintenance

Planned maintenance is used to prevent or delay failures from developing. Planned service is carried out with the explicit additional objective of detecting weak points and ensuring perfect functioning by replacing the defective parts. Thus, after every service, a machine becomes as good as new and acquires high degree of reliability till the next cycle comes. Planned maintenance employs statistical methods to determine the life expectancy of parts and materials and it thereby establishes more accurate measurement. Planned maintenance requires planning of workload for the maintenance team in advance. This entails both a planning effort, which may be considerable, and a faithful implementation, and of course proper record-keeping. Planned Maintenance

Preventive

Predective

2.3 Types of maintenance.

Proactive

Evaluation of Maintenance

Quality Based

Computer Analysis Managed Maintenance

Role of maintenance

13

In order to obtain the greatest benefit from the system and to operate at maximum economy, planning should be thorough and recording must be followed up. Analysis of recorded data would assist in manpower scheduling and maintenance planning by indicating servicing time. Past failures may point to inferior parts or materials that need to be avoided in future. In addition, analysis of reasons for breakdown may indicate the need for action concerning fitter training, materials used for spares and machine itself.

2.4

Flow chart of planned maintenance.

2.3.1

Preventive maintenance

Preventive maintenance is a periodic or time-based maintenance to ensure the reliability of any machine to run on with its original capacity, and to focus primarily on maintaining the machine based on its known condition. Preventive maintenance tasks should be done where failures cannot be detected in advance. This mechanism provides as much attention as the equipment requires to the best judgment and ability of the planner. Scheduling is done on the basis of maintenance guidelines and recommendations of manufacturers. The shorter the interval and the more detailed the service, the better is the assurance we have against breakdowns. As more experience becomes available, the periods may be stretched and some items of work may be omitted to achieve maximum economy. Timing may be based on the days, intervals and hours of use. A time-based preventive program is subdivided into planned activities, which include replacement of machine parts or accessories on time basis, i.e. daily maintenance, weekly maintenance, monthly maintenance, quarterly, biannually and annually. The most important requirement of preventive maintenance is procedures and discipline. Procedure means that appropriate actions are taken at right time and in a proper way as per the work instructions. Discipline means all the activities are planned and controlled so that everything is done at a proper time interval, i.e. as per established program.

14

Modern approach to maintenance in spinning

For good programming and control, following things are essential. 1. List of all the machines and activities to be carried out. 2. A master schedule for a year that breaks down the tasks on the daily, weekly and monthly basis. 3. Assignment of responsible fitter or foreman to do the work. 4. Updating of records to show when the activity is done and when next preventive task is due. Preventive maintenance has the following disadvantages: 1. 2. 3. 4.

High moderate maintenance cost. Over-maintenance creates more problem than corrected one. Repetitive repair because of no root-cause analysis. Production loss.

2.3.2

Predictive maintenance

Predictive maintenance is another method used for planned replacement. This can be used wherever the failure development process can be predicted; where the failure mechanism gives some form of early warning signal through detectable changes in the condition of the machine part. In this system, one regularly monitors the actual mechanical condition of the machine and process system that provides the data required for deciding the machine to be taken under maintenance. Three demands must be fulfilled for the use of condition monitoring process. 1. The rate of deterioration must be slow enough to permit detection of failure development, and then to make use of the result to plan and rectify the fault before failure occurs. 2. The deterioration process must exhibit sufficient (detectable) change in condition parameters that are relevant. 3. Proper measuring equipment/tool or adequate competence must be available to detect and interpret the condition. In predictive maintenance, maintenance is still scheduled, but is based on the individual components’ proven needs, rather than a recurring schedule. Condition is usually determined by a combination of non-invasive techniques: oil analysis, vibration, electronic system testing, operational data recording (temperature, speed load, working time verses idle time), etc. The data are evaluated in terms of trends and/or deviation from normal trends. The basic principle of condition monitoring is to select one or more suitable measurements which are sensitive to component deterioration and then to take regular reading of this measurement so that any deteriorating

Role of maintenance

15

upward or downward trend can be detected and taken as an indication that a problem exists in the machine. Condition-based maintenance is ideal for spinning machinery, which contains components that fail progressively rather than suddenly; such as wires, cots and aprons. Condition monitoring is an intelligent and efficient tool with the help of which one can do need-based planning for corrective action before failure. To monitor the condition of item in spinning plant, it is necessary to find some characteristics of its behaviour, which can be measured, and which gives an indication of deterioration such as nep removal efficiency in card, yarn end breakage in ringframe, etc.

2.3.3

Proactive maintenance

In this system management, hybrid of the preventive and predictive maintenance is ideal for spinning plant because most of the vital components earmarked for planned replacement are such that they fail gradually and progressively. Here failures are not mechanical failures, i.e. the machine does not stop but the quality of material processing on the machine deteriorates. For example, the metallic wire on cards, half lap and top comb needles on combers, and synthetic cots on ringframes do not break but give poor working. Fortunately, most of the major repair and replacement activities can be made condition based rather than arbitrarily fixing their service life by choosing suitable measurement methods which are sensitive to component deterioration and/or to poor performance of the concerned machine parts. Routine and simple activities like cleaning, lubrication and maintenance of pneumatic components are also done at regular intervals for advantage of establishing a routine. These are not appropriate for condition-based monitoring. Condition-based monitoring procedure would become very inconvenient and rather costly if we go for making a condition-based procedure for such small activities also.

2.3.4

Evaluation of maintenance program

Audit and review of existing maintenance program not only informs about the current situation, but provides guidelines for future improvement – being a superb tool for identifying and implementing improvements that lead to greater profitability. Machinery audit should generally cover the following aspects: 1. Review the viability of the machine Carry out the depth analysis of all the critical components, including electrical and mechanical, which influence the productivity and quality of

16

Modern approach to maintenance in spinning

machine, and suggest replacement of parts or machines based on obtained economics. 2. Review the system of maintenance and inventory A critical review of current maintenance programs, such as method of operations, maintenance schedule, inspection procedure, staff employed and organization, should be done. A detailed investigation of the machine condition in different departments, like machine alignment, wear and tear of components, damages, etc., should be conducted. General aspects, relating to maintenance tidiness, housekeeping, tools and equipments used, should be reviewed. 3. Optimizing machine settings and processing parameters All the steps right from mixing to ring spinning, such as cleaning efficiency, nep removal efficiency, imperfection and breakage, rogue spindles, ideal spindles, etc., should be studied for balancing production and quality of product. This will improve the quality of product which in turn will increase the profitability.

2.3.5

Computer-managed maintenance system

Good maintenance is followed by proper record keeping. Computermanaged maintenance system is the best solution for record keeping and proper follow-up. CMMS is a computerized method of controlling the planning of all tasks involved in maintenance. CMMS schedules, tracks and monitors maintenance activities, and also provides cost, component item, tooling, personnel and other reporting data and history. 1. CMMS analysis determines the critical item which needs maintenance. 2. CMMS package can assist the users in tracking materials in storeroom and allows the work-order administrators to choose from a list of materials needed to do the work. 3. CMMS package helps manage the whole process of purchasing and tracking all the costs associated with it. 4. Eliminate the nightmare of paperwork. 5. Helps maintenance department to shift from corrective maintenance to preventive maintenance, which not only keeps the organization running more smoothly but also impacts safety and quality of life. 6. Makes work force more efficient; it helps workers plan their effort. 7. It also helps in planning/revising the maintenance schedule for next year and thus to forecast the budgetary requirements.

Role of maintenance

2.3.6

17

Analysis

Maintainability of the plant needs to be assessed through analysis after every one or two years, and must be improved further on the basis of such analysis. The purposes of analysis are as follows: 1. 2. 3. 4.

To reduce the down time. To reduce work load. To assure product quality. To improve work environment and safety of maintenance personnel during the performance of maintenance.

Important points to be considered during annual analysis are 1. To uncover any special needs for the system for streamlining the performance of maintenance. 2. To identify tools and remedies necessary for improved maintenance. 3. Such detailed analysis would assist in determining the overall effectiveness of maintenance efforts and for planning subsequent maintenance schedule in a better way.

2.3.7

Continuous improvement

Maintenance management has two major components: 1. Maintenance 2. Improvement The objective of the maintenance function is to maintain the present technological, managerial and operating standards. Continuous improved management means improvement in standard functions continuously. Continuous improvement principle can be implemented by a gradual move from the culture of dealing with regular failure to a changed culture of continuous monitoring, diagnosis and prevention of failure so that one can achieve process stability. Under the improvement function, management works continuously towards revising the current standards, once they have been mastered, and establishing higher ones. Improvement function can be divided into innovation and Kaizen. Innovation involves a drastic improvement in the existing process and requires large investments. Kaizen signifies small improvements as a result of coordinated continuous efforts by all employees.

2.4

Unplanned maintenance

Concept behind the unplanned maintenance is that maintenance doesn’t take place until the machine fails to work. The operator lubricates or cleans

18

Modern approach to maintenance in spinning

the machine externally only. The maintenance department comes into picture only after machine stops working completely. This maintenance is also known as breakdown maintenance. The plant does not spend the money on maintenance until a machine or system fails to operate. In this system management follows no-maintenance approach. This is the most expensive method of the maintenance. The major expenses associated with this system are (1) high machine down time, (2) high production loss, (3) high overtime and (4) high inventory cost. This type of maintenance approach results in B grade quality product and impacts negatively on expediting the delivery schedule of end product. Generally, in this kind of maintenance approach, cost is three times higher than the planned maintenance. Unplanned Maintenance Down Time

Preparing

Repairing

Waiting Spare

Repairing

Planned Maintenance Down Time

Preparing

Repairing

2.5 Comparison of down time.

2.5

Quality-based maintenance

In a spinning mill, planed maintenance also includes setting and adjustment of the machine depending upon the fibre to be processed. A cotton fibre is a peculiar object and has not truly fixed length, width, thickness, shape and cross-section. Such variations exist because of the large number of varieties in cultivation which not only differ widely in several key properties but also grown under divergent agro-climatic conditions. Besides interseasonal variations, the same variety displays variation at different locations and even in the same season. This is due to the fact that, apart from the genetic constitution of variety, the quality of cotton is influenced by various factors such as soil, climate, moisture levels of soil and atmosphere during

Role of maintenance

19

crop growth, nutrient supply, pests, disease infestation, picking time and method, post-harvest handling. Hence, it is a known fact that cotton fibre characteristics vary from bale to bale. In order to process the cotton fibre in a spinning mill, the machines need adjustments like roller settings, gauge and speed settings in drawframes, speedframes and cards from time to time in order to optimize the process with respect to fibre.

2.6

Role of maintenance department in spinning mill

In every spinning mill, the performance of the plant depends on the reliability, availability and maintainability of the plant, all of which are of primary importance for ensuring an excellent and affordable product. The concept of maintenance has changed substantially over the years; its main function now is to prevent mechanical and quality breakdowns. Quality breakdown does not mean that the quality of whole lot is low; but it means the lot is rejected due to poor quality of yarn on few bobbins or cones. Hence to maintain excellent quality, one must be capable of judging spindle to spindle variations in ringframes, speedframes and winding, and machine to machine variations in preparatory. Thus, maintenance department plays the following roles in the spinning mill: 1. To prepare a policy statement for the maintenance department, which would explain the basic objectives based on the organizational objectives, and to write standard maintenance procedures, maintenance schedules, lubrication charts, etc. 2. To prepare maintenance charts for individual equipments and to train the maintenance personnel in implementation of these. 3. To coordinate with the production people to ensure that a regular maintenance will be implemented without affecting important production schedules. 4. Carry out the scheduled preventive maintenance programs and ensure that plant is available for production for the maximum duration. 5. Carry out the overhaul of the machinery at the scheduled time without fail. 6. Calibrate various instruments put at various points in the plants. 7. Record all the work systematically in the record books, with details of work done, material used, work force applied, time taken to complete the job and expenses made. 8. Maintenance records should be reviewed from time to time so that any corrective actions to be taken and be implemented in the future. 9. Try to standardized equipments, purchased items, tools, fixtures based on the prior experiences.

20

Modern approach to maintenance in spinning

10. Always keep a close watch on inventory of spare parts and maintenance materials. Coordinate with stored and procurement department to initiate new demands in time. 11. Start energy-saving programs in the plant and also teach the operators and maintenance staff about various energy-saving techniques. 12. Recruit and train new maintenance staff and workers in place of skilled personnel who have retired or left. 13. At the start of financial year, prepare a budget for maintenance. Include all major or minor repair replacement jobs in it. 14. Ensure that the provisions in the budget are being utilized as per schedule and keep a close watch on the expenses. 15. Start the cost-reduction and cost-control projects in the plants. 16. Develop a management information system giving all the relevant details about the maintenance and replacement techniques. 17. To adjust the different machines in the process according to the fibre processed

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

BANGA T . R ., AGARWAL N . K ., SHARMA S . C. (1993) Industrial Engineering and Management Science, Khanna Publishers, Delhi. . South India Textile Research Association (1999) Maintenance Management in Spinning. NIJHAWAN N . (2006) Comprehensive Hand Book of Maintenance in Spinning Part-1, The Textile Association (India). SHARP J ., Maintenance Planning and Scheduling, University of Salford, UK. HIGGINS L . R. (Ed.) (1988) Maintenance Engineering Handbook, , McGraw-Hill Book Company, New York. NIEBEL B . W . (1994) Engineering Maintenance Management, Marcel Dekker, Inc., New York. MOBLEY R . K . (1999) Maintenance Fundamentals, Butterworth-Heinemann, Inc., Boston. MOBLEY R. K . (2002) An Introduction to Predictive Maintenance, ButterworthHeinemann, Inc., Boston. DHILLON B. S . (2002) Engineering Maintenance: A Modern Approach, CRC Press, Florida. KELLY A . (2006) Maintenance Systems and Documentation, ButterworthHeinemann, Inc., Boston. CATO W . W . and MOBLEY R . K . (2002) Computer-Managed Maintenance System, Butterworth-Heinemann, Inc., Boston.

3 Proactive maintenance

3.1

Introduction

This helps to improve maintenance through better design, workmanship, installation, scheduling, and maintenance procedures. The characteristics of proactive maintenance include practicing a continuous process of improvement, using feedback and communications to ensure that changes in design/procedures are efficiently made available to item designers/ management, ensuring that nothing affecting maintenance occurs in total isolation, with the ultimate goal of correcting the concerned equipment forever, optimizing and tailoring maintenance methods and technologies to each application. It performs root-cause failure analysis and predictive analysis to enhance maintenance effectiveness, conducts periodic evaluation of the technical content and performance interval of maintenance tasks, and integrates functions with support maintenance into maintenance program planning. It is the hybrid of both the preventive- and conditionbased maintenance. Daily Checks TBM

Periodic Checks Periodic Inspect

Proactive Maintenance

Periodic Service Visual CBM Instrument

TBM = Time-based Maintenance CBM = Condition-based Maintenance 3.1 Kinds of proactive maintenance.

21

22

Modern approach to maintenance in spinning

3.2

Preventive maintenance

Preventive maintenance is a time-based maintenance. Timing may be based upon the use of hours and pre-determined interval. This kind of maintenance anticipates failures and adopts necessary actions to check failures before they occur. It heavily depends on the prior knowledge that certain parts do need replacement in specific time interval. It is carried out with specific objectives like detecting and locating weak areas and ensuring perfect functioning, by even replacing certain critical parts which could still be used. Planned preventive maintenance is regular, repetitive work done to keep equipment in good working order and to optimize its efficiency and accuracy. This activity involves regular, routine cleaning, lubricating, testing, calibrating and adjusting, checking for wear and tear and eventually replacing components to avoid breakdown.

3.2.1

Fundamental requirements of preventive maintenance

Establishing intervals of maintenance After determining what has to be done, the frequency of the task must be decided. A heavily used item must be cleaned and checked more frequently than one which is used less often; however, minimum standards must be set. The frequency suggested in the manufacturer’s manual can be used as a guide, but the actual usage should determine the maintenance procedure required. Maintenance schedule Maintenance schedule consists of the instructions required while doing routine maintenance of equipments with the frequency specified. A typical schedule card will give the following information: 1. 2. 3. 4. 5. 6.

Name of the equipment. Type of labour required. Nature of activity to be done with details. Time required to complete the work. Frequency of operation. Any special instructions.

Thus schedules will specify which equipment has to be maintained, what work has to be done, how often it should be done, who should do it and what is the standard time to do it. A separate schedule should be prepared for each type of equipment.

Proactive maintenance

23

Work order release system This is the trigger to start the maintenance activity at the correct frequencies. It is a sort of authority given to the maintenance worker to do the maintenance as per schedule. The release of work order can be done by the supervisor to workers in the morning so that he can talk to workers and discuss the jobs. Personnel Individuals who are qualified and available to do preventive maintenance must be identified. A list should be drawn up of personnel who are readily available. Once the personnel have been listed, specific responsibilities should be assigned, perhaps in the form of a work order, giving clear instructions for the task. Each person should have a clear knowledge of his or her responsibilities. Job assignments must correspond to the training, experience and aptitude of the individual. Liaison with production department An effective system should be made to ensure that there is a complete agreement between the user of machine and maintenance department as to when the maintenance work can be done. Technical library A full technical library should be available. Installation and recommended spare parts manuals, annotated with the number of the corresponding machine, should be kept. Feedback of information The success of control system depends on proper feedback. All efforts should be made to develop an effective management information system so that the maintenance manager gets correct and timely information about all activities of maintenance. Cost control There are two basic costs involved with maintenance work. One of them is labour cost, the other being material cost. To reduce the labour cost, we must employ proper motivation, encouragement, appreciation of good work done, impartial treatment, good training programs and humanly treatment to all.

24

Modern approach to maintenance in spinning

Quality of work Checking of quality during the job is one of the main functions of control system. The foreman or supervisor of that section must check the machine before handed over the machine to maintenance department. Spare part inspection Spare part in terms of import trade control is “a part of machine which because of wear and tear need replacement”. Spare parts play a major role in maintenance of equipments as without appropriate spares no equipment can be restored to original condition for correct functioning. The spare parts should be first inspected to check whether it is as per the specifications or not. Some of the methods to inspect the spare parts are as follows: If the supplier is old and reliable and has own inspection department, which inspects the spares before delivery the user, then the inspecting authority can accept the whole lot without any inspection. The best method is to choose a sample of the lot based on the various sampling techniques developed in Statistics. Check each part of the sample and then based on results decide weather to accept/reject. Work completion report A formal record is desirable for every inspection and preventive maintenance job. If the work is at all detailed, a checklist should be used. The complete checklist should be returned to the maintenance office on completion of the work. Any open preventive maintenance work orders should be kept until the supervisor checks the results for quality assurance and signs off approval. Recording and analysing All the maintenance work done must be recorded systematically in respective record book with details of work done, material used, work force applied, etc. Review the records of maintenance work done from time to time so that any corrective actions to be taken and be implemented in future. Based on the experience gained from the past records, try to standardize equipments, purchased items, tools, fixtures, etc.

3.3

Condition-based monitoring

Predictive maintenance is one of the four tactical options available to ensure the reliability of any asset to ensure it fulfils its function, and it focuses primarily on maintaining the equipment based on its known condition. In

Proactive maintenance

25

modern spinning mills in India, the loss of production time for maintenance work is controlled within a small range of 0.5–1.0% for ringframes and 2–3% for other machines, of which unscheduled maintenance stoppages are less than 0.1% for ringframes and less than 0.5% for other machines. With regular preventive maintenance, there is however a problem in determining the optimum maintenance interval. No machine component fails at really regular intervals and the criteria for ‘failure’ are not welldefined. A mechanical breakdown such as a broken tooth of a gear is easy to identify; but when exactly does a worn out bearing bush would fail is difficult to define. If the maintenance interval is made too short, there will be no failure in the service; but on most occasions the replacement will be found unnecessary. If, on the other hand, the maintenance interval is increased to avoid unnecessary replacement, then there will still be some service failures resulting in lower production rates, more downtime, or greater incidence of faulty production. Condition-based monitoring is the right way to optimize maintenance interval for inspection/repairs and also for replacement of parts/accessories. The machine will be shut off only when it needs to be, and most service failures during actual operation can be avoided. To be able to do maintenance in this way, however, it is necessary to have means of knowing the condition of the machine part or accessory. Condition monitoring helps to maintain the spinning machinery with minimum cost and minimum total down time while ensures high level of productivity and low incidence of faults.

3.3.1

Principle of condition-based monitoring

The basic principle of condition-based monitoring is to select a suitable measurement (or a set of measurements) which is sensitive to component deterioration, and then to take regular readings of this measurement so that any upward trend can be detected and taken as an indication that a problem exists in a machine. Figure 3.2 shows how this general principle operates. If the measure of deterioration is the magnitude of vibration of a gear box, the ‘mechanical failure’ would be the breakage of a gear tooth somewhere. If the measure is ‘neps per gram’ and the neps increase sharply after a certain time interval after grinding, either another grinding or replacement of cylinder and doffer wires is called for. Another way of looking at mechanical troubles which lead to machine stoppages is to consider the time that elapses between successive machine failures. No failure at all takes place for a long time on any machine. Then the frequency of breakdown starts increasing till it reaches the peak level

26

Modern approach to maintenance in spinning Mechanical Failure Level

Deterioration

Lead Time

Running Time 3.2 Machine deterioration versus Time.

and then starts decreasing. After a certain time every machine would fail at least once. The bell-shaped curve in Fig. 3.3 represents this behaviour. If the period after which the machine has to be overhauled to prevent breakdown is selected ‘short’ then it is safe but is expensive. If the period is selected ‘long’, then too much failure would occur. Therefore a compromise period is usually selected for preventive maintenance or for condition-based maintenance. When the items as well as time intervals of cyclic- and condition-based preventive maintenance are chosen optimally, the breakdown become rare and the cost effectiveness of total system is maximum.

Long Overhaul Period Many Failures Occur Frequency of Failure

Compromise Period

Short Period

Time between machine failures

3.3 Frequency of failure time.

Proactive maintenance

3.3.2

27

Use of condition-based monitoring in a spinning mill

Condition-based maintenance and its associated condition monitoring procedures are ideal for spinning plant because most of the vital components earmarked for planned replacement are such that they fail gradually and progressively. These failures are repairable. Some failures are not mechanical failures i.e. the machine does not stop working but the quality of material processed on the machine deteriorates. For example, the metallic wire on cards, half lap and top comb needles on combers, and synthetic cots on ringframes do not break, but give poor working. Fortunately, most of the major repair and replacement activities can be made condition-based rather than fixing arbitrarily their service life. Routine and simple activities like cleaning, lubrication and maintenance of pneumatic components are also done at regular intervals for the advantage of establishing a routine. These are not appropriate for conditionbased monitoring. Condition-based monitoring procedure would become very inconvenient and rather costly if we go for making a condition-based procedure for such small activities also. Hence our maintenance system must include three basic maintenance strategies. (a) Cyclic maintenance – In this type, machine is checked at regular intervals for overhauling and replacing the major components. (b) Break down maintenance – In spite of preventive and condition-based maintenance, unexpected machine breakdowns do occur and need to be repaired. (c) Condition-based maintenance – In this type, repairment and replacement is done when there is an indication of future wear and tear.

3.3.3

Condition-based monitoring methods

To monitor the condition of a part of a machine or an accessory, it is necessary to find out some characteristics of its behaviour which gives an indication of deterioration and which can be measured. Several basic methods are used for checking component function: visual inspection of surfaces for wear and leakage, measuring temperature, and vibration and noise, wear debris and system performance. Visual inspection In many cases, function checking involves some form of visual inspection either directly or by using some means of visual assistance such as microscope or magnifying glass to observe the condition of the components.

28

Modern approach to maintenance in spinning

The metallic wire of cylinder and lickerin is an example of such an inspection. Visual inspection is a powerful technique because of the extreme effectiveness of the human eye but has some limitations if it is to be used for trend monitoring. Trend monitoring requires some recording of what has been seen, preferably with some numerical measure associated with it, so that changes with time can be properly assessed and permanently recorded. Fortunately, visual observation can be converted into numerical measures by assigning grades to severity or extent of damage with reference to 3 or 5 standard levels. Such gradation is done by at least 5 observers and the average value becomes quite a reliable numerical measure of deterioration. Examples of using ’visual inspection’ for judging the service life of components of carding and ringframes are given below:

3.4 (a) Condition of cylinder clothing; (b) Tooth of wire after grinding.

With some experience, the condition of cylinder clothing can be correctly judged using a magnifying glass. Figure 3.4(a) shows a worn tooth point which indicates the need to grind the wire. Figure 3.4(b) shows the tooth of the wire after grinding and helps to decide how many passages are needed to grind the cylinder wire. Normally, for the first grinding 2–4 passage are needed; second grinding needs 10–12 passage, third grinding needs 20–25 passages.

New 3.5 Lickerin wire.

Worn

Proactive maintenance

29

Wear is clearly visible running in traces on the edge of teeth. For comparison the edge parts of lickerin, which are not in contact with the fibres, may be used.

New Tooth Point 3.6 Combing segment.

Worn Out Tooth Point

In the worn out tooth, running in traces are clearly visible on the edge of tooth. One should take teeth at the end of the segment which are not in continuous contact with fibres for comparison with those in the middle of the segment which are always in contact with fibres. Doffer wire

3.7 Worn out tooth point.

With some experience, the condition of doffer clothing can be wellassessed using a magnifying glass. Figure 3.7 shows a worn tooth point which needs grinding.

3.8 Tooth re-sharpened with TSG.

30

Modern approach to maintenance in spinning

Figure 3.8 shows the tooth of the wire as seen after grinding and indicates how many passages are needed to grind the doffer wire. Normally, 2–4 passages are needed. Flat tops

New

Worn Out

Resharpened

3.9 Flat tops.

Figure 3.9 shows the difference between the new flat tops and worn out flat tops. It helps to decide the number of rounds needed to obtain prefect grinding. Stationary flat clothing

New Clothing

Worn out clothing

3.10 Stationary flat clothing.

3.3.4

Leakage

For seals, leakage is the obvious indication of a breakdown of their function apart from surface stains which often give a good indication of leakage. It is a good practice to look at the seals occasionally and also every time bearing is removed for inspection and cleaning. The purpose of a seal is not simply to keep out moisture and dirt but also to retain the

Proactive maintenance

31

lubricant in bearing. A leakage in seals or elsewhere should therefore be investigated immediately. The reason for leakage may be that one of the seals has worn out, or that the joint between the mating surfaces of bearing has become slack, or that the grease has broken down, thereby releasing free oil.

3.3.5

Thermal

Temperature measurement is an ideal and simple monitoring method for checking the components like bearing or electric motor. The temperature of bearings should be checked regularly. If it is high, it indicates the bearing is operating in abnormal condition and should be examined immediately, because high temperature in itself may be detrimental to the bearing of lubricant. Temperature over 150°C reduces the hardness of the bearing material and has a detrimental effect on the load carrying capacity and the life of bearing. The material does not regain its original hardness even when the temperature drops; hence the damage is permanent. Overheating of bearing can be for different reasons. 1. Excessive quantity of lubricant is used, or lubricant of high viscosity is used. 2. Internal clearance is not sufficient for the application which in turn overloads the bearing in running condition. 3. Misalignment during mounting may cause overloading, hence more heat generation. The bearing used may not be the only cause of overloading. It is quite possible for heat to be transmitted through the shaft of other component which may be the cause of trouble.

3.3.6

Vibration

The movement of a component of machine generates vibrations and the measurement of such vibrations can be used to indicate the condition of machine and its component. Vibration is generated at the moving component and the vibration signal therefore contains information on how the component is moving including any inconsistencies in the movement associated with components defect. For example, if a roller bearing is pitted due to fatigue, the rolling element will no longer rotate in a uniform and steady way. It will bounce in and out of the surface defects. This effect will be reproduced in the vibration signal generated by this faulty bearing.

32

Modern approach to maintenance in spinning

The vibration generated by the machine component travels out through the machine structure towards the outer surface. An appropriate transducer can therefore be fitted on the machine to pick up the vibration and convert it to an electrical signal for the measurement and analysis. Unlike visual gradation with reference to ‘standards’, the vibrations felt by human touch cannot be rated on the measurement scale. Instrumentation becomes a necessity.

3.3.7

Noise

Vibration may cause the outer surface of a machine to generate some noise which can be picked up by the human ear. While this provides a direct means of detecting faults, it is not as sensitive as picking up the vibration directly using an appropriate instrument and to interpret it correctly. Human hands touching the surface can feel vibrations of even small amplitudes and very high frequencies. Much higher amplitudes and small range of frequencies can be heard by the human ear. Rotating the blade of a Stethoscope can easily check the running of bearing and make the noise audible which is transmitted. If everything is satisfactory only a soft pouring sound will be heard. A squeaking noise may be caused by inadequate lubrication. A metallic tone sometime indicates that the clearance is not sufficient. A smooth but clear tone may be produced by outer damaged bearing. When the sound varies regularly with each revolution, it indicates the inner ring is damaged. This variation occurs when the damaged portion passes through alternately loaded and unloaded zone. A bearing noise which occurs intermittently may indicate that the ball is damaged: the noise occurring when the ball rolls on its damaged area.

3.3.8

Wear debris

Parts of a machine that move relative to each other tend to generate wear debris from their interactions, particularly if their operation is not entirely smooth and well-lubricated or if the surfaces are highly stressed and prone to local fitting or pitting. If the components are flushed with the fluids such as lubricating oils, the wear debris that is generated tends to be carried away by fluids and can be extracted from them. By examining the quantity and type of wear debris that has been generated, one can assess the condition of two mating parts. The amount of debris generated gives an indication of the existence of a problem and its severity. Loss in weight is also a measure of wear and can be used in situations where debris cannot be collected. The wear of travellers rotating on a ring is a good example of how loss in weight helps to assess the extent of wear.

Proactive maintenance

3.3.9

33

System performance

Another method of monitoring the condition of a machine is to check important aspects of its performance at intervals of time so that any deteriorating trend can be detected and taken as an indication that a problem has started to build up. In situations where the cost of replacement is high and also the adverse impact on the machine performance from worn out component is large, it is worthwhile to assess the machine performance before taking a replacement decision. Visual inspection alone is usually not sufficient or reliable in such cases. Important components for such assessment are card wires, rings and cots and aprons at ringframes. An illustration of how system performance assessment can help a spinning mill to reduce maintenance cost is given below. Carding machine performance A carding department consists of group of cards. The components of same make of each card can wear differently from others working on same material. This fact is helpful in implementing condition-based monitoring system in carding. Neps in card sliver can increase over a period of time as card wires on lickerin cylinder and doffer wear out because of passage of fibres. A control chart should be generated to measure carding performance in terms of nep generation and used also for determining the timing of maintenance action. The control chart for each card has neps per gram on Y-axis and time in weeks on the X-axis. Card sliver should be tested once per week and the result should be posted on the chart for particular week. When the nep level exceeds the upper control limit on any particular card, the card needs maintenance i.e. either grinding or replacement is due. The upper control limit for each card group/mixing is given by: Average neps/gram +

2

average neps/gram

where averaging is done over all cards of once make working on a given material by taking reading for 6–8 weeks. When level of neps on one or two cards in the group card rises beyond the upper control limit but the level on the cards in the group and the group average level are not changed, it shows that the cause of increase is not due to any change in the quality of fibre materials. The card showing higher neps than the limits should be taken for cylinder and doffer wire grinding. Use of average level of neps in card sliver and the control chart together for scheduling maintenance can reduce the overall cost of carding

34

Modern approach to maintenance in spinning

maintenance. Mill studies have shown that it is possible to process 900– 1000 tons of cotton instead of the 450 tons recommended by manufacturers as a safe general guideline. Moreover, grinding schedules can be extended and full setting schedules can be relaxed from once in six months to even up to once in a year if neps in the carded sliver do not exceed the desired preset upper limit for nep count. Cost for card wires is one of the largest expenses in a spinning mill. Extension of grinding and full setting intervals in cards helps to improve the utilization of machine as well as in to reduce labour cost. For measuring system performance of rings cot and apron etc, the right measure is the percentage of defectives. Defective rings would give more breakage and defective aprons and cots would give more uneven and/or weak yarn.

3.4

Benefits of condition-based monitoring

It is important to note that the general guidelines provided by machinery makers have perforce to err on the ‘safer’ side, therefore condition-based monitoring usually succeeds in lengthening the intervals to suits the quality need of a spinning mill. 1. Machine running time can be increased by maximizing the time between overhauls. The time needed for overhauling can also be reduced since the nature of problem is known and the spares and men can be kept ready before opening the machine. 2. The service life of replaceable parts is optimized i.e. it is maximized without letting the quality of the product deteriorate. 3. The lead time given by condition monitoring permits machines to be stopped before they reach a critical condition and suitable corrective action can be taken. 4. Measurements on machines when new, at the end of the guarantee period, and after the first overhaul give useful comparative values for reference. 5. The experience of the operation of present machinery is recorded in numerical scales and thus become useful for future.

3.5

Implementation of condition-based maintenance

Condition-based maintenance is applicable in the following spinning sections on selected components as shown in the Table 3.1. The actual replacement has to be done on the basis of condition monitoring.

Proactive maintenance

35

Table 3.1 Spinning components on which condition-based maintenance is applicable

S. No.

Components

Conditionbased assessment

Schedule (tons)

Department – Blow room 1.

Beater wire rep lacement

Visual inspection/machine performance

2000–4000

2.

Combing seg ment replace ment

Visual inspection/machine performance**

2000–4000

Department – Carding 3.

Cylinder wire replacement

Visual inspection/machine performance **

450–1000

4.

Doffer wire replacement

Visual inspection/machine performance **

450–1000

5.

Flat tops repla cement

Visual inspection/machine performance **

450–1000

6.

Cylinder and doffer grinding

Visual inspection

160–200

Flat grinding

Visual inspection

7.

machine performance ** 80–100

machine performance ** Department – Comber 8.

Unicomb

Nep removal efficiency and combing efficiency

1000–2000

9.

Nipper

Physical checking

10–15 years

Department – Ringframe 10.

Rings replace ment

Visual inspection/ End breakage/ hairiness *

2–4

11.

Bottom and top apron

Visual inspection/ Uster imperfection and evenness trend*

1–1.5

**

Neps/gram

*

Percentage defectives determined as those lying outside the normal variation

36

Modern approach to maintenance in spinning

References 1. NSK Roller bearing Catalogue and operating manual (cat no. E1101e). 2. Operating instructions for the high production card C1/3 issued in November 1987. 3. S.K.F interactive engineering catalogue, CD version 2.0. 4. Fag catalogue CD version 3.1. 5. Trutzschler Card DK 903 instruction manual, second edition year 1999. 6. Rieter Card C-61 instruction manual year 2002. 7. S.K.F Machine Analyst CD version 1.00. 8. S.K.F Bearing Maintenance Hand book, year 1992. 9. Technical Catalogue NBC Bearing, edition 2001. 10. Comprehensive hand book on maintenance by NEERAJ NIJHAWAN.

Planning and scheduling

37

4 Planning and scheduling

4.1

Introduction

Planning is the heart of good inspection and preventive maintenance. The first thing in maintenance is to work out which machines need maintenance, what kind of maintenance activity should be carried out, how much human resource is needed, how much time is required and what should be the best procedure to carry out this task. The following points must be considered while planning: 1. Every instruction for maintenance must be clearly defined. 2. The purpose should be outlined. 3. Tools, reference documents, and any parts should be planned in advance. 4. Safety and operating cautions must be considered. The objectives of planning and scheduling the maintenance activities in a spinning mill are as follows: 1. To achieve optimum productivity from the machines at lower production cost. 2. To ensure that expected quality of the product is achieved. 3. To eliminate delays caused by lack of materials, manpower and equipments at the job site i.e. during scheduled and breakdown maintenance. 4. To provide management with appropriate information on status, effectiveness and cost of maintenance work and to use the information as a guide to prepare subsequent maintenance schedule. 5. To control maintenance expenditure to the maximum.

4.2

General principles of planning

In order to get a good result from the maintenance team, following principles must be followed by the planning head or by the planning team.

37

38

Modern approach to maintenance in spinning

1. Centralized control. 2. Insistence on specific, definite and complete information from all contributing sources. 3. Continuous active and close supervision of maintenance work. 4. Standardised forms, procedures and paper work should be kept as few and as simple as possible, consistent with adequate control. 5. The planning effort should be directed towards aiding, complimenting and strengthening the supervision of the maintenance department for excellent performance. 6. Detailed information on costs of maintenance should be available. 7. The plan should lay specific emphasis on preventive maintenance rather than on break down maintenance. 8. The plan should be flexible to meet any emergency and to take corrective actions as quickly as possible.

4.3

Procedure of planning

One must follow the following steps for good planning in the maintenance department: 1. Estimating the work Maintenance engineer must plan all the work to be carried out in the maintenance. He should make the list of all work and must hand over this to the foreman of particular department to avoid confusion. Foreman, in advance, must plan everything required for the maintenance work to avoid idle time during the maintenance process. 2. Estimating the time Since most of the maintenance activities involve standardized procedure with little variation, the tasks and time required can be accurately estimated. Methods to be considered while estimating the time required are: (i) Equipment manufacturers’ recommendations, (ii) Industrial engineering time-and-motion studies, (iii) Experience. 3. Estimating labour cost One should estimate, in advance, the human resource needed to carry out the activities. If any help is required from other department, it should be informed to the concerned department in advance. If there is any delay due to lack of workers, it should be immediately reported.

Planning and scheduling

39

4. Estimating the material Most equipments and materials that are used for preventive maintenance are well-known and can be identified in advance. Consumables such as lubricating oil, emery paper should be on their consumption pattern. No inventory should be kept for planned replacement and overhauling spares. Based on the planned replacement and overhauling schedules, indents should be prepared at the beginning of year and delivery should be demanded one month before the scheduled time. 5. Feed back from actual The time and cost required for every work order should be reported and analyzed to provide guidance for more accurate planning in future. It is important to determine what causes the time and cost to change. Blindly assuming that the future would be like past, or that the past was perfect may be an error. Comparisons should certainly be made between different individuals doing the same tasks to evaluate results in the amount of time required, what was accomplished during that time, quality of workmanship, and equipment performance as a result of their efforts. 6. Co-ordination with production department There are cases when machine is not available for preventive maintenance as per the schedule. So, a cooperative attitude should exist between the production and maintenance departments. This is best achieved by a meeting between the maintenance manager and production manager so that everything gets planned and coordinated in advance. The cooperation of the individual machine operators is of prime importance. As they are on the spot and most able to detect unusual events that may indicate equipment malfunctions in case of any machine problem. Maintenance department must give the list of all equipments that are needed for inspections and preventive maintenance. As soon as the work is complete, the maintenance person should notify the production supervisor so that the machine may be put back into use. 7. Ensuring completion of work A formal record is desirable for every inspection and preventive maintenance job. If the work is at all detailed, a checklist should be used. The completed checklist should be returned to the maintenance office on completion of the work. The collected data should then be entered into a computer system for tracking.

40

Modern approach to maintenance in spinning

4.4

Scheduling

A mill must organize the preventive maintenance activities in a systematic manner. The secret of success of maintenance system in the company lies in its simplicity. The entire system should be structured on three principles that have validity for any industry. These principles are as follows: 1. The frequency of inspection rounds and jobs to be taken up or done during each inspection must be standardized. 2. Fixed cyclic schedule for inspection must be planned. 3. Spare parts planning must be linked with maintenance plans and schedules.

4.5

Principle of standardization of frequencies and jobs

This is a major decision to be taken by a maintenance manager. To fulfil the actual needs of different equipments, the frequency of inspection rounds as well as jobs to be completed during the rounds should be standardized. Three frequencies most commonly used for inspection are as follows: (a) Daily for routine inspection (after taking charge of department) (b) Cleaning schedule (c) Preventive maintenance

4.5.1

Daily routine inspection

This is for external inspection of equipments for noise vibration, bearing, seal leakages and checking all stop motions. Inspection should be done as per checklist/format. Minor jobs, such as tightening of loose parts, topping of gearbox oil, etc, should be attended immediately. Major jobs involving replacement of parts or the major repair work are identified. After completion of round, a brief report should be made mentioning: (a) List of minor jobs attended, and (b) List of major parts to be attended. Above report should be shown to the concerned supervisor with suitable instructions for follow up.

4.5.2

Cleaning schedule

Inspection during this round is very detailed and involves checking of gears, shafts and bearings, etc. and replacing and repairing of above items

Planning and scheduling

41

in case of unacceptably high wear. Replacement of all such minor items reduces random, unexpected failure and thus improves utilization. Another objective should be to clean and lubricate the machine as per the schedule.

4.5.3

Preventive maintenance

This is mostly clubbed with the cleaning schedule in order to avoid duplication. In this inspection parts are dismantled and checked fully. If needed they are replaced. Different settings of machine are checked and corrected. In this inspection standard parts which have a fixed life are also replaced if their life is due.

4.6

Principle of cyclic schedule for the maintenance team

In cyclic schedule, manager gives a fixed cycle of work in detail for each working day of each month to every foreman and his team to attend specific machines. The foreman and his team inspect the machine and do preventive maintenance according the fixed cycle of work. The list of machines to be taken and work to be done each day of month is fixed. Such cycles must be religiously followed, without permitting any dislocation since jobs to be done on each machine in each cycle are standardized beforehand. In this way it is possible to utilize the worker of maintenance team in a better way. The maintenance manager is able to control the performance of his maintenance team effectively as he has the cyclic schedule on his table. He should involve himself once in a while in the inspection of machines and cross-check/ supervise the work of his subordinates/ juniors.

4.7

Principle of interlinking spare part planning with maintenance plan and schedule

Always link the spare parts planning with maintenance plan and schedules. All spare parts are classified into three categories: (i) Emergency spare, (ii) Planned replacement and overhauling spares, and (iii) Consumables. The last two categories are clearly defined and service life is estimated. The consumables are indented as per estimated consumption pattern. This helps in planning of procurement and in control of inventory. The cost of consumable items is negligible as compared to durable spare. No inventory should be kept for planned replacement and overhauling spares. Based on the planned replacement and overhauling schedules,

42

Modern approach to maintenance in spinning

indents should be prepared at the beginning of year and delivery should be demanded one month before the scheduled time so that these items are utilized during their respective schedules. This simple decision leads to low levels of inventory and, at the same time, to reduce the chances of stock-outs. Spares are available, whenever needed, as a result of linking spare part planning with maintenance plans and schedules. Cyclic schedule results in the following benefits: ● ● ● ● ● ● ●

4.8

Improvement in the condition of equipment. Reduction in the cost of maintenance. Accurate forecasting of labour and material needs. Accurate analysis of cost and maintenance level. Eight hours of productive work by each worker. Availability of actual data required for evaluation of performance. Timely corrective action.

Operators must act as machine keepers

Machine operators are expected to manage the machines on which they work and the equipment they use. Through these they manage production of quality output with zero defects. To produce defect-free product every time, the operators need to have good knowledge of the process they are responsible. They must be thoroughly familiar with routine maintenance. Operators must act as machine keepers also. Operators must be encouraged to work closely with maintenance staff in carrying out the routinemaintenance activities that help to keep the machine in good health. In a spinning mill, the quality of products delivered by machine depends mostly on machine parameters set by the spinning staff. The main role of the machine operator is to follow work practices (taught to him during training) single time and avoid any faulty work such as bad piecing, etc. He should also look for and identify defectively functioning machine parts or accessories so that maintenance persons can replace the defective items at the earliest (e.g., worn out apron, eccentric roller, etc). A major part of good work practice for machine operators in a spinning mill is the cleaning of machine. If the fibres and other materials which keep accumulating on different machine parts are not removed timely by the machine tenter, faults of different kind – mainly thick places get generated in the sliver, roving or yarn. Standardised cleaning schedules are given here for spinning machines starting from ringframes. Spinning supervisor should ensure that these are followed properly by all operators of all machines.

Planning and scheduling Table 4.1 Cleaning schedule for ringframe Parts to be cleaned

Frequency (hours)

Cradle neck Front roll Front top roll Back top roll Front roll bearing Tension pulley Back roll Knee brake Cradle patti Top clearer Under clearer Jockey pulley

8 8 8 8 8 24 24 24 24 24 72 48

Table 4.2 Cleaning schedule for speedframe Parts to be cleaned

Frequency (hours)

Drafting zone cleaning Creel Flyer Bobbin rail Back cover Waste fan Back side of machines Under clearer Top clearer

2 24 At every At every At every At every At every At every 1

doff doff doff doff shift shift

Table 4.3 Cleaning schedule for pre-comber drawframe Parts to be cleaned

Frequency (hours)

Drafting zone cover cleaning Machine cover cleaning Top clearer cleaning Bottom roll stripper cleaning Fan waste Scanning roll Top roll interchange Top roll cleaning by water Creel cleaning

2 4 2 8 1 8 1 2 At every batch

Table 4.4 Cleaning schedule for comber Parts to be cleaned

Frequency (hours)

Drafting zone cleaning Machine cover cleaning Top clearer cleaning Bottom roll stripper cleaning Top nipper cleaning Feed roll cleaning Top comb cleaning Top roll cleaning by water

4 8 2 8 4 24 1 24

43

44

Modern approach to maintenance in spinning Table 4.5 Cleaning schedule for drawframe Parts to be cleaned

Frequency (hours)

Drafting zone cover cleaning Machine cover cleaning Top clearer cleaning Bottom roll stripper cleaning Fan waste Scanning roll Top roll interchange Top roll cleaning by water Creel cleaning

2 4 2 8 1 8 1 2 At every batch

Table 4.6 Cleaning schedule for unilap Parts to be cleaned

Frequency (hours)

Table cleaning Drafting zone cleaning Creel cleaning Top clearer cleaning with water Fan waste Machine cleaning Top roll cleaning by water Cover cleaning Drum cleaning Table calendar roll cleaning

4 4 At every batch 8 4 8 8 1 At every batch 2

Table 4.7 Cleaning schedule for card

4.9

Activities

Frequency (hours)

Calendar roll stripper cleaning Card can cleaning Web checking Cover cleaning

1 24 24 2

Maintenance schedule

The maintenance person undertakes cyclic schedule for maintenance which includes thorough cleaning on a stopped machine, oiling/greasing to lubricate running parts, resetting the different machines parameter at desired level and also improving the mechanical condition of worn out parts by means such as polishing, grinding, etc. Schedule is given department wise here from blowroom to doubling. These schedules are meant for cotton spinning; for manmade fibres the replacement intervals may become 20% shorter.

Planning and scheduling Table 4.8 Maintenance schedule Activities Cleaning and greasing of all machines in blowroom Grid bar polishing By pass valve checking Ventilator checking and greasing Saw tooth beater wire Disc beater Pin roller beater Oil change

Frequency (month) 1 6 6 6 20,000–40,000kg 20,000–40,000kg 100,000 kg Manufacturer recommendations

Table 4.9 Maintenance schedule Activities

Frequency (months)

Cleaning Full setting Greasing Oil change Flat gauge checking Activities Flat grinding Cylinder grinding with TSG Doffer Grinding with TSG Cylinder wire replacement Doffer wire replacement Flat tops Lickerin wire Stationary flat above lickerin Stationary flat above doffer Stationary flat below lickerin Redirecting roll wire All cleaning roller brush In case of three lickerin I lickerin II lickerin III lickerin

2 6 6 or manufacturer recommendations Manufacturer recommendations 1 Frequency (Tons) 80–100 160–200 160–200 800–1000 800–1000 400–500 150–200 160 450 With lickerin 2000 450 2000 450 450

Table 4.10 Maintenance schedule Schedule

Frequency (months)

Cleaning and greasing Cots buffing Oil change Cots Can plate opening and cleaning

0.5–1.0 0.5–1.0 Manufacturer recommendation 6–12 1

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46

Modern approach to maintenance in spinning Table 4.11 Maintenance schedule Schedule

Frequency (months)

Cleaning 0.5 Cots buffing 3 Overhauling 8–10 years Full setting 6 Proximity switch setting checking 6 Cots change 36 Table 4.12 Maintenance schedule for comber Schedule

Frequency (months)

Cleaning Greasing Nipper gauge checking Unicomb gauge checking Brush gauge checking Oil change Drafting gauge checking Proximity switch setting Nipper pin change Overhauling Detaching top roll Drawbox cot buffing Detaching top roll Drawbox cot change Brush change Top comb Unicomb

0.5–1 Manufacturer recommendation 6 6 Three Manufacturer recommendation 6 6 36 96–120 6 3 18 36 36 12 60–72

Table 4.13 Maintenance schedule Schedule

Frequency (months)

Cleaning 1 Saddle gauge and bottom roll gauge checking 6 Oil change Manufacturer recommendation Bobbin trough levelling 4 Flyer cleaning 1 Top apron and bottom apron washing 6 Top apron change* 1.5 Bottom apron change* 1 Arbour greasing 6 Overhauling 96–120 Lifter shaft bearing greasing 6 Reversing gear play clutch gauge checking 2 Finger checking 1 Pressure checking in case of pneumatic 6 Top roll buffing 4–6 Cot change 24–27 False twister 24 Front and back arbour greasing 6/36** Middle arbour 6/life time *In case of imported apron one can increase the life of aprons. **Applicable for TG-5 grease.

Planning and scheduling Table 4.14 Maintenance schedule for ringframe Schedule

Frequency (months)

Bottom roll greasing Cleaning Oil change

1 1–6 manufacturer recommendation

Drum shaft bearing greasing Saddle gauge checking Spindle oil change Separator washing Suction tube washing Top apron washing Bottom apron washing Jockey pulley greasing Spindle gauge, ABC ring centering, lappet hook centering and height level of all these thing Ring change*

4 12 6 18 18 6 6 12 12 /With ring change/need base

Hose pipe and ribs Piston O.H. In case of G5/1 ringframe Top variator pulley O.H. Bottom variator pulley O.H. Machine over hauling Gear box opening and checking Front cot buffing Back cot buffing Front arbour greasing Middle arbour greasing Back arbour greasing Cots change Top apron change – Indian – Imported Bottom apron change – Indian – Imported Spindle tape Lappet hook Bottom roll eccentricity checking ** Applicable for TG-5 grease

Very coarse count – 18 Coarse count – 24 Middle count – 30–36 Fine count – 40–48 60 60 9 12 120 12 1–1.5 4 2 /36 ** 12/ Life time** 12 /36 ** 12 12 24 12 24 12–18 48–60 12

47

48

Modern approach to maintenance in spinning Table 4.15 Maintenance schedule for Autoconer 238/338 Schedule

Frequency (month)

Machine cleaning Splicer head cleaning and lubrication Tension assembly cleaning and lubrication Cam cleaning and spray Locking device cleaning Cradle adopter greasing Cradle adopter silicon oil Auto doffer cleaning and spray Auto coner overhead travelling cleaner O.H.

1/2 6 12 2 2 6 2 1 12

Table 4.16 Maintenance schedule for Machconer 7-V Schedule

Frequency (month)

Cleaning Winding head over hauling Reduction motor oil change

1/2 6 Manufacturer recommendation 3

Cam shaft cassette gear, housing, suction motor drive greasing Cradle adopter bearing, conveyor pulley greasing Auto doffer cleaning and spray Auto coner overhead travelling cleaner O.H. Conveyor belt pulley O.H. Dust collector checking Ballcon alignment checking

3 3 12 12 1 1

Table 4.17 Maintenance schedule for Two-for-one twister Schedule

Frequency (month)

Cleaning Gear box oil change

2/3 Manufacturer recommendation 6 6 6 3

Inner pot bearing/protection pot/guide roll Spindle oil change/spindle greasing Belt guide roll greasing Centering disc greasing

Table 4.18 Maintenance schedule for Cheese winding Schedule

Frequency (month)

Cleaning Drum shaft bearing greasing Cradle adapter bearing greasing Oil change

1 3 6 Manufacture recommendation 12

Over head blower over hauling

Planning and scheduling

49

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

13. 14.

15. 16. 17. 18. 19. 20. 21.

NIJHAWAN NEERAJ ,

Comprehensive Hand book on Spinning Maintenance. Operating Instruction for the high production card C1/3 issued in November 1987. Trutzschler Card DK 903 instruction manual second edition year 1999. Rieter CardC-61 instruction manual year 2002. Murata Machconer /Linkconer No. 7 instruction manual revised May 1988. Kirloskar Toyada Ringframe RXI240 instruction manual year 1999. Rieter Ingolstadt Drawframe RSB 951 year 1996. Rieter Unilap E32 operating instruction manual10055921. Rieter Comber E62 operating instruction manual 10013753. Lashmi Speedframe LF 1400 operating instruction manual year 1990 Lashmi Ringframe G5/1 operating instruction manual year 1990 Roving Frame Instruction Manual FL-16 By Toyada Automatic Loom Works edition 1997, Toyada FL 100 Roving Frame Instruction manual seventh edition Augus 2001 PRERNA LEEWHA , Two For One Twister for spun yarn PRN –140- LW Instruction manual. Texmaco zinser ringframe instruction manual issued in January 1969 reprinted april 1973. Zinser Speedframe 660 instruction manual year 1990, Zinser Drawframe 720 instruction manual year 1990, Zinser Ringframe 321 instruction manual year 1990. High Speed Simplex Fly Frame instruction manual RME Howa Machinery Limited Edition august 1993 Drawframe Cherry DX –500 – E2 instruction manual, Drawframe Cherry D– 400 MT instruction manual Savio Orion instruction manual, manual code 11645.0004.1/0 revision index :01 date of issue : 06.01 Two for one Twister instruction manual Leewha LW 560 SA Rieter Unifloc A11 instruction manual edition 2000, Ringframe G33 instruction manual year 2001, CardC-61 instruction manual year 2002. Murata Process Coner 21-C instruction manual revised October 2002, Schlaforst Autoconer 338 instruction manual year 2003.

50

Modern approach to maintenance in spinning

5 Maintenance audit

5.1

Introduction

Maintenance audit helps in improving the existing maintenance system. It also helps in early detection and prevention of mechanical faults, which may remain undetected and unidentified for too long if one relies only on instrumentally testing of the product. Machinery audit may be defined as “Methodical in-depth examination of the total operating system with relevance to the maintenance of the machinery.” Maintenance audit includes the physical inspection of the machine parts that have a large effect on the productivity of the machine and/or on the quality of the product delivered by machine. The overall objective of the maintenance audit is to review and critically assess the existing maintenance system to judge the reliability and maintainability of the plant with a view to suggest improvements. The specific objectives of maintenance audit are as follows: 1. To study the existing systems and procedures with respect to maintaining health of machines and safety of workers. 2. To review the implementation status of the existing maintenance systems, procedures, plans and programs/schedules. 3. To carry out physical inspection of the machines with regard to safety, standard and uniform setting, and mechanical condition of individual parts of machines. 4. To recommend measures for improving effectiveness of implementation of the total maintenance system, for improving the existing procedures and for setting up of new procedures if required.

5.2

Methodology

The overall methodology consists of the following five stages:

5.2.1

Preliminary information gathering

Collection of preliminary information regarding the maintenance system through a questionnaire developed by auditor before undertaking actual field work.

50

Maintenance audit

5.2.2

51

Examination of maintenance system

Types of maintenance system: 1. Unplanned maintenance, 2. Planned maintenance includes preventive maintenance, 3. Planned maintenance includes both preventive and predictive maintenance. Now-a-days, modern mills having 50% of the maintenance activities must be based on the condition-based monitoring system. The auditor should go through all the maintenance records like schedule register, history register corrective action and preventive action register, etc form a tentative judgment on the efficiency of the maintenance system and of the condition of the machines.

5.2.3

Safety audit

The objective of a general safety audit in maintenance is to review and assess the safety methods employed to prevent and control hazards in the plant with a view to suggest improvements wherever necessary. (a) Are working surfaces even, free from dust, wastes, spillages, loose objects, cables/hoses lying around? (b) Are floor openings kept covered or guarded with rails while working? (c) Is there a schedule for periodic floor cleaning? Has man power been assigned or time allocated for this work? (d) Are tools and fixtures kept on racks instead of machine? (e) Are platforms, benches, seats in good condition? (f) Are drip trays provided and regularly cleaned? (g) Is material properly stacked in racks? (h) Is there a schedule for depositing the scrap to the scrap yard? The specific safety precautions connected with each machine are covered in the maintenance checklists for physical inspection of the machines.

5.2.4

Inventory system audit

The object of auditing the inventory system is to check how they are linking the spare part management with the maintenance schedule. Auditor must check the following points: 1. 2. 3. 4.

Downtime was high due to part shortages. Spare parts were kept haphazardly in cabinets and on open shelves. Maintenance technicians wasted time looking for parts. Parts were often not labeled, mislabeled, obsolete or unidentifiable.

52

Modern approach to maintenance in spinning

5. Emergency purchase orders were frequent and expensive. 6. Automatic reordering capabilities were not used. 7. Ordering practices were loosely defined, leading to incorrect inventory levels. 8. No one knew what items had been or needed to be ordered. 9. No one knew when items were due to arrive or if they had already been received. 10. Received parts were frequently lost, resulting in unnecessary and expensive reorders. 11. Inventory records are created for all parts with the following details: (a) Item number (b) Description (c) Inventory type (d) Quantity on hand by location (e) Minimum and maximum stock level

5.2.5

Maintenance effectiveness

In maintenance is there any system that records the number of failures and then analyses the root cause of failure. To see the effectiveness of the maintenance department, one must check the following points: 1. 2. 3. 4. 5.

Number of failures, Root cause of failures, The maintenance cost associated with no. of failures, The production cost associated with no. of failures, and The ratio of planned maintenance work to unplanned maintenance work.

Secondly, maintenance system must have key performance indicators for maintenance cost, utilization loss and overtime hours for each machine, etc.

5.2.6

Maintenance budgeting and cost control

Maintenance cost is defined as the cost associated with maintenance activities. Maintenance budgets including expenditure budget and utilization budgets are made on the basis of assessment of activities they expect to perform. One must check how many report the actual cost against the budgeted activities.

5.2.7

Daily scheduling and job control

There should be a system that determines how the work is allocated to the

6 Role of manpower in maintenance

6.1

Introduction

“The process by which management determines how the organization should move from its current manpower position to its desired man power position. Through planning management endeavours to have right number and right kind of people at right place at right time, doing things which result in both, the organization and the individual receiving maximum long run benefits”. Manpower planning deals with the computation of the least but the most effective manpower requirement in any organization considering job analysis, job description and job evaluation. These principles apply also to the planning of manpower for maintenance of machinery and equipments in spinning mills. Job analysis consists of observing and recording the time required to do each detailed element of maintenance activity. With the help of this technique, the standard time required to complete each element of activity is determined. The job descriptions of different categories of maintenance workers are also standardized. Based on these two, number of persons needed to complete the total job in the shortest time is determined. Job evaluation is used to decide the wages/salaries to be paid to maintenance workers of different job descriptions and corresponding responsibilities. After determining the time needed for each activity, and the worker requirements, the total man power requirement for the predetermined cyclic schedule of maintenance is finalized.

6.2

Factors affecting manpower planning

The factors which need to be considered for planning of maintenance man power in spinning mills are: product mix, worker performance, man hours lost, type of machines, and schedules laid down for maintenance.

6.2.1

Product mix

Product mix means the production program based on the production capacities at different stages of processing and in the market requirement.

55

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Modern approach to maintenance in spinning

The type of fibre used plays a major role: cotton, manmade fibres, such as polyester acrylic, viscose acrylic or their blends, fibre dyed or dope dyed, or grey and single or ply yarns etc are differences in the product mix that influence the number of maintenance worker needed. Synthetic yarn plant of same capacity require more man power than cotton yarn: for example, cleaning needs to be done more frequently and several spares/ accessories etc need to be replaced after shorter service life. Even changes in the production program i.e. the number of different counts being produced and their quantities may be more frequent with synthetic and blended yarns.

6.2.2

Skill of worker

The rate of performance of maintenance workers has direct effect on the man power requirement. If the workers are skilled and their performance is good, fewer workers will be needed. In addition, suitable incentive plans also help to improve the efficiency of skilled workers. If the existing performance rate is seen to be low, appropriate training needs to be given to improve the skill and the work methods of those who bring down the average. If some workers fail to improve to the standard level, they need to be given other jobs and more efficient workers should replace them. This way a mill can put the right man at right job, and employ the least possible no of workers for the maintenance activity.

6.2.3

Idle time

The less the productive man hours lost, the more are the available productive hours of the maintenance workers for their real job. Productive hours are lost due to the following reason: 1. 2. 3. 4. 5. 6.

Time wasted in searching for tools and equipment. Due to non availability of proper tools and spares. Waiting for instruction; getting unclear instructions. Rectification and rework due to poor workmanship. Idle time due to waiting for machine to be available for maintenance. Due to poor production planning, i.e. market requirements are not cleared.

Good maintenance manager ensure that the causes 1, 2, 3 do not exist, take care of 4th through retraining workers and co-ordinate with the production supervisors to eliminate 5 and 6. The man power planning should be and normally is done with the assumption that no undue man hours will be lost. Extra losses due to changes in production programme need to be lived with i.e. accepted as unavoidable since they represent the mills response to market demands.

Role of manpower in maintenance

6.2.4

57

New generation machine

The latest spinning mill have high production and Automated machines, which are required in smaller numbers to produce a given quantity of yarn as compared to machines of earlier models and makes. Moreover, the modern machinery is designed to need much less maintenance and to provide easier access to machine parts which need maintenance. A modern mill therefore will need less manpower for the same production capacity than a mill with machinery of earlier generation.

6.2.5

Type of maintenance

It also depend whether the organization follow only preventive maintenance or the hybrid of both preventive and predictive maintenance. The cyclic schedules developed for preventive maintenance normally result in overmaintenance. Hence it requires more man power.

6.2.6

Absenteeism

After deciding upon the required manpower strength on the basis of the 5 factors mentioned above, it is necessary to ensure that such standard strength is available everyday, all through the year. To ensure this the Maintenance Manager has to take into account the absenteeism rate and the permitted leaves of maintenance workers. Usually the absenteeism of maintenance workers is less than that of machine operatives, and ranges between 5% and 15% so keeping about 10% extra staff in semi-skilled categories is worthwhile. Similarly, the turnover rate of the maintenance staff of different categories needs to be taken into account. Planned retraining, upgrading the skills, and giving internal promotion is usually better for keeping the morale and the work efficiency high. New recruitment every time when a vacancy occurs takes away the enthusiasm of existing maintenance team. Of course, new recruitment is desirable when the right skill is not available amongst the existing workers/staff.

6.3

Manpower norms

The standard for maintenance man power in cotton spinning industry producing single yarn is 1 worker per 1000 spindles including winding. For synthetic yarn spinning mills it is 1.0–1.2 workers per 1000 spindles including winding.

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Modern approach to maintenance in spinning

Spinning mills consist of 4 sections The man power distribution for each section is given below for a 25000 spindle spinning mill working 24 hours a day, 7 days a week. Section Blowroom and card Preparatory area Spinning area Winding area Total

Maintenance workers/day Cotton

Synthetic

4 7 10–12 4–6 25–28

5 8–9 10–12 6 29–32

The standard strength given above does not include extra staff needed to cover absentees and workers on leave.

6.4

Maintenance organization structure

The head of maintenance department should always report to the technical head or to the chief of the operating officer of the unit. The operation chief is responsible for the total performance of the spinning mill and usually does not deal the finance and marketing etc. he is technical head for the spinning mill. It would be un-desirable to place the maintenance function under the supervision of the person in charge of production function. Maintenance function is totally different from production. Production is a line function where as maintenance is a service function. Performance of the production department is measured in terms of fulfilment of production targets. Performance of the maintenance department is measured in terms of trouble free service it renders at minimum cost and minimum utilization loss. It has to achieve standards of reliability, machine availability and longer life of equipment. In case the maintenance were to be organized as a sub-function of production, the availability of production machines for maintenance work is likely to be sacrificed to meet the production targets. Since maintenance is a vital service function, the Maintenance Head should preferably report to same level to which production in charge also reports in that mill. In that position he is able to enlist co-operation from the heads of other departments to the maintenance program. In modern spinning mills the top managements ensures that both production and maintenance head understand the important roles each has to play, and built system to reduce the apparent conflict between the two functions. Production person realize that any temporary advantage gained by not stopping maintenance for due maintenance results in much longer losses in long terms through poor productivity and the greater proportion of defects

Role of manpower in maintenance

59

The organisation structure and strength of staff in each category are shown in chart 6.1., 6.2 and 6.3 Chief Executive Head of Maintenance Department Maintenance Engineer

Maintenance Clerk

Blowroom & Card Foreman

Preparatory Foreman

Spinning Foreman

Post Spinning Foreman

Fitter

Fitter

Fitter

Fitter

2 cleaner

Running Fitter

Runnig Fitter

2 cleaner

4 cleaner

Roller Coverer 6 cleaner

6.1 Manpower required for cotton mill with 25000 spindles. Chief Executive Head of Maintenance Department Maintenance Engineer

Maintenance Clerk

Blowroom & Card Foreman

Preparatory Foreman

Spinning Foreman

Post Spinning Foreman

2 Fitter

2 Fitter

2 Fitter

2 Fitter

6 cleaner

2 Running Fitter

2 Runnig Fitter

6 cleaner

8 cleaner

2 Roller Coverer 12 cleaner

6.2 Organization chart for cotton mill with 50000 spindles.

6.5

Concept of common gang

The concept of common gang is the need of the hour in maintenance: With increase competition owing to globalization the need is to minimize the manpower need for maintenance without adversely affecting the effectiveness of maintenance in any way. The term common gang refers to the deployment of common members in cross-functional areas of the maintenance department, as distinct from the conventional system of keeping distinct separate teams for the 4 different spinning sections.

60

Modern approach to maintenance in spinning Chief Executive Head of Maintenance Department 2 Maintenance Engineer

Maintenance Clerk

Blowroom & Card Foreman

Preparatory Foreman

Spinning Foreman

Post Spinning Foreman

3 Fitter

3 Fitter

3 Fitter

3 Fitter

10 cleaner

3 Running Fitter

3 Runnig Fitter

10 cleaner

10 cleaner

3 Roller Coverer

16 cleaner 6.3 Organization chart for cotton mill with 75000 spindles.

The concept has evolved over the past decade or so. The conventional working in 1980s consisted of deployment of man power section-wise and each person from a section confined to working in that particular section as shown in Fig. 6.4. Maintenance Department

Blow Room

Card

Comber Speedframe & Drawframe

Ringframe

Automatic Non winding Automatic winding

6.4 Conventional working pattern in 1980s.

As competition between mills increased due to pressure from domestic and international markets, mills experimented with the idea of reducing the manpower costs of maintenance by multiskilling and grouping. The structure that emerged in 1990s is shown in Fig 6.5. Maintenance Department

Blowroom & Card

Comber Speedframe & drawframe

Ringframe

Automatic & Non automatic winding

6.5 Working pattern in 1990s.

Blowroom was merged with card; speed frame, drawframe and comber were merged and conventional winding and autowinding together was considered as one section. Such grouping required considerable multiskilling of maintenance operatives.

Role of manpower in maintenance

61

The next appropriate step for the 21st century, is to make a single common maintenance team for the entire spinning mill. This Common Gang concepts means deployment of same man power team for all machines in a spinning mill. Any compartmentalization of spinning department is completely abolished. The entire emphasis is on multiskilling of all the maintenance workers. Each of them should be able to do maintenance jobs on several different kinds of machines from blowroom to winding. Such multiskilling and making of Common Gang for the entire mill permits and encourages job rotation for the team members. The objective of making a Common Gang is not just the most efficient utilization of manpower through rationalisation. When properly formed and implemented, it helps to avoid monotony in jobs, to enhance knowledge and to give opportunities for career growth to individuals. Use of Common Gang means much reduce dependency on few individuals. It leads to enhancement of team spirit amongst the maintenance staff, while reducing production losses due to machine down time to the minimum.

6.5.1

Implementation of the common gang concept

The Maintenance Manager supported by the top management and the production manager should take following steps to implement Common Gang concept in the maintenance department: 1. Training of maintenance staff to help them to develop multiple skills and to learn technology of different machines. The training program has two components: class training program for imparting technological information and practical training on machines other than which they have been working earlier. 2. Develop the concept of common gang in the workers: through lectures and question answer sessions. No maintenance ‘section’ should be mentioned on worker’s card, only maintenance ‘department’ should be indicated. 3. One foreman and one fitter should be made the head of the planning gang and the rest of the team should work under their leadership. Importantly this process must be on rotational basis and the rotation cycle should be minimum of one month. 4. Each section will be named as maintenance room no. 1, 2, 3, 4 and not by their section name their section name. 5. All foremen and fitters should meet in the evening to plan their next day work and to allocate work as required by the predetermined schedule of the mill accordingly. 6. Leaves of cleaners should be sanctioned by the foreman and fitter

62

7.

8. 9. 10.

Modern approach to maintenance in spinning

who head the Common Gang for that month and the leaves of foreman and fitter should be sanctioned by the maintenance engineer. Every cleaner must be given a chance to work as a running fitter in different departments. Every cleaner works for three months as running fitter Running fitters should be two: one for blowroom to speedframe, and another for ringframe to winding section. Work manual for different machines should be prepared in local language to standardize the training of workers. Checklist should be designed to evaluate the skill of foremen, fitter and seniors workers in performing maintenance activities on different machines, and to determine their individual training needs.

Table 6.1 Manpower for common gang

S ize o f mi ll

25000 spi ndles

50000 spindl es

75000 spindl es

Maintenance worker /day Maintenance head Maintenance engineer Maintenance clerk Foreman Fitt er including rol ler coverer R unni ng fit ter C leaner Total

6.6

1 1 1 4 5 2 9 23

1 1 2 4 10 4 +2 18 42

1 2 3 4 15 6+ 2 27 60

Responsibilities at various positions

The role to be played by each level of the hierarchy shown in the organization chart is explained in terms of responsibilities

6.6.1

Head of maintenance department

1. The Maintenance Head is responsible for planning execution of all maintenance functions. Once the policies regarding scheduled replacements, corrective maintenance, preventive maintenance, etc. have been decided in consultation with the technical head, the responsibility for preparation of plans & for executing the plans effectively and efficiently rests with him. 2. His responsibilities are to prepare schedules for routine and preventive maintenance, consistent with the maintenance budget of civil work according to the plant layout and drawing. 3. To supervise actual maintenance work & check the work being done by the maintenance team.

Role of manpower in maintenance

63

4. To plan for the timely replacement of worn out spares & subsequently raise the indent in order to ensure the procurement of scheduled replacement item well in time through the materials department. 5. To raise the indent for spares on machine manufacturer as per the machine, catalogue number, drawing number. 6. To procure local items samples/specimen/dimensions should be given as and when required. 7. To correspond with accessory, tool, material, and machine manufacturers and help seniors/colleagues with regard to finalizing orders for the above. 8. To prepare the maintenance budget for the financial year and to control the maintenance cost accordingly. 9. To arrange for calibration of all equipment (like micrometer, vernier callipers, leaf gauges etc.) Used for maintenance purpose. 10. To implement of the concepts like task force, Q.I.P. and Kaizen in the maintenance department. 11. To recruit trainees and skilled workmen in maintenance department in close co-ordination with industrial relation department. 12. To modify machine cleaning schedules, maintenance schedules, process standards etc if needed, after consulting with the technical head and production head. 13. In case the mill undertakes expansion i.e. addition to capacity etc, to take up the responsibilities of project planning, erection and commissioning of plant and technical evaluation.

6.6.2

Maintenance engineer

The maintenance engineer new the wok of foreman/fitters and ensures implementation of planned work: 1. Highlights any non-conformity in cleaning and maintenance schedule to Maintenance head and suggest corrective action. 2. He carries out inspection of the machines/equipment himself to ensure that his team adheres to high technical standards all the time. 3. He prepares and implement the monthly plan for preventive maintenance and overhauling within allocated budgets. 4. He ensures that effective methods are used and repairs are done economically while carrying out the maintenance activities. 5. He is responsible along with the concerned foreman to attend to any breakdown as and when it occurs. 6. Raises material issue slips for procuring from the mill stores all the items required for the planned maintenance work.

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Modern approach to maintenance in spinning

7. Raises indent for spares to be bought from machine manufacturer as per catalogue number, drawing number etc. 8. Provides samples/specimen/dimensions as and when required for procuring local items.

6.6.3

Maintenance clerk

He is responsible for documentation and for keeping track of maintenance items coming to use by the maintenance department. 1. Maintaining various documentation of maintenance department and preparing reports asked for by his seniors. 2. Filling the issue slip as per the requirement of respective department and get it duly signed by maintenance head/maintenance engineer. 3. Keeping track of monthly requirement of various departments. 4. Writing memos to the purchase and store department regarding procurement of pending items as directed by maintenance head/ maintenance engineer. 5. Keeping track of material coming to the receipt section of the main maintenance store and intimating such arrivals to his concerned maintenance engineer.

6.6.4

Senior foreman/foreman

He shall be responsible for: 1. Planning and execution of the maintenance work of his department. 2. Ensuring conformance with the specified maintenance schedules of his department. 3. Giving Instruction for work to his juniors. 4. Intimating his seniors if any part is in short supply or is urgently needed. 5. Co-ordinating with the engineering department foreman for any repair in the workshop, or any other work related to engineering department. 6. Giving practical training to his subordinates when needed. 7. Reporting to Maintenance Engineer departmental problem and resolving them based on suggestions/maintenance engineer advice. 8. Inspecting materials coming to the receipt section of stores and giving feedback to maintenance engineer about their suitability or otherwise. 9. Bringing all materials which are required for maintenance from Store. 10. Going through the checklist, charge register and running reports and taking appropriate actions.

Role of manpower in maintenance

65

11. Inspect the records maintained by fitters and to take suitable actions if luccane are found.

6.6.5

Sr. head fitter/head fitter/astt. head fitter/sr. fitter

He shall be responsible for: 1. Carrying out the maintenance activities correctly as per standard work instruction relevant to respective department/machines. 2. Completing his job in the specified given time schedule. 3. Checking that tools, gauges etc. are kept and maintained well. 4. Informing the foreman of any breakdown or any delay in time schedule and giving feed back on corrective actions taken 5. Guiding his juniors in doing these jobs.

6.6.6

Fitter/astt. fitter /cleaning fitter/sr. cleaning fitter/ jr. fitter

He shall be responsible for: 1. Cleaning the machine, changing the damaged spare part and conveying any problem related with his machines to his foreman. 2. To carry out planned replacement and preventive maintenance if required with the help of his seniors. 3. Guiding his juniors regarding work. 4. Rectifying any fault in found to occur on running machines.

6.6.7

Running fitter

He shall be responsible for: 1. Taking charge of each and every machine in his section and showing the report to fitter/ foreman and getting it signed by shift officer and maintenance engineer. 2. Attending to minor items such as idle spindles etc. 3. Making changes on machines – gear and settings as per requirement of the production department. 4. Making a written report of the work done by him and showing it to the foreman.

6.6.8

Senior machine cleaner/cleaner

He shall be responsible for: 1. Cleaning of all assigned machine parts as explained to him by his Fitter.

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Modern approach to maintenance in spinning

2. Changing the oil & grease in various parts as told by his Fitter. 3. Changing parts/accessories as a part planned replacement with the help of Assistant Fitter/Fitter. 4. Reporting to fitter in case of any non-conformity related to machines during his work.

6.7

Human error in maintenance

Humans play an important role during the equipment life cycle in the design, production, and operation and maintenance phases. Even though the degree of their role may vary from one type of equipment to another and from one equipment phase to another. Human error may be defined as the failure to perform a specified task (or the performance of a forbidden action) that could lead to disruption of scheduled operations or result in damage to property and equipment. Some of the causes of human error include poor work environment, poor work layout, improper work tools, inadequate training, and poorly written equipment maintenance and operating procedures. Human error may be classified into five categories: assembly, inspection, installation, operation, and maintenance. Maintenance error occurs due to incorrect repair or preventive actions. Two typical examples are incorrect calibration of equipment and application of the wrong grease at appropriate points of the equipment. It is usually an accepted fact that the occurrence of maintenance error increases as the equipment ages due to the increase in maintenance frequency.

6.6 Most common reasons for human failure.

Role of manpower in maintenance

6.7.1

67

Reason for maintenance error

There are many reasons for the occurrence for the maintenance error. Some of these are listed as: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Poor work layout Poorly written maintenance procedures Complex maintenance tasks Improper work tools Poor environment (i.e., temperature, humidity, lighting, etc.) Fatigued maintenance personnel Outdated maintenance manuals Inadequate training and experience and Worker’s negligence

6.7.2

Guidelines for reducing human error in maintenance

1. Ensure, as much as possible, that standard work practices are followed all across maintenance operations. 2. Periodically review documented maintenance procedures and practices to ensure they are accessible, realistic, and consistent. 3. Periodically examine work practices to ensure that they do not differ significantly from formal procedures. 4. Evaluate the ability of checklists to assist maintenance persons in performing routine operations. 5. Offer periodic refresher training to maintenance professionals with emphasis on maintenance procedures. 6. Do not keep the person on overtime more than four hours. 7. Supervisors oversight need to be strengthened, particularly in the final hours of each shift as the occurrence of errors becomes more likely. 8. Shift handover can be a factor in maintenance error. One particular guideline concerns ensuring the adequacy of shift handover practices by carefully considering documentation and communication, so that incomplete tasks are transferred correctly across shifts.

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Modern approach to maintenance in spinning

6.8

Crew size required for various activities in maintenance department

Department – Blowroom Acti vity

Schedule (m = month; t = tons)

Crew size (F = fitter; C = cleaner)

Time requ i re d (h )

Uni fl oc cle ani ng Uni cle an cle ani ng Bl en do mat Axi flo w Uni mix MC M and C VT3 ER M L VSA / Co nd en ser Be ater de -mounti ng mounti ng Beater replacement

1 m 1 m 1 m 1 m 1 m 1 m 1 m 1 m 20 00 –4 00 0 t

1 1 1 1 1 1 1 1 1

1–2 0.5 1.5 0.5 2.0 2.0 1.0 1.5 3.0

2000–4000 t

1 F and 2 C*

F F F F F F F F F

and and and and and and and and and

2 2 2 2 2 2 2 2 2

C C C C C C C C C

4.0

* One foreman

Department – Card A cti vity

Scheduled (m= mo nth ; t= tons)

C rew size ( F = fi tte r; C = cleaner)

Time re qu i red ( h)

1 m 2 m

1 F and 2 C 1 F and 1 C

1.5 1.5

C onventi onal cards New generati on cards Flat de- mounti ng Flat mounti ng C yl in de r an d do ff er mounti ng C yl inder gri ndi ng Dof fer grinding Flat grinding

6 m 6 m 450 –800 t 450 –800 t 450 –800 t

1 F and 2 C

8.0

2 C 1 F 1 F and 2 C

4.0 24 32

As per schedule As per schedule As per schedule

1 F and 1 C 1 F and 1 C 1 F and 1 C

Oil change Lickerin de-mounting mounting

As per schedule 200 t

1 C 1 F and 1 C

1.0 1.0 2–4 de pend on no. of r ounds 0.5–1 3.0

Card cl eaning C onventi onal cards New generati on cards F ull se tti ng

69

Role of manpower in maintenance

Department – Drawframe A ctivi ty

Drawframe cl eaning On e de li v e ry T wo de li v ery Oil change

S che du le d ( F = fi tte r; C = cle ane r)

C rew s iz e

T im e re qu i re d ( h)

0 .5 m 0 .5 m As per schedule

1 F and 2 C 1 F and 2 C 1C

0 .7 5 1 .5 0.5

Department – Unilap Activi ty

S che du le d ( m = mon th; t = to ns)

Cre w si ze (F = fitt er; C = cl ean er)

T im e re qu i re d ( h)

Unil a p c le a ni ng Oil change

0 .5 m As per schedule

1 F a nd 3 C 1C

1 .5 – 2. 0 0.5

Department – Comber Activi ty

Sch ed ul e d (m = mo nth; t = ton s)

Cre w si ze (F = fitt er; C = cl ean er)

T im e re qu i red ( h)

Comb er cle ani ng Nipp e r g a ug e Unico m b gau ge Unico mb bru sh gau g e Oil change

0. 5 m As pe r s c h edu le As pe r s c h edu le As pe r sch edu le As per schedule

1 F 1 F 1 F 1 F 1C

1 .5 1 .5 1 .0 0 .5 0.5

and a nd a nd and

3 1 1 1

C C C C

Department – Speedframe Activi ty

S che dul e d ( m = mo nth ; t = to ns)

C rew size ( F = fi tte r; C = cle ane r)

T im e re qu i red ( h)

Spe ed fram e c l ea n in g

1 m

1 F and 6 C

2 .5

Top arm pressur e checki ng

A s p er sch ed ul e

1 F an d 1 C

2 .0

Sadd le g aug e

A s p er sch ed ul e

1 F

2 .0

Bob bi n tro u gh l ev e ll i ng

A s p er s c h ed ul e

1 F and 1 C

1 .5

Collar cleaning and foot step oil change

As per schedule

1 F and 4 C

3.0

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Modern approach to maintenance in spinning

Department – Ringframe Acti vity

S che du le d ( m = mon th; t = to ns)

C rew size ( F = fi tte r; C = cle ane r)

Ti me req u ired ( h)

Ri ng frame cle ani ng Gui de pu ll ey be ari ng chan ge Gui de ring and be arin g change Sp in dl e o il ch ang e T op arm p ressu re ch eckin g Ri ng ch ang e Ri ng rai l, l app et ho o k, A BC ring hei ght setti ng an d the i r ce nt rin g T op variato r p u ll ey O.H. Bo ttom variato r p u ll ey O. H. Jocke y p ul le y g reasi ng Drum shaft greasing

1 –6 m A s p er sched ul e A s p er sched ul e

1 F an d 8 C 1 F an d 2 C* 1 F an d 6 C*

1. 5 2. 5 7. 0

As As As As

1 F an d 5C 1 F and 1 C 1 F an d 5C 1 F an d 4 C*

1. 5 2. 0 4. 0 6. 0

1 F an d 1 C 1 F an d 2 C 6 C 2C

1. 0 1. 5 1. 0 1.0

p er p er p er p er

sched ul e sched ul e sched ul e sched ul e

A s p er sched ul e A s p er sched ul e A s p er sched ul e As per schedule

Department – Winding (a) Automatic winding A ctivi ty

S che du le d ( m = mon th; t = to ns)

Cre w si ze ( F = fitt er; C = cl ean er)

T im e req u ire d ( h)

M a c hc o ne r c l ean in g Winding head O.H.

1 m 6m

1 F a nd 4 C 1 F and 2C

3 .5 4 winding head/4 h

(b) Two-for-one twister A ctivi ty

Schedul ed ( m = month; t= tons)

C rew si ze ( F = fitt er; C = cl eaner)

Ti me requi red (h)

TFO cleani ng Spindle oil change

1 m 6m

1 F and 4 C 1 F and 4 C

3. 5 4

References 1. Industrial Engineering and Management Science (1993) by T. R . BANGA, N. K. AGARWAL , S . C . SHARMA . 2. Maintenance Management in Spinning (1999) by South India Textile Research Association, Coimbatore. 3. Industrial Management and Operation Research (1993) by PROF K. K. AHUJA. 4. Comprehensive Hand Book on Spinning Maintenance by NEERAJ NIJHAWAN.

7 Maintenance repair inventory and its control

7.1

Inventory

Inventory is an unused asset, which lies in stock without participating in value adding process. Unused equipment, raw material, WIP and finished goods, consumables, spare parts, bought out parts, tools and tackles, gauge and fixtures, etc.

7.1.1

Symptoms of poor inventory management

1. An increase in the number of backorders, indicating too many stock outs. 2. Dead stock of items starts increasing. 3. Inventory of slow moving item is very high. 4. Rising inventory investment. 5. An increasing number of cancelled orders. 6. Insufficient storage space – too much inventory in hand.

7.2

Types of inventory

Inventory is normally of four types: 1. Raw materials Raw material inventory has been purchased, but not processed. The items can be used to separate suppliers from the production process. 2. Work-in-process (WIP) WIP exists because of the time it takes for a product to be made (called cycle time). Reducing the cycle time reduces inventory. 3. Finished goods Finished goods inventory is completed and awaiting shipment. Finished

71

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Modern approach to maintenance in spinning

goods may be inventoried because customer demands for a given time period may be unknown. 4. Maintenance, repair and operating (MRO) MROs are inventories devoted to maintenance/repair/operating supplies. They exist because the need and timing for maintenance and repair of some equipment are unknown. In this we deal with only maintenance repair and operating inventories.

7.3

Inventory carrying cost

1. Material costs of inventory These are the costs of purchasing the goods including transportation and handling costs. 2. Ordering costs Any manufacturing organization has to purchase materials. In that event, the ordering costs refer to the costs associated with the preparation of purchase requisition by the user department, preparation of purchase order and follow-up measures taken by the purchase department, transportation of materials ordered for, inspection and handling at the warehouse for storing. At times even demurrage charges for not lifting the goods in time are included as part of ordering costs. 3. Carrying costs These are the expenses of storing goods. Once the goods have been accepted, they become part of the firm’s inventories. These costs include insurance, rent/depreciation of warehouse, salaries of storekeeper, his assistants and security personnel, financing cost of money locked-up in inventories, obsolescence, spoilage and taxes. 4. Cost of funds tied up with inventory Whenever a firm commits its resources to inventory, it is using funds that otherwise might be available for other purposes. The firm has lost the use of funds for other profit making purposes. This is its opportunity cost. Whatever the source of funds inventory has a cost in terms of financial resources. Excess inventory represents an unnecessary cost. Note: The inventory carry cost comes out to be normally 20-25 % of total inventory.

Maintenance repair inventory and its control

7.4

73

Material and repair inventory

Spare parts management needs special treatment, somewhat different from the inventory management of regular items. This is because the purpose of keeping a stock of these items are different – to serve as a replacement to the worn-out parts in the machinery. One of the realities of the spare parts management scene is stockouts of spares in the midst of high stock levels. Even when the shelves of a spinning mill’s stores are overflowing, the maintenance engineers would not get some desired spares when needed. The word spare or spare part is used here as a general term for indicating all kind of items needed by the maintenance department. Spares would include all spare parts of machines, accessories used on machines, lubricants and miscellaneous items such as emery paper and chalk powder. The problem arises because management of spare parts inventory is essentially different from management of raw materials and in process inventory. The techniques applicable to managing direct materials are not applicable to managing spare parts. The most visible characteristic of spare parts inventory is the large variety. There are several thousand items each with different specification, for different requirements and different behavior in terms of consumption rate etc. If any technique is applied blindly without consideration of the nature of their behavior, a mill would end up with huge stocks of non-moving items. How much inventory one mill should have? A spinning mill should have a store inventory of about 20–30 % of total annual year consumption. Any inventory of more than 30% value of yearly consumption is considered ‘abnormally high’ by today’s standards. The equipment suppliers could be unwillingly responsible for huge stock of spares. In order to ensure that they err on the safer side they usually recommend a large number of spares. If one follows their recommendations blindly, one ends up with a huge stock level – large part of which becomes non-moving or slow moving in due course of time.

7.5

Different methods for controlling the inventory

In industry different organization are using different methods like VED analysis, ABC analysis, control limits, etc., for controlling the inventory but all these methods are useful mainly for the raw material inventory or finished goods inventory. In this chapter we explained some of them briefly. The most useful method is the FISPO method which we have explained in detail.

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Modern approach to maintenance in spinning

7.5.1

Using control limits

Many mills try to introduce maximum and minimum control limits to control inventory levels of spare parts. This standard technique, however, is not truly applicable in the case of a spinning mill which has to take account of insurance spares and of planned replacement of accessories and parts. The maximum and minimum control limits are decided based on two factors: namely, the rate of consumption and the procurement lead-time. Neither of these two factors can be predicted with any degree of confidence for spare parts. The rate of consumption fluctuates widely in the case of most of the spares even with good machinery maintenance. The procurement lead-time depends on the urgency of need and the extent of follow-up actions. It can vary from one week when an item is closely followed-up to as high as three months when no follow-up action is taken. Such is the case, how can one predict lead time and consumption rate and how can one fix the maximum and minimum control limits for machinery spare parts? Fortunately the commonly needed store consumption items are only few: such as old dhoti, emery papers, chalk powder, bottle cleaning brush, lubricants, and also the monthly requirement of four or five consumable accessories items like skived apron, lappet hook and roving guide, etc. We can apply maximum and minimum control limits for such items where lead time is also stable for a mill in any locations. But all these items are low cost items which contribute only a small portion (10%) of the total inventory cost and do not need close inventory control at all.

7.5.2

ABC analysis method

The ABC analysis of inventory class ‘A’ is made up of inventory items which are either very expensive or used in massive quantities like metallic wire, apron and cots, electronic circuit board, etc. Thus these items, though few in number contribute a high proportion of the value of inventories. Class ‘B’ items like bearing and belts are not so few in number, but also they are not too many either. Value wise also, they are neither very expensive nor very cheap. Moreover, they are used in moderate quantities. Class ‘C’ contains a relatively large number of items. But they are either very inexpensive items or used in very small quantities so that they do not constitute more than a negligible fraction of the total value of inventories. The control of inventory through ABC analysis is exercised as follows: ‘A’ class items merit a tightly controlled inventory system with constant attention by the purchase and stores management. A larger effort per item

Maintenance repair inventory and its control

75

on only a few items w ill cost only moderately, but the effort can result in large savings. ‘B’ class items merit a formalized inventory system and periodic attention by the purchase and stores management .For ‘C’ class items still relaxed inventory procedures are used. For ‘A’ class items, the inventory policy, i.e. order quantity and re-order point should be carefully determined and the close control over the usage of materials is desirable. For ‘B’ class items, the economic order quantities and reorder level calculations can be done and larger stocks can be maintained. The review of these items may be done quarterly or half-yearly. In case of ‘C’ class items, generally one year supply can be maintained. Periodic review once a year may be sufficient. The technique tries to analyze the distribution of any characteristics by stock values of importance in order to determine its priority. This technique can be applied in all facets of organisation. Many organisations are applying this technique in materials management and spare parts management to identify the contribution made by the materials/spares in the total inventory value. On the basis of stock value, materials procurement strategy and consumption strategy is decided.

7.5.3

VED classification

Experts for the classification of spares give different models. Some of these are of academic interest and have no practical value in the case of machinery spares in a spinning mill. Take the example of VED classification. In this technique all spares are classified as V = Vital E = Essential D = Desirable From the maintenance engineer’s point of view even a small item like bolt is vital or critical since equipment cannot function without it. Even when some one considers some items more critical and vital than others, but their degree of criticality is not clearly defined. Thus, it is confusing to classify the spares as per above classification. As if this is not enough, some textbooks recommend simultaneous application of ABC and VED classifications by developing matrix as shown below. All these items are classified into nine categories and for each category, decision rules in terms of desirable inventory levels are specified. For example, if an item is in A class as well as vital (1), such items are kept as, say one-month requirement.

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Modern approach to maintenance in spinning

A B C

V

E

D

1 2 3

2 4 6

3 6 12

But such systems are of little use to the maintenance manager because these systems do not link the spare part requirement with maintenance.

7.5.4

Recommended method of classification

Any rational classification of spares must permit the maintenance department to carry out indenting, periodic review and annual budgeting of spares. A good classification system should enable us to link maintenance plans and schedules with inventory levels. It should integrate the needs of maintenance engineers with those of the stores manager. All the stores items required for a spinning mill should be classified into 5 categories shown below as FISPO. 1. 2. 3. 4. 5.

F – Fast moving spares I – Insurance items or vital items S – Standard ‘open market’ consumables P – Planned replacement spares O – Overhauling spares

The rules for stock levels and the period of review for each of the above categories are different. 1. Fast moving items Maintenance spares The rate of consumption or usage of spares can be derived from historical data regarding failure of the different components in the machinery. Failure statistics is an important basic information for this analysis. If the failure times show a negative exponential distribution, the failure rates are distributed by means of Poisson distribution. If the failure times show a normal distribution due to aging or wear, then the failure rates will also show a normal distribution. From the failure statistics one can know the mean consumption rate of these spares and also find the level of consumption expected with a corresponding probability of its occurrence. These are usually relatively low cost accessories or spares. Normally, they are well-stocked in stores. The desirable levels of inventory to be maintained in this class of items depend upon the previous record of consumption. For example belts, bearing and lubricants and gears, etc.

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Table 7.1 An illustrative list of maintenance spares Machine

Fast moving items

Ringframe

Anti-balloon control rings Lappet hooks Gears Skieved aprons Spindle tape Spindle lock Separator holders Rubber gaskets Ring Travellers Separators Spindle buttons Spacers Roving guide Top synthetic clearer

Speedframe

Skived aprons Gears Inlet condensers Spacer

Unilap Drawframe

Drawbox Strippers Drawbox Strippers

Carding

Gears Flat safety keys Carding leaf gauges Flat emery paper

2. Insurance items The purpose of these spares is to provide an insurance against the relatively remotely possible breakdown or failure of an equipment/ component. The probability that such a component/equipment will survive the life-time of the machinery or plant is quite high. The reliability of such spares has been observed to be as high as 95–99% over the life-span of the machinery. These spares are sparingly needed. Insurance items are costly items and are stocked to ensure against probability of failure. If such a vital item is not readily available, the entire machine would remain out of production till the time it is supplied. If the concerned production machine is critical for ensuring continuity in production chain, then the importance of the spare part is still higher. Each such item should be stocked depending on the leadtime of procurement and its cost. Many of these spares are, also, high value items. These spares are, by and large, procured along with the capital equipments. At the time of the purchase of the capital equipment itself a decision regarding the purchase of the insurance spare is also

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Modern approach to maintenance in spinning

made. Generally, the decision with regard to insurance spares may be to buy either no spare or to buy a spare. It is desirable to make a common sub-store for all the Insurance items at the corporate level, when a business group operates several spinning mills even when located on different regions. Table 7.2 An illustrative list of insurance items for different machines S. no.

Machine

Insurance items

1. 2. 3. 4.

Unifloc A-11

Running roller Horizontal Cover tape Vertical cover tape Impeller wheel

5. 6. 7. 8.

Blendomat

Horizontal Cover tape Vertical cover tape Rope Supporting roll

9.

Uniclean

Perforated sheet

10. 11.

Unimix B7/3 R

Conveyor lattice Inclined lattice

12. 13.

Mixing bale opender

Conveyor lattice Inclined lattice

14. 15. 16. 17.

Card c-4/c-10

Cylinder undercasing Flat cyclo gear Flat brush cyclo gear Fluid coupling

18. 19. 20. 21. 22. 23. 24. 25. 26. 27.

Unilap

Seal kit of pistons Joint shaft Fine adjusting valve Booster pump Electromagnetic clutch Nipper Unicomb Top comb holder Differential gear Nipper supports

28. 29. 30.

Speedframe

Combers

Machconer

Differential gears Conderum Impellers

3. Standard consumables These items are reviewed according to a review calendar fixed by the store and purchase department. Desirable inventory levels are maintained in this class of items. The control limit mentioned in mentioned in Table 7.1 should be used for these items.

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Table 7.3 An illustrative list of consumable items S. No.

Store consumable items

1.

Old dhoti

2.

French chalk powder

3.

Glue for joining skieved apron

4.

Washing powder

5.

Bathing soap

6.

Emery paper

7.

Bottle cleaning brush

8.

Brass wire brush

9.

Steel wool

10.

Torch cell

11.

Torch bulb 3.8 v

12.

M seal

13.

Nylon hammer head

14.

Fevicol

15.

Teflon tape

16.

Painting brush 5 cm

17.

Braso

18.

Palm broom

19.

Hexa blade

20.

Araldite

21.

Knotter blade

22.

Johnson buds

4. Planned replacement items These items have a known specific service life decided in advance depending upon the production rate. Delivery schedule should ensure availability of each item one month prior to the date fixed for replacement. Procurement of all such items is to be planned immediately after finalization of maintenance schedule for given year.

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Table 7.4 An illustrative list of planned replacement items Machine

Item name

Life

Unifloc

Impeller Cover tape Running roller Chain Beater Cover tape Rope Beater Conveyor lattice Inclined lattice Beater Stripper of evener roll Grid bar Feed roll Beater Feed roll Grid bar Traverse plate Pin beater 2nd beater 3rd beater Feed roll Inclined conveyor lattice Conveyor lattice Combing segment Conveyor lattice Beater pins Cylinder wire

6m 5 y/ nb 2y 1y 12000 t 7 y/ n b 2y 12000 t 7 y/ n b 7 y/ n b 4000 t 4 y/ n b 5 y/ n b 5-7 y/ n b 4000 t 12 y/ n b 12 y/ n b 12 y/ n b 3y 4000 t 400 t 7y 2y 5y 4000t 7 y/ n b 8y 600-1000 t

Doffer wire Flat tops Lickerin wire Stationary flat above lickerin Stationary flat under lickerin Stationary flat above doffer Flat chain Flat cleaning brush Flat post cleaning brush Redirecting roll wire Redirection roll cleaning brush Cyclo gear for flat Cyclogear for flat cleaning brush Cylinder wire Doffer wire Flat tops Stationary flat above lickerin Stationary flat under lickerin Stationary flat above doffer Flat belt Flat cleaning brush Flat post cleaning brush

600-1000 t 600-1000t 200 ton 160 t With lickerin 450 t 7y With wire With wire 2000 t With wire 10 y/ n b 10 y/ n b 600 -1000t 600-1000 t 600-1000t 160 t With lickerin 450 t 5y With wire With wire

Blendomat

Unimix

ERM

CVT-3

MCM-6 Uniclean Card C-4/ C10, C-51, C-61

Card DK 903/803

Maintenance repair inventory and its control Machine

Drawframe SB-2/ RSB-1, RSB-951, RSB-851

Drawframe Do/6

Speedframe Lf 1400/FL16,FL 100

Ringframe G5/1

Item name

Life

Redirecting roll wire Redirection roll cleaning brush 1st lickerin 2nd lickerin 3rd lickerin Cots

2000 t With wire 2000 t 450 t 450 t 6–12 m

Arbour with end bush Guide roll for can change Slides for bottom roll Bottom roll Waste screen Arm Trumpet Funnel Coiler Drawbox cot Stripper Drafting roll membrane Bearing saddle Drafting roll plunger Pressure bar Bottom roll Trumpet Coiler tube and plate Top roll with end bushes Top apron

5 y/ n b 10 y/ n b 10 y/ n b 15 y/ n b 5 y/ n b 5 y/ n b 7 y/ n b 7 y/ n b 10 y/ n b 1y 2y 3–4 y 6y 6y 4–5 y 12–13 y 2–3 y 1012 y 7–8 y 1y

Bottom apron Bottom roller Top roller Cradle Nose bar False twister Pressure finger Pressure hose Top arm Bottom roll needle bearing Top and bottom roll clearer cloth Guide tube Guide tube key Cots Flyer Bobbin wheel pin Top apron

1y 12–15 y 6–7 y 7–8 y 12–15 y 2y 6–7 y 10–12 y 7–8 y 8–10 y 2y 12–15 y 5–6 y 2y 15 y 8y 1y 2y 1y 2y 1y 10–12 y 7–8 y 12–15 y

Bottom apron Cots Bottom roller Needle bearing Cradle

81

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Modern approach to maintenance in spinning

Machine

Comber E62, E60, E7/5

Winding Machconer no. 7

Winding Autoconer 238/338

Item name

Life

Arbour Pressure hoses Lappet hook ABC ring Rings Spindle tape

5–6 y 5–6 y 6y 10–12 y 2–5 y 1–1.5 y 2.5–3 y 12–15 y 5y 12–15 y 12–15 y 10 y

Spindle assy Bobbin holder Drive pulley Jockey pulley Drum shaft 45 NPB bearing and guide ring Separator Guide pulley bearing Creel rod PVC tubing Nipper Half lap Top comb Ratchet Nipper pin Detaching roll cot Drawbox cot Draw box top roller with end bushes Detaching roller with end bushes Detaching roll stripper Drawbox stripper Table trumpet Detaching top roll clearer Splicing cutter ceramic Shutter cutter ceramic Bearing center Bearing center bearing bushes packing Brake shoes Thread guide Drum belt Empty conveyor belt Package conveyor belt C.B.F. cylinder small stroke length C.B.F. cylinder large stroke length PU tubing CBF guide lever Empty tube Splicing cutter steel Tension cutter Wax shaft Opening arm Suction arm Suction tube clamp

5–7 y 7y 10 y 10–12 y 15 y 6y 1y 6y 6y 1.5–2 y 2–3 y 8y 8y 3–4 y 1–2 y 10 y 1y 8–10 y 8–10 y 6–7 y 2y 4–5 y Nb 2–3 y 5–6 y 8–10 y 6m 2y 5–6 y 2–3 y 3y 5–6 y 5–6 5y 4–5 4–5 4–5

y y y y

Maintenance repair inventory and its control Machine

T.F.O.

Item name

Life

Exhaust channel Brake liner Drum Package conveyor belt Empty tube conveyor belt Tangential belt Guide roll Capsule Brake shoe Multiple tension device Separator Pig tail thread guide Stop motion wire

4–5 y 6–7 y 15–20 y 5–6 y 5–6 y 3–4 y 4–5 y 4–5 y 4–5 y 8–10 y 6–7 y 10 y 8–10 y

83

m = month, y= year, nb = need base, t = tons Note: The life of planned replacement shown in the table are guidelines; the actual service life would vary from mill to mill depending on the production rate, fibres processed and effectiveness of maintenance.

5. Overhauling items These items are wear and tear items needed once in two or three years when a machine or an equipment is taken up for overhauling. The total quantity procured is as per overhauling program. No stocks are maintained and every item procured is expected to be consumed. Review of overhauling items is done four to five months prior to overhauling schedules and indents are raised at that time. Most often the different types of bearings and shafts, keys, gears, etc, constitute overhauling items. 6. Repairable spares These are the reusable spare parts, which after their breakdown can be reconditioned and re-used. Typical examples are the reconditioning of motors and repairing of PCB and shafts etc. Since these have more than one life, the cycle of their various lives needs to be taken into consideration in the analysis of their inventory policy.

7.6

How to implement the spare parts management?

The best way to plan and execute spare parts management is to make an expenditure budget at the start of financial year, based on the above classification of spares. The budget enables the maintenance department to link spare part with maintenance plan and schedule. The budget is of real practical value in spare part management. It is a

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Modern approach to maintenance in spinning

management tool which helps in spare part planning, review, indenting, procurement and inventory control. A proper use of budgets eliminates emergency indents, adhoc indents and rush and super rush orders; each of which cause undue stress on persons and unnecessarily large expenses for the mill.

7.6.1

Expenditure budget

The maintenance expenditure budget is prepared with objectives of (a) Making a planned and timely execution of maintenance activities. (b) To ensure availability of spares at the right time and thus to prevent disruption in normal working of the production department and also to plan for additional investments required for acquiring new equipment and/or tools for improving the effectiveness of maintenance. Procedure for making expenditure budget The procedure for budgeting for next year begins in the last month of the current financial year i.e. in the beginning of March each year. The final budget for the coming financial year is ready by the end of March. Budget provisions are made for expenditure under the same heads as given under the recommended FISPO method of classification. These are 1. Fast moving spares These are small items which get broken during the normal working like spindle tapes, lappet hooks, ABC rings, spares, bearings belts, etc. Based on the previous consumption pattern, a provision is made for all such items in the coming financial year. Oils and lubricants Based on the requirement of lubricants of each machine as recommended by the manufacturer, an estimate is made for the requirement of all type of lubricants and accordingly a provision is made. Ball bearings and belts Based on the past consumption data and some future requirement, an estimate for the coming year is made.

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85

2. Insurance spare Keeping in mind stock position in stores and sub-store and the departments and the estimated requirement of the department, a provision is made for the purchase of such items which have to be procured during the financial year. Comber nipper, conveyor belts and major components fall under this category. 3. Planned replacement This head cover all such items which have a definite life cycle like card wire, cots aprons, rings, etc. The life cycle of these parts is determined by the production rates and the type of material running on the machine. Modification Modifications and innovations should be the way of life in modern mills who wish to grow in spite of fierce competition in the globalize market. Therefore depending on the size of the mill and the budget of respective departments, a provision for some amount should be made, and efforts put in to install incremental modification and innovations to improve quality and productivity, or to permit manufacture of specialty yarns of different kinds. 4. Store consumable stores This head covers all those items which are consumed on day-to-day basis such as detergents, adhesive etc. Based on their previous consumption pattern and considering the estimated future requirement, provision is made for these also. 5. Contingency Even the best estimates may not actually be able to meet all the requirements of as departments as the year proceeds. Some provision must be made in the budget to take care of such exigencies. Usually about 10% of the total budget would be sufficient as contingency amount. The budget prepared by the maintenance department is sent to the top management for approval. Once the budget is finally approved, procurement of spares is planned and indents are placed accordingly.

7.6.2

Review of maintenance budget

After finalization of the maintenance program and the expense budget, it is imperative to ensure that maintenance activity is carried out as per budget and expenses are incurred within the budgeted limits.

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Modern approach to maintenance in spinning

Review of budget helps in identifying any deviation from the plan termed variance, in determining its cause. It further helps in deciding corrective actions to eliminate or to minimize variance and also to avoid its recurrence. If these happen to be genuine reason for a variance – either the lower or on higher side from the budget, it should be considered and the specific variance should be accepted as worthwhile. The future budget exercised should be planned accordingly. 1. Benefits of reviewing budget A properly implemented budgetary control on maintenance expense helps the management in controlling the total expense on maintenance in an optimum manner. It acts as a tool for the administration to control the expenses being incurred from time to time over the year, without risking to compromise on production efficiency. It indicates where and when executive action is required to obtain the desired result in quality and productivity. Budgetary control periodic comparison of actual with planned aids the measuring of the performance of each maintenance team and each production department. 2. Essential requirement for applying budgetary control In small mills, the preparation of budget is the responsibility of the cost or management accountant. In large spinning mills, the budget committee is entrusted with this task. The budget committee is composed of executives in charge of major functions; purchase manager, maintenance manager and production manager. The chief executive acts as a chairman and the cost accountant acts as a secretary. The maintenance budget will be prepared by the maintenance manager and submitted to committee for approval. The committee makes necessary amendments after discussions. The main functions of committee are as follows: 1. To help the maintenance manager by providing past information to prepare budgets. 2. Proper targets. There should be adequate check and safeguards against adoption of too high or too low targets. 3. Continuous monitoring of budget. Although the budgets are prepared for a year, these must be reviewed at quarterly intervals or at least one in six months. 4. Provision for flexibility. Budget should always be flexible to meet changed conditions like major shift in customer demands etc. However, flexibility should not be taken by the maintenance manager as an excuse for lowering the standards set for performance unless specific reasons are identifiable. Any desired change should be made with the approval of budget committee.

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87

Table 7.5 Form to keep the budget versus outstanding orders date

Budget versus outstanding orders date Budget Sancti one d Total bu dge t used Budget i n hand Purchase orde r rel eased till date Balance budget aft er consid erin g purchase ord er Invento ry stock

7.6.3

Other points which help in controlling inventory

1. Set up vendors list and list all items supplied by each vendor. 2. Create inventory records in for all parts with the following details: (a) Item number (b) Description (c) Inventory type (d) Quantity in hand (e) Location (f) Substitute parts (g) Minimum and maximum stock level 3. Track all inventory transactions regularly. 4. Perform a physical inventory every six months.

References 1. Comprehensive Hand Book on Spinning Maintenance by NEERAJ NIJHAWAN. 2. Industrial Engineering and Management Science (1993) by T . R . BANGA , N . K . AGARWAL and S . C . SHARMA . 3. Maintenance Management in Spinning (1999) by South India Textile Research Association, Coimbatore. 4. Operating Instruction for the high production card C1/3 issued in November 1987. 5. Trutzschler Card DK 903 instruction manual second edition year 1999. 6. Rieter CardC-61 instruction manual year 2002. 7. Murata Machconer /Linkconer No. 7 instruction manual revised May 1988. 8. Kirloskar Toyada Ringframe RXI240 instruction manual year 1999. 9. Rieter Ingolstadt Drawframe RSB 951 year 1996. 10. Rieter Unilap E32 operating instruction manual10055921. 11. Rieter Comber E62 operating instruction manual 10013753. 12. Lakshmi Speedframe LF 1400 operating instruction manual year 1990 13. Lakshmi Ringframe G5/1 operating instruction manual year 1990

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Modern approach to maintenance in spinning

14. Roving Frame Instruction Manual FL-16 By Toyada Automatic Loom Works edition 1997, Toyada FL 100 Roving Frame Instruction manual seventh edition August 2001. 15. Prerna Leewha Two-for-one Twister for spun yarn PRN –140- LW Instruction manual. 16. Texmaco zinser ringframe instruction manual issued in January 1969 reprinted in April 1973. Zinser Speedframe 660 instruction manual year 1990, Zinser Drawframe 720 instruction manual year 1990, Zinser Ringframe 321 instruction manual year 1990. 17. High Speed Simplex Fly Frame instruction manual RME Howa Machinery Limited Edition august 1993. 18. Drawframe Cherry DX –500 – E2 instruction manual, Drawframe Cherry D –400 MT instruction manual. 19. Savio Orion instruction manual, manual code 11645.0004.1/0 revision index :01 date of issue : 06.01. 20. Two for one Twister instruction manual Leewha LW 560 SA. 21. Rieter Unifloc A11 instruction manual edition 2000, Ringframe G33 instruction manual year 2001, CardC-61 instruction manual year 2002. 22. Murata Process Coner 21-C instruction manual revised October 2002. 23. Schlaforst Autoconer 338 instruction manual year 2003.

8 Maintenance information systems

8.1

Computer-managed maintenance system

Presently most of the mills in India are running without the computermanaged maintenance system. Without computer-managed maintenance system, maintenance manager faces lots of problems regarding the analysis of feed back received from the maintenance department. It is seen in most of the systems prevailing in textile industry that too much paper work would burden the maintenance manager; too little makes him operate in a vacuum. When a manager is flooded with mass of information and control data, he gets tied down to the table. He gets little time to provide attention to the equipment and to the ongoing maintenance work. Likewise without an adequate information base, the manager is likely to take a wrong or a non-optimum decision, which may cost the company dearly. It is a pity that the discussions on information systems for maintenance are associated only with the job orders and work orders. These documents are essential but they should be last on the list of priority. They are useless without supporting information such as method followed on the job, check list and frequencies, list of tools and tackles, crew-size, job standards and list of spares with consumable pattern. All such information is included in an effective maintenance information system (MIS). Such MIS should be developed and installed by the maintenance manager and placed within hand’s reach of each engineer. Only then can he become an effective supervisor who takes the right decisions at the right time. The primary objective of the maintenance management is to achieve the optimum balance between the plant availability and maintenance resource utilization. The effective matching of labour and material resources for maintenance planning and control is a dynamic activity. The latest approach has concentrated on supplying management with reliable information on both the equipment performance and cost that would allow them to make the informed decision. Thus, it becomes essential to adopt to technique that would provide adequate and timely information for making the maintenance function more meaningful. The implementation of computer-managed maintenance system is one of the successful ways for achieving the goal.

89

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Modern approach to maintenance in spinning

The main objective of the maintenance department is to (1) provide a quality of effective maintenance services that support facility operational requirement, (2) reduce unscheduled equipment down time through effective maintenance planning, (3) utilize CMMS report generator to provide meaningful management report that will enhance the control of maintenance, (4) utilize CMMS to ensure that maintenance is performed efficiently through organized planning, coordinated use of material, manpower and time, and (5) create and maintain measurement of maintenance performance within CMMS. Objectives

Demand

Control

Work

Systems to be Maintained

Resources

Feedback

Execution

Maintained Systems

8.1 Flowchart of computer-managed system.

One of the highest priorities of the maintenance manager is to keep the machine around the clock, i.e. reduce down time. With CMMS system, we can enter and track the down time. We can retrieve the down time of any machine compared with the last month, last year and last week. With this information one can take the right decision in future in short span of time as more facts are available to him.

8.2

Benefits of CMMS

Improved planning – easier scheduling of work orders, balanced workloads and a focus on preventative maintenance. Better quality reporting and ease of access to historical information – real-time data collection ensures that professional information is captured and shared between team members. This collective bank of information is unaffected by staff changes. Clearer, more useful reports – flexible, user-defined, reporting can both alert to issues and provide insights to their cause.

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91

Reduced management overhead – the CMMS aids planning, scheduling and communication; it also encourages collective responsibility reducing the strain on management. Fewer breakdowns – a focus on planned, preventative maintenance reduces equipment downtime. Less time at the stores counter – real time, online stock management means that you don’t need to make multiple journeys to check, book or obtain parts. Reduced stock-outs – better inventory management keeps you one-step ahead to minimize disruption and downtime.

8.3

Components of CMMS

The basic components of good MIS are given below:

8.3.1

Asset register

The plant register is a list of all production machinery and equipments owned by the mill. Its purpose is to give bird’s eye view on the equipments, their type, location, age etc. It is obvious that too much information should not be crowded in the plant register. Again the equipments should be properly grouped in the register. The sole purpose of the register is to present elementary information in a summarized form. The format of plant register is given below. This information is necessary when some problem occurs in the machine and complaint has to be lodged to the machine manufacturer and at the time of indenting as it is necessary to give the machine no. and year of manufacturing. Format of asset register Machine

8.3.2

Make

Model

M/c no.

Year of manufacture

Commissioning date

Technical file

The purpose of technical file is to record technical specifications and commercial information about each production machines such as speeds, kW, productive capacities, accessories, etc; and purchase price installation cost, depreciation charges, etc. The foundation diagram, having detailed

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Modern approach to maintenance in spinning

information like exhaust opening, electrical and pneumatic holes, etc, is provided for each machine. All such information is directly reproduced from manuals supplied by the equipment suppliers and placed in the equipment file to make it readily available to all maintenance engineers. This information is required when any shifting of production machine is required.

8.3.3

Preventive maintenance procedure library control

Maintenance manuals are needed to plan, monitor and control maintenance activities. Manuals give in detail the sequential steps to carry out the job, crew size, allowed time, frequency and guide lines to attend to different problems arising on the different machines. If the above information is kept up-to-date, authentic and readily available, it is useful in a number of ways. Since all information is available at one place, unnecessary delays in receiving instruction, in collecting the needed tools and tackles are eliminated. Since the engineer knows the details of the job to be done, the quality of his supervision improves. These manuals provide a base from which improvement and refinement of the existing methods and practices can be taken up. It is necessary that every company develop its own manuals. Although the exhaustive manuals are provided by equipment suppliers to give the above information, it is found to be in a scattered form. Therefore, it becomes very difficult and time consuming to retrieve the required information. In making these in-company manuals, information must be of course borrowed from supplier’s manuals but the past experience must be used to ensure that the information is arranged to suit the needs of maintenance engineer, as defined by the culture of company.

8.3.4

Spare part catalogue

The spare part catalogue supplied by the equipment supplier is of limited use. This is because all the spare parts – most of which do not need regular replacement are listed in them. Only fraction of 5–15% of spares need regular replacement. In such 80% cases the indents of the items gets repeated. Most of the mills, therefore, follow the practice of giving a different material code no. which is to be filled along with part no. of the spare part while issuing the material from store or while indenting. Items are classified according to consumption pattern estimated from the past experience gained within the company. Maintenance engineers prepare their own spare part catalogue by eliminating large number of spare items, which are not needed. The indenting of spares becomes easy as well as accurate when engineers have spare part catalogues made as above. Availability of the catalogues allows proper inventory planning and budgeting of maintenance expenditure.

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93

Format for spare part catalogue Department : Model :

Part name

8.3.5

Catalogue no.

Part no.

Material code no.

Quantity per machine

Scheduling of planned maintenance

In this plan total work is prescribed with suitable allowances for holidays so that given targets are completed in each month. Weekly schedules of routine inspection and monthly, quarterly, half-yearly and yearly schedules of preventive maintenance are planned in such a manner that a fixed work cycle is established for the maintenance team of a particular section. Since cleaning schedule is the schedule which is repeated most often, so as many other schedules should be clubbed with the cleaning schedule in order to reduce the machine down time to the minimum. CMMS must include maintenance scheduler. When scheduler run its scan each machine department wise and check the period when maintenance is required, it then looks at the last maintenance date for each period and if due create a planned maintenance work instruction for the machine. The planned maintenance schedule rolled forward work instruction for each weak and adding them to the list of outstanding work. User may be required to decide whether they should prefer the scheduler run automatically or intervention at a particular time, i.e. each day, weekly or monthly. This monthly plan should be given to the foreman of each department at the start of every month so that he follows it without having to be given daily instructions. The system should allow the planned work orders to be separated into various departments, units and location before they printed. Most of the companies like to design their own work order format. The work order format is given below for ready reference. Schedule plan format with example Unit no. 1 Department: Ringframe Month: June

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Modern approach to maintenance in spinning

Cleaning schedule

Maintenance activity, i.e. to be clubbed with machine cleaning

Machine no.

Date

Activity

Machine no.

4

1.06.00

Top variator pulley O.H.

2, 4

5

2.6.00

Bottom variator pulley O.H.

5, 10

10

3.6.00

Spindle, lappet hook ABC gauge

15, 16

14

4.6.00

Spindle oil change

20

15

5.6.00

Top apron change

2, 25

16

6.6.00

Bottom apron change

5, 10

20

8.6.00

Jockey pulley greasing

26, 27

25

9.6.00

–

–

26

10.6.00

–

–

27

11.6.00

–

–

1

12.6.00

–

–

2

13.6.00

–

–

8

15.6.00

–

–

9

16.6.00

–

–

The above format clearly shows which machine has to be taken for cleaning on which date and which activities are to be clubbed with cleaning.

8.3.6

Viewing the outstanding maintenance schedule

Maintenance manager and supervisor are expected to quickly check the pending schedule. The system should support a quick and easy method selectively displaying the list of the schedules, which are outstanding, machine wise and department wise.

8.3.7

Corrective action register

This register is a system for tackling breakdowns or reducing them over years. All the breakdown jobs undertaken within each department are recorded. The information listed in the corrective action register includes description of the breakdown, name of the mechanic who attended the problem, time started, time completed, list of parts replace, corrective actions taken. This register has to be maintained by the running fitter and duly signed by his senior on day-to-day basis. This

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95

register helps to take suitable preventive actions so as to avoid repetition of breakdowns. Format for corrective action register Department: Machine no.: Date

8.3.8

Description of breakdown

Time started

Time completed

List of spare replaced

Action taken

Sign. of fitter

History registers

These registers are to record major events that occur on each equipment or machine. This is a very important document because it provides vital information about the criticality of machine behaviour and the performance of its components so that suitable steps can be taken to eliminate recurring causes of failure. History registers are maintained in two ways: 1. Component history register – Component or spare part wise for selected items. 2. Breakdown history register – Department wise, with causes of failure, for each machine. Over a period of time, useful information gets collected in these registers. Analysis of history registers can lead to solutions of many problems which have proved to be major headaches for the plant. These registers are helpful in following ways: 1. Identifying the built-in-design defects within the equipment and getting them corrected. 2. Analysing the performance of critical spare parts of the machine.

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Modern approach to maintenance in spinning

3. Identifying the department/machine of plant or part of the equipment where frequent service is needed. 4. Offering help in resolving the conflicts between production and maintenance regarding uses and abuses of the equipment. In view of their usefulness, mills should make it a practice to review history records of each part/department at least once/twice a year. Formats of component and breakdown history record registers are given below: Components/Spare part history format Unit no. ............................. Part name ......................... Department ..................... Specification .................. Part no. ......................... Machine no.

Quantity

Date

Quantity

Date

1 2 3

Breakdown history formats of various machines are given below: Blowroom break down history register format

Machine no./ Date

Month : .......................... Machine name : .............. Model : ........................... Unit : ...............................

1 2 3 4 5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Maintenance information systems

97

Legend A – Beater jam B – Feed roll jam C – Pipe line chocked problem D – Belt broken E – Chain broken F – Bearing damage G – Rich waste problem H – Beater damage problem

Card break down history register format Month : ................................ Machine name : .................... Model : ................................. Unit : .................................... Ma- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 chine no./ Date 1 2 3 4 5

Legend A – Sliver coiling problem B – Web cut problem C – Web falling from doffer D – Fan jam E – Flat loading F – Flat jam problem G – Flat cleaning brush jam problem H – Lickerin jam problem I – High C.V. problem J – Belt broken K – Gear broken L – Coiler jam problem M – Rich waste problem N – Aero feed problem O – Material not coming from aerofeed P – Fluid coupling oil leakage problem Q – Coiler cover piston problem R – Cylinder jam problem

98

Modern approach to maintenance in spinning

Drawframe break down history register format Month :........................ Machine name : ........... Model : ........................ Unit : ............................ Ma- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 chine no./ Date 1 2 3 4 5

Legend A Coiler jam problem B Web cut problem C More fan waste problem D Belt breakage problem E Sliver cut problem from feed table F Peak problem in spectrogram G Creel earthing problem H Breakage at trumpet I Filter screen chocking problem J Cot burnt problem K Lapping problem L Fly accumulation at scanning roll M Coiling disturb problem

Speedframe break down history register format Month : ........................ Machine name : ........... Model : ....................... Unit : ......................... Machine 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 no./ Date 1 2 3 4 5

Maintenance information systems

99

Legend A – Rail jam at reversal position B – Doff spoiled problem C – Creel vibration problem D – Creel jam E – Rail jam in the middle position F – Fluid coupling oil leakage G – Doff overfilled problem H – Cone drum belt broken problem I – Dead weight wire broken of conundrum J – Roving loose at doff K – Gear damage problem L – Suction tube chocking problem M – Conundrum belt does not reset N – Dead weight chain broken O – Lifting chain broken P – Air leakage problem Q – Undrafted problem

Ringframe break down history register format Month : ............................... Machine name : ................... Model : ................................. Unit : ..................................... Machine no./ Date

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

1 2 3 4 5

Legend A – Side cut after power fail B – Additional drive problem C – Bottom roll shifting problem D – Speed variation problem E – Fan jam problem F – Doff spoiled G – 71/32 T Gear damage H – Pressure down I – Main drive belt broken J – Timing belt broken K – Undrafted problem L – Lappet tilting before spindle stop

100

Modern approach to maintenance in spinning

M – ABC Ring locking and unlocking problem N – Doff over filled problem O – Ring rail jam after doffing P – Pressure regulator bowl breakage problem Q – Lifting tape broken problem R – Start up position problem S – Pressure leakage problem T – Bottom roll jerk problem U – Coarse wrapping problem V – Ring cut problem W – Hose pipe leakage problem Z – High or less back winding problem AA – High or less under winding problem AB – Underwinding is not at proper position AC – Side cut at every doff

Comber break down history register format Month : .................................... Machine name : ....................... Model : .................................... Unit : ....................................... Ma-chine no./ Date

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

1 2 3 4 5

Legend A – Side cut after batch change B – Cut problem C – Drawbox top roller jam problem D – Detaching top roll jam problem E – Feed roll jam problem F – Can changer problem G – Pressure leakage problem H – Main drive belt broken I – Coiler jam problem J – Coiling disturb problem

8.3.9

Daily report

At the end of the day each foreman should prepare a daily report. The information listed in the daily report are the description of the jobs

Maintenance information systems

101

done, name of the fitter and team to whom the jobs were entrusted, time started, time completed and list of major spares replaced. The attendance of members of maintenance team and the overtime given are also recorded. This gives at glance information about on-going and pending job as well as projected workload on each fitter. It also gives information about how the priorities are set and decision made regarding the deferral or cancellation of planned work in order to incorporate the daily breakdown. Daily report format Department : ........................................ Foreman : ............................................. Date : ....................................................

Unit no.

Job description

Corrective action

Down time

Attendance – Leave –

From

To

Absenteeism – Overtime –

Break down

Preventive maintenance work

8.3.10 Overtime maintenance record The maintenance engineer should regularly inform the industrial relation/ timekeeper office about the man-hours engaged in each department as overtime. Workers need to work late hours due to four type of work in a spinning mill: erection work, backlog of maintenance work, changing work (production plan) and machine break downs. The management should be informed at the end of month by the maintenance head the man-hours engaged in the different department as overtime for each type of work. This is possible only when a separate register is maintained by the maintenance engineer for recording the overtime engagement. This helps the management to control the total amount overtime payment. Such a control is also an indirect control over the performance of a particular department or of each maintenance team.

102

Modern approach to maintenance in spinning

Overtime record format Department : .............................

S. No.

Name of worker

Production

Maintenance Erection

Break down

Total man hours

Total man hours

8.3.11 Maintenance cost Even with the best of efforts to maintain the actual maintenance cost within the budgeted cost, it may exceed sometime. At the end of the financial year maintenance incharge should compare the actual maintenance cost with the budgeted maintenance cost. If the incurred maintenance cost differs substantially (>10%) from the budgeted cost on any item, then he should provide explanation/justification for excess cost as well as for reduced cost. Using the new understanding generated from these explanation, he should propose the next year budget and then present this sheet to the top management. Format for comparing the actual cost with budgeted cost Cost centre

Budgeted cost (last year)

Actual cost (last year)

Budgeted cost (new year)

Oil and lubrication Belt Bearing Machinery repair Planned replacement Store consumption Total maintenance cost

Note: Explanations/justification for large differences (>10%) if found between budgeted cost and actual cost of any of the items.

Maintenance information systems

103

8.3.12 Utilization loss Machine utilization gets reduced due to the maintenance activities. Maintenance aims to secure economical manufacture of product by maximum utilization of the production facilities through a smooth operation. This means that the down time for maintenance activities should be minimum. Therefore, the computation of utilization loss helps to assess the performance of a particular department. At the end of year, the maintenance incharge will compare the actual utilization loss with the budgeted. If the utilization loss exceeds the budgeted loss, then he provides an explanation for excess loss and the same sheet is presented to management. Format for comparing actual loss to budgeted loss S. no.

Loss centre

Budgeted loss (last year)

Actual loss (last year)

Budgeted loss (new year)

Avoidable loss 1.

Break down

Unavoidable loss 2.

Cleaning

3.

Maintenance work

4.

O.H. work Total utilization loss

8.3.13 Condition monitoring Condition monitoring is a form of predictive maintenance where continuous monitoring of the performance of machine or condition of the specific part is monitored which will affect the quality of the product. Condition-based maintenance and its associated condition monitoring procedures are ideal for spinning plant because most of the vital components earmarked for planned replacement are such that they fail gradually and progressively. These failures are truly serviceable. Failures are not mechanical failure when the machine does not stop but the quality of material processing on the machine deteriorates. For example, the metallic wire on cards, half lap and top comb needles on combers, and synthetic cots on ringframes do not break, but give poor working. Fortunately most of the major repair and replacement activities can be made condition-based rather than fixing arbitrarily their service life by choosing suitable measurement methods which are sensitive to component deterioration and/or to poor performance of the concerned machine parts.

104

Modern approach to maintenance in spinning

8.3.14 Linking of spare part with schedule Monthly or weekly scheduling system permits the allocation of job on the machine on a particular day so that spare can be delivered just in time so that equipment can be taken for maintenance prior before the spare part arrived. This helps to reduce the inventory. CMMS also help in taking the effective decision.

8.3.15 Stock control and purchasing It helps to access the maintenance person to the store data base allowing him to find out the spare part number and checkout the stock level of maintenance spare. Before making the purchase order one can check that spare is available in the store or not. Secondly, it gives the last price of spare and when it is purchased. This helps in reducing the repeated order.

8.3.16 Preventive maintenance checklist It is the tool which gives the maintenance engineer detailed information about the health of each machine. Checklists help to make sure that no inspection point is overlooked and give information on who is responsible for each specific activity and its frequency. It helps in identifying the need of suitable corrective action for the discrepancy or faults that get revealed through inspection. The preventive checklist must be filled on the machine by the fitter at the time of preventive maintenance or inspection. The completed checklist should be returned to the maintenance incharge for information and follow-up action. Model checklists for machines of 1or 2 models of each department are given at with necessary explanation at the end of this chapter. Mills should take these checklists as guidelines and make their own checklist depending upon the type and the mechanical condition of the machine.

8.3.17 Engineers weekly report At the end of every week the supervisor/engineer should prepare a weekly report which includes the time taken by the mechanics over different jobs and remarks on quality of work, any fault repetition and remarks relating any breakdown with the preventive maintenance. He concludes whether the man-hours spent were productive/justified or non-productive/not justified. Later, group meeting of fitters should be held in engineer’s cabin to discuss the report and to help the fitters to improve their performance. Such meetings help fitters to give useful feedback to the engineer. Preventive checklist for full setting of card DK 803/903 Here fitter is responsible.

Maintenance information systems Activity

Standard setting and condition

Δ

1.

Feed roll lickerin

12–40

4

2.

Mote knife to 1st lickerin

48

2

3.

Combing segment to 1st lickerin

22

4

4.

Mote knife to 2nd lickerin 71

2

5.

Combing segment to 2nd 22 lickerin

4

6.

Mote knife to 3rd lickerin

80

2

7.

Combing segment to 3rd lickerin

22

4

8.

Between 1st and 2nd lickerin

7

1

9.

Between 2nd and 3rd lickerin

7

1

10.

Wing setting for 2nd lickerin

0-3

11.

Wing setting for 3rd lickerin

0-3

12.

Lickerin to cylinder

7

1

13.

Back bottom plate

20–48

4

14.

Web cleaner lickerin side

14–16

4

15.

Back suction hood

30–60

4

16.

Back mote knife

20–40

1

17.

Flat gauge all points 4/6

8–14

1

18.

Front top plate

18–60

4

19.

Front top suction hood

9–25

1

20.

Front bottom suction hood

9–25

1

21.

Web cleaner doffer side

8–10

4

22.

Front bottom plate

20–40

4

23.

Doffer to cylinder

4–5

1

24.

Doffer to redirecting roll

5–7

2

S. no.

R.H.

M

105 L.H.

Gauges

(Contd.)

106

Modern approach to maintenance in spinning Standard setting and condition

Δ

Between to cross roll

4–20

4

27.

Web late to cross roll

20–40

4

28.

Between two calendar roll

4–8

1

29.

Flat and back side of front 28 top plate

4

30.

Flat and back side of back 28 top plate

4

31.

Check the basic setting gauge for wing 1

At 0° it is 28

1

32.

Check the basic setting gauge for wing 2

At 0° it is 28

1

33.

Cylinder under casing gauge at back

60–72

4

34.

Cylinder under casing gauge at back

60

4

35.

Tongue gauge

40–160

4

S. no.

Activity

25.

Redirecting roll to cross roll

26.

R.H.

M

L.H.

Condition of spare parts 36.

Cylinder

37.

Doffer

38.

Flat

39.

Stationary flats

40.

Front bottom plate

41.

Front top plates

42.

Back bottom plate

43.

Back top plates

44.

Cylinder under casing

45.

Redirecting roll wire

46.

Doffer under casing

47.

Redirecting roll undercasing (Contd.)

Maintenance information systems S. no.

Activity

48.

Flat cleaning brush

49.

Flat stripping brush

50.

Redirecting roll cleaning brush

Standard setting and condition

Δ

Safety 51.

Machine will not start if any cover is open

52.

Machine will not start if waste suction pressure is low

53.

Cylinder speed monitoring

54.

Lickerin speed monitoring

55.

Double lap monitoring

56.

Magnetic substance monitoring

Speeds 57.

Cylinder speed

It should be same in all cards

58.

Lickerin speed

It should be same in all cards

59.

Flat speed

It should be same in all cards

60.

Aero feed beater speed

It should be same in all cards

Belts and pulley 61.

Condition of belts

62.

Belts are properly aligned

63.

Condition of pulleys

R.H.

M

107 L.H.

108

Modern approach to maintenance in spinning

Preventive checklist for Drawframe RSB-851 S. Activity no.

Standard setting and condition

Date

Responsibility

Frequency

Actual report 1.

Bottom roll gauge

Gauge

1 mm

Fitter

Schedule

2.

Top roll gauge

Gauge

1 mm

Fitter

Schedule

3.

Pressure bar gauge Gauge

1 mm

Fitter

Schedule

4.

Bottom stripper

Condition of bottom and top roll stripper

Cleaner

Cleaning

Gauge of bottom stripper paper should not pass between the bottom roll and stripper.

Cleaner

Cleaning

Check for any crack in the cots.

Cleaner

Cleaning

Check for channelling formation in the cots.

Cleaner

Cleaning

Use only servo system 68 no.

Fitter

Schedule

Check oil level, i.e. in the middle of the glass.

Fitter

Cleaning

Check for oil leakage.

Fitter

Cleaning

Check the condition of belts.

Fitter

Cleaning

Alignment

Fitter

Cleaning

Tension of the belt is proper or not.

Fitter

Cleaning

Check the condition of filter screen.

Fitter

Cleaning

Check for any air leakage.

Fitter

Cleaning

Check for any damage needle bearing.

Cleaner

Cleaning

Check for bearing cover to properly fit.

Cleaner

Cleaning

Check all the bearings should have grease nipple.

Cleaner

Cleaning

5.

6.

7.

8.

9.

Cots

Gear box oil

Belts

Filter screen

Bottom roll

Maintenance information systems S. Activity no.

Standard setting and condition

Date

109

Responsibility

Frequency

Check for any bearing has red grease.

Cleaner

Cleaning

It should not wear out.

Fitter

Cleaning

Its diameter suits to the hank of delivery sliver.

Fitter

Cleaning

11. Web guiding tube

It should not wear out.

Fitter

Cleaning

12. Pressure bar

It should not wear out, i.e. its surface should not be wavy.

Fitter

Cleaning

13. Top arm

It should not wear out, i.e. there should not be play in top arm.

Fitter

Cleaning

Both side of the arm should be properly levelled.

Fitter

Cleaning

Pressure should be of 64 kg.

Fitter

Cleaning

14. Bottom roll slides

It should not wear out.

Fitter

Cleaning

15. Suction hoses

These should not crack.

Fitter

Cleaning

16. Coiler

It should not wear out, i.e. there should not be any scratches on the surface of coiler which comes in contact with the sliver.

Fitter

Cleaning

Coiler speed should not be too high to create false draft.

Fitter

Cleaning

Sliver coil should be of 20 mm less than the diameter of can.

Fitter

Cleaning

17. Guiding roll for can changer

It should not wear out.

Fitter

Cleaning

18. Scanning roll

Its size must suits the weight of feeding sliver.

Fitter

Cleaning

It should not wear out.

Fitter

Cleaning

Actual report

10. Trumpet

110

Modern approach to maintenance in spinning

S. Activity no.

Standard setting and condition

Date

Responsibility

Frequency

The gauge between two scanning roll should be proper, i.e. the upper surfaces of two scanning roll should not touch each other.

Fitter

Cleaning

The loading should suit the type and weight of sliver.

Fitter

Cleaning

Its size must suits the weight of delivery sliver.

Fitter

Cleaning

Gauge between the calendar roll is 0.05 mm.

Fitter

Cleaning

Machine will not start if any cover is open.

Fitter

Cleaning

Machine will not start if waste suction pressure is low.

Fitter

Cleaning

Top roll lap monitoring

Fitter

Cleaning

Creel stop motion, i.e. sliver should not go in drafting if sliver breaks at the creel.

Fitter

Cleaning

Coiler stop motion, i.e. machine should stop if there is any jam in the coiler.

Fitter

Cleaning

Web guide stop motion, i.e. if sliver breaks at the bottom front, roll machine should stop.

Fitter

Cleaning

Actual report

19. Calendar roller

20. Safety

Check list for speed frame LF 1400 S. Activity no.

Standard setting and condition

Date

Responsibility

Frequency

Actual result 1.

System pressure

0.6–6.5 bar

Fitter

Cleaning

2.

Drafting pressure

0.8–1.0 bar

Fitter

Cleaning

Maintenance information systems S. Activity no.

Standard setting and condition

Date

111

Responsibility

Frequency

Actual result 3.

Braking pressure

1.8 bar

Fitter

Cleaning

4.

Minimum pressure switch for system pressure

Check that machine stop when pressure reduces to 5.5 bar.

Fitter

Cleaning

5.

Safety valve for drafting

Air start leaking the machine when drafting pressure increases more than 1.3 bar.

Fitter

Cleaning

6.

Regulator and dial indicator

Check regulator for proper working.

Fitter

Cleaning

Check dial indicator for proper working.

Fitter

Cleaning

Check apron for cracks.

Cleaner

Cleaning

Check the apron for channelling.

Cleaner

Cleaning

Check the bottom apron for shifting wrt top apron.

Cleaner

Cleaning

Check the bottom apron tension.

Cleaner

Cleaning

Apron tension pulley should not be jammed with flies.

Cleaner

Cleaning

Remove the bottom apron and check the tension pulley for smooth movement.

Cleaner

Cleaning

Check for more play in the arbour.

Roller coverer

Buffing

Check for noise in the top roll bearing.

Roller coverer

Buffing

Check cots for crack.

Roller coverer

Buffing

Check cots for channelling.

Roller coverer

Buffing

Check for suction tube setting.

Fitter

Cleaning

7.

8.

9.

Top apron and bottom apron

Top roll

Suction tube

112

Modern approach to maintenance in spinning

S. Activity no.

Standard setting and condition

Date

Responsibility

Frequency

Check suction tube for scratches inside the tube.

Cleaner

Cleaning

Check suction for fly jam.

Cleaner

Cleaning

Check suction tube holder breakage.

Cleaner

Cleaning

Check for suction tube pressure 20 mm, 30 mm and 40 mm at the gear end, middle and off end.

Fitter

Cleaning

Check for top arm pressure. It should be 22, 13.2 and 16 kg at front, middle and back.

Fitter

Schedule

Check for saddle spring.

Cleaner

Cleaning

Check all the top arm should be tightened with 0.9 Nm torque.

Fitter

Schedule

Check for top arm centring.

Fitter

Schedule

Check for bottom roll eccentricity, i.e. it should not be more than 3 points on each spindle.

Fitter

Schedule

Check for any damage needle bearing.

Cleaner

Cleaning

Check for bearing cover to properly fit.

Cleaner

Cleaning

Check all the bearings should have grease nipple.

Cleaner

Cleaning

Check for any bearing have red grease.

Cleaner

Cleaning

Check for wear of any cradles and nose bar.

Cleaner

Cleaning

Check for missing of spacer.

Cleaner

Cleaning

Actual result

10. Top arm

11. Bottom roll

12. Cradles and nose bar

Maintenance information systems S. Activity no.

Standard setting and condition

Date

113

Responsibility

Frequency

Actual result 13. Gears

Check gear for damage of teeth and meshing between two gears.

Fitter

Cleaning

14. Filter screen

Check the condition of filter screen.

Fitter

Cleaning

Check for any air leakage.

Fitter

Cleaning

Check the condition of belts.

Fitter

Cleaning

Alignment

Fitter

Cleaning

Check tension of the belt is proper or not.

Fitter

Cleaning

Check for any crack in the cots.

Roller coverer

Buffing

Check for channelling formation in the cots.

Cleaner

Cleaning

17. Greasing point

Used grease AP-3

Fitter

Cleaning/s chedule

18. Starting position

30mm

1mm

Fitter

Cleaning

19. Cop diameter

Flyer diameter –10 mm

Fitter

Cleaning

20. End position

30 mm

Fitter

Cleaning

21. Gear box oil

Use only servo system 100 no.

Fitter

Cleaning

Check oil level, i.e. in the middle of the glass.

Fitter

Cleaning

Check for oil leakage

Fitter

Cleaning

Use only servo spin 32 no.

Fitter

Cleaning

Check oil level, i.e. in the middle of the glass.

Fitter

Cleaning

Check for oil leakage.

Fitter

Cleaning

Check that all clearer should be moving properly.

Cleaner

Cleaning

15. Belts

16. Cots

22. Fluid coupling

23. Top and bottom clearer

1mm

114

Modern approach to maintenance in spinning

S. Activity no.

Standard setting and condition

Date

Responsibility

Frequency

Check that cleaning comb of all clearer clean the clearer.

Cleaner

Cleaning

Check that spindles are not hot.

Cleaner

Cleaning

Spindles are not jammed.

Cleaner

Cleaning

All spindles are fitted on the same height.

Fitter

Cleaning

Spindles are not eccentric.

Fitter

Schedule

Flyers are not jammed with flies.

Cleaner

Cleaning

Check for any wear out in any twist master.

Cleaner

Cleaning

Check if the twist master is not loose on the flyer.

Cleaner

Cleaning

Check that pressure fingers are not bended.

Cleaner

Cleaning

Check that pressure fingers are not wear out.

Cleaner

Cleaning

27. Bobbin trough

Bobbin trough is properly levelled.

Fitter

Schedule

28. Conedrum

Check for the condition of conedrum.

Fitter

Cleaning

Check the condition of rope.

Fitter

Cleaning

Check that belt is moving smoothly on conedrum.

Fitter

Cleaning

29. Reversing clutch

Check the gauge of reversing clutch.

Fitter

Schedule

30. Balancing of bobbin trough

Bobbin rail should be properly balanced.

Fitter

Cleaning

Check the condition of slides for bobbin rail.

Fitter

Cleaning

Gauge

Fitter

Schedule

Actual result

24. Spindle

25.

26. Flyer

31. Bottom roll gauge

1 mm

Maintenance information systems S. Activity no.

Standard setting and condition

Date

115

Responsibility

Frequency

Actual result 32. Top roll gauge

Gauge

1 mm

Fitter

Schedule

33. Top arm guide tube setting

For 27 mm bottom roll

Fitter

Schedule

36 mm cage = 288.6 43 mm cage = 289.6 50 mm cage = 290.0 59 mm cage = 290.6 For 30 mm bottom roll 36 mm cage = 290.6 43 mm cage = 291.6 50 mm cage = 292.0 59 mm cage = 292.6

34. Condensers

All the condensers should be tight fit.

Cleaner

Cleaning

35. Stop bridge

Setting of stop bridge should be proper, i.e. machine should not stop at reversal point in case of any stoppage.

Fitter

Cleaning

36. Over run safety

It is working properly; limit switch b19 and b20.

Fitter

Cleaning

37. Cone belt relief safety

Only when cone is fully lifted, reversing motor can be switched on.

Fitter

Cleaning

38. Door safety

Machine is not started if any cover is open.

Fitter

Cleaning

40. Creel

There is no jerky motion in the creel.

Fitter

Cleaning

All the rows of the creel should move.

Fitter

Cleaning

The guide roll of the creel should be properly aligned.

Fitter

Cleaning

116

Modern approach to maintenance in spinning

Checklist for Unilap E-30/E32 S. Activity no.

Standard setting/conditions

Date

Respon Frequency -sibility

Actual report Fitter

Cleaning

Standard time is 7 Take up monitor, i.e. if the battery is not seized second by the new tube after lap change. The yoke remain in bottom position the machine must stop after some time.

Fitter

Cleaning

3.

Standard setting = Gauge of holding plate 380 mm for the tube feed, i.e. check the distance between the edge of the holding plate and the top edge of the base plate

Fitter

Cleaning

4.

Check the distance between calendar roll and lap roll

Standard setting = 1 mm

Fitter

Cleaning

5.

Check when the calendar roll is pressing

Proximity switch b59 and b60 must be on

Fitter

Cleaning

6.

Check gauge between the calendar roll and guide and guide plate

Standard setting = 0.2 mm

Fitter

Cleaning

7.

Check for pneumatic pressure for lap flange

Standard = 10 bar

Fitter

Cleaning

8.

Check for drafting pressure

4.5–4.8 bar

Fitter

Cleaning

9.

Check for calendar roll pressure

2.5–3.0 bar

Fitter

Cleaning

Conicity is not more than 6 mm.

Fitter

Cleaning

1.

Distance between tube and lap roller with loading

2.

10. Check the setting for pressure bar

1 mm

Width of upper position of pressure bar = 75 mm Bottom position pressure bar width = 79–81 mm

Maintenance information systems S. Activity no.

Standard setting/conditions

Date

117

Respon Frequency -sibility

Actual report 11. Check for contact pressure

In bottom position of yoke maximum = 2.0–2.5 bar

Fitter

Cleaning

In upper position of yoke maximum = 4 bar 12. Check for drafting pressure monitoring

Machine must stop when drafting pressure reduce to 3.5 bar.

Fitter

Cleaning

13. Check for lap contact pressure monitoring

Machine must stop when pressure reduces to 0.7 bar.

Fitter

Cleaning

14. Suction pressure

With tube insertion it should be 600 pa

Fitter

Cleaning

15. Suction pressure monitoring

Machine must stop when pressure reduces below 550 pa.

Fitter

Cleaning

16. Check for bottom roll gauges

There should not be variation of more than 1 mm.

Fitter

Cleaning

Range: Break draft = 40–60 mm Intermediate draft = 40–60 mm Main draft = 40–60 mm 17. Top roll diameter

Max 40 mm and minimum 37 mm

18. Clearer cloth

Check the condition of clearer cloth.

Fitter

Cleaning

Its movement is smooth.

Fitter

Cleaning

Check the condition of stripper.

Cleaner Cleaning

Contact surface must be angle of 90 degree to the direction of material flow.

Cleaner Cleaning

19. Stripper under bottom roll

Roller Buffing coverer

118

Modern approach to maintenance in spinning

S. Activity no.

Standard setting/conditions

Date

Respon Frequency -sibility

Actual report 20. Sliver guide

Setting should be such that sliver lie close to one another.

Fitter

Cleaning

21. Tension bar

Setting of tension bar should be proper.

Fitter

Cleaning

22. Drafting stop motion

Machine must stop in case of lap up.

Fitter

Cleaning

Pasttle must be set at 0.5 mm from stop flap.

Fitter

Cleaning

23. Table calendar roll monitoring

When a thick place in sliver occurs or there is a lap on calendar roll machine must stop.

Fitter

Cleaning

24. Sensors on feed frame

Machine should not start if the sliver is not present on feed table.

Fitter

Cleaning

25. Belts

Check the condition of belts.

Fitter

Cleaning

Alignment

Fitter

Cleaning

Tension of the belt is proper or not.

Fitter

Cleaning

Use only servo system 150 no.

Fitter

Cleaning

Check oil level, i.e. in the middle of the glass

Fitter

Cleaning

Check for oil leakage

Fitter

Cleaning

Check the condition of filter screen

Fitter

Cleaning

Check the condition of rotary drum

Fitter

Cleaning

Check the condition of play of piston and proper working

Fitter

Cleaning

26. Gear box oil

27. Filter screen

119

Maintenance information systems

Check list of comber E7/5A and E60/E62 S. Activity no.

Standard setting

Date

Responsibility

Frequency

Actual 1.

Main door drive safety

Limit switch S26, i.e. machine is not operated at fast speed after opening the main drive door.

Fitter

Cleaning

2.

Back door safety

Limit switch s23 and s22 machine is not after opening the back drive.

Fitter

Cleaning

3.

Detaching top roll cover safety

Limit switch s24 s25 machine is not operated after opening the detaching roll cover.

Fitter

Cleaning

4.

Detaching top roll

Diameter of top detaching roll should not be less than 23.5 mm and the diameters of all detaching roll in the same machine are equal.

Roller coverer

Buffing

Condition of top detaching roll, i.e. groove formation is not there.

Cleaner

Cleaning

Condition of bottom detaching roll stripper

Cleaner

Cleaning

Gauge of bottom stripper paper should not pass between the bottom roll and stripper.

Fitter

Nipper gauge

Condition of clearer roller

Cleaner

Cleaning

5.

Bottom stripper and clearer

6.

Vacuum gauge

It should between 14–18 mm

Fitter

Cleaning

7.

Ratchet wheel

No. of teeth of ratchet wheel should be same on all heads in the machine.

Cleaner

Cleaning

Condition of ratchet wheel, i.e. teeth have worn out condition or ratchet is cracked or not.

Cleaner

Cleaning

8.

Feed amount

4.3, 4.7, 5.2, 5.9

Fitter

Cleaning

9.

Feed change gear

52–73

Fitter

Cleaning

10. Lap tension

Tension should be between 8% and 12%.

Fitter

Cleaning

11. Feed

Forward feed and backward feed

Fitter

Cleaning

120

Modern approach to maintenance in spinning

S. Activity no.

Standard setting

Date

Responsibility

Frequency

Condition of ratchet pawl

Fitter

Cleaning

Condition of torsion bar, i.e. rubber on which ratchet pawl is fixed

Fitter

Nipper gauge

Condition of brush

Fitter

Brush gauge

Diameter of brush 95–110 mm

Fitter

Brush gauge

Speed of the brush 1000 or 1200 mm

Fitter

Brush gauge

Brush gauge should be perfectly OK

Fitter

Brush gauge

14. Table draft

0.2–68 standard is 3.8

Fitter

Cleaning

15. Table funnel and table calendar roll

Size of table funnel: 3.7–6.5

Fitter

Cleaning

Condition of table funnel

Cleaner

Cleaning

Table funnel stop motion

Cleaner

Cleaning

Condition of table calendar roll

Cleaner

Cleaning

Type of circular comb 5015 or 5014

Fitter

Cleaning

Fitter

Unicomb gauge

Condition of nipper, i.e. they are not bended.

Fitter

Nipper gauge

There should not be play between nipper pin and nipper, i.e. nipper pin should not wear out.

Fitter

Nipper gauge

Actual 12. Ratchet pawl

13. Brush

16. Circular comb

Condition of circular comb 17. Circular comb gauge It should be 27 1 mm at index 36 if circular comb working angle is more than >90 . It should be 27 1 mm at index 38 if circular comb working angle is more than <90 . 18. Nipper

121

Maintenance information systems S. Activity no.

Standard setting

Date

Responsibility

Frequency

Check the supporting ring in the top nipper. It should be same in all the heads and depends upon the feed as it affects the movement of ratchet wheel.

Fitter

Nipper gauge

19. Nipper gauge

Nipper gauge should be proper; it should be checked at index 24 and waste index 5 with go and no gauge.

Fitter

Nipper gauge

20. Cam eccentrics to check the spring power

It should be done at index 24 and waste index. Both the gauge will touch each other.

Fitter

Nipper gauge

The setting between cam and bearing should be 0.2 mm.

Fitter

Nipper gauge

21. Gauge between circular comb and nipper

It should not be less than 0.2 mm at index 38.

Fitter

Nipper gauge

22. Top comb

Condition of top comb should be good, i.e. needles are not bend and rusty.

Cleaner

Cleaning

Specifications of top comb should be same on all the heads, i.e. 26/30 needles per cm.

Cleaner

Cleaning

23. Top comb gauge and Top comb penetration should front position be same on all the heads, i.e. – 1 to 1

Fitter

Nipper gauge

The distance should be 0.1 mm between the top comb and gauge fitted on the bottom detaching roller.

Fitter

Nipper gauge

24. Safety for penetration depth

Check at index 39; the gauge between the top comb and unicomb is never less than 0.5 mm.

Fitter

Nipper gauge

25. Draw box gauge

41–60 mm; it should be same on all the machines running on the same count.

Fitter

Nipper gauge

26. Bottom roll

Check the eccentricity of bottom roll.

Fitter

Nipper gauge

Actual

122

Modern approach to maintenance in spinning

S. Activity no.

Standard setting

Date

Responsibility

Frequency

Diameter of top draw box roll; it should not be less than 44 mm and the diameter of all top roll in the same machine is equal.

Roller coverer

Buffing

Condition of top roll, i.e. groove formation and cut is not there.

Roller coverer

Buffing

Lap weight Gauge 0.1 mm

Fitter

Nipper gauge

It should be between –2 and 2 as it affects the overlapping of fibre during piecing.

Fitter

Mixing change

The appearance of fleece should be good.

Fitter

Mixing change

30. Fly duct setting

It should vary from 16 to 28 mm from head 1 to 8.

Fitter

Nipper gauge

31. Sliver coiling

The sliver coiling should be 8 to 10 mm less than wall can.

Fitter

Cleaning

32. Sliver tension or sliver coiling appearance

Check the gap between the variator pulleys.

Fitter

Cleaning

33. Calendar roller gauge

It should be 0.05 mm; there is a play between the calendar roller without material.

Fitter

Cleaning

Fitter

Sliver hank change

Actual 27. Drafting top roll

28. Fleece guide gauge

1.8 65

2.0

70

2.2

75

2.4

80 29. Control dial setting

34. Calendar roller pressure 35. Centring of lipped funnel in relation to stepped roll

Lipped funnel should be in the centre of two stepped roll. Check washer is provided it or not.

Fitter

Nipper gauge

36. Can turnable gauge

There is a gauge of 2 mm all round.

Fitter

Cleaning

37. Centring roll

There is a distance of 5mm between the can and can centring roll.

Fitter

Cleaning

Maintenance information systems S. Activity no.

Standard setting

Date

123

Responsibility

Frequency

Actual 38. System pressure

6 kg

Fitter

Cleaning

39. Top detaching roll pressure

2.5–4 bar

Fitter

Cleaning

40. Drafting system front top roll

2.5–3 bar

Fitter

Cleaning

41. Drafting system 2nd and 3rd roll

3.5–4 bar

Fitter

Cleaning

Fitter

Cleaning

Fitter

Cleaning

42. Minimum pressure 2.1 bar for top detaching roll The machine should stop when the top detaching roll pressure falls below the 2.1 bar. 43. Funnel arm of drafting system

Condition of funnel

Fitter

Cleaning

Safety shut down proximity switch b50.

Fitter

Cleaning

44. Basic setting of funnel arm

It should be such that there is a distance of 1 mm between the conveyor belt and funnel.

Fitter

Cleaning

45. Stripper of calendar roller

Condition of stripper of calendar roller.

Cleaner

Cleaning

46.

(1) Oil used should be mobil oil SCH 629

Fitter

Cleaning

Check the condition of belts

Fitter

Cleaning

Alignment

Fitter

Cleaning

Tension of belts

Fitter

Cleaning

Check the condition of pulleys

Fitter

Cleaning

Responsibility

Frequency

Gear box

(2) Check oil level (3) Check for oil leakage 47. Belts

48. Pulley

Check list for Ring Frame RXI240 S. Activity no.

Standard setting and condition

Date

Actual report

124

Modern approach to maintenance in spinning

S. Activity no.

Responsibility

Frequency

(a) Used servo spin EE-10 no. oil

Fitter

Cleaning

(b) Check oil level, i.e. 50 mm minimum – 100 mm maximum in 10 spindles

Fitter

Cleaning

Standard setting and condition

Date

Actual report 1.

Spindle Oil

2.

Greasing point (a) Grease used – recommended grease or not

Fitter/cleaner

Cleaning

3.

Starting position

10 1 mm from bottom of bobbin

Fitter

Cleaning

4.

Cop diameter

Ring diameter – 3 mm

Fitter

Cleaning

5.

End position

10 1 mm from top of bobbin

Fitter

Cleaning

6.

Chase length

8–12% of ring diameter

Fitter

Cleaning

7.

Lappet hook setting

2 × d +5 mm

Fitter

Cleaning

8.

Thread traversing

(a) It should be 8–10 mm.

Fitter

Cleaning

(b) It should be in the middle of cot of each spindle.

Cleaner

Cleaning

Fitter

Cleaning

(b) Underwinding position should be 5 1 from bottom of bobbin.

Fitter

Cleaning

(a) Ring rail should rise slowly and fall slowly.

Fitter

Cleaning

(b) There should not be any jerky motion.

Fitter

Cleaning

(c) Check the condition of heart cam and follower.

Fitter

Cleaning

(a) Check for the separator holder breakage.

Cleaner

Cleaning

(b) Check for separator wear out at the bottom and catching the fly.

Cleaner

Cleaning

9.

Under winding (a) Underwinding should be setting 2–3 coils after doffing.

10. Ring rail motion

11. Separator

Maintenance information systems S. Activity no.

Standard setting and condition

Date

125

Responsibility

Frequency

Cleaner

Cleaning

Fitter

Schedule

Fitter

Schedule

Cleaner

Cleaning

Fitter

Schedule

Actual report 12. Anti balloon ring

(a) Check for any scratch on inner diameter of anti-balloon ring. (b) Check for the centring of the anti-balloon ring w.r.t. spindle (tolerance 0.5 mm). (c) Check for height setting of anti-balloon ring.

13. Lappet hook

(a) Check for any scratch and cut in the lappet hook. (b) Check for the centring of lappet hook with plumb w.r.t. spindle. (c) Check for height setting of lappet hook.

Schedule Fitter

14. Gears

Fitter

Cleaning

Fitter

Cleaning

Fitter

Schedule

(d) Check for missing of fly catcher.

Fitter

Schedule

(e) Check for loading of flyer.

Cleaner

Cleaning

(f) Check for fly catcher gauge 0.1 mm.

Cleaner

Cleaning

(a) Check gear for damage of teeth and meshing between two gears. (b) Check for oil circulation.

15. Rings

(a) Check for any wear out of rings. (b) Check out for centring of rings w.r.t. spindle tolerance 0.5 mm. (c) Check for height setting of ring rail.

126

Modern approach to maintenance in spinning

S. Activity no.

Responsibility

Frequency

(a) Check for breakage of any cradle.

Cleaner

Cleaning

(b) Check for missing of spacer and mix spacer.

Cleaner

Cleaning

(c) Check for missing of spring of cradle.

Cleaner

Cleaning

Standard setting and condition

Date

Actual report 16. Cradle

17. Foot step

Check for load on foot step by slight hammering.

Fitter

Cleaning

18. Sensor

Check for sensor setting px10, px11, px14, px15, px16 and px12.

Fitter

Cleaning

19. Top arm

(a) Check for top arm pressure. It should be green.

Cleaner

Cleaning

Cleaner

Cleaning

Fitter

Schedule

(d) Check for top arm centring.

Cleaner

Cleaning

(e) Check for height gauge.

Fitter

Schedule

Cleaner

Cleaning

(b) Check spindle and bolster for vibration.

Cleaner

Cleaning

(c) Check spindle for button.

Cleaner

Cleaning

(d) Check spindle and bolster for shortage of breaks.

Cleaner

Cleaning

(e) Check for spindle locks.

Cleaner

Cleaning

Fitter

Schedule

(b) Check for saddle spring. (c) Check all the top arm should be tightened with 0.7 Nm torque.

20. Spindle bolster (a) Check spindle and bolster for heating.

(f) Check whether by applying break spindle will stop or not. (g) Check spindle for speed variation with stroboscope.

Maintenance information systems S. Activity no.

Standard setting and condition

Date

127

Responsibility

Frequency

Fitter

Schedule

Cleaner

Cleaning

Cleaner

Cleaning

Cleaner

Cleaning

Cleaner

Cleaning

Fitter

Cleaning

Roller coverer

Buffing

Actual report 21. Bottom roll

22. Top roll

(a) Check for bottom roll eccentricity, i.e. it should not be more than 3 points on each spindle. (b) Check for any damage needle bearing. (c) Check for bearing cover to properly fit. (d) Check all the bearings should have grease nipple. (e) Check for any bearing have red grease. (f) Check for gap between sensor and deflection plate. (a) Check for more play in the arbour. (b) Check for noise in the top roll bearing. (c) Check cots for crack. (d) Check cots for channelling.

23. Top apron and bottom apron

-doBuffing -do-do-

-do-do-

Fitter

Cleaning

Cleaner

Cleaning

(d) Check the bottom apron tension, i.e. it should be 2 or 3 and setting should be same in all the section.

Cleaner

Cleaning

Cleaner

Cleaning

(e) Apron tension pulley should not be jammed with fly.

Cleaner

Cleaning

Fitter

Schedule

(a) Check top apron for cracks. (b) Check the apron for channelling. (c) Check the bottom apron for shifting w.r.t. top apron.

(f) Remove the bottom apron; check the tension pulley for smooth movement.

128

Modern approach to maintenance in spinning

S. Activity no.

Responsibility

Frequency

(a) Check for proper lappet hook tilting after doffing.

Fitter

Cleaning

(b) Gap between sensor and deflection plate.

Fitter

Cleaning

(a) Oil used should be 320.

Fitter

Schedule

(b) Check oil level.(c)Check for oil leakage.

Fitter

Cleaning

Fitter

Cleaning

(a) Check for suction tube setting, i.e. it should be of 0.5–1.5 mm from bottom roll.

Fitter

Schedule

(b) Check suction tube for scratches inside the tube.

Cleaner

Cleaning

(c) Check suction for fly jam.

Cleaner

Cleaning

(d) Check suction tube is not touching the yarn.

Cleaner

Cleaning

(e) Check suction tube holder breakage.

Cleaner

Cleaning

Fitter

Cleaning

(a) Oil used should be 320.

Fitter

Schedule

(b) Check oil level.

Fitter

Cleaning

(c) Check for oil leakage.

Fitter

Cleaning

(a) Oil used should be 320.

Fitter

Schedule

(b) Check oil level.

Fitter

Cleaning

(c) Check for oil leakage.

Fitter

Cleaning

Standard setting and condition

Date

Actual report 24. Lappet hook tilting

25. G.E. box change

23. Suction tube

(f) Check for suction tube pressure 12, 15, 17 at the gear end, middle and off end. 24. Worm gear box

25. Building gear box

Maintenance information systems

129

Responsibility

Frequency

Fitter

Cleaning

(b) Check the position of jockey pulley lever weight in case of single jockey pulley.

Cleaner

Cleaning

(c) Check for the condition of jockey pulley lever weight.

Cleaner

Cleaning

(d) Check the condition drum pulley.

Cleaner

Cleaning

(e) Check jockey pulley for movement.

Cleaner

Cleaning

(f) Check the spindle tape for centring on jockey pulley and drum pulley.

Cleaner

Cleaning

(a) Check condition of filter screen.

Fitter

Cleaning

(b) Check for air leakage and seals of the door.

Fitter

Cleaning

28. Main drive belt (a) Check for the alignment of main drive belt.

Fitter

Cleaning

(b) Check the condition of main drive belt.

Fitter

Cleaning

(a) Check for creel alignment.

Fitter

Cleaning

(b) Creel height should be same in all ring frames.

Cleaner

Cleaning

S. Activity no.

Standard setting and condition

Date

Actual report 26. Spindle tape

27. Filter screen

29. Creel alignment

(a) Check condition of spindle tape.

(c) Check bobbin holder for free movement, i.e. creel breakage. 30. Timing belt

Check for the condition and tension setting and alignment of timing belt.

Fitter

Cleaning

31. Back roller twist prevention

Check for safety.

Fitter

Cleaning

32. Over lifting or lower lifting

Check for safety check for the sensor of setting px3 and px6.

Fitter

Cleaning

130

Modern approach to maintenance in spinning

Checklist of Machconer winding head overhauling Here the responsibility is of fitter. S. no.

Activity

1.

Is the friction of unit cassette type gear joint appropriate?

2.

Are the parallel and longitudinal positions position of the cradle on each spindle is appropriate?

3.

Increase setting of cradle is same on all the spindles

4.

Drum feeler Drum feeler with respect to drum is same on all the spindles

Standard setting and condition

1

0.5 mm

When the drum feeler with drum winding is operated, does the yellow button extend? 5.

Drum brush on each spindle contact the drum evenly

6.

Is the end missing prevention cover properly positioned on each spindle?

30.5 mm

7.

Drum cover gauge with respect to drum is same on all spindles

1 mm

8.

Is the suction mouth gauge is prefect on all the spindles?

When cone diameter is 150–200 mm, the gauge should be of 1–3 mm

9.

Is the suction mouth pad suited the particular type of adopter on each spindle?

3 20’ 4 20’ = N 5 57’ 9 57’=L

10.

Is the sufficient wax adhered to the yarn?

11.

Does the waxing device operate smoothly?

12.

Is the distance between the retie pipe and unit is same on all the spindles?

128–130mm

13.

Is the opening of the retie clamp is prefect when retie pipe is stopping and descending?

Upper position = 5 mm

14.

Drum belt is in prefect condition or not.

15.

Is the distance of gate feeler appropriate?

16.

Does the gate feeler correctly sense the

Bottom position 2–4 mm

4–4.5 mm

Actual report

Maintenance information systems S. no.

Activity

Standard setting and condition

joining and the bobbin change? 17.

Dose the tensor rotate properly?

18.

Does the tensor open sufficiently?

19.

Does the tensor disc rotate normally?

20.

Is the drum starting time appropriate?

21.

Are the spinning bobbin and balloon breaker aligned?

22.

Is the height of balloon breaker appropriate?

15 mm from bobbin tip

23.

Is the distance of pre-clearer appropriate?

5–7 times the diameter of yarn

24.

Does the drum rotate smoothly?

25.

Does the cradle lifter operate normally?

26.

Does the package brake operate?

27.

Is the initial pressure setting is same on all the spindles?

28.

Is the holding position of kink removing wire is appropriate?

29.

Does the splicing appear normal?

30.

Opening and splicing pressure is same on all the section.

31.

Setting of s10 screw is same on all spindles.

4–5 turn

32.

Length lever Ln setting is same on all spindles.

1–8

33.

The setting of untwisting pipe should be same on all spindles.

34.

Prism should not be broken.

35.

Holding lever setting should be same on all the spindles and suited to particular type of lever.

36.

Front plate separator and holding lever should be same on all the spindles.

37.

Condition of splicer cutter should be good.

38.

Is not the screw for splicer cutter is loosened?

131 Actual report

132

Modern approach to maintenance in spinning

S. no.

Activity

39.

Does the shutter cutter close smoothly?

40.

Is the stroke of yarn trap appropriate?

41.

There should be no air leakage in mechanical valve.

42.

Is the bunch winding guide positioned properly?

43.

Is the peg centred properly?

44.

Is the chute door centred? Properly

45.

Is the trap door centred properly?

46.

Does the magazine rotate smoothly?

47.

Does the magazine suction operate properly?

48.

Does the bobbin chute operate accurately?

49.

Does the bobbin plow operate accurately?

50.

Does the trap door opened and close smoothly?

51.

Does the chute door open and close smoothly?

Standard setting and condition

Actual report

References 1. 2. 3. 4. 5. 6. 7. 8.

Trutzschler Card DK 903 instruction manual, 2nd edition year, 1999. Murata Machconer /Linkconer No. 7 instruction manual revised, May 1988. Kirloskar Toyada Ringframe RXI240 instruction manual, 1999. Rieter Ingolstadt Drawframe RSB 951, 1996. Rieter Unilap E32 operating instruction manual 10055921. Rieter Comber E62 operating instruction manual 10013753. Lakshmi Speedframe LF 1400 operating instruction manual, 1990. Lakshmi Ringframe G5/1 operating instruction manual, 1990.

All figures, tables and graphs are sourced from the above references

9 Safety while maintenance

9.1

Accident

The danger to life of humans is increasing with scientific development in spinning industry. The importance of industrial safety was realized because millions of industrial accidents occur which result in either death or temporary/permanent disablement of employees and involve large amount of losses to property and working hours. Technology helps an industry to grow but it is a proven fact that technology can give the best results only when people are ready to achieve the best out of it. People can and will give their best only when their personal welfare is well attended, i.e. when safety is ensured at work. Studies have shown that accidents occur mainly due to unsafe actions, unsafe conditions and negligence. Today, the textile industry is equipped with complicated and fast-moving production machines; so it is necessary that everyone has the correct information and knowledge about these machines, and that everyone follows safety precautions in order to prevent accidents. Hence, an accident is an unplanned and unexpected event that causes (or is likely to cause an) injury to a person and/or damage to property and environment. Moreover, from managerial perspective, the importance of safety during work in any organization may be concluded by following facilitation: 1. Treatment – the industrial safety management provides treatment for injuries and illness at the work place. 2. Medical examination – it carries out medical examination of staff joining the organization or returning to work after sickness or accident. 3. Hazard identification 4. Provision of protective devices 5. Consultancy – it provides medical advice on conditions that affect human health e.g. works canteen etc. 6. Education – it provides safety and health training.

133

134

Modern approach to maintenance in spinning

9.2

Effects of an accident

There are three types of effects of any accident: 1. Personal effects. 2. Social effects. 3. Other effects. 1. Personal effects include – (a) Death, (b) Disability, (c) Physical suffering, (d) Psychological suffering, (e) Loss of ability for efficient working, (f) Loss of earning capability. 2. Social effects include – (a) An asset in the form of earning hand becomes a liability. (b) Social status may get lost. (c) Family humiliation of disability is prolonged or permanent. 3. Other effects are (a) Loss of man hours (b) Loss of machine hours (c) Loss of material (d) Damaged machinery (e) Damaged property (f) Loss of capital

9.3

Accidents and its related losses

Accidents occur as a result of unsafe actions or exposure to unsafe mechanical and/or physical conditions. Accidents can also happen due to human failures. Accident levies heavy cost as it includes loss directly or indirectly and the losses that are visible and invisible. The latter ones are immeasurable and cannot be valued in monetary terms. Whenever an industrial accident occurs, it gives rise to pain for the victim and his family and further de-motivate the other employees. It results in financial losses to the employee and the employer.. We can classify the losses to any company due to the accidents in term of direct loss and indirect loss. (a) Direct loss is the wage of employee because of the loss of working hours, compensation and the cost of medical aid; the cost incurred on training a new worker; loss due to waste of raw materials and loss of production and quality arising out of the inexperienced new employee.

Safety while maintenance

135

(b) Indirect loss includes the following: 1. The government has to incur more cost to employ more number of factory inspectors to check accidents and spend more on the employee’s health insurance and other social security benefits. 2. The loss of working hours of the injured worker. 3. The loss of working hours of other employees who assisted the injured worker. 4. The loss due to the cost incurred on the machine or tools that might have been damaged and/or the cost incurred on the spoilage of material because of the accident.

9.4

Cause of accidents

To prevent accidents, one should examine how they are caused and what the causes are and then take appropriate actions to eliminate the identified causes. Two major factors can give rise to accidents 1. Unsafe mechanical and physical conditions The biggest reason for the accident is defective equipments, tools, materials, etc. These can be termed “Technical causes”. They arise when there are 1. 2. 3. 4.

improper or inadequate safety guards on machines; when improper personal protection equipment is installed; when mechanical designs of machine are defective and unsafe; when control devices, which have been installed to make the operation of machines safe and accident free, are lacking or defective; 5. when there is an absence of proper maintenance and supervision of these devices. 2. Unsafe actions Unsafe actions may be the result of lack of awareness or knowledge about the right practices or lack of skill on the part of a worker. Quite often, however, wrong attitude is the main reason: even workers with the good knowledge ‘take chances’ or ‘take it easy’ and do not follow the correct practices. Below are some of the ignorance practices followed by the workers: 1. Operating without authority, 2. Failing to secure equipments, or warning other employees of possible danger,

136 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Modern approach to maintenance in spinning

Failing to use safe attire or personal protective equipment, Throwing materials on the floor carelessly, Operating or working at unsafe speed, either too fast or too slow, Making safety devices inoperative by removing, adjusting and disconnecting them, Using unsafe equipments, or using equipments unsafely, Using unsafe procedures in loading and placing, Taking unsafe positions under suspended loads, Lifting improperly, Carelessly cleaning, adjusting, oiling, repairing and moving an hazardous equipment, Distracting, teasing, abusing, startling, quarrelling and daydreaming horseplay.

9.5

How to prevent accidents?

9.5.1

Training

Training and retraining of employees to follow ‘safety’ guidelines has been traditionally recommended as a means for improving safety performance. Investigations into most of the accidents – which took place on the shop floor, irrespective of whether they arise out of unsafe physical working, prevailing conditions or actions of person – reveal underlying causes which relate to inadequacy of lack of training. Needs for safety training program are (a) Training activities indirectly demonstrate company’s interest in employees. This leads to good human relations at work. (b) Gaining knowledge and skill helps to improve perceptions and hence improves safety performance. (c) Training saves the time spent by the supervisor to instruct and correct. (d) Training helps to change the attitudes of persons.

9.5.2

Motivating

By motivating the employee we can reduce accidents in a mill. Reward and disciplinary applications are two simple methods for motivating the workers to follow safety guidelines for self, others and equipments.

9.5.3

Habits of safety

Despite all the safety measures adopted by far, the best and the most successful method is the creation of habits to follow safety guidelines. Such habits can be developed through training and other similar methods.

Safety while maintenance

9.5.4

137

Personal factors

Some of the personal factors responsible for accidents in a mill are 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Underage Ill-health Lack of knowledge and skill Improper attitude towards work Fatigue Carelessness and recklessness Emotional instability, e.g. jealousy Mental worries Improper use of safety devices Working at unsafe places Improper use of tools

9.5.5

Safe workplace layout

Although most of the accidents take place because of unsafe acts of the employees, the role of the workplace layout cannot be ignored in determining the cause of accident. To prevent accidents, the layout should be such that every employee has enough space to move and operate. Passageways between working places, roads, tracks and alleys (narrow passage way), etc., must never be obstructed. Worker operating on the machine should have easy access to the safety switches provided on the machine/near workplace. Windows should be of adequate dimensions in order to make full use of natural daylight.

9.5.6

Working conditions

If accidents are to be prevented, then the working conditions should be improved. The temperature, air purity and humidity of air in the working premises should be as required so that it may not lead to discomfort because these affect directly on the workers health as well as to some machines also.

9.5.7

Proper speed of work

Accidents frequently occur when the work is performed at a speed much greater than the desirable. Therefore, the pace at which the worker is working in a mill should be controlled. Workers should be encouraged to work at such a speed that they can maintain their efficiency and work throughout the day without unnecessary fatigue.

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9.5.8

Illumination

The performance of a worker also depends upon his eye vision and the available illumination level. Good lighting always helps the worker to be more alert and to concentrate, leading to quicker fault detection and to better quality of work. Poor lighting is one of the main causes of accidents in Indian textile mills. A study has shown that about 40% of the accidents can be prevented if the illumination level is increased only by 50 to 100 lux. Good lighting means adequate illumination, uniform lighting, appropriate contrast, no glare and avoidance of flickering and stroboscopic effect. In many cases it has been seen that the mill is equipped with adequate lighting equipments but these are not properly maintained. Dust is accumulated on the tubes and other artificial lighting equipments, and half the light emitted is absorbed by severe dust accumulation. Therefore, regular cleaning is required. Secondly, lighting equipment needs replacement at regular intervals to maintain the planned level of illumination. Table 9.1 gives good value of illumination recommended for spinning mills, which are implemented by all modern mills in India. Table 9.1 Illumination levels for spinning mills (Colour of ceiling should be white)

Area type

Height

Il lumination level

Type of roof

So rti ng ro o m Fi ni shed goods godown Bl ow roo m Preparatory Spinni ng Post spinni ng - I Post spinni ng - I I Yarn conditi oni ng Inspection and packing Humi di ty plant Compressor room Mai nte nan ce ro om Store Waste godown To il ets Drin king wate r Office S. Q.C . D.G. house

4 .3 6.1 4 .3 4.3 4.3 4.3 4.3 4.3 4.3 6.1 4.4 4 .4 4.4 6.1 4.4 4.4 4.4 4 .3 6.1

50 0 10 0 20 0 250 300 300 300 200 300 100 150 20 0 150 – 10 0 10 0 300 30 0 150

AC F AC S AC F AC F AC F AC F AC F AC F AC F R. C. C R. C. C R. C. C R. C. C AC S R. C. C R. C. C R. C. C AC F ACS

9.5.9

Personal protective equipment

The primary goal of every mill management is the total removal of hazards at the source but 100% removal has not been possible. In many situations,

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such as sudden failure of equipments and machineries, and during scheduled preventive maintenance, workers do get exposed to hazards. Under such circumstances, we are left with no alternative but to use personal protective equipments (PPEs). These equipments do not eliminate injury but help to minimize injury. PPE is defined in the Regulations as ‘any equipment (including clothing affording protection against the weather) which is intended to be worn or held by a person at work and which protects him against one or more risks to health or safety’, e.g., safety helmets, gloves, eye protection, high-visibility clothing, safety footwear and safety harnesses. Personal protective equipment must be selected depending upon the following requirements: (a) (b) (c) (d) (e) (f) (g) (h) (i) (j)

Nature of the hazard Severity of the hazard Type of contaminant Concentration of the contaminants Duration or work Location of the contaminated area with respect to a source of respirable air Expected activity of the wearer Operating characteristic and limitations of the equipment Reliability of the equipment Acceptance of the wearer

1. Worker dress Proper working dress is an important factor for safety while working on any machine because many accidents occur owing to loose clothing and/ or hanging sleeves getting caught into the moving parts. Long hair, rings and jewellery items can also get caught and cause accidents while working on the machine. It is always better to have a dress with short sleeves, shirt tucked in, no loose cuff on shirt or trousers. If one has a long hair, one must roll it up or put it under a cap so that it does not get entangled in any machine. 2. Eye and face protection Eyes are exposed to a variety of hazards in a spinning mill. Some of them are (a) Impact of flying particles during chipping, grinding, scaling and other similar operations.

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(b) Dust and mist while cleaning of machines in blowroom, cards and winding, etc. (c) Splashing of liquids such as any adhesive or lubricants. (d) Harmful radiation, glare, reflected light during gas or arc welding and cutting work. Most commonly used equipments for eye protection are gas tight rubber goggles, plastic face shield and welding hand shield.

3. Ear protection Noise has become a major problem in modern mills. Noise not only impairs hearing but also affects the nervous system. Ear protectors fall in two groups: ear plug and ear muff. These, when properly fitted and used, can reduce noise level by 30–40 dB.

Plug

Muff

The severity of noise pollution depends upon the intensity of noise and its duration. High speed machines produce lot of noise which affect working efficiency and may cause deafness if exposed to it for long duration. Noise increases the blood pressure, the heart beats and the breathing rate which may lead to heart disease. Exposure to sound level below 70 dBA can assumed to be safe. Table 9.2 gives exposure limit for noise levels.

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Table 9.2 Exposure limit for noise levels

Sound level (dBA )

Durati on ( h)

90 92 95 97 1 00 1 02 1 05 1 07 1 10 115

8 6 4 3 2 1.5 1 0.75 0.5 0.25

Exposure to sound of more than 115 dBA to unprotected ears is harmful. 4. Head protection Safety helmets provide very good protection to the head from injury from falling bodies, flying objects, electrical shock, etc. Helmets not only protect the head but also protect the neck, the face and the back to same extent. Helmets are made of various materials like reinforced plastic, aluminium alloy, etc. Spinning mills, mainly, use HDPE helmets because of their superior resistance. All such helmets are designed for an impact load of 40 foot pounds. Secondly, protective caps are used to protect the hair from coming in contact with the moving parts of machinery. They also protect the hair from dust, dirt and other undesirable contacts.

5. Hands and arm protection 1. Hand protection is next in priority, since this part of the body is employed in carrying out most of work. Gloves are commonly used as protective equipment. They are generally made of rubber, PVC, leather or cotton canvas. Hand gloves must be used in handling a lubricant, detergent or any thing that can damage the eye or the skin.

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If any of these come in contact with eye or skin, wash immediately the affected part with water as first aid and then get proper medical treatment.

6. Foot protection One must wear shoes with non-skid soles, as foot injuries are mostly caused by falling objects while handling heavy materials, or by puncture from nails or by sharp objects, etc.

7. Respiratory protection One should put on face mask while cleaning dust with compressed air to avoid inhaling of dust particles.

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8. General protection For working at heights of more than 10 ft, one should wear safety belts. Belts are generally made of cotton webbing and leather. Resistance to impact loading on webbing is three or four times greater than leather of the same size. All safety belts should be capable of withstanding a tensile load of 1800 kg without breaking or without causing permanent deformation.

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9.6

Electrical safety

Failure to take precautions against electrical hazards may lead to serious injuries. Statistics show that 15–20% of electrical accidents turn out to be fatal. The most common electrical injuries are shock or burn. Electrical shock is “The flowing of current through a human body”. A person may lose his balance on receiving shock or may be thrown away causing bodily injury. If strong electrical current passes through the heart then the shock may become fatal. Burns are caused when some part of the body comes within the flashing distance of a high voltage current of a short circuit.

9.6.1

Tips on electrical safety

1. Permit only qualified persons to undertake electrical repairs. 2. Do not take short cuts, follow safe procedure. 3. Ensure that extension wire is free from cuts, damaged insulation, kinks or joints. 4. Check that the pins of socket are not loose. 5. Ensure easy access to shut off power supply. 6. Use switches which clearly indicate ON or OFF; and of proper amperage. 7. In case of a short circuit, put off the main switches immediately. 8. While using any portable electrical equipment, ensure that it is properly earthed and there is no leakage of current through the body of the equipment. 9. Disconnect equipment when not in use. 10. Never over load electrical equipment. 11. Do not have any unsafe temporary connections, naked joints/wiring. 12. Do not stand on wet area when using electrical equipment, or don’t use electrical equipment with wet hands. 13. Do not use trial and error methods with electrical circuits. 14. Avoid tampering with fuses. Do not replace a blown fuse until the fault is detected and rectified. 15. Do not use water for extinguishing electrical fire, instead use dry sand, CO2 or DCP extinguishers. 16. Periodically wipe off flies accumulating around the electrical motors to avoid fire. 17. Periodically clean the area around the panel or control box of fibre fly bar to avoid fire.

9.7

House keeping

Excellent house keeping contributes greatly to safety at work and reflects on the work culture of the organization. Indian statistics reveal that 15–

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20% accidents like falling, striking and slipping on the objects are mainly due to poor house keeping. Poor house keeping means objects or equipments lying out of place, improperly stacked material, accumulation of waste and empty containers, dusty windows–walls and dirty floors. Good house keeping can be achieved by proper planning. This includes a wellplanned process layout, orderly arrangement of equipments, systematic material storage and systematic waste disposal coupled with day-to-day maintenance of clean and neat work place. All levels of personnel in maintenance have a role to play in ensuring high standards of housekeeping: management in providing the necessary arrangements and assigning responsibilities, workers maintaining order and cleanliness daily at their work locations, and supervisors ensuring that the non-complying workers are not allowed to get away with sloppy practices. Care should be taken of the following aspects. 1. All floor/working surfaces should be even and free from dust and wastes of any kind. 2. All floor openings are adequately filled and/or kept secured by covered or guarded with rails.

3. All trenches/pits are free from accumulation of rubbish. 4. Parts must be washed in a water proof tray so that the floor is not stained, thus reducing the possibility of persons from slipping and/ or falling. There must be a schedule for periodic floor cleaning.

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5. There must always be a clear and safe access to switches, fire extinguishers and emergency exits. 6. Power cables and air inlet piping should be installed in a proper way so that falling of person by striking/entangling with them is avoided.

7. All tools must be kept in racks in an arranged state to prevent accidental falling.

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1. All platforms, work benches and seats must be in good condition: no uneven surfaces, sharp protrusions, etc. should exist. 2. All trays provided for work must be regularly cleaned. 3. Material must be piled and stacked in containers or on racks. 4. All scrap must be collected in containers which are located at convenient places.

Scrap

5. There must be a schedule for disposal of waste from the workplace/ workshops. It must be cleared at least once a week.

9.8

Workshop/workplace

Workshop is a place where a maintenance worker performs different tasks for a long period of time. It must be designed based on the reach, the size, the muscle strength and the visual capabilities of those who are there to work. The dimensions should be so chosen that any unnecessary job stress is eliminated, and productive work increases.

9.9

Machine guarding

The main aim of guarding is to prevent workers coming in contact with dangerous and moving parts of machines. Today, most machines manufacturers provide good safety and provide guards in the machines to prevent accidents. But in many cases, fitters and technicians bypass the safety precautions provided by the manufacturers. They think that they can thus reduce maintenance cost, or keep the machine running while repairing it, etc. Everyone must understand that safety devices are not at all a hindrance to production but are a good help to do certain operations without any fatal accidents.

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Following conditions are considered while designing machine guards: 1. To provide complete protection, and to make danger zones inaccessible. 2. Not to unnecessarily interfere in the production processes. 3. Not to cause discomfort or inconvenience to the operator. 4. Not to constitute a hazard by itself. The supervisor/senior fitter/foreman must ensure that the guards provided by manufacturers are used properly all the time.

9.10

Methods and procedure

The methods and procedures according to which various routine activities are carried out in the course of industrial work are covered here.

9.10.1 Safety in material handling Accidents like fracture, back pain, slip disc, strains and sprains are the typical cases of injuries which occur due to poor way of material handling. About 25–40% of industrial accidents are caused during material handling activity. Therefore, there is a great need to improve material handling and re-handling techniques for better efficiency and higher productivity. Safe methods have been identified that are helpful for shop floor workers and to workers involved in loading and unloading, where lifting and laying down of heavy objects is involved. 1. Place your feet correctly 25–30 cm apart close to the load with one foot ahead of the other in the direction of movement. This position

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helps to give a good balance and a wide enough base to perform the lift.

2. Bend knees, keep back straight and tighten your stomach muscles to help support your back. A straight back keeps the spine, the back muscles and other organs of human body in right alignment. Keep the load close to body. Place your arm and elbows into the side of body.

3. Get a good hold on the object, i.e. take a firm grip on the object using palm and not the finger tips. The fingers and hands should be extended around the object you are going to lift.

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4. Hold the chin up so that spine remains in straight position. Avoid bending your head down, up, forward, back, side-ways or in twisted position.

5. Lift the load by straightening the leg by giving an upward thrust, and reverse the process while lowering the load.

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6. If the weight exceeds 20 kg, always lift jointly by two or three persons, as the volume or shape so require.

9.11

Safety in shifting material

1. Before starting the work always check the machine or equipment to make sure that they are functioning properly. 2. Never stand between the wall and the load during transportation.

3. While transporting material from one place to another, never lift it more than 200 mm from the floor surface. 4. Always fix the load with a rope or any other means so that it prevents the load from falling during transportation.

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5. When carrying a load with hand, pilot truck or hand trolley, always push it and never pull it. 6. While inserting wooden block under the load, never place fingertips between the load and the floor.

7. While lifting the material with rope, please ensure the rope is in good condition.

Rope is breaking at this point

9.12

Safety while unpacking and cleaning

1. Any received new spare part is always coated with rust preventive oil. Take care while carrying such part to avoid slippage from hand.

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2. When washing parts in kerosene, make sure to put a tray underneath to prevent the floor from staining.

3. Carefully handle unpacked boxes, fixtures such as metal plate, steel bands and nails. Do not step on them or touch them carelessly so as to avoid injury.

9.13

Precautions for handling machine under maintenance

The safety precautions, which need to be taken whenever any machine is under maintenance, are listed here. (a) Keep the machine, under maintenance, switched off and put some safety caution plate that says ‘the machine is under maintenance’. This plate must be removed after the work is completed.

Machine under maintenance (a) Select location for placing the dismantled parts and ensure good passage area so as not to obstruct the operators of other machines. (b) Select and inspect the tools suitable for the specific job. (c) Never place a tool or any other object on the machine frame. (d) Use proper tools and personal protective equipments. (e) Use proper ladder for operation. Never try any work which is out of range, i.e. never try to do any work by stretching the hands fully, instead use ladder.

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(e) Never place any part of the body under the item of work while ducting or piping. (f) Put a gauze mask or wear safety goggles in the work shop or maintenance shop while grinding or brazing. (g) Never stain the floor with oil or grease to prevent accidents by slipping. (h) Clear away all bolts, tools, other objects, around the machine frame before re-starting the machine. (i) Confirm tightening of all bolts, etc., of the machine, and that the safety cover, etc., is re-installed. (j) Never start the machine without signalling to other members of operating team and without obtaining or getting the return signal.

9.14

Precautions during spinning operation

1. Do not touch the running portion of any machine.

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2. Never open or remove safety covers of running machines. 3. Do not wear loose clothing – loose jackets, long sleeves, etc. 4. Never put any tool, scissors or comb, etc., in an open-type chest pocket to avoid any chance of falling on a running machine while cleaning, etc. 5. Never try to remove yarn or fly from any rotating part.

9.15

Safety tags

These tags are a temporary means of warning all the persons of an existing hazard till appropriate measure has been adopted to eliminate the hazard. Tags must be printed in the language so that the majority of workers can read and understand.

Machine under maintenance (a) Exhibit the above tag before starting the maintenance work. (b) Shut off the power supply as a precautionary measure before commencing maintenance work. (c) Take all the necessary precautions to guard against any hazard, existing or likely to occur. (d) Remove the tag when maintenance work is completed before starting the machine.

Machine under maintenance (e) Use one of the plates depending upon whether machine is out of order or under maintenance.

References 1. PANDEY D., Industrial Health and Safety. 2. Roving Frame Instruction Manual FL-16, Toyada Automatic Loom Works (1997), Toyada FL 100 Roving Frame Instruction Manual (2001), seventh ed.

156 3. 4. 5.

6. 7. 8. 9. 10. 11. 12. 13. 14.

Modern approach to maintenance in spinning Two for One Twister for Spun Yarn PRN –140-LW Instruction Manual. Toyada Fl –16 Roving Frame Instruction Manual. Texmaco Zinser Ringframe Instruction Manual (1969), reprinted in 1973. Zinser Speedframe 660 Instruction Manual (1990), Zinser Drawframe 720 Instruction Manual (1990), Zinser Ringframe 321 Instruction Manual (1990). High Speed Simplex Fly Frame Instruction Manual (1993), RME Howa Machinery Limited. Drawframe Cherry DX–500–E2 Instruction Manual, Drawframe Cherry D– 400 MT Instruction Manual. Savio Orion Instruction Manual (2001), manual code 11645.0004.1/0 revision index:01. Two for One Twister Instruction Manual, Leewha LW 560 SA. Operating Instruction for the High Production Card C1/3 (1987), Lakshmi Machine Works Ltd. Rieter Unifloc A11 Instruction Manual (2000), Ringframe G33 Instruction Manual (2001), CardC-61 Instruction Manual (2002). Murata Process Coner 21-C Instruction Manual (2002), Murata Machconer / Linkconer No. 7 Instruction Manual (1988). Schlaforst Autoconer 338 Instruction Manual (2003). Trutzschler Card DK 903 Instruction Manual (1999). PRERNA LEEWHA .

10 Lubricants

10.1

Types of lubricants

In all types of machines, resistance is offered when one moving surface slides over the other. Such resistance offered to any movement is called friction. Due to this friction, a large amount of energy in the form of heat is dissipated. This heat damages the machine parts and results in welding of two parts. The above bad effect can be reduced by using a thin layer of substance between two moving surfaces. Any substance which is used to reduce the frictional resistance between two moving parts is called lubricant. The process or technique employed to reduce wear of one or both surfaces in close proximity and/or moving relative to each another by interposing a substance called lubricant between the surfaces to carry the load (pressure generated) between the opposing surfaces is called lubrication. The interposed lubricant film can be a solid, (e.g. graphite, MoS 2), a solid–liquid dispersion, a liquid, a liquid–liquid dispersion (e.g., greases).

10.1.1 Boundary lubrication This type of lubrication occurs when a complete fluid film does not develop between two rubbing surfaces, and the film thickness may be reduced to permit the contact between friction surfaces at micro asperities. In this kind of lubrication, the thickness of lubricating film between two moving surfaces is so thin that it cannot stay there for long time. This condition occurs due to low viscosity lubricant as compared to high temperature. High friction and heat generation result when two surface move with or against each other. This heat generation further results in welding of two metals. The most common example of boundary lubrication is on a bearing which normally operates at the principle of fluid film lubrication but experiences boundary lubrication at the stopping and starting of the equipment. The most common boundary lubricants are probably greases. Greases are so widely used because they have the most desirable properties of a boundary lubricant. They not only shear easily but also flow. They

157

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also dissipate heat easily; form a protective barrier for the surfaces, preventing dust, dirt, and corrosive agents from harming the surfaces. Boundary Lubrication Direction of load movement

Lubricant Film

Direction of load movement Lunricating film is too thin to provide total surface separation. Contact between surface asperities occur 10.1 Boundary lubrication

10.1.2 Hydrodynamic lubrication When a thick lubricating film is applied between two moving surfaces, causing complete separation of two surfaces such that there is no contact and less friction, it is called hydrodynamic lubrication. This thick lubricant film prevents direct surface-to-surface contact so that the friction can be reduced to great extent to prevent wear and tear. The small friction would Hydrodynamic Lubrication Direction of Load movement

Lubricating Film

Direction of Load Movement Lubricating film separate the surfaces hence there is no metal to metal contact 10.2 Hydrodynamic lubrication

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remain only due to the internal resistance between the particles of the lubricant moving over each other. In such a system, friction depends on the thickness and viscosity of the lubricant and on the relative velocity and area of the moving/sliding surfaces; the co-efficient of friction is as low as 0.002–0.03 for fluid film lubricated system. The most common method of lubrication of sleeve bearing is hydrodynamic method. When two surfaces of bearing and shaft move rapidly relative to one another then the oil is carried along the shaft to fill the gap between shaft and bearing. When the moving components become separated completely by a cohesive film of lubricant, hydrodynamic lubrication occurs. Hydrodynamic lubrication prevents wear as there is no metallic contact between the two surfaces.

10.1.3 Elasto hydrodynamic lubrication This type of lubrication is implemented when the bearings are under heavy load and when the balls roll along the raceway at the point of load. The ball is deflected and flattened slightly (elastic deformation). It may be due to the lubricant that would be forced away from the point of contact and the surface would be in direct contact with the other, and also viscosity increased dramatically. When the ball passes the point of load, it returns to its original shape and viscosity returns to original condition. Rolling Element

Lubricant

Lubricant

race area Direction of race movement Area of defromation 10.3 Elasto hydrodynamic lubrication

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10.2

Functions of lubricant

Functions of lubricants are as follows: 1. It reduces the maintenance and running cost of the machine. 2. It reduces unsmooth relative motion of the moving surfaces. 3. It reduces the loss of energy in the form of heat, i.e. it acts as a coolant. 4. It reduces waste of energy, so that the efficiency of machine can be increased. 5. It reduces surface deformation by avoiding the direct contact between the moving surfaces. 6. It reduces the expansion of metals by local frictional heat. 7. Some times, it also acts as a seal, preventing the entry of dust and moisture between the moving surfaces. 8. It minimizes corrosion. Lubricants are broadly classified into three categories: liquid lubricants, semisolid lubricants and solid lubricants.

10.3

Liquid lubricants

Oils of different kind are commonly used as liquid lubricants. Use of oil minimizes the friction and wear by providing a thin layer of continuos fluid film between the moving or sliding surfaces of a machine. They also act as a cooling medium and as a sealing agent. Oil keeps the parts clean, reduce formation of deposits and dissipation of heat, and eliminate corrosion. Liquid lubricants are further classified depending on the origin: animal, vegetable or mineral oil. In early days, only animal and vegetable oils were used as lubricants.

10.3.1 Animal and vegetable oil Animal and vegetable oils are glycosides of higher fatty acids. They have very good oiliness. However, they are costly, undergo oxidation very easily, and have a tendency to hydrolyze when contact with moist air or water. These oils undergo decomposition on heating without distilling, and hence they are called “fixed oils”. They are used as additives to improve the oiliness of petroleum oils. Some of the commonly used vegetable oils are olive oil, palm oil and coconut oil. Most common animal oils used as lubricants are tallow oil and neal foot oil.

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10.3.2 Petroleum oil The foremost amongst mineral oil is the petroleum oil. It is obtained by fractional distillation of crude petroleum oil. The length of the hydrocarbon chain varies from C12 to C50. It is inexpensive and is available in abundance. But this oil contains lot of impurities, like wax, asphalt, etc., which prevent it from being used as single oil. No single oil possesses all the properties needed to be a good lubricant. In order to use petroleum oil as a good lubricant, some additives must be added to obtain certain desirable properties. Such oils containing additives are called blended oils. Blended petroleum oils are further classified depending upon their constituent hydrocarbon chain. Any petroleum happens to be mixture of paraffin (CnH2n+2), naphthalene (CnH2n) and aromatics (CnH2n-6). The presence of aromatics is undesirable. So industrially used petroleum oils mainly consist of paraffin and naphthalene types of hydrocarbons. Depending upon the major constituents, the lubricating oil is called either paraffinic oil or naphthalenic oil. A comparison of these two types of lubricant is given in Table 10.1. Table 10.1 Paraffinic oil versus Naphthenic lube oil

Paraffi n (C n H 2n+2 )

Naphthal eni c ( C n H 2n )

Less prone to oxidation Vi scosi ty i ndex is hi gh High pour point due to presence of wax * Poor sol vency characteri stics Appl icati on Used mostly as a lubricant and as an industrial oil

More prone to oxi dati on Vi scosi ty i ndex is low Low pour point High sol vency characteri stics Used as refrigerator, and transformer oil

* Render to use it to low temperature.

10.3.3 Lubricating oil Lubricating oil is the base oil with high paraffin content and additives blended together under controlled conditions. The proportion of the base oil ranges from 75 to 100%, while that of the additives ranges from 0 to 25%.

10.3.4 Synthetic oil Mineral oils cannot be used effectively as they tend to get oxidized at very high temperature, while wax separation will occur at very low temperature,

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so synthetic lubricants have been developed, which can meet the severe operating conditions such as in aircraft engines. The same lubricants may have to be in the temperature range –50–250 °C. Polyglycol ethers, fluoro and chloro hydrocarbons, organophosphates and silicones are the most common base fluids used for synthetic lubricants.

10.3.5 Additives Any substance that is added to oil in order to improve the lubricating properties of the oil is called an additive. Additives are chemical compounds added to lubricating oils to impart specific properties to the finished oils. Some additives impart new and useful properties to the lubricant; some enhance properties already present, while some act to reduce the rate at which undesirable changes take place in the product during its service life. (a) Pour point depressants Certain high molecular weight polymers function by inhibiting the formation of a wax crystal structure that would prevent oil flow at low temperatures. Two general types of pour point depressants are used. (i) Alkylaromatic polymers adsorb on the wax crystals as they form, preventing them from growing and adhering to each other. (ii) Polymethacrylates co-crystallize with wax to prevent crystal growth. The additives do not entirely prevent wax crystal growth, but rather lower the temperature at which a rigid structure is formed. (b) Viscosity index improvers Viscosity Index (VI) improvers are long chain, high molecular weight polymers that function by causing the relative viscosity of an oil to increase more at high temperatures than at low temperatures. Generally this result is due to a change in the polymer’s physical configuration with increasing temperature of the mixture. It is postulated that in cold oil the molecules of the polymer adopt a coiled form so that their effect on viscosity is minimized. In hot oil, the molecules tend to straighten out, and the interaction between these long molecules and the oil produces a proportionally greater thickening effect. Among the principal VI improvers are methacrylate polymers and copolymers, acrylate polymers, olefin polymers and copolymers, and styrene butadiene copolymers.

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(c) Defoamants The ability of oils to resist foaming varies considerably depending on type of crude oil, type and degree of refining, and viscosity. In many applications, there may be considerable tendency to agitate the oil and cause foaming, while in other cases even small amounts of foam can be extremely troublesome. In these cases, a defoamant may be added to the oil. Silicone polymers used at a few parts per million are the most widely used defoamants. (d) Oxidation inhibitors When oil is heated in the presence of air, oxidation occurs. As a result of this oxidation, both the oil viscosity and the concentration of organic acids in the oil increase, and varnish and lacquer deposits may form on hot metal surfaces exposed to the oil. In extreme cases, these deposits may be further oxidized to form hard, carbonaceous materials. Two general types of oxidation inhibitors are used: those that react with the initiators, peroxy radicals, and hydroperoxides to form inactive compounds, and those that decompose these materials to form less reactive compounds. (e) Rust and corrosion inhibitors Corrosion can occur due to organic acids that develop in the oil itself and due to contaminants that are picked up and carried by the oil. Rust inhibitors are usually compounds having a high polar attraction toward metal surfaces. By physical or chemical interaction at the metal surface, they form a continuous film that prevents water from reaching the metal surface. Typical materials used for this purpose are amine succinates and alkaline earth sulfonates. (f) Antiwear Additives Antiwear additives are used in many lubricating oils to reduce friction, wear, and scuffing and scoring. Fatty oils, acids and esters are mixed with lubricating oil to reduce the friction. (g) Extreme pressure additives At high temperatures or under heavy loads, compounds called extreme pressure (EP) additives are required to reduce friction, control wear and prevent severe surface damage. These materials function by chemically reacting with the sliding metal surfaces to form relatively oil-insoluble surface films.

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Extreme pressure agents are usually compounds containing sulphur, chlorine or phosphorus, either alone or in combination. The compounds used depend on the end use of the lubricant and the chemical activity required in it. Sulphur compounds, sometimes with chlorine or phosphorus compounds, are used in many metal-cutting fluids. Sulfur–phosphorus combinations are used in most industrial and automotive gear lubricants. These materials provide excellent protection against gear tooth scuffing and have the advantages of better oxidation stability, lower corrosivity, and often lower friction.

10.3.6 Properties of liquid lubricant (a) Pour point It is the lowest temperature expressed as a multiple of 3°C at which the oil is observed to flow, when cooled and examined under prescribed condition. (b) Cloud point It is the temperature expressed as a multiple of 1°C at which a cloud or haze of wax crystals appears at the bottom when oil is cooled under prescribed condition. (c) Kinematic viscosity It is a measure of flowing characteristics of a fluid, caused by the force of gravity. Kinematic viscosity may be defined as the force per unit area required to maintain a unit velocity gradient (velocity difference of one unit in the liquid layer which are unit distance apart). The unit of velocity is stroke. The kinematic viscosity of fluid is measured in centistroke and it is measured at 40°C. Viscosity is the single most important property of lubricating oil, as it is the main determinant of the operating characteristic of lubricating oil. If the viscosity is too low then a liquid film cannot be maintained between two moving surfaces, which could result in high wear of parts. (d) Viscosity index The viscosity of every fluid decreases with increase in temperature. Lubricating oil becomes thinner as the operating temperature increases. Viscosity index is an arbitrary number indicating the effect of change of temperature on the kinematic viscosity of oil. A high viscosity index signifies relatively small change of kinematic viscosity with temperature.

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(e) Flash and fire point Flash point is the lowest temperature at which a lubricant gives off enough vapour that ignites for a moment when a small flame is brought near it. Fire point is the lowest temperature at which vapour of oil burns continuously for at least 10 s when a tiny flame is brought near it. All lubricants have a flash point above 180°C, and the fire point is 5–40°C above the flash point for different lubricants. (f) Carbon residue It is the amount of carbon residue left after evaporation and pyrolysis of oil; so it signifies the coke forming tendency of oil. (g) Aniline point It is defined as “the minimum equilibrium solution temperature for equal volume of aniline and oil sample”. A lower aniline point of oil means a higher percentage of aromatic hydrocarbons in it. Aromatic hydrocarbons have a tendency to dissolve natural rubber and certain types of synthetic rubbers. Thus, good lubricating oil should have high aniline point. Aniline point gives an indication of the possible deterioration of oil in contact with rubber sealing, packing, etc. Aromatic hydrocarbons have a tendency to dissolve natural rubber and certain types of synthetic rubbers. Consequently, low aromatic content in the lubricants is desirable. (h) Neutralization number Lubricating oil’s acidity or alkalinity is determined in terms of neutralization number. Comparing the total acid number and total base number with the values of a new oil will indicate the development of harmful products or the effect of additive depletion. If acid number is greater, the oil is usually taken as an indication of oxidation of the oil.

10.3.7 ISO VG classification of industrial oils This classification indicates lubricant viscosity in centistokes at 40°C. The higher the grade and the more the viscous, thicker will be the flow of oil. Viscosity grade 2 3 5 7

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Modern approach to maintenance in spinning

10 15 22 32 46 ⇐mean oil viscosity within 41.4–51.2 CST at 40°C 68 100 150 220 320 460 680 1000 1500

10.4

Semisolid lubricants

Semisolid lubricant is also known as grease. Grease is used in the machines where frequent lubrication is not possible. The conditions under which grease is the preferred lubricant are as follows: (1) Where leakage and drippage is present (2) In hard-to-reach places, where lubricant circulation is impractical (3) Where sealing is required in a high-contaminant environment (i.e., water and air particles) (4) To protect metal surfaces from rust and corrosion (5) To lubricate machines that are operated intermittently (6) To suspend solid additives such as molybdenum disulphide during slow-speed, high-load sliding conditions (7) For use in sealed-for-life applications such as electric motors (8) To lubricate under extreme or special operating conditions (9) To lubricate badly worn machines (10) Where noise reduction is important

10.4.1 Composition of grease Grease is a semisolid lubricant obtained by thickening lubricating oil with the addition of a metallic soap. It is used where the temperature and the speeds are not high and in sealing arrangements where oil does not offer satisfactory results. Grease consists of a dispersion of soap in lubricating oil. By varying the quantity and quality of soap, oil and additives, it is possible to produce greases for a wide variety of applications. Hence grease is manufactured by the combination of three components: oil, thickener and additive.

Lubricants

167

Composition of grease (a) Base oil Generally, mineral oil is used for the manufacture of grease in industries. The viscosity of oil used depends upon the application of grease. Synthetic oil is used as base oil when grease is used for high temperature applications. (b) Thickener The thickener, such as metallic soap, is used in the grease. Most commonly used metallic soaps are calcium, sodium and lithium. (i) Calcium grease These greases do not dissolve in water but cannot be used at a temperature above 60°C. These greases also provide a protection against salt water. (ii) Sodium grease These are not water-resistant as these are soluble in water and can be used at a temperature above 150°C. (iii) Lithium grease Their ability is to adhere to metal, and their stability at high temperature is excellent. These greases are used in wet conditions where the temperature is too high for calcium grease. (iv) Synthetic-based grease These consist of synthetic lubricating oil such as polymer alpha-olefins, ester and silicon. They do not oxidise as rapidly as the mineral oils to which the various thickeners such as lithium soap are added. These greases are often used where the temperature is -7°C. (c) Additives These are added to the grease to improve the properties like oxidation, rust inhibitors, pour-point depressants, extreme pressure additives, antiwear additives, etc.; molybdenum disulphide and graphite may also be added to grease to improve the load-carrying capacity.

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Modern approach to maintenance in spinning Thickener

Based oil

Additives 0-10%

Additive Thickener 0-15%

Base oil 80-90%

10.4 Composition of grease.

10.4.2 How grease works? The structure of lubricating grease is like a sponge with all pores filled with water. The soap is a gelling agent that imparts interconnected structure with cavities filled with oil. In almost 90% of cases, the thickener is a metallic soap. Under operation, heat gets produced in greased bearing due to friction between parts, which in turn results in a rise in temperature of the grease. Due to this rise in temperature, the oil bleeds from the soap cavities and reduces the friction between two parts. The rate of release is called the bleed rate (or the oil separation rate). Typical oil bleed rates of greases for bearing lubrication are 1–5%.

10.4.3 Grease characteristics The type and quantity of thickener and a viscosity of base oil plays a very important role in determining the characteristics of grease. The following characteristics which affect the performance of grease are given below. (a) Consistency Consistency is defined as the degree to which a plastic material resists deformation under the application of a force. It is defined as the degree of stiffness of grease and depends upon the type and the quantity of the thickener used. It is expressed as NLGI number given by National Lubricating Grease Institute. It is expressed as the depth of penetration in 1/10th of millimetre that a standard cone can penetrate vertically into the sample under standard conditions (load 150 gram and temperature 25°C and time 5 s).

Lubricants

169

Cone

Grease

Cup of Grease

NLGI number

Worked penetration index

000 00 0 1 2 3 4 5 6

445–475 400–430 355–385 310–340 265–295 220–250 175–205 130–160 85–115

(b) Mechanical or structural stability tests The ability of grease to resist changes in consistency during mechanical working is termed its mechanical or structural stability. This is important in most applications because grease that softens excessively as a result of the mechanical shearing encountered during service may begin to leak or get hardened. Leaking of grease or hardening results in the failure of equipment. (c) Oxidation properties Resistance to oxidation is an important characteristic of grease as organic acids usually develop and lubricant becomes acidic in nature; hence, this affects the grease structure causing hardening and softening of grease. Both the oil and fatty constituents in grease oxidise with temperature. Oxidation increases with increase in temperature. (d) Oil separation The resistance of grease to separate the oil from thickener involves certain compromise as bleeding of oil is necessary to perform the lubricating

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Modern approach to maintenance in spinning

function. If the oil separate too readily from the grease then a hard, concentrated soap residue may accumulate which in turn would clog the equipments and prevent the flow of grease. (e) Water resistant The ability of grease to resist water that may splash or impinge directly on a bearing is an important property, especially in case of paper industry. (f) Extreme pressure greases These contain sulphur and phosphorus compounds. They are added to increase the load-carrying capacity of the grease. Viscosity of the base oil is less than 200 mm2 s -1 at 40°C. Their consistency corresponds to 2 on NLGI scale. These greases should not be used at a temperature below 30°C or above 110°C. (g) Compatibility Grease mixing of different greases could result in altering performance or physical properties (incompatibility), which could lead to grease (mixture) that exhibits characteristics inferior to that of grease before mixing. The mixing of incompatible greases will alter properties such as consistency, pump ability, shear stability, oil separation, and oxidation stability. Generally, when two incompatible greases are mixed, the result is a softening, which can lead to increased leakage as well as loss of other performance features.

10.4.4 Operating temperature The consistency and the lubricating capacity of grease depend upon the operating temperature at which it has to function. Therefore grease is further classified into four categories by the temperature ranges in which they can be used. (a) Low-temperature greases These are used when operating temperature or ambient temperature is below 0°C, and used for bearing with light loads. (b) Medium-temperature greases These are used for bearings, which operate at a temperature between –3 to 80°C. The viscosity of the base oil of this grease type ranges from 75 to 200 mm2 s-1 at 40°C, and the consistency is normally 2–3 according to NLGI scale.

Lubricants

171

(c) High-temperature greases These are used when bearings operate at temperatures above 80°C.

10.4.5 Temperature range of different greases The temperature range over which greases can be used depends largely on the type of base oil and thickener as well as additives used to prepare the grease. The lower temperature limit, i.e. the lowest temperature at which the grease allows the bearing to be started up (from the idle, rest position) without difficulty, is largely determined by the base oil and its viscosity. At upper temperature limit, the grease provides good lubrication for the bearing and is governed by the type of thickener used. Grease type

Recommended temperature range

Li thi um base Li thi um compl ex Sodi um base Sodi um complex Cal cium complex base Calcium lime base

–30–110° C –20–140° C –30–180° C –20–140° C –20–130° C –10–60 °C

10.4.6 Re-lubricating interval of grease The re-lubricating interval should be the same as given by supplier of machine if temperature is below 70°C. But if the temperature exceeds 70°C then re-lubricating interval should be reduced to half for each increase of 15°C. It is necessary to lubricate more frequently in applications where there is a risk of heavy contamination and wet environment. Moreover for bearings on vertical shaft, the interval should be reduced to half as compare to the bearing on horizontal shaft.

10.4.7 How much grease should be used? The formula, which determines the quantity of grease to be used, is as follows. G = 0.005 DW where, G = quantity of grease in gm D = outer diameter in mm W = width of bearing in mm.

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10.5

Solid lubricants

Solid lubricants are solids applied to friction surfaces to reduce friction and wear and prevent surface damage. They may be in the form of powders, films or composite materials. They include substances with layered structures such as molybdenum disulfide and graphite. These solid lubricants are highly anisotropic, with weak bonding between particular crystal planes or molecules. Their self-lubrication properties provide low-friction coefficients. Solid lubricant are used where (1) The lubricant film made by oil or grease cannot stay for sufficient time. (2) The operating temperature and load is too high even for semi-solid lubricant. (3) The surrounding atmosphere contains dust or grit particles in large numbers per unit volume and therefore is unacceptable for lubricating with oil and grease. Main methods of application for solid lubricants include the following: (1) They are mixed with fatty acid and fatty oil. (2) Solid lubricants are applied directly to sliding surfaces. The most common solid lubricants are graphite and molybdenum disulphide.

10.5.1 Graphite It consists of a multitude of flat plates, which are held together by weak vander Walls forces, so the force required to shear the crystals parallel to the layers is low. It is used either in powder form or as suspension in oil or in grease. Graphite powder is very soft to touch, is non-inflammable, and does not get oxidized in air below 375°C. In the absence of air, it can function as lubricant at much higher temperatures. . The size of the particle should be 0.2mm. When graphite is dispersed in oil, it is called ‘oildag’, and when graphite is dispersed in water, it is called ‘aquadag’.

10.5.2 Molybdenum disulphide It has a sandwich-like structure: a layer of molybdenum atoms lies between two layers of sulphur atoms. The weak vander Waals forces, acting in between the layers, can be destroyed easily. It possesses very low coefficient of friction and can work at a temperature of 800°C. It can be used in the form of a paste or a fine dry powder or as suspension in oil and grease; its size of particle should be 0.2mm. It is used in the racks of speed frame bobbin rail.

Lubricants

10.6

173

Lubricant used in spinning mill

In the textile machinery used for spinning mill, consideration must be given to three factors while selecting the lubricant: low power consumption, protection against corrosion and resistance against staining of yarn. In all machines a certain amount of power is required to overcome the friction within the lubricating film itself. Friction of this kind is largely a function of the viscosity of the lubricant. To minimize power consumption, it is necessary to use oil with optimum viscosity; which means minimum viscosity that is compatible with satisfactory lubrication and which suits to other considerations such as splashing and oil consumption. Oxidation tends to cause thickening of oil in use. So it is advantageous to use lubricants with high oxidation stability, which would result in less viscosity change as temperature increases. Since the ambient atmosphere is always humid in spinning mills so the lubricant used should be capable of protecting parts from corrosion. Excessive lubrication has to be avoided to reduce chances of staining the fibre material in process. Some staining is unavoidable even with less lubrication. Therefore, oils which can be readily removed by scouring should be used. In case scouring is not to take place in further processing, highly stable colourless oils must be used. The choice of oil to be used for lubricating gears depends mainly on the tooth load and speed of gears. If the tooth load is more and the speed is less, high viscosity oil is desirable. If the speed is more and the tooth load is less, then oil with less viscosity is preferable. Low viscosity oil is preferable over high viscosity oil as it gives better separation from water and other insoluble contaminants and has a less tendency to foam. One can use less viscosity oil with extreme pressure additives when the tooth loading is more. Every one knows that viscosity of oil decreases with increase in temperature. Mineral oil oxidises rapidly above 90°C. At low temperature, paraffin crystallises out of the oil. There is a thumb rule that the service life of oil is 30 years at 30°C and it is reduced to half for each temperature increase of 5°C. Above 100°C synthetic oil should be used.

10.6.1 Application of oil Bearing and gear lubrication Industrial gear may be of the enclosed type or of open type. In the enclosed type, the level of oil is maintained at an optimum level. In the gearbox, teeth of the bottom gear are dipped into the oil and gears are lubricated by means of splash. The oil level should not be too high so as to prevent

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Modern approach to maintenance in spinning

excessive churning of oil which would result in consequent rise in oil temperature and in power loss. The optimum depth to which the bottom gear should be dipped is twice the tooth length: this level is just sufficient for splash lubrication and for minimizing excessive churning. Hand or manual lubrication In this method, the application of lubricating oil is done by hand with an oil can or through oil pumps. The application of lubricant by a hand spray to open gears or to exposed gears is also considered as hand or manual lubrication. Centralized pump In this system, the lubricant, stored in a centralised source or sump, is supplied with pressure with the help of oil pump through system of pipes and metering valves. These valves measure and deliver a precise quantity of lubricant to each individual point of lubrication. Air line oiler and oil mist lubrication Air line oilers are used to deliver a mixture of oil and air in the form of fog or mist. An adjustable feeding device controls the mixture of oil and air. In general, the oil mist lubrication is atomized into a mist of microscopic particles by means of an air stream and this mist is then carried by the air stream through tubings to the different parts requiring lubrication. As the fog strikes the part to be lubricated, the oil content from the mist collects on the surface of the part as a film to be lubricated.

10.6.2 Important points in lubrication 1. Use the proper lubricating agent as required for temperature, load etc and recommended by supplier. 2. Apply it at correct intervals. 3. Apply it in the prescribed quantity. 4. Ensure that it reaches the desired lubricating point. 5. Ensure that lubricating point is in the prefect state. 6. Take care not to mix grease of different base. (When greases of different bases are used, the resulting base some times becomes softer or thicker. If different grease with different base needs to be used, then first drain out the old grease, and then re-lubricate at half the normal interval for the first time then onwards the normal frequency should be resumed.)

Lubricants

175

7. Always lubricate bearings with the recommended grade of grease or oil. (If grease or oil of recommended grade of grease is not available, then always lubricate the bearing with a lower grade grease/oil and shorten the interval of re-lubricating the bearing. 8. Always follow the recommended schedule of re-lubrication given by machine manufacturer. 9. Clean hands while lubricating to avoid any contamination. 10. Clear the grease nipple and the area around the grease nipple while re-lubrication.

10.7

Lubricants handling and storage

Storage of lubricant plays a very important role in the lubrication as everyone knows that contamination can drastically reduce the performance and life of lubricant and components where it is applied. (1) Inside storage It is better that lubricants should be stored inside but with certain precaution (a) The temperature of storage should remain moderate but should not be subjected to wide fluctuation. (b) The storage area should be located far from the industrial contamination like industrial fume and dust. (c) The storage area and tools used for distribution of lubricant should be cleaned as per the cleaning schedule. (d) Labels and markers on the containers and equipments should be properly maintained to avoid cross-contamination and incorrect application. (e) Grease should be kept in the original container until used up and should never be left uncovered or open to avoid contamination. After taking out grease from container the cavities in the grease mass should be levelled off. (f) Storage and use of the container should be done as per FIFO (First In First Out principle). (g) Drums should be stored on wooden planks or in the racks well above the grounds. (h) Wooden paddles should never be used to remove the grease from the drum or the container because of risk of contamination. (2) Storage of grease inside the working area Three types of grease storage problems are most common

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Modern approach to maintenance in spinning

(a) Separation of oil from bulk of grease The tendency of the oil to separate is inherent in the nature of grease. It is aggravated for those greases where there are voids – empty spaces in grease where oil can accumulate. Oil separation also gets aggravated under high temperature storage. (b) Contamination with deburr This problem occurs mostly when grease container are partially used and then stored for long interval before further use. The situation is worsened if the container is stored in an area where there is a high level of airborne particles. If contaminants enter grease, they may be carried in lubricated parts, where they can cause damage. (c) Reaction of grease with atmospheric component This less common phenomenon is usually noted after fairly long storage periods. The most usual observation is oxidation of the surface layer of grease. However, after more time, atmospheric component such as CO2 and water vapour may also react with the components of particular grease formulation. When containers are stored where they are exposed to warm moist air, and then are subjected to cooling, accumulation of water in the grease is possible. (d) Outside storage If the storage is unavoidable, then following precautions should be taken. (i) Ensure that bungs on drum are screwed tightly. (ii) Store the drum in horizontal position, this prevents the seal from drying out and leaking. (iii) Drum stored on the sides should be clear of the ground and preferably rest on the wooden and steel beams. (iv) Drums should be covered preferably with a plastic cover to get them protect from contamination. (vi) Outdoor storage locations should be away from dusty areas. (vii) Smaller package sizes (e.g. pails) should be covered and examined regularly and kept to a minimum to provide a quick turnover. (viii) Lubricating storing place must be “NON-SMOKING AREA”. (e) Handling of lubricant Lubricating oils and greases are generally harmless materials but care

Lubricants

177

should be taken to avoid skin contact and inhalation of oil mist. Some general guidelines for handling lubricating oil and grease are as follows: (i) Fresh oil should be preferably filtered before supplying for lubrication. (ii) If lubricant needs to be transferred from a defective drum, one should always use a recently emptied drum of same grade. (iii) Proper supervision of ‘issuing’ is a must to ensure the delivery of right product. (iv) Never let any drum fall as it may burst at the seam causing contamination/leakage. (v) Use protective equipment to avoid skin contact. In case, quickly remove it if it does get on the skin. Do not use gasoline, kerosene or similar solvents to remove lubricants from the skin as they take the natural oils from the skin and cause dryness. Use only mild soap and warm water or a recommended hand cleaner to remove lubricating oil and grease from the skin. (vi) Clean-up lubricating oil and grease spill immediately, so dispose of them quickly. (f) Shelf-life The properties of lubricating oil will remain intact for 5 years provided they have been kept in protected storage and not exposed to temperature fluctuation. Grease can be stored for 1 year in a protected storage without affecting the lubricating properties.

10.8

Conservation of lubricants

Lubricants need to be conserved simply because of the basic need to use any product efficiently. The annual expenditure of a spinning mill on lubricant forms a substantial part of maintenance budget. Moreover, conservation of it is the best alternative energy source because most of these are petroleum products. Steps for conservation The steps to be taken for lubricant conservation are 1. Selection of right lubricant – Adhere to manufacturer’s recommendations, adhere to oil/grease supplier’s recommendation, and follow the recommended program of lubrication in terms of frequency, etc. 2. Prevention of contamination – (a) Ensure that storage and handling practices are good.

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(b) Do not allow water, fuel, solvents to contaminate the lubricant. (c) Maintain the oil reservoir properly. 3. Avoiding early deterioration during usage – Most of the manufacturers of the machine play safe by giving the early schedule for changing the oil. The ‘quality’ of lubricants in use needs to be tested to develop the most suitable frequency for any specific machine. (a) Take assistance of the oil supplier for sampling and testing. (b) Practice regular sampling of lubricating quality and adjust relubricating schedule accordingly. (c) Avoid mixing lubricants; mixture always deteriorates quickly than expected. 4. Avoid pilferage and leakage – The biggest culprit responsible for excessive consumption is leakage of lubricating oils from containers and gear boxes. Looking for and stopping all leakages is preventive maintenance. Keep the records of receiving and issuing of materials, so that pilferage can be adjusted as ‘excess consumption over expected from schedules’. 5. Extended useful life of lubricants – (a) Monitor the lubrication system through testing samples of lubricants in use and then conduct field trials to verify whether the new cycles, whenever extended on the basis of testing, are appropriate.

10.9

Summary

Conservation of lubricants at low cost (a) (b) (c) (d) (e) (f) (g) (h) (i) (j)

Good storage conditions. Segregation of lubricants, grade wise. Stoppage of all oil leaks. Lubricants adjusted for the right feed. All losses systematically eliminated. No overfilling done. Topping up only when required. Not exposing oil to abnormal temperature. Avoiding oil contamination in service. Find alternate use for used oils.

Conservation of lubricants at high cost (a) Using superior grades. (b) System modification. (c) Purification of used oils.

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179

Table 10.2 Oil and grease grade used in Indian spinning mills Oi l gr a de

Vi s c os ity Cs

L ig h t g e a r h y dr au l ic o i l

6 8±6 . 8

He a v y g ea r o il

L ig h t s p i nd le o il

Vi s co s ity in d ex

M in . fl a sh p oi n t

P o ur p o in t

95

24 0

-6

1 00 ±1 0 1 50 ±1 5 2 20 ±2 0 3 20 ±3 2

90 90 90 90

24 0 23 0 23 0 23 0

-9 -9 -9 -3

1 0±1

90

18 6

-6

2 2±2

90

18 6

-6

A dh e si v e o il

2 20 ±2 2

98

19 2

- 12

Antirust, antifoam additives and adhesive added give less oil consumption due to adhesive properties.

L ig h t E .P . oi l

6 8±6 . 8

90

21 4

-6

1 00 ±1 0 1 50 ±1 5

90 90

21 4 21 4

-6 -6

Th i s i s e x tre m e p re s su re in d us tr ia l g e ar oi ls wh i ch c o n ta in s s cu l pt ur e an d p h os ph o ru s c om p o un d s a nd p os s e s se s be tt er th er mal s ta b i li ty a n d hi g he r o xi d a tio n re s is ta n c e a nd low fo a mi n g te nd e nc y . Pr ov i de ru s t and c or ros i o n p ro tec t io n to m et a l s u rfa c e s. It is us e d fo r e nc l os e d ge a r l u b ric a ti o n f or te mp e ra tu re up to 10 0 °C .

Th i s o i l h as l on g s e rv ic e l if e a n d e x c ell en t l u bri c a ti on c ha ra c te ris t ic s . Th is oi l is b le n d ed wit h a d d itiv e s wh ich en d o w pr op e rti es l ik e a nti ru s t, a n ti fo a m, a n tiox i d an t an d a n ti wea r . Th i s o il is bl e nd e d w ith a dd i tiv e s g i v in g a nt io x id a n t, a n ti w e ar a nd a nti ru s t pr op e rtie s . It i s u se d f or th e lu b ric a ti o n of hi g h s pe e d s p in dl e .

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Modern approach to maintenance in spinning

Table 10.3 Grease

Mul tipurpose grease

E.P. grease

W ork penetra - NL GI ti on at 25 °C scal e

Drop poi nt

R emarks

265295

2

180

220 250

3

180

P ossesses excel lent water resistance, high o xidation stabi li ty, and superior anti ru st properti es.

265295

2

180

Extreme pressure grease is lithium based, prevent welding and seizure of moving parts caused by shock loading and presist water washout.

Table 10.4 Equivalent oil and grease of Indian manufacturers Oi l t yp e

Com pa ny na m e

Light gear and hydraulic oil

Indi a n o il ( I OC )

H in dus t a n P et r ol eum (HP)

Bha r a t P et r ol eum ( B P)

Ind rol C a s tr ol

68± 6.8

S ER V O S Y S TE M 68

EN B L O 68

H Y D RO L 68

H Y S PI N A WS 6 8

100 ±10

S ER V O S Y S TE M 10 0

EN B L O 100

H Y D RO L 10 0

HYSPIN AWS 100

68± 6.8

S ER O M E SH 68

PA R THA N68

AM OC A M 68

AL PH A Z N68

100 ±10

S ER O M E SH 10 0

PA R THA N10 0 AM OC A M 100 AL PH A Z N10 0

150 ±15

S ER O M E SH 15 0

PA R THA N15 0 AM OC A M 150 AL PH A Z N15 0

220 ±20

S ER O M E SH 22 0

PA R THA N22 0 AM OC A M 220 AL PH A Z N22 0

320 ±32

S ER O M E SH 32 0

PAR THA N 320 AM OC A M 320 AL PH A Z N32 0

N LG I 2

S ER V O G E M 2

U TH A N 2

TE X TR O L15

AP - 2

N LG I 3

S ER V O G E M 3

U TH A N- 3

TE X TR O- 22

AP - 3

S ER V O G E M E P 2

U TH A N E P - 2

LAN THA X - 2

EP-2

SERVOWAY220

WAYLUBE220

METAMOL220

MEGNACF2

Gea r oi l

Gr ea se

E. P . g re as e N LG I 2 Ad hes iv e oi l 220±20

E N E RG O L H L P 6 8

E N E RG O L H L P 100

6 8 ± 6. 8

1 0 0 ±1 0

G R- X P 1 5 0

G R- X P 2 2 0

G R- X P 3 2 0

1 5 0 ±1 5

220±20

3 2 0 ±3 2

NLGI2

ENERGOL LS-EP2

E N E RG O L L S - 3

NLGI 3

E.P. Grease

E N E RG O L L S - 2

NLGI 2

G r e ase

G R- X P 6 8

G R- X P 1 0 0

6 8 ± 6. 8

1 0 0 ±1 0

G e a r o il

BP

L i g h t g e ar an d h y d r au l i c o i l

O il t yp e

MOBIL LUX-EP2

MO BI L L U X - 3

MO BI L L U X - 2

632

630

629

627

626

DTE27

DTE26

MO BI L

ALVINAR-EP2

AL V I N A R- 3

AL V I N A R- 2

O M AL A3 2 0

O M AL A2 2 0

O M AL A1 5 0

O M AL A1 0 0

–

TELLUS 100

TELLUS 68

SHE LL

Table 10.5 Equivalent oils and greases of foreign manufacturers

MULIS EP-2

M U L TI S - 3

M U L TI S - 2

C A RT E P E P - 3 2 0 N

C A RT E P E P - 2 2 0

C A RT E P E P - 1 5 0

C A RT E P E P - 1 0 0

C A RT E P E P - 6 8

–

–

T O T AL

C o m p an y n a m e

MULTIFAK EP2

MU L T I F AK 3 0

MU L T I F AK 2 0

ME RO P A – 3 2 0

ME RO P A – 2 2 0

ME RO P A – 1 5 0

ME RO P A – 1 0 0

ME RO P A – 6 8

RA N D O N H D - E 1 0 0

RA N D O N H D C- 6 8

T E X AC O

SPHEEROL EP-2

S P H E E RO L AP - 3

S P H E E RO L AP - 2

AL P H A S P 3 2 0

AL P H A S P 2 2 0

AL P H A S P 1 5 0

AL P H A S P 1 0 0

AL P H A S P 6 8

HYS PIN AWS 100

HYS PIN AWS 68

CA S T RO L

BEACON-EP2

BE A CO N - 3

BE A CO N - 2

S P AT R A N E P 3 2 0

S P AT R A N E P 2 2 0

S P AT R A N E P 1 5 0

S P AT R A N E P 1 0 0

S P AT R A N E P 6 8

NUTO H 100

NUTO H 68

ES SO

Lubricants

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Modern approach to maintenance in spinning

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

11. 12. 13.

Indian Oil catalogue. Castrol catalogue. Hindustan petroleum catalogue. Bharat petroleum catalogue. Operating instruction for ring spinning frames G5/1 by Lakshmi Machine Works Limited Coimbatore, edition May 1996. Comprehensive Hand book on Maintenance by NEERAJ NIJHAWAN. The Lowdown on Lubricants For Rolling Bearings, written by JERRY MCLAIN, SKF USA Inc. Wednesday 01 July 2009. Grease Basics written by RAY THIBAULT, CLS, OMA I & II, Contributing Editor, Wednesday, 01 July 2009. Lubrication Theory by THOMAS YOON. Book on Hydrodynamic Lubrication by YUKIO HORI, DR. Eng. Vice President, Kanazawa Institute of Technology 7-1 Ohgigaoka, Nonoichi, Ishikawa 921-8501, Japan Professor Emeritus, University of Tokyo. Rolling Bearing Lubrication FAG OEM und Handel AG, a company of the FAG Kugelfischer Group. Lubricating Fundamentals by D . M . PIRO and A . A . WESSOL (Exxon Mobil Corporation). Lubricant Handbook 2005 by PETRO CANADA .

11 Belt drive and its maintenance

11.1

Introduction

Belts are used to transmit power from one part to another. The belt drive consists of an endless belt which is wrapped tightly over two pulleys called the driving and the driven pulley mounted on their respective shafts. The motion from the driving pulley is transmitted to the driven pulley by the frictional resistance between belt and the surface of the pulley. There are three most common type of belt drive exist in the industry: 1. Flat belt drive – it works on the principle of frictional engagement on the outer pulley. Belt

Surface of pulley

Flat Belt 11.1 Flat belt drive.

2. V-belt drive – it works on the principal of frictional engagement between the lateral wedge surface of belt profile. V belt

V belt Drive

Wedge surface

11.2 V-belt drive.

3. Timing belt – it gives the positive drive by engaging a gear like teeth with mating gears in the pulley.

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11.3 Timing belt drive.

11.2

Flat belt drives

Flat belt mostly consists of two outer layer made of elastomer called friction cover and two intermediate layers covering the traction layer which absorbs the force extended on the belt when power is transmitted. Friction cover ensures the peripheral force acting on the belt pulley is transmitted to the belt and vice versa. Elastomeric Friction Cover Bonding Agent

Polyamide fabric

Traction or Tension member

11.4 Construction of flat belt.

Advantages 1. Flexibility, shock absorption and efficiency at high speed. 2. It allows long distances between the shaft. 3. Simplicity, low cost smoothness of operation, low maintenance cost long life and noiseless as compared with gear transmission.

11.2.1 Types of flat belt drive (a) Open belt drive In this shaft are arranged parallel and rotate in the same direction. In this drive the centre distance may be large and the tight side of the belt should be on the lower side.

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185

11.5 Open belt drive.

(b) Cross belt drive In this drive the shafts are arranged parallel but rotate in the opposite direction since the belt cross each other there will be too much wear and tear hence only leather belts are used in this drive.

11.6 Crossed belt drive.

(c) Stepped pulley drive This drive is used for stepped changing of angular speed of the driven shaft when the angular speed of the driving shaft is constant. This type of drive is used in rieter drawframe.

11.7 Stepped pulley drive.

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(d) Cone drive This drive is used where speed ratio constantly changes. This drive is used for constantly changing of angular speed of the driven shaft when the angular speed of the driving shaft is constant. This type of drive is used in building motion of speedframe.

11.8 Cone drive.

(e) Compound drive Compound belts are used when power is transmitted from one shaft to another through a number of pulleys.

11.9 Compound drive.

(f) Belt drive with idler pulley A belt drive with idler pulley is used with the shafts arranged parallel and when the open belt drive cannot be used to small angle of contact on the smaller pulley. This type of drive is provided to obtain high velocity ratio when the required belt tension cannot be obtained by other mean.

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187

11.10 Belt drive with idler pulley.

11.2.2 Tolerances for flat belts Belts should be tested for specification by thickness, length and width: the lots received must confirm to be prescribed tolerance given for ready reference. Table 11.1 Belt tolerance in thickness Thickness (mm)

Tolerance (mm)

Leather belts 3.0 3.5 4.0 5.0 6.0 7.0 8.0 9.0

±0.30 ±0.30 ±0.30 ±0.40 ±0.50 ±0.50 ±0.50 ±0.50

Nylon belt 1.5 2.0 2.5 3.0 3.5 4.0

±0.20 ±0.20 ±0.20 ±0.20 ±0.20 ±0.20

Table 11.2 Belt tolerance in length Flat belt length (mm)

Tolerance (mm)

Up to 500 5001000 10012000 20014000 40018000 800116000 More than 16000

±2 ±4 ±8 ±14 ±22 ±34 ±0.2%

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Flat belt width (mm)

Tolerance (mm)

Up to 20 2160 61150 151300 301600 Exceeding 600

±0.5 ±0.9 ±2.0 ±3.0 ±4.0 ±5.0

11.2.3 Installation of flat belts The procedure for installing new flat belt is different from those old belts. (a) New flat belt 1. Before installing the belt, check parallelism of shaft and alignment of pulley and ensure that both are true/OK. 2. Make a mark 1000 mm apart on the un-tensioned belt. In case the centre distance is small make a mark of 500 mm and 200 mm apart. 3. Mount the belt on the pulley. 4. Tension the belt by increasing the distance between the driving and driven pulley till the distance between the measuring marks increases to the value of initial tension. For example if the initial tension was 2.30%, then the distance between the measured mark on un-tensioned belt of 1000 mm should be increased till the it reaches 1023 mm. To verify that tracking of belt is proper give several full turns to pulley and ensure that the belt does not run off.

Belt shifted to one side

11.11 Correct way to install belt.

Running in Center

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189

5. Re-measure the distance, make it correct, (1023 mm in example) if required. (b) Reinstalling an old belt 1. Before relaxing the belt for reinstalling, measure the distance between the existing measuring marks with the help of measuring tape.

11.12 Reinstalling old belt.

2. Completely relax and demount the belt. 3. For reinstalling, mount the belt on, and increase the tension on the belt until originally measured distance between the marks is reached. Caution Never adjust tension of flat belt by feeling at by hand: this method is not at all accurate and would lead to slippage of speed or to over tensioning and consequent faster wear.

11.2.4 Jointing procedure of flat belt (a) Type of belt joint Mostly five types of joints are used in flat belts. In this chapter we are going to explain thermofix which is most commonly used in the spinning industry.

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Thermofix

Flexproof

Quickmelt

Longitudal joining 11.13 Type of joints.

(b) Belt length calculation The belt length is calculated by adding the joint length to the endless length of the belt. Joint lengths for different thickness are given below: Table 11.4 Joint lengths for different thickness Thickness (mm)

Joint length (mm)

0.6 0.9 1.6 1.8 2.4 3.0 3.3 4.0

18 26 58 62 67 77 81 90

(c) Scarifying of splice laps (i) Measured the belt length by placing the steel tape tightly on the belt. Total length L = Endless length+ joint length. (ii) Cut off the belt at an angle 60° by using a grinder to prepare for splicing into an endless belt. The process of making a tapered portion is called scarifying of splice laps.

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191

(iii) Use a double faced adhesive tape to attach the belt end to the cam in such a way that (the 60 degree) cut off edge runs flush with the front end of the cam (Figure 11.2.5c) (iv) Turn the cam in the direction B until it hits the stop. Swing the cam fore and back in the direction A–B during the grinding process. While doing so slowly adjust the eccentric lever in the direction as indicated by the arrow. The splice edge of the belt is forced against the drum until it has become wedge shaped ending in a very thin featheredge as shown in Fig. 11.14.

Cam Emery Paper

11.14 Scarifying of splice laps.

(d) Application of adhesive Apply the adhesive supplied by the manufacturer of the belt on to the two jointing lengths that have been cleaned with trichloroethylene and then dried. (e) Joining two ends in hot press An electrical hot press is used to join the spice laps firmly. (i) Place a heat resistant foil between the lower press platen and belt. (ii) Place both the joint part the splice laps that have been prepared and applied with adhesive in the hot press. Mate the scarified laps on the lower plate and align them before clamping them. (iii) Cover the splice with heat resistant foil and a smooth piece of sheet metal. (iv) Close the press and tighten the nuts. (v) Heat the press till the temperature reaches 100–110°C. (vi) After heating time open the press and remove the splice without bending it and let it cool off keeping it under pressure. (vii) Trimming the edges around splice and the belt is then ready for use.

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Flat Belt placing in the belt jointing machine 11.15 Placing of flat belt.

11.3

Spindle tape

Spindle tapes are essentially flat belts used to drive the spindles on a ringframe and two for one twister. It is made up of fabric layer, nylon fabric and thin rubber cover layer as shown in the figure 11.3b. Fabric layer is used on spindle wharve side so that friction resistance between spindle tape and wharve side is reduced when the knee brake is applied. Fabric later is given special treatment so that it will not catch the fly while running hence helps in the energy saving and reduce maintenance. Rubber covering has a high coefficient of friction and that side is made to run the drum shaft pulley so that high power transmission is ensured and rotation is stabilized.

Drum Shaft Pulley

Jockey pulley 11.16 Spindle tape drive.

Spindle Tape

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193

Fabric layer

Rubber covering

Nylon Fabric

11.17 Construction of spindle tape.

11.3.1 Jointing procedure for spindle tape 1. Check the spindle tape length and correctness of joint length. 2. Connect the press to A.C. mains single phase –220 volts. 3. When the press is getting hot check the temperature with thermometer. It should be between 100 and 130°C.

11.18 Checking the temperature of press.

4. Pass the tape over the tin pulley. 5. Twist the tape (either right hand twist or left hand twist in case of single jockey pulley: no twist is necessary for the double jockey pulley system) as required. 6. Apply a thin film of the joining adhesive supplied by the manufacturer on rubber side of the skived portion. Apply thin coat of fixol Fixol with brush. Dry it for two minutes skieved surface No adhessive

11.19 Applying fixol on rubber side of skeived surface.

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7. Wipe out excess adhesive with a cloth leaving a thin trace of adhesive.

11.20 Wiping excess adhesive.

8. Press the fabric side skived portion on rubber side skieved portion on which the adhesive was applied. 9. Insert the joint portion in the spring plate in the press keeping the rubber side on the top.

11.21 Inserting the joint portion.

10. Close the press and keep the tape for two minutes and then remove it from the press.

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195

11.22 Pressing the joint.

11. Do not pull the tape at the joint portion while it is hot. 12. Projected dry adhesive to be trimmed with scissors evenly.

11.23 Trimming the dry adhesive.

13. Install the tape keeping the rubber side touching the tin roller and white face touching the spindle wharve. 14. Do not give any extra twist to the tape while mounting. 15. Ensure that the tape runs exactly in the centre of tin roller and the jockey pulley and the spindle wharve without touching the spindle lock. * For two-for-one twister the mounting procedure is same but the time is only 5 minute.

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11.3.2 How to ensure long the life of tape? Checklist on stopped machines (i) No spindles should have broken spindle lock. Spindle locks/brakes should be positioned properly so that they do not touch the tapes. (ii) Jockey pulleys should rotate freely without wobbling (change the bearings or provide nylon bushes if they wobble). (iii) Jockey pulley arms/rods should not ‘dance’. If found dancing, provide nylon bushes in the collars. Jockey pulley arms should swing only back and forth – not sideward. Checklist on running the machines (i) Check all jockey pulleys for free rotation. Clean the accumulated fluff. Fall out of tapes occurs mostly due to stuck up, jockey pulleys.

11.24 Accumulated stuff.

(ii) After every doff, ensure that all tapes are in position. If any fall out is seen, remount that tape before restarting.

11.25 Free from unwanted stuff.

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197

(iii) While remounting the rubber face of the tape should not touch the tin roller and the white face should run touching the spindle wharves. (iv) Verify that no tape runs with more twists than needed i.e. single jockey pulley – one twist either right hand or left hand; for double jockey pulley –no twist. (v) Ensure that tapes run exactly in the centre of jockey pulley, tin roller and spindle wharves. (vi) Wherever a tape gets cut, make a note in the register by spindle number and report to the supervisor.

11.4

Flat pulley

Pulleys are used to transmit power from one shaft to another by means of the flat belt. Both the pulleys must be in prefect alignment in order to allow the belt to travel in a line normal to the pulley faces. The pulleys are made of cast iron or pressed steel. Cast iron has good friction characteristic. Pulleys made from pressed steel are lighter than cast iron pulley but in many cases they have low friction resistance, which results in excessive wear. In order to obtain optimal frictional behavior between the flat belt and the pulleys, the pulley surface is designed with roughness Rz25.

11.4.1 Crowning of pulley Flat belts running over cylindrical pulleys quickly wander off the pulleys. To prevent this, at least one pulley is ‘crowned’, machined to a slightly ‘spindle’ shaped profile. When the flat belt on such a pulley is off-center and the pulley rotating, the belt quickly moves up to the largest radius at the top of the crown and stays there. The crown is important to keep the belt ‘tracking’ stable, preventing the belt from ‘walking off ’ the edge of the pulley. A crowned pulley eliminates the need for pulley flanges and belt guide rollers. The flat pulley is made with a rounded rim. The slight convexity is known as crowning. Care must be taken to keep the crowning height at optimum. Excessive crowning would cause intolerable strain on the belt and would shorten its life. The recommended optimum crown height is 0.5 mm per 100 mm of pulley width i.e. 0.5% to 0.75% of pulley width.

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Crowning of Pulley

Pulley Crosssection 11.26 Flat pulley.

11.4.2 Relation of pulley width and diameter to crown

h

11.27 Crowning of pulley. Table 11.5 Diameter to crown ratio of pulley width <250 mm Diameter (mm)

Curvature height h (mm)

40112 125140 160200 200250 250400 400560 560800 8001000* 10001400*

0.3 0.4 0.5 0.6 0.8 1.0 1.2 1.2 1.5

For rim width greater than 250 mm, the height h is 1.5 and 2.0 mm. (i) When the pulley is mounted on horizontal shaft, the big pulley must be crown in shape. If the speed ratio is more than 1:3, then the small pulley can be designed cylindrical (i.e. without crown). (ii) When the pulleys are mounted on vertical shafts then both the pulleys must be crowned shape.

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199

11.4.3 Relation of belt width to pulley width The width of the belt should be always less than that of the pulley. Table 11.6 gives a guideline. WP Wb

11.28 Relation of belt width to pulley width. Table 11.6 Relation of belt width to pulley width

11.5

Pulley width (mm)

75

100

150

200

300

400

Belt width (mm)

70

90

140

175

275

365

V belts

A V belt is required when a machine is driven by a separate motor located very close to the driven pulley. Hence V belts are used to transmit power from one pulley to another when the centre distance between two pulleys is less. These belts are trapezoidal in cross-section and are manufactured endless belts. These belts transmit power owing to wedging action between the belt and V groove in the pulley. The included angle is α/2 = 40°. The more power and load to be transmitted, the more is the number of belts. In such multiple drives all the belts should get stretched at the same rate so that the load is equally distributed on the belts.

11.5.1 Construction of V belts The cover is made of fabric molded with rubber in order to provide strong abrasion resistance on the pulley groove to protect the inner part of the

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belt. The Flexible section: withstands bending stress without fatigue. In the load carrying section, tension member polyester cords ensure the length stability in storage as well as in the drive. It imparts high strength and elongation. In the cushion section, adhesive rubber binds cord firmly and acts as a binding force between topping and base section. The compression section is a special compound to resist compression fatigue and heat there by imparting a longer service life. Flexible Section

b

Load carrying Section

Cushion Section Compression Section

Cover

α 11.29 Cross-section of V belt.

11.5.2 Types of conventional V belts V belts are made of five types A, B, C, D, E as shown in Fig. 11.5.2 a. and their properties are given in Table 11.7.

9/16 (14 mm)

7/16 (11 mm)

11/32 (8 mm)

A

7/8 (22 mm)

21/32 (17 mm)

1/2 (13 mm)

B

C

11.30 Cross-section of conventional V belts

11/4 (32 mm)

11/2 (38 mm) 3/4 (20 mm)

D

1 (24 mm)

E

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201

Table 11.7 Detailed specifications of V belt

Sec- Top Thick- Angle Range tion width ness (mm) (mm)

Length (mm)

Tensile Elon- Recommended strength gation Pitch diameter (kg) at (mm) break %

A B C D E Z

13 17 22 32 38 10

8 11 14 19 25 6

40° 40° 40° 40° 40° 40°

A18-A74 B25-B195 C45-C235 D120-D390 E180 E418

493-4456 678-4996 1199-6101 3127-9985 4664-10709

300 425 806 460 460 200

15 15 15 5 5 15

75 125 200 355 500

11.5.3 Wedge belts These belts are a modified version of the traditional V belts: They have slightly deeper section and narrow cross-section; and are made from rubber and special rubber compound. These belts can transmit greater power than traditional V belts.

10 mm

13 mm

10 mm

8 mm SPZ

16 mm

13 mm

SPA

25 mm

22 mm 18 mm SPC

SPB

11.31 Wedge belt. Table 11.8 Dimension of wedge V belts

Belt type

Top width (mm)

Thickness (mm)

SPZ SPA SPB SPC 8V

10 13 16 22 25

8 10 13 18 23

Recommended pitch diameter (mm) 63 90 160 224 300

23 mm 8V

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11.5.4 Quad power V belt This raw edge high capacity belt transmits more power and handles greater speed ratios with smaller pulleys than other conventional belt. They have raw edge construction. Their molded notches reduce and evenly distributed thermal and bending stress. While their deeper side walls give uniform wedging action.

11.32 Quad power V belt. Table 11.9 Dimension of quad power V belt

Belt type

Width (mm)

Thickness (mm)

Angle

XPZ/3VX XPA XPB/5VX

10 13 16

8 10 13

40° 40° 40°

11.5.5 Double V section belts This construction enables the belt (Fig. 11.33 and Table 11.10) to drive on both sides on serpentine drive. It is available in four categories: Table 11.10 Dimension of double V section belts Belt type

Width (mm)

Thickness (mm)

Angle

AA BB CC

13 17 22

10 14 17

40° 40° 40°

Belt drive and its maintenance

1/2 (12.7 mm)

21/32 (16.5 mm) 13/32 (10.3 mm)

203

7/8 (22.2 mm) 17/32 (13.5 mm)

11/16 (17.6 mm)

11.33 Double V section belts.

11.5.6 V belts for variable speed drives These belts are used on variable speed pulleys. These belts adjust themselves to the pulley groove without difficulty and provide a wide range of speed and speed ratios.

11.34 V Belts for variable speed drives.

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Modern approach to maintenance in spinning Table 11.11 Dimension for V belts for variable speed drives

Type

Top width (mm)

Thickness (mm)

Angle

W16 W20 W25 W31.5 W40 W50 W63

16.6 20.7 25.9 32.6 41.5 51.8 65.3

5 6.5 8 10 13 16 20

24° 26° 26° 26° 28° 28° 30°

11.5.7 How to store V belts? 1. All types of V belts should be stored in a cool and dry place, and should not be subjected to direct sunlight. 2. Avoid placing these belts on the floor and ground in close coils. Hang it on a wall to avoid any possibility of kinking or distortion. 3. Keep the belts away from grease, oil or dirt. 4. Damp storerooms are unsuitable. This leads to mildew formation which affects the belt jacket. 5. V belts should always be without any stress and tension so as to avoid permanent deformation and cracks. 6. Belts can be coiled on shelves or hung on pegs. Avoid sharp bends and stresses that can cause permanent deformation and cracks. Stack belts no higher than 12" to prevent damage to bottom belts. When hanging, coil longer belts to prevent distortion from belt weight. 7. If V belt have been stored for long duration before being taken up for use, then run the V belt without any load for 20–30 minutes. Such free running helps in making the belt flexible again.

11.5.8 Installation of V belt 1. Check the dimension of the groove of the pulley if the belt is to be mounted on a new pulley. All the grooves should be of same dimension.

11.35 Fit V belt with groove.

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205

2. The groove should be free from burr, rust oil dirt and grease. V groove of pulleys wear out in service: so, worn out pulley should be replaced immediately.

Worn out groove

11.36 Worn groove.

3. Too small diameter of pulley causes unnecessary flexing of the belt and may lead to premature bearing failure on the machine. Too Large pulley required more space and cost disadvantages.

11.37 Optimum pulley diameter.

4. If a tension pulley of groove type is being used for tensioning the belt then it must be placed on the inside of belt and closer to larger pulley.

11.38 Positioning of tension pulley.

5. Tensioning pulley diameter must be equal to that of the smaller pulley of the drive. 6. If tension pulley of flat type is to be used then it should be placed on the outside of the belt and at one third of centre distance from the driving pulley.

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11.39 Use of flat tension pulley.

7. Belts should not be subjected to extreme heat and cold. Standard belt sustain temperature between –18 to 70°C without damage. 8. The base plate for the drive should be rigid to prevent variation in the belt tension due to vibration.

11.40 Base plate.

9. The drives should not be totally enclosed. Grill covers should be used for proper air circulation.

11.41 Grill covers.

10. Don’t mix used and new belts on a drive. Used belts will ride lower in the sheave groove due to side wall wear and normal stretch. New belts will ride higher in the sheave, travel faster, and operate at higher tension. Running used and new belts together will overload and damage the new belts. Used belts may be used elsewhere on a light duty drive, or for emergencies. 11. Don’t mix belts from different manufacturers. Because dimensions and constructions vary among manufacturers, running such “mismatched belts” won’t give full service life. 12. Use correct type and cross section belt. Match the correct belt cross section to the corresponding sheave groove — A to A, 3V to 3V, etc. Don’t use a B section belt in a 5V sheave, or vice versa.

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207

11.5.9 Mounting procedure 1. Check the bearings of shafts and pulleys on which the v belts are to be mounted; replace bearing if worn. 2. Ensure perfect alignment of the shafts and the pulleys. Pulleys are not parallel

Shafts are not in correct allignment

Shafts are parallel but pulleys are not alligned Correct installation Both pulleys and shaft are in correct allignment 11.42 Figure Alignment of shafts and pulleys.

Alignment procedure Using a piece of thread or a straight edge, place it along the face of one pulley. If the pulleys are properly aligned, then the string or straight edge will touch all the points

11.43 Correct way of alignment.

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3. Rotate the pulleys slowly and check for wobble and for bent shaft. 4. Never use old and new belts in the same set. This may reduce the life of belts due to unequal tension. 5. Reduce the centre distance or slacken the tension roller so that belt can be mounted without using any force. 6. After mounting the belt, it should be properly tensioned with the procedure described below: (i) Calculate the deflection distance as 16 mm deflection per meter of centre distance.

Upper Ring

Force N

Center Distance

Lower Ring

Deflection mm

Force

deflection 16 mm per meter of center distance

11.44 Defelction.

(ii) (iii) (iv) (v)

(vi) (vii)

Use a proper tool for tensioning the belt. Set the lower marker ring at the desire deflection distance in mm on the scale. Set the upper marker ring against the bottom edge of the top tube. Place the belt tension indicator on the top of the belt at the centre of the span. Apply force at right angle to the belt and deflect it to the point where the lower marker ring is level with the top of adjusting belt. Read off the force value indicated on the top edge of upper marking. Compare this value with that given in the Table 11.12 and adjust the tension till it is equal to the value of force.

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209

Table 11.12 Recommended tensioning force

Belt type

Force required to deflect belt 16 mm per meter of span Small diameter (mm)

Newton

Kgf

SPZ

5695 100140

1320 2025

1.32.0 2.02.5

SPA

80132 140200

2535 3545

2.53.6 3.64.6

SPB

112224 236315

4565 65115

6.68.7 8.711.7

SPC

224355 375560

85115 115150

8.511.5 11.515.0

8V Z A B C D E

335 and above 56100 80140 125200 200400 355600

150200 57.5 1015 2030 4060 70105 132183

11.515.0 0.50.8 1.01.5 2.03.1 4.16.1 7.010.5 13.218.3

11.5.10 Maintenance of V belt 1. In a multiple V drive belt, always replace the set of belts if one or more belt breaks. Replacement of one belt only results in undue stretching of the new belt and which moves with a different velocity. This will reduce the life of new belt. 2. In multiple V drive, putting one or two belts less than the number required, reduces the life of the belt by 30–50%. 3. Check the pulley for wear before putting the belt. 4. When the drives are expected to remain stationary for long period, relax the operational tension. 5. Always give proper tension to the belt and check the belt tension regularly. 6. Do not use sharp tools to mount the belt forcibly. 7. Keep the free from oil and grease and belt dressing lubricant should never be used.

11.5.11 Reason of failure of V belt The major reasons for failure of V belts, as observed in mill practice are given in Table 11.13.

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Table 11.13 Causes and remedy

Problem

Reason

Remedy

Side of the belt is worn

Slippage of the belt due to less tension

Re-tension the belt until the belt stops slipping

Misalignment of pulley

Realign the pulley

Belt slippage causes heat buildup and gradual hardening of rubber base compound

Re-tension to prevent slippage

Poor quality of belt

Good quality belt should be used

Tensioning roller is fitted on the wrong side of the belt

Always placed groove type pulley on the inside of the belt, and flat type pulley on the outside of the belt

Misalignment of pulley

Realign the pulley

Bottom of the belt cracks

Belt turns over and run out

Foreign material in the groove

Remove foreign material

Incorrect pulley groove section or excessive groove wear

Use correct size pulley

Tension is less

Re-tension the belt

Problem

Reason

Remedy

Belt snaps off

Tension is more

Reduce the tension

In multiple V drive less no of belts are used

Mount correct no. of belts

In step pulley drive, groove alignment is wrong

Put the belt in the correct groove in both the pulleys

Extreme shock load

Remove cause of shock loads

Belt coming out of the drive

Align the pulley

Drive misarranged

Realign

Incorrect belt tension

Retention

Overload drive

Redesign drive

Unbalanced pulleys

Use balanced pulleys

Noise

Excessive belt vibration

Insufficient belt on drive

Check drive design and modify

Center distance too long

Reduce center or use inside idler on the slack side

Low belt tension

Re-tension

Unbalanced pulley

Use suitably balanced pulley

High shock loading

Re-design drive

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11.6

211

V pulleys

These are used to transmit full power along with V belts without undue wear. V pulleys must have correct groove dimensions. Other important factors are listed below. 1. V pulleys should be free from porosity or blow holes in the groove faces. 2. Sides of the grooves should be free from burrs. 3. Top corners of all grooves should be rounded. 4. Worn out pulleys should be replaced by new pulleys. 5. Any V pulley smaller than the recommended minimum pitch diameter should not be used. 6. Side wobble and runout should be within tolerances given below: Pulley diameter (mm)

Tolerance mm/m

Up to 500 500 to 1500 Over 1500

1 1.5 2

11.6.1 Pulley groove dimension The specifications for pulley dimensions are shown in Fig. 11.45 a are given in Table 11.14 for V pulley with different cross-section.

FACE WIDTH f

R

w

e A°

D

11.45 V pulley groove dimension.

IP b

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Table 11.14 Specifications for V pulley with different cross-sections

Minimum height of groove above pitch line (b) mm ±0.13

Groove Pulley pitch Groove Minimum cross- diameter angle top width section (mm) (A) of groove W (mm)

Minimum groove depth (D) +0.03, +0.0 (mm)

Center to center of groove (e) +0.15 (mm)

SPZ

UPTO 80 OVER 80

34 38

9.7 9.9

11

12

8

A

UPTO115 OVER 115

34 38

13 13.3

13.8

15

10

11

3.3

SPA

UPT0118 OVER 118

34 38

12.7 12.9

13.75

15

10

11

2.75

B

UPTO 190 OVER 190

34 38

16.6 16.9

17.5

19

12.5

14

4.2

SPB

UPTO 190 OVER 190

34 38

16.1 16.4

17.5

19

12.5

14

3.5

C

UPTO 315 OVER 315

34 38

22.7 22.9

23.8

25.5

17

19

5.7

SPC

UPTO 315 OVER 315

34 38

21.9 22.3

23.8

25.5

17

19

4.8

D

UPTO 475 OVER 475

36 38

32.3 32.6

28

37

24

27

8.1

E

UPTO 360 OVER 360

36 38

38.3 38.6

33

44.5

29

32

9.6

Edge of the pulley to centre of groove (f) ±0.3 (mm)

Pitch width mm (lp) (mm)

8.5

2.0

11.6.2 Adjustable pitch pulley In this type of pulley the pitch diameter of pulley can be adjusted within a limited range. Any adjustment is made only when the pulley is stationary. It allows an adjustment to be made in speed of the driven/driver pulley to suit change in operating condition. (This type of drive is used in the coiler drive of drawframe RSB-1 and comber E60H.This pulley consists of two flanges made of cast iron. The first flange is screwed on to the driving part and has a finely extended boss which carries the adjustable flange. After adjustment, second flange is locked by means of screws.

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213

O.D. Dia

Max P.C. Dia.

Min P.C. Dia.

11.46 Construction of adjustable pitch pulley.

11.7

Timing belts

Timing belt is basically flat belt with a series of evenly spaced on the inside circumstances, there by combining the advantage of the flat belt with the positive grip feature of chain and gears drives. These belts are used where positive drive is required. A timing belt is constructed with gear like teeth to engage with mating teeth in the timing pulley giving or a perfectly synchronous speed drive. Such belts are used for power transmission or to interchange rotary motion and linear motion, where either high loads or maintaining a specific drive ratio are important. A timing belt does not stretch or slip; consequently, transmits power at constant angular velocity with an efficiency of 97–99%. It requires no lubrication and is quieter than gear and chain drive.

11.47 Timing pulley drive.

1. The positive drive characteristics provide exact synchronization eliminating speed loss inherent in other belt drives. There is no chordal rise or fall of pitch line as in case of roller chain hence no belt creep and slippage. 2. They allow positive drive characteristics at speeds much higher than those common to most chain drives.

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3. When properly designed and installed, timing belt drives are less critical to tension maintenance than V or flat belt drives due to the positive drive characteristics and high modulus, low stretch tensile cord used in their construction. 4. They need no lubrication or oil encasement. 5. Their thinner cross-sections reduce heat generation induced through bending stresses. 6. The positive engagement of belt teeth in pulley grooves makes synchronous belt drives less critical than V or flat belts to inadvertent exposure to drive lubricants such as oil or water, although extended exposure will result in premature belt degradation. 7. They are quieter than most chain drives. Construction of typical timing belt is shown in Figure 11.7b. Tensile member are made of fiberglass cord provided at the pitch line to impart high tensile strength and resistance to elongation. The pitch remains same it does not depend upon the thickness of backing. The backing is a durable flexible sheet made from neoprene binding the tensile member. The teeth are molded with neoprene rubber having good shear resistance. Tough wear nylon fabric for the tooth facing gives low coefficient of friction needed for smooth interaction with the toothed pulley.

Backing

Teeth

Tensile

Tooth Facing

11.48 Construction of timing belt.

11.7.1 Tensioning rollers A timing belt requires tension rollers (also called jockey pulley to give tension in the loose side of the timing belt. Jockey pulleys are required to compensate for length difference to tension the timing belt and to increase the angle of contact. They reduce the service life of timing belt because they bend the belts at the point of contact. Tension rollers are either internal tensioning roller or external tensioning roller depending upon their placement in relation to the belt inside or outside respectively (Figure 11.7.1).

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215

Loose Belt portion Loose Belt portion

External Tensioning Roller Internal Tension Roller 11.49 Tensioning rollers. Table 11.15 Details of tensioning rollers

Internal

External

Placed closer to the larger pulley to avoid decrease of angle of contact of smaller pulley. The diameter of jockey pulley is equal to or greater than the smaller pulley.

Placed closer to the smaller pulley in order to increase the area of contact of smaller pulley. Jockey pulley diameter is at least 1.25 times the smaller pulley.

11.7.2 Conventional timing belts These types of timing belts have trapezoidal tooth form and can transmit power up to 150 KW and peripheral speed up to 80 m/s. Six standard series are commonly used (Table 11.16). Table 11.16 Dimension of conventional timing belt

Service

Designation

Pitch

T (mm)

B (mm)

0.51 1.27 1.91 2.29 6.35 9.53

1.14 2.3 3.5 4 11.4 15.2

(inch) Mini extra light Extra light Light Heavy Extra heavy Double extra heavy

MXL XL L H XH XXH

2/25" 1/5" 3/8" 1/2" 7/8" 5/4"

These belts are designated by their length, pitch and width. The length is shown in the first part of the belt designation. The pitch length is given in tenths of an inch. Example: 300L075 means 300/10 = 30 inches pitch length. The pitch is the distance between the centre of one tooth to the center of another teeth in inches measured at pitch line. It is designated by the second part

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Modern approach to maintenance in spinning

of the belt designation. In the above example belt is with 3/8” pitch. The width is showed in the last part of designation in hundredths of inches. The belt in the example is 75/100= 0.75 inch wide. The number of groove, pitch and width are used in designating the timing pulley. The only way of determining the pulley size is the no of groove corresponding to the number of teeth on a gear or sprocket. This is shown in the first part of the pulley designation. Example: 20L075, this is a pulley with 20 grooves. The pitch and the width are designated in the same way as that of the belt.

11.7.3 High torque timing belt These belts have a curvilinear tooth form which gives a more distribution of shear stresses within a tooth, (Figure 11.50) and better transition of tooth load to the tensile member in the belt.

11.50 High torque timing belt.

There are five standard series. Table 11.17 Dimension of timing belt

Service

Pitch (mm)

T (mm)

B (mm)

Width * (mm)

3M 5M 8M 14M 20M

3 5 8 14 20

1.2 2.1 3.4 6 8.4

2.4 3.8 6 10 13.2

6,9,15 9,15,25 20,30,50,85 40,55,85,115,170 115,170,230,290

* Standard widths available commercially

These belts are designated by Length, pitch and width. The pitch length in mm is shown in the first part of belt designation. Example: In 1440-8M-20, here a 1440 mm pitch length. Pitch is the distance between the centres of one teeth to the center of another teeth in millimeter measured at pitch line. It is shown in the second part of designation. 8M means pitch is 8 mm. Width is shown in the last or the third f the designation 20 mm. The pulleys are specified by the number of grooves, pitch and width.

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217

The only way to determine the pulley size is to specify the numbers of groove in the pulley. Example: 30-8M-20 This is the pulley with 30 grooves, pitch of 8 mm and width 20 mm.

11.7.4 Twin power This belt possesses the double and directly opposite teeth. It can transmit up to 100% load from either side of the belt alternately. It can transmit the load on both sides provided the sum of the load does not exceed the maximum capacity. It is available in XL, L, H, 5M, 8M and 14M Pitches. It is designated as TP150 L075; here TP means – Twin Power L is the pitch i.e. 3/6 inch and width is 0.75 means 3/4 inch.

11.51 Conventional series twin belt. Table 11.18 Dimensions of conventional series

Type

Pitch (inch)

W (mm)

T (mm)

XL L H

1/5 3/8 1/2

0.508 0.762 1.372

1.27 1.91 2.29

11.52 High torque twin series Table 11.19 Dimensions of high torque twin series

Type

Pitch (mm)

W (mm)

T (mm)

5M 8M 14M

5 8 14

1.143 1.372 2.774

2.1 3.45 6.02

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Modern approach to maintenance in spinning

11.7.5 Polyurethane synchro power belt It is made of tough polyurethane compound of consistent quality. It consists of steel tensile members. It is resistant to oils, ozone and abrasion. It can function in wide temperature ranges form –30 to 80°C. It is made in three standard series.

B

11.53 Teeth of polyurethane synchro power belt. Table 11.20 Dimensions of Polyurethane synchro power belt

Belt type

Pitch (mm)

B (mm)

W (mm)

Width (mm)

T2.5 T5 T10

2.5 5 10

1.3 2.2 4.5

0.7 1.2 2.5

4,6,8,10,12 6,8,10,12,16,20,25 10,12,16,20,25,32,50

Width, pitch and length designate the belt. Example – PU 25T5-200 PU means polyurethane 25 mm, represent widthT5 represent 5 mm pitch, whereas 200 gives the length in mm.

11.7.6 Double-sided polyurethane belt These belts are available in two series. T B

11.54 Teeth of double-sided polyurethane belt. Table 11.21 Dimensions of double-sided polyurethane belt

Belt type

Pitch (mm)

T5DL T10DL

5 10

B (mm) 3.4 7

T (mm)

Width (mm)

1.2 2.5

6,8,10,12,16,20,25,32 10,12,16,20,25,32,50

Belt drive and its maintenance

219

11.7.7 RPP polyurethane belt The parabolic profile of the belt results in a very low interference between belt and pulley during meshing. It has an angle of pressure that increases from the base to the top of tooth.

Parabolic Shape 11.55 Teeth of RPP Polyurethane Belt. P

H1

H

11.56 Dimensions of RPP Belt. Table 11.22 Dimensions of RPP belt

P H H1 Standard Width mm

RPP5

RPP8

RPP14

5 3.8 2.0 10, 15, 20, 25, 50, 85, 100, 150

8 5.5 3.2 10, 15, 20, 25, 50, 85, 100, 150

14 10a 6 10, 15, 20, 25, 50, 85, 100, 150

11.7.8 Installation of a timing belt 1. The teeth should be free from burr, rust oil dirt and grease. 2. If using a tension pulley of teeth type for tensioning the belt then it must be placed on the inside of the belt and closer to the larger pulley. 3. If using a tension pulley of flat type, then it must be placed on the outside of the belt and at one third of center distance from the driving pulley. 4. Provision should be made for adjustment of drive centre distance to allow for the installation of the belt around the pulley. Mounting 1. Check the bearings of the shaft and the pulley on which timing belt is to be mounted.

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Modern approach to maintenance in spinning

2. Ensure perfect alignment of the shaft and pulley by using a piece of string or a straight edge to touch the pulley. If the pulleys are properly aligned, then the string or the straight edge will touch all the points indicated in figure (refer Figure 5.3.9b). If the pulley is not properly aligned rapid belt wear will occur due to misalignment.

11.57 Pulley alignment allowance. Table 11.23 Dimensions of Pulley alignment

Belt width Allowance Degree è

10 mm 1/200 17

20 mm 1/400 9

Over 30 mm 1/600 6

3. Rotate each pulley slowly and check for wobble and or bent shaft. 4. Never forced the belt over the pulley flanges because internal belt damage will be caused. 5. Tensioned the belt properly by applying a force F in Newton at midspan to deflect the belt at a distance related to the length of centre distance i.e. 20 mm per meter of span length. S d F

S = Centre distance, d = deflection, F = force in Newton 11.58 Proper tensioning of timing belt. Table 11.24 Dimensions of tensioning

Belt

Force N

L050 L075 L100 H075 H100 H150 H200 H300

2.7 4.3 6.1 11 15.6 24.3 33.4 52.3

Belt drive and its maintenance

221

11.7.9 Maintenance 1. A Timing belt must be cleaned by wiping with rag slightly dampened with a light, non volatile solvent. 2. Never sand and or scrap the belt with a sharp object to remove grease or deburr. 3. Never push the timing belt on the disc with undue force or pull the timing belt hard over the rim of the tension roller. Loosen the tension roller sufficiently to ensure the installation of belt without any force.

11.7.10 How to store timing belts? 1. Belts should be stored in a cool and dry place and should not be subjected to direct sunlight. 2. The belts should be kept away from grease, oil or dirt. 3. Damp storerooms are unsuitable. This leads to mildew formation which affects the belt jacket 4. Belts should be stored in the original packing without any sharp bend and crimping which would damage the belt.

11.7.11 Causes and remedy Table 11.25 Causes and remedy for belts

Problem Broken Belt

Cause

Remedy

• •

• •

• • •

Under-designed drive Sharp bend cause tensile cord damage Belt was forced on the drive Foreign object in the drive Belt rub on to the pulley flange

• •

Redesign drive Follow proper installation guide lines Shield drive Align pulley

Excessive side wall wear

• •

Misaligned centers Bent flange

• •

Aligned drive Straighten flange

Cracks in Belt Backing

•

High temperature

• •

Remove heat source Improve ventilation

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Modern approach to maintenance in spinning

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

15. 16. 17.

OPTI belt catalogue. ESCON v belts catalogue. Rofolex belt catalogue. Fenner belt catalogue. Habashit belt catalogue, edition April 1996. Siegleing belt catalogue. Nitta belt catalogue. Simta spindle tape catalogue. Elgitex belt catalogue. A Text Book of Machine Design by DR . P . C . SHARMA and DR . D. K. AGARWAL. Proper Installation and Maintenance Can Prolong the Life of V-Belts by JOHN C . ROBERTSON , maintenance reliability specialist. Timing belt from Wikipedia. V belt and timing belt installation and maintenance by BANDO. GatesFacts™ Technical Information Library (Gates Compass™ Power Transmission CD-ROM version 1). The Gates Rubber Company Denver, Colorado USA. Basics of belt drive by JOSEPH L. FOSZCZ, Senior Editor, Plant Engineering Magazine – Plant Engineering. Take the right steps to ensure proper drive belt alignment By DAN PARSONS, Senior Project Engineer, Gates Corp., Denver — Plant Engineering, 6/1/2006. Comprehensive Hand Book on Spinning Maintenance Part-3 by NEERAJ NIJHAWAN.

Steel wire and chain

223

12 Steel wire and chain

12.1

Steel wire rope

Wire rope is metal in its strongest form. It consists of a group of strands laid helically around a core. The strands of a wire rope or cable consist of a number of individual wires laid about a central wire. These ropes are used when a large amount of power has to be transmitted over long distance from one pulley to another, to guide, to tie down, to hold back, to counterbalance, to lift the parts, etc. The wire ropes run on grooved pulleys but they rest on the bottom of the groove and do not wedge between the sides of groove. In spinning industry they are used in can changers, blendomat for counter balancing the arm and speedframe cone drum area.

12.2

Construction

Wire rope is composed of wires, strands and a core. Wire rope is composed of wires, strands and a core. Wire cores are made in two different forms. Core Wire Center wire

Strand

Wire

12.1 Construction of wire.

223

224

Modern approach to maintenance in spinning

The most commonly used is a wire rope of suitable size to serve as a core. It is called as independent wire rope core (IWRC). The other type of wire core is a wire strand structure (WSC or SC). This consists of multiplewire strand and may have the same construction as the main rope strands. A wire rope is made of strands and each strand is made up from one or more layers of wires. The number of strands means the number of group of wires laid over the central core (Fig. 12.1).

12.3

Design of wire

Various types of wire rope have been designed to meet a wide range of uses and operating conditions. These types are designated by the kind of core; the number of strands; the number, sizes and arrangement of the wires in each strand; and the way in which the wires and strands are wound, or laid, about each other. The standard constructions of rope fall into four general classifications: 6 × 7, 6 × 19, 6 × 37 and 8 × 19. In a numerical classification of rope construction, the first number is the number of strands; the second is the number of wires in a strand.

6×7

6 × 19

12.2 Designation of rope.

For example 6 × 19 refer Fig. 12.2 mean that wire rope is made of 6 strands and each strand is made of 19 wires. Table 12.1 Most common type of steel wire ropes used in the industry Wire type

Nominal diameter (mm)

6×7

8, 9, 10.11, 12, 13, 14, 16, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 31, 35 8, 9, 1013, 14, 16, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 31, 36, 38 8, 9, 1013, 14, 16, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 31, 36, 38 8, 9, 1013, 14, 16, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 31, 36, 38, 40, 44, 48, 52, 58

6 × 19 6 × 17 6 × 37 8 × 19

8, 9, 1013, 14, 16, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29

29, 35, 35, 35,

Steel wire and chain

12.4

225

Classification of steel wire ropes

The classification of ropes depends on the direction of twist of individual wires in the strand and that of the strands relative to each other. In regular lay ropes the direction of twist of the wires in the strand is opposite to the direction of the twist of strand. Ropes with regular lay are easy to handle and have greater resistance to crushing than those with lang lay. In lang lay rope the direction of twist of the wire in the strand is same as that the direction of the twist of the strand. In composite-type of rope the wires in two adjacent strands are twisted in opposite direction. It results in more resistance to same direction; more resistance to abrasive wear and bending fatigue; easier abrasive wear and bending fatigue; easier to kink and untwist, more difficult to kink and untwist, more difficult to handle. Right Regular lay

Left Regular lay

Right lang lay

Left lang lay

12.3 Design of wires.

12.5

Measuring wire rope

Normally, manufacturers of wire keep the diameter of wire slightly more than nominal diameter. The maximum tolerance is up to 4% as when ropes are put in to the service, wire diameter slightly reduces due to load. Rope diameter are always measured across the larger dimension from the outer limit of the strand never across the flat.

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Modern approach to maintenance in spinning

Wrong

Right 12.4 Measurement of rope.

12.6

Wire pulley or sheave

Wire rope can be damaged due to the sharp bend so the diameter of sheave plays an important role in determining the life of wire. The thumb rule is that the diameter of sheave should not be less than 20 times the diameter of wire. On new equipment too small groove of the sheave pinch and bind the rope causing excessive abrasion and fatigue. Too large pulley will not fully support and guide the rope.

Sheave Groove Matches Rope

Sheave Groove Sheave Groove too Small too Large

12.5 Adjustment of sheave groove.

12.7

Lubrication

The role of the wire rope lubricant is to reduce scuffing wear on the outer strands and sheaves, lubricate the rubbing between strands and importantly to protect against corrosion. Lubrication plays a very important part in the life of wire. Most of the ropes are lubricated during manufacture but after putting into the service they loose their lubrication with time. While wire ropes passes around sheaves and drums rubbing take place between wire and pulley. The smaller the sheave diameter and multiple sheaves mean the greater the wire adjusting movement and the more rapid that rubbing and fatigue wear may occur. Fatigue life of ropes can also be greatly extended by proper lubrication, when the wires can move freely to equalize

Steel wire and chain

227

stress distribution caused by sheaves or drums. Finally, lubricant must reach fibre cores or they will absorb moisture and encourage corrosion from the centre. It is better to use NLGI 00 semi-fluid grease is a tacky, water resistant, semi-fluid lubricant that penetrates all wire rope strands ensuring smooth operation and extended cable life.

12.8

Reason for failure of wire

Wire fails due to the following reasons 1. Fatigue A wire rope subjected to repetitive bending over a sheave will develop cracks in individual wires with time. Broken wires develop primarily in sections that move over sheaves. Once breaks are developed one must replace the wire.

12.6 Valley break.

2. Abrasion Abrasion is one of the most common destructive conditions affecting wire rope. It usually occurs on drums and sheaves or whenever rope rubs against itself or other material. Abrasion also occurs internally in the wire whenever wire rope is loaded or bent and it weakens the rope simply by wearing away metal from inside and outside wires. When excessive wear is encountered in an operation, the problem frequently stems from faulty sheave alignment, incorrect groove diameters, inappropriate fleet angles or improper drum winding.

12.7 Worn out sheave due to abrasion.

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Modern approach to maintenance in spinning

3. Corrosion It usually occurs in the wire due to the lack of lubrication. Corrosion cause discoloration on the wire; it means wire need lubrication. If the wire is running without lubrication for long time, it promotes premature failure of the wire. 4. Diameter reduction Diameter reduction of the wire is caused due to the following reasons: 1. 2. 3. 4. 5.

Excessive abrasion of the outside wires Loss of core diameter/support Internal or external corrosion damage Inner wire failure A lengthening of rope lay

12.9

Chains

Chains give a positive drive like gears. A chain can be used both for short as well as long distances up to 8 m approximately. A chain drive consists of endless chain links running over two sprockets. Advantages of chain drive are as follows: 1. Less load on the shaft as compared to the belt drive, 2. Transmit high efficiency as high as 97–98% when operate under good ideal condition. 3. It is possible to transmit power to more than one shaft with one chain and having a small compact size as compared to flat belt drive. Disadvantages are as follows: 1. Due to wear of chain link joints, the chain gets stretched, and results in a faulty drive. 2. It needs more maintenance than belts. 3. More complicated design, hence high production cost.

12.8 Roller chain.

Steel wire and chain

229

12.10 Construction of chain A chain consists of two rows of inner and outer plates. The outer row of plates is known as pin link or coupling-link whereas the inner row of plates is called roller link. Pins are fitted in the pin link and pass through a bush which is press-fitted into the rollers thus joining them. The chain rollers are mounted on the bushings and then roll over the sprocket during motion. The pins are free inside the bush. The load transmitting capacity of chain wheel depends on the larger pitch and larger sprocket. To avoid longer sprocket chains, sprockets are made in double and triple -strand of width.

Connecting Link

Pin Link

Single Cranked Link

Roller Link

Double Cranked Link

12.9 T ypes of chain link.

12.11 Designation of chain Three dimensions are required to designate a chain: pitch, width and diameter. Pitch is the distance from centre to centre of adjacent pin. Width is the nominal width of the link or length of pin measured within the side plates. Diameter refers to the actual diameter of pin. Pitch

Roller Diameter Width 12.10 Designation of chain.

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Modern approach to maintenance in spinning

12.12 Chain lubrication Unlike the belts and ropes, chains need regular lubrication. The chain drive consists of a series of pins connecting travelling metallic bearings which need proper lubrication. If proper lubrication is not done, the chain gets elongated due to wear. This lengthening of a chain during service results from the wear on pins and the bushing surfaces. Chain also needs lubrication for the following reasons. 1. To cushion impact load, 2. To dissipate heat that gets generated, 3. To flush away any foreign material, 4. To lubricate chain-spocket contact surface, and 5. To retard formation of rust, or corrosion.

12.12.1 Tips for lubricating chain The main objectives of lubrication are to reduce wear between pin and bushes, dissipate heat and prevent corrosion between the mating parts and reduce chain impact with spocket, so care must be taken while selecting the lubricant for chains. 1. If a lubricant has to be effective, it should be applied to the moving parts, pins, bushing rollers, etc. This will help to avoid stretch due to wear occurring between pins and side bars. 2. It is better to lubricate the chain on slack side so that the oil can penetrate ore easily. 3. Too little lubricant applied to the chain cannot adequately provide protection to moving parts while too much is wasteful and causes abrasive material to collect. One must use right quantity of lubricant. 4. The lubricant should be applied at the right time to avoid wear. 5. Immersing of chain in oil bath: Keep one set of chain extra for lubrication. After the period of operation of one year, immerse the chain in oil bath for one day in an oil of viscosity of 150. Clean the spocket chain before immersing it in oil bath. Move the chain for sometime so that oil can spread fully in all the parts. Chain

Oil

12.11 Immersing of chain in lubricant.

Steel wire and chain

231

12.12.2 Qualities desired in lubricant The lubricant should penetrate into the pin and bush area and form a separating wedge film between the pin and bushing in the chain joint. The viscosity of lubricant greatly affects its film strength and its ability to protect the moving parts. The high viscosity of the oil which flows between the chain link plates and fill the pin bushing area, provide the best wear life. Oil should be such that it will minimize the metal to metal contact and also act as cooling medium and minimize impact dampening at higher speeds.

12.13 Chain installation Chain drive installation is relatively simple and good results may be obtained when the following conditions are met: 1. 2.

The roller chain, sprockets and other components are in good condition. The sprockets are properly aligned as misalignment results in uneven loading across the width of the chain and may cause roller link plate and sprocket tooth wear.

12.12 Aligning spocket.

3. 4. 5.

6.

Roller chain should be free of grit and dirt. Wash chain in kerosene before mounting. Provision is made for adequate lubrication. Fit chain around both sprockets and bring the free ends together on one sprocket for connection, the sprocket teeth will locate the chain end links. Install the connecting link cover plate and the spring clip or coffer pins. On larger pitch chains or heavy multiple strand, it may be necessary to lock the sprockets for this operation. When press fit cover plates are used, be careful not to drive the plate on so far as to grip the roller links. Stiff joints can result if this is done. The chain is correctly tensioned.

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Modern approach to maintenance in spinning

12.14 Maintenance of chains All chain drives should receive regular maintenance. Each drive should be inspected after the initial 100 hours of operation. Thereafter, most drives may be inspected at 500 hour intervals. 1. Check lubrication On slow speed drives, where manual lubrication is used, be sure the lubrication schedule is being followed. If the chain is covered with dirt and debris, clean the chain with kerosene and re-lubricate it. 2. Check chain tension Check chain tension and adjust as needed to maintain the proper sag in the slack span. If elongation exceeds the available adjustment, remove two pitches and reconnect the chain. 3. Check chain wear Measure the chain wear elongation; and if elongation exceeds functional limits or is greater than 3%, replace the entire chain; or chain length increases to such an extent that the chain can be raised to half the height of the sprocket teeth. Do not connect a new section of chain to a worn chain because it may run rough and damage the drive. Do not continue to run a chain worn beyond 3% elongation because the chain will not engage the sprockets properly and it may damage the sprockets. 4. Check for sprocket wear Inspect the sprocket teeth for reduced tooth section and hooked tooth tips. If these conditions are present, the sprocket teeth are excessively worn and the sprocket should be replaced.

12.14.1 When to replace the chain The effect of wear on a roller chain is to increase the spacing of the links, causing the chain to grow longer. Note that this is not from any actual stretching of any metal, as too many engineers and mechanics intuitively believe but is due to the effect of wear at the pivoting parts. It could be said that the roller chain loosens with wear. After a long period of running time the pitch of the chain increases uniformly which results in an increase in the length of the chain. It is advisable either to monitor the exact length of a drive chain (the generally accepted rule of thumb is to replace a roller

Steel wire and chain

233

chain which has elongated 3% on an adjustable drive or 1.5% on a fixedcentre drive). The chain then runs over a greater reference cycle. When the chain length increases to such an extent than the chain can be raised to half the height of the sprocket teeth, i.e. when the meshing is reduced to half then the chain needs to be replaced by a new one.

Time to change the Chain

New Chain 12.13 Worn out chain.

12.15 British standard roller chain Simple chain A1

B D1

D2 G h

h

12.14 Dimension of simple chain. Table 12.2 Dimension of simple chain Chain no. Pitch Inside in mm width (h) in mm (B) 04B-1 05B-1 06B-1 08B-1 10B-1 12B-1 16B-1 20B-1 24B-1 28B-1 32B-1 40B-1

06.00 08.00 9.53 12.7 15.88 19.05 25.40 31.75 38.1 44.46 50.80 63.50

2.8 3.0 5.8 7.75 9.65 11.7 17.02 19.6 25.4 27.94 29.21 39.37

Roller diameter in mm (D1) 4.0 5.0 6.35 8.51 10.16 12.07 15.88 19.05 25.40 27.94 29.21 39.37

Pin diameter in mm (D2)

Plate depth gauge in mm (G)

Conn. pin length in mm (A1)

1.85 2.31 3.28 4.45 5.08 5.72 8.28 10.19 14.63 15.90 17.81 22.89

5.0 7.1 8.2 11.8 13.7 16.1 21.0 25.4 32.3 37 42.2 52.9

8.4 8.4 13.4 16.6 19 22.3 35.1 40.5 53.1 65.1 63.6 79

Average breaking load

Approx mass (Kg/m)

3000 4520 9025 18150 22560 29.43 64146 113400 193550 226900 295860 400000

0.123 0.18 0.37 0.7 0.95 1.30 2.9 3.7 7.1 8.6 9.6 15.80

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Duplex chain D2

D1

B A1

E

12.15 Dimension of double chain. Table 12.3 Dimension of double chain Chain no.

Pitch in Inside Roller mm width B diameter mm in mm (D1)

Pin diameter in mm (D2)

05B-2 06B-2 08B-2 10B-2 12B-2 16B-2 20B-2 24B-2 28B-2 32B-2 40B-2

8 9.53 12.7 15.88 19.05 25.40 31.75 38.1 44.46 50.80 63.50

2.31 3.28 4.45 5.08 5.72 8.28 10.19 14.63 15.90 17.81 22.89

3 5.8 7.75 9.65 11.7 17.02 19.6 25.4 27.94 29.21 39.37

5 6.35 8.51 10.16 12.07 15.88 19.05 25.40 27.94 29.21 39.37

Plate depth gauge mm (G) 7.1 8.2 11.8 13.7 16.1 21.0 25.4 32.3 37 42.2 52.9

Conn pin length mm (A1)

Avera- Approx. Tramass verse ge pitch in break- Kg/m mm (E) ing load

17.4 23.1 30.6 35.75 41.8 68 79.7 101.8 124.7 126 154

8000 17660 36300 45125 58860 129500 226900 387300 453800 590850 805300

0.36 0.78 1.4 1.8 2.3 5.3 7.25 13.75 17.3 18.8 29.9

5.64 10.24 13.92 16.59 19.46 31.88 36.45 48.36 59.56 58.55 72.29

Triplex chain D2 D1 B E A1 E

12.16 Dimension of triplex chain.

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Steel wire and chain Table 12.4 Dimension of triplex chain Chain no.

Pitch in Inside mm width in mm (B)

Roller diameter in mm (D1)

Pin diameter in mm (D2)

Plate depth gauge mm (G)

06B-3 08B-3 10B-3 12B-3 16B-3 20B-3 24B-3 28B-3 32B-3 40B-3

9.53 12.7 15.88 19.05 25.40 31.75 38.1 44.46 50.80 63.50

6.35 8.51 10.16 12.07 15.88 19.05 25.40 27.94 29.21 39.37

3.28 4.45 5.08 5.72 8.28 10.19 14.63 15.90 17.81 22.89

8.2 11.8 13.7 16.1 21.0 25.4 32.3 37 42.2 52.9

5.8 7.75 9.65 11.7 17.02 19.6 25.4 27.94 29.21 39.37

Conn Average Approx Traverse pin breaking mass pitch length load kg/m in mm mm (A1) 33 44.6 52.3 61.4 99.9 116.1 150.2 184.6 184.6 227.2

26500 54450 67700 88300 194250 340300 580500 680700 887600 1208000

1.18 2.10 2.60 3.40 7.8 10.85 20.50 25.75 27.95 44.80

10.24 13.92 16.59 19.46 31.88 36.45 48.36 59.56 58.55 72.29

12.16 American standard roller chain Single chain A1

B D2

h

D1

h

12.17 Dimension of single chain. Table 12.5 Dimension of single chain Chain no.

Pitch in mm

Width in mm (B)

Roller diameter in mm (D1) (A1)

Pin diameter in mm (D2)

Plate depth gauge mm (G)

Conn. pin length in mm

35 40 41 50 60 80 100 120 140 160 180 200

9.53 12.7 12.7 15.88 19.05 25.40 31.75 38.1 44.46 50.80 57.15 63.50

4.8 7.9 6.4 9.65 12.7 16 19.05 25.4 25.4 31.8 35.8 38.1

5.08 7.92 7.77 10.16 11.91 15.87 19.05 22.22 25.4 28.58 35.71 39.68

3.59 3.96 5.08 5.94 7.92 9.53 11.10 12.70 14.30 17.46 19.84 22.89

8.3 11.5 13.7 16.2 24 29.6 34.6 42 48.26 53 58 79

12.8 16.3 15 20.45 25.4 33.05 39.9 49.9 53.9 63.9 79.3 78.1

Average breaking load

9300 16400 8900 27200 37800 64500 106500 151000 205000 258000 357000 422800

Approx. mass Kg/m

0.3 .60 .41 1.01 1.40 2.50 3.90 5.50 7.4 9.80 13.50 15.80

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Duplex chain D1

D2

B A1

E

12.18 Dimension of duplex chain.

Table 12.6 Dimension of duplex chain Chain no. Pitch in mm

Inside width in mm (B)

Roller diameter in mm (D1)

Pin diameter in mm (D2)

35-2 40-2 50-2 60-2 80-2 100-2 120-2 140-2 160-2 180-2 200-2

9.53 12.7 15.88 19.05 25.40 31.75 38.1 44.46 50.80 57.15 63.50

4.8 7.9 9.65 12.7 16 19.05 25.4 25.4 31.8 35.8 38.1

5.08 7.92 10.16 11.91 15.87 19.05 22.22 25.4 28.58 35.71 39.68

Plate depth gauge in mm (G) 3.59 3.96 5.08 5.94 7.92 9.53 11.10 12.70 14.30 17.46 19.84

Conn Average Approx. Traverse Traverse pin breaking mass pitch in pitch in length load Kg/m mm (E) mm (E) in mm (A1) 8.3 11.5 13.7 16.2 24 29.6 34.6 42 48.26 53 58

22.9 30.8 38.9 48.3 62.35 75.7 95.3 102.8 122.3 145 149.5

18600 33000 54300 75700 12900 213600 303000 410000 517000 714000 846000

0.74 1.22 13.92 16.59 19.46 31.88 36.45 48.36 59.56 58.55 72.29

10.13 14.38 18.11 22.78 29.29 35.76 45.44 48.87 58.55 65.80 71.55

Triplex chain D2 D1 B E A1 E

12.19 Dimension of triple chain.

Steel wire and chain

237

Table 12.7 Dimension of triplex chain Chain Pitch no. in mm

Inside Width in mm (B)

Roller diameter in mm (D1)

Pin diameter in mm (D2)

Plate depth gauge in mm (G)

Conn Average pin breaking length load in mm (A1)

Approx Traverse mass pitch in Kg/m mm

35-3 40-3 50-3 60-3 80-3 100-3 120-3 140-3 160-3 180-3 200-2

4.8 7.9 9.65 12.7 16 19.05 25.4 25.4 31.8 35.8 38.1

5.08 7.92 10.16 11.91 15.87 19.05 22.22 25.4 28.58 39.68 –

3.59 3.96 5.08 5.94 7.92 9.53 11.10 12.70 14.30 17.46 19.84

8.3 11.5 13.7 16.2 24 29.6 34.6 42 48.26 53 58

33 28000 45.3 49400 57 81500 71 113500 91.8 193600 111.5 320400 140.7 454000 151.6 614000 180.8 774990 210.8 1071252 221 1269400

0.80 1.32 2.10 3.18 5.73 7.86 11.82 14.16 19.50 26.16 32.70

9.53 12.7 15.88 19.05 25.40 31.75 38.1 44.46 50.80 63.50 –

10.13 14.38 18.11 22.78 29.29 35.76 45.44 48.87 58.55 65.80 71.55

12.17 Leaf chain Leaf chains act as balancers between moveable part and counterweight (i.e. to balance the movement of part), or low-speed pulling is required (tension linkage), for example, for balancing the rail movement in speedframe or ring rail. This type of chain is also called balance chain. Normally, two type of chains are provided: AL type and BL type. It is designated by number of plates used in the chain and thickness of plates and pitch of chain. Link Plates

Bearing Pins

Inner Link Plates

Chain Pitch 12.20 Leaf chain.

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Table 12.8 Designation of chain by number of plates Lacing

2×2

4×4

6×6

6×3

3×4

4×6

1. In roller chains, all the link plates have higher fatigue resistance due to the compressive stress of press fits. In leaf chains, only two outer plates are press fit. Therefore, the tensile strength of leaf chains is high, but the maximum allowable tension is low. 2. The more plates used in the lacing, the higher the tensile strength. 3. The pins articulate directly on the plates, and the bearing pressure is very high. The chains need regular lubrication. The use of SAE 30 or 40 machine oil is suggested for most applications. 4. When the chain speed is greater than 30 m/min., or if the chain is cycled more than 1000 times in a day, it will wear very quickly, even with lubrication. In either of these cases, use RS roller chains. 5. AL-type should be used only under the following conditions: I. There are no shock loads. II. Wear is not a big problem. III. Number of cycles is less than 100 a day. Under other conditions, BL-type should be considered.

12.18 Silent chain Silent chains are used in high speed transmission. Silent chains have a very simple construction: only plates and pins. Today’s silent chains are designated by the standard pitch, width, and kilowatt ratings of the chains and sprockets. There are eight different pitches from 9.52 to 50.8 mm.

12.21 Silent chain.

It consists of notch plate, guide plate and pin. The link plate receives tension and has a notch for engaging the sprockets. There is no notch on the guide

Steel wire and chain

239

plate. These plates act as guides for the sprockets. Pins may be round or have other shapes, such as D-shape.

LINK PLATE

GUIDE PLATE

PIN 12.22 Silent chain components.

All of the chain components share the tension. Silent chains have higher capacity than roller chains of the same width. Because the link plates of silent chain strike the sprocket at an angle, the impact and the noise are reduced; this is why these chains are called “silent”. The higher the chain speed, the greater is the difference from roller chains.

12.23 Silent chain strikes the sprocket at an angle, reducing noise.

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Modern approach to maintenance in spinning

Table 12.9 Causes and remedies of chains Problem

Cause

Remedy ●

●

Dirt or foreign material in chain joints Inadequate lubrication

●

Misalignment

●

●

Internal corrosion or rust

●

●

Overload bends pins or spreads roller

●

●

●

Tight Joint

Clean and re-lubricate the chain Replace the chain. Reestablish proper lubrication. Replace sprockets and chain if needed. Realign sprockets. Replace the chain. Eliminate the cause of corrosion or protect the chain. Replace the chain. Eliminate the cause of overload.

Inadequate lubrication

Replace the chain. Re-establish the proper lubrication.

Overload

Replace the chain. Eliminate the cause of overload.

Extreme overload

Replace the chain. Replace the sprockets if indicated. Eliminate the cause of overload or redesign drive for larger pitch chain.

Turned Pins

Enlarged Holes Broken Pins

Broken Link Plates

Broken, Cracked or Deformed Rollers

●

Speed too high

●

●

Sprockets too small

●

●

Chain riding too high on sprocket teeth

●

Replace the chain. Reduce the speed. Replace the chain. Use larger sprockets, or possibly redesign drive for smaller pitch chain. Replace the chain. Retension the chain more often.

References 1. 2. 3. 4. 5.

Mechanical Engineering Design (1989) by JOSEPH EDWARD SHIGLEY. Mechanical Machine Design (1996) by DR . R. C . BEHL and V. K. GOEL. Comprehensive Hand Book on Spinning Maintenance by NEERAJ NIJHAWAN. A Text Book of Machine Design by DR. P . C . SHARMA and DR . D. K. AGARWAL. The Complete Guide to Chain, the Tsubakimoto Chain Co.

Steel wire and chain

241

6. Instruction Manual Connect/Disconnect Instructions for Silent Chain, published by the member companies of the American Chain Association. 7. Renold Leaf Chain catalogue. 8. Connect & Disconnect Instructions for Ansi B29.1 Roller, published by the member companies of the American Chain Association. 9. Roller Chain Drives installation by Maintenance Resources, Inc. 10. Chain Maintenance by Sheldon “Reformed Chain Smoker” Brown. 11. Chain care, wear and skipping, From: Jobst Brandt Date: January 10, 2002, revised November 23, 2004. 12. Renold Chain Troubleshooter by RENOLD. 13. Wire rope catalogue by UNIROPE. 14. Crane Wire Rope Damage and Nondestructive Inspection Methods by HERBERT R . WEISCHEDEL , NDT Technologies, Inc. P.O. Box 637, South Windsor, CT 06074. 15. Extend the wear life of roller chains. Reliable Plant Magazine, 2007. 16. Failure of Wire Rope on Crane by DR DAVID J GRIEVE. 17. Wire Rope information by Stren-Flex.com

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13 Temporary fasteners

13.1

Introduction

Every machine is made up of thousands of parts. Parts are joined together to form a fixed joint. Machine joints are classified as permanent joints and temporary joints or fastening elements. The permanent joint can not be disassembled without destroying the connecting components. Such joints are made at the manufacturing locations. These joints are made by welding, brazing, soldering, riveting and adhesive joints. Since these parts are not involved in the maintenance of machinery, their detailed description is not needed in this book. Temporary fastening allows separation of units without affecting the fastened elements and the connecting components. The different types of temporary fastenings are 1. 2. 3. 4. 5. 6. 7. 8. 9.

Screwed joints washers Locking nuts Keys Tension elements Pins Retaining rings Universal joints Clamp

13.2

Screwed joint

Screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main use is a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. It can also be defined as an inclined plane wrapped around a shaft. A screwed joint is used to connect two parts by using threaded parts composed of one or two elements called the screw or the bolt and the nut. Cutting a helical groove on a cylindrical bar forms a screw thread.

242

Temporary fasteners

243

External thread Male

Internal thread Female 13.1 Screwed joint.

Screw may be right- and left-hand thread depending upon the direction of the helix. A right-hand thread is that which gets tightened into the nut when it rotates in the clockwise direction. A left-hand thread is that which rotates in the anti-clockwise direction while tightening. When L.H. is not written, it is understood that the thread is right handed. Left-handed threads are used ●

● ●

where the rotation of a shaft would cause a conventional right-handed nut to loosen rather than to tighten, e.g. in a ringframe one side bottom roll is provided with left hand and other side is provided with right hand. in combination with right-handed threads in turnbuckles. in some applications of a lead screw, for example the cross slide of a lathe, where it is desirable for the cross-slide to move away from the operator when the lead screw is turned clockwise.

Screws and bolts are made with a wide range of materials, with steel being perhaps the most common, in many varieties. Where great resistance to weather or corrosion is required, stainless steel, titanium, brass, bronze, monel or silicon bronze may be used, or a coating such as brass, zinc or chromium is applied. Screws with a single helical groove are most common and are called single start screws. If two separate helical grooves are formed on a cylindrical bar, the screw is known as double start screw. The number of starts on most threads is one (single start). Multiple starts are used to increase the lead (linear advancement per revolution). In most cases, increasing the number of starts is preferable to increasing the pitch because larger pitches reduce the minor diameter. A small minor diameter decreases the screw stiffness and makes it more difficult to tap nuts because of the likelihood of the tap breaking during tapping. Also, for the same lead,

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Modern approach to maintenance in spinning

increasing the number of starts actually increases the thread contact area when compared to a thread with the same lead but using fewer starts and a coarser pitch. Close examination of the thread will reveal the number of starts. Simply place a pencil or marker pen in the thread groove and rotate the thread one revolution. If the end of the pencil mark is in the adjacent of thread groove, the screw has a single start. If there is one thread between the beginning and the end of the mark, it is a two start thread, two grooves, a three start thread and so on. 0

1

1 Start 0

1

2

2 Start 0

1

2

3

13.2 Different types of multiple threads.

The advantage of the screwed joints are that they are easily assemble/ disassemble, readily available and relatively cheap, since their types and dimensions are standardised. Their major disadvantage is that depending upon load conditions; they may fail due to stress concentration at the threaded portion. The screwed joints are to be used in places where they would be subjected to tensile shear load. No bending of fasteners should be involved or be expected to be minimum. Bending of a screw occurs only due to improper tightening and/or due to misalignment of holes of mating components.

13.2.1 Thread nomenclature A screw or bolt is a specialized application of the inclined plane. The inclined plane, called its thread, is helically disposed around a cylinder or

Temporary fasteners

245

shaft. That thread usually either fits into a corresponding (negative or female) helical thread in a nut, or forms a corresponding helical cut in surrounding softer material as it is inserted. Crest F Pitch

Major dia D

p

Minor dia Dc Pitch dia Dp

Root t

Depth h Thread Angle 13.3 Nomenclature of thread.

1. Crest The top surface of the thread, denoted by F. 2. Root The bottom surface between two adjacent threads, denoted by t. 3. Flank It is the surface between the crest and the root of the thread. 4. Thread angle It is the angle between the flanks measured in axial plane. 5. Depth of thread It is the distance, measured perpendicular to the axis, between the crest and the root. It is denoted by h. 6. Pitch The distance measured axially between two corresponding points on the consecutive threads form along the axial plane, and on the same side of the axis, is known as pitch. P denotes it.

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Modern approach to maintenance in spinning

7. Lead It is the axial distance by which the screw thread advances in one rotation. On single start threads, the pitch and the lead are equal. On double start thread, the lead is double the pitch. 8. Major diameter It is the largest diameter of a screw thread. The screw is specified by this diameter, D. 9. Minor diameter It is the core or root diameter of screw. It is denoted by Dc. 10. Pitch diameter This is the effective diameter at which the ridges on the bolt are in complete mesh with the ridges of the corresponding nut. Dp denotes it.

13.2.2 Designation of Indian Standard thread These threads are designated by the letter M, followed by major diameter and pitch; and the latter two must be separated by the sign X. When there is no mention of pitch, it shall mean that the coarse pitch corresponding to the specified diameter will be used. Three major classes thread namely, fine, medium and coarse, denoted by letter f, m, and c respectively. Table 13.1.2 Series for fine and coarse thread Designation

Pitch (mm)

Minor diameter Bolt (mm)

Nut (mm)

Coarse series M1 M1.1 M1.2 M1.4 M1.6 M1.8 M2 M2.2 M2.5 M3 M3.5 M4 M4.5 M5

0.25 0.25 0.25 0.3 0.35 0.35 0.4 0.45 0.45 0.5 0.6 0.7 0.75 0.8

0.693 0.793 0.893 1.032 1.171 1.371 1.509 1.648 1.948 2.387 2.764 3.141 3.580 4.0-17

0.729 0.829 0.929 1.075 1.221 1.421 1.567 1.713 2.013 2.459 2.850 3.242 3.688 4.134

Temporary fasteners M6 M7 M8 M10 M12 M14 M16 M18 M20

1 1 1 1 1.25 1.5 1.75 2 2

M8x1 M10 x 1.25 M12 x 1.25 M14 x 1.5 M16 x1.5 M18 x1.5 M20 x1.5 M 22 x1.5 M24 x 2 M 26 x 2

1 1.25 1.25 1.5 1.5 1.5 1.5 1.5 2 2

4.773 5.773 6.466 8.160 9.853 11.546 13.546 14.933 16.933

247

4.918 5.18 6.647 8.367 10.106 11.835 13.835 15.294 17.294

Fine Series

13.3

6.7733 8.466 10.466 12.160 14.160 16.160 18.160 20.160 21.546 24.546

6.917 8.647 10.647 12.376 14.376 16.376 18.376 20.376 21.835 24.835

Different types of bolt/screw

I. Through bolt It is made of cylindrical – round bar – with a threaded portion for nut at one end and a head at the other. The components to be joined must have a hole so that they can be clamped together by fastening the nut at the threaded end. The ideal length of the bolt is that in which one or two threads are left after tightening of the nut. Head of bolt

Component 1 and 2

Nut

Thread

13.4 Through bolt.

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Modern approach to maintenance in spinning

II. Stud It is a round bar with threaded portion at both ends. Out of the two components to be joined, one must have a threaded portion tapped to the size of the stud so that one end of the stud is screwed into the part to be fastened while the other receives a nut. These studs are mainly used for screwing cover. Thread

Nut

Component with through hole Component with threading

13.5 Stud.

III. Set screw This is a round bar with a threaded portion throughout the length, with head or without head. A set screw is used to prevent relative motion between two parts by means of pressure on the points exerted by one end of the set screw on a specific point on another surface. This resists any relative motion between the two parts by means of friction between the point of screw, and the point on other parts. Out of the two parts, one part has a threaded portion equal to the size of the hole through which the set screw is threaded. Set screws may be used instead of key or in connection with a key to prevent the axial motion between an assembly and a shaft, or a gear and a shaft.

13.6 Use of set screw.

Temporary fasteners

Slotted

Hexagonal Socket

Cone point

Flat point

Oval point

249

Fluted Socket

Cup point

Full Dog point Half Dog point

13.7 Different types of set screws.

IV. Carriage bolt It is used when it is difficult to fit a tool on the head of the bolt for tightening the nut. This bolt is of cylindrical shape with a threaded portion at one end for taking a nut and a round head which rests on the component to assemble. This part of round bar near the head has a square cross-section to prevent the bolt from turning when the nut is tightened.

Round Head

Square Portion

A nut come on this threaded portion 13.8 Carriage bolt.

V. Tap bolt This kind of bolt passes through a hole at one part and is screwed into a tapped hole at the second part (thus holding the two parts together, it is called a tap bolt).

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Modern approach to maintenance in spinning Head Component with through hole Component with thread

13.9 Tap bolt.

Hexagonal Head

Round Head Flat Head Slotted Slotted

Socket Head Socket Head Fillister Head Hexagonal Fluted Slotted

13.10 Different types of tap bolt.

13.3.1 How to indent various types of bolts and screws The type of bolt and screw, length of the threaded portion, thread size, type of head and point in case of bolt type of unthreaded length should also be given in the indent. L

Thread Size

Type of Head Type of point 13.11 Nomenclature of bolt.

Temporary fasteners

13.4

251

Washer

Washer is a cylindrical piece of metal like a coin with a hole. It is placed between the nut and the head of a screw and the joining part so that tightening force is uniformly distributed on to the part to be joined and prevent the screw head from digging into the joint material. A washer also prevents loosening of bolt and nut because the compressed metal of washer exerts pressure to regain its original shape owing to its strong elasticity. Thus, it acts like a spring and maintains a high friction resistance. Therefore, it is also called spring lock washer. Most commonly used washers as locking device are spring washer and tooth washer. The washer is placed under the nut to be tightened. One edge of the washer is caused to dig itself into the component when the nut is fully tightened. This results in increasing the resistance, and so prevents loosening of the nut.

Flat Type

Screw Cup

Wave Washer

Different Type of Spring Washer

Different Type of Tooth Washer 13.12 Different types of washers.

13.4.1 How to indent various types of washer? We can order the washer by giving the type of washer, its inner and outer diameter and thickness.

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Modern approach to maintenance in spinning

ID OD

Th 13.13 Nomenclature of washer.

13.5

Nut

The primary function of the nut in any threaded assembly is to act as the instrument through which the tension is induced into the bolt or screw and to continue to retain that tension and thus, the clamp load in the assembly. The vast majority of nuts have hexagon drive faces. Correct strength combinations of nuts and bolts will ensure that the nut is capable of tensioning the mating bolt to breaking point rather than the nut stripping.

Hexagonal Nut

Hexagonal Cap Nut

Hexagonal wheel Nut

13.14 Different types of nut.

13.6

Locking device

An adequately tightened nut remains under constant load. But it loosens when subjected to the variable load on machine which results due to machine vibrations. To avoid such loosening, the position of the nut must be secured by using some locking device. The commonly used locking devices are described below:

13.6.1 Chuck nut It is also known as a lock-nut. In this system two nuts are used instead of one. The first one is tightened down by normal force and the second nut is tightened down upon it. Then the upper nut is then tightly held by a spanner and while the lower nut is slightly loosened back against the upper one. Due to this action, the threads in the nuts get wedged tightly against those of bolts.

Temporary fasteners

253

Bolt Upper Nut Lower Nut

13.15 Chuck nut.

13.6.2 Castle nut This is hexagonal nut with upper end as cylindrical portion. This cylindrical portion has a through hole at its centre. When the nut is tightened, its hole matches with the hole provided in the bolt so that a split pin can be inserted in the bolt and nut. Split Pin

Cylindrical Body

13.16 Castle nuts.

13.6.3 Sawn nut It is also called a slotted nut. This nut has a cut on one side and has a small screw on that side.

Small Screw

Slot

13.17 Sawn nut.

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Modern approach to maintenance in spinning

After tightening the nut on the component, the small screw provided on the cut side of the nut is tightened which pulls the slot together and results in pinching the threads thereby generating greater friction between the bolt and the nut.

13.6.4 How to order various type of locking nut? Nut can be ordered by giving the type of nut, height, thread size and head size. F

G

Thread size 13.18 Nomenclature of locking nut.

13.7

Key

A key is a machine element made of mild steel and is used for preventing relative motion between a shaft and a gear or hub of a pulley mounted on it. The key is inserted between the shaft and hub making a joint between the shaft and pulley or gear. A key way is cut on the surface of the shaft equal to half the size of the key, parallel to the axis of shaft, and also in the hub or gear to be mounted. For mounting a hub or a gear, a key is firmly placed in the key-way of the shaft. Then match the key-way of the part to be mounted is matched and the part is slide from one end of the shaft till it is fully engaged with the key-way. After assembly, the key is partly in the shaft and partly in the hub of mating part.

Square or Driving Key Sink Key 13.19 Types of keys.

Wood Ruff Key

Temporary fasteners

255

13.7.1 How to order various types of keys? The order of the key is done by giving height, length and width. L h

w

Driving Key

L h

w

Sunk Key

L w Wood Ruff key h

13.20 Nomenclature of different types of keys.

13.8

Tension element

d

When a key is used for making a joint, the entire load is carried by the key and the key-way cut into the shaft thereby reducing the load carrying capacity of the shaft. The stress concentration near the shaft and reduction in the cross-section of the shaft, (or in other words the reduction in the torsional strength of the shaft) leads to the failure of shaft from key-way. Therefore in case where jerky motions are in use, keys are not to be used. The use of tension element is recommended. With the tension element the whole load is distributed over the shaft. A tension element consists of two parts: male and female.

Female

D

Male

13.21 Tension element.

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Modern approach to maintenance in spinning

Precautions to be taken while mounting are as follows: (1) Both the male and female elements should be cleaned, and coating of mosil should be applied. (2) The direction of placing of each element of each pair must be correct. (3) Only required tightening should be done. (4) The tightening should be checked after three months.

13.9

Pins

They are used in the shaft to secure a rotating element such as a gear and a pulley. Pins are used for axial positioning and for transfer of torque and thrust.

L

O’

P

l P

l

l

Split Pin

Taper with Notches

Dowel Pin

Taper Pin

13.22 Pins.

13.10 Retaining rings It is also called a circlip. A circlip is used where it is difficult to make a shoulder or sleeve on a shaft or a bearing housing to axially position a component on a shaft or in ahousing. A groove is cut in the shaft or in the bore of housing to accommodate a circlip, which is called external and internal circlip, respectively. The taper design of both the internal and the external circlip, or E-ring ensures that a uniform pressure is exerted against the bottom of the groove. F

F Inner Circlip

F Outer Circlip

13.23 Types of retaining rings.

E - ring

Temporary fasteners

257

13.11 Taper lock Taper lock is a convenient way to mount the pulleys/impeller on motor or machine shaft. When taper cut lock is used, the load gets uniformly distributed on the shaft. Taper lock has a round tapered body with a hole at its centre that matches with the shaft diameter on which it is to be mounted. It consists of four to five holes depending up to the size of pulley/ impeller. Out of these four/five holes, one/two is used for dismounting and three are used for mounting.

13.24 Taper lock.

13.11.1 Mounting procedure 1. Clean the tapered lock bore of oil and dirt, insert the lock in the hub of the pulley and check that the hole of the hub and outer diameter of the lock are matching. 2. Place screws loosely in the 3 holes threaded in the hub. 3. Clean the shaft and fit the hub of the pulley to the shaft and position it at the proper place. First step

Insert the lock in the hub of pulley Second Step

Tight the screw with finger 13.25 Mounting procedure.

Third Step

Place the pulley on the shaft Fourth Step

Tighten the pulley on the shaft

258

Modern approach to maintenance in spinning

4. Use an Allen key to tighten the screws gradually and alternately. 5. Fill the empty potion of holes with the grease to prevent entry of dirt and rusting dirt.

13.11.2 Dismounting procedure 1. Slacken all the screws and remove screws depending upon the number of removal hole. 2. Insert the screws in the holes and tighten the screws alternately until the bush is loosened in the hub and the assembly is free on the shaft. 3. Remove the assembly from the shaft.

Removal Holes

Removing a taper lock 13.26 Dismounting procedure.

13.12 Universal joint These joints are used to connect two shafts which have the same angular velocity, and when the two shafts are not on same central lines. The two shafts are misaligned but working angle is up to a maximum of 45°. Universal joint is of two types: single and double.

D

E

E L

13.27 Single universal joint.

B

S

H

Temporary fasteners

259

B

D

E

E C

R

R

L

13.28 Double universal joint.

13.13 Screw hose clamps Screw clamps consist of a band into which a screw thread pattern has been cut or pressed. One end of the band contains a captive screw. The clamp is put around the hose or tube to be connected, with the loose end being fed into a narrow space between the band and the captive screw. When the screw is turned, it acts as a worm drive pulling the threads of the band, causing the band to tighten around the hose (or when screwed the opposite direction, to loosen). Screw clamps are normally used for hoses 1/2 in diameter and up, with other clamps used for smaller hoses.

13.29 Screw hose clamp.

References 1. 2. 3. 4. 5. 6.

Mechanical Engineering Design (1989) by JOSEPH EDWARD SHIGLEY. Mechanical Machine Design (1996) by DR. R . C. BEHL and V. K.GOEL. A Text Book of Machine Design by DR. P. C . SHARMA and DR. D. K. AGARWAL. ANSI screw and Nut Thread size Chart by Engineers Edge. Screw by Wikipedia Wikimedia Foundation, Inc. Screw Thread by Wikipedia Wikimedia Foundation, Inc.

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Modern approach to maintenance in spinning

7. National Bureau of Standards Handbook H28 (1957). See Appendix A. ASA B1.7 Standard on Nomenclature, Definitions and Letter Symbols for Screw Threads. ANSI B1.1 Unified and American Screw Thread Standards. Industrial Fasteners Institute Metric Fasteners Standards, 1976. 8. Screw Thread Specification by OSG Corporation. 9. Catalogue on Screw by Asiahan Industrial Ltd (China/Turkey). 10. Training Manual on Screw by James Glen Pty Ltd. 11. A comprehensive catalogue on socket screw by Unbrako.

14 Oil seal and gasket

14.1

Introduction

Oil seal is used for sealing applications in gear boxes and housings to prevent the leakage of non-pressure fluids and grease. Normally, there is a shaft that is rotating inside a housing or bore. Because of friction, there must be some clearance between the shaft and the bore. The function of the oil seal is to stop whatever fluid is inside from leaking out the clearance between the shaft and housing. The seal may also be used to prevent outside materials, such as dirt, from moving in through the clearance. “Dynamic sealing” is the relationship between the rotating shaft and the seal and is handled by the sealing element. A garter spring may be used in the oil seal to increase the radial interference between the seal lip and contact point on the shaft. In order to achieve this interference, the oil seal’s ID must be slightly smaller than the diameter of the shaft. “Static sealing” is the relationship between the housing and the seal. In order to achieve this interference, the oil seal’s OD must be slightly larger than the diameter of the housing or bore.

14.1 Oil seal.

An oil seal normally consists of three basic components: the sealing element, the metal case and the spring. The purpose of the sealing element

261

262

Modern approach to maintenance in spinning

is to stop the fluid from leaking between the shaft and housing. The metal case will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The spring will help make the sealing element more effective. All materials must be selected depending on the environment in which the oil seal will function.

14.2

Material selection

Seal materials can be fully evaluated only in terms of specific operating conditions and performance requirements. The demands made on the material must take into account the environmental conditions and the function of the seal. Some of the requirements associated with environmental considerations are as follows: 1. Good chemical resistance 2. Good resistance to heat and low temperature 3. Good resistance to ozone and weathering The performance demands include: 1. 2. 3. 4.

High resistance to wear Low friction Low compression set Good elasticity

These effects are studied on newly installed seals as well as the seals aged with prolonged use with specific material. The following materials are used in the manufacture of seals to impart the properties described above.

14.2.1 Nitrile compounds (NBR) Their operating range is from –45C to +120°C. When compounding seal material for the lower temperature limit of –45°C, the upper temperature limit 120°C must be lowered. When compounding for high temperature limit, the extreme low temperature has to be sacrificed. Nitrile compounds are recommended for general use in ‘retaining lubricants’ which are designed for excluding mud, dirt and water etc. These compounds results in low volume swell when used with low aniline contents. Nitriles are the low cost range of oil seal compounds Advantages (a) Fair dry running characteristics (b) Good processing (c) Good–low temperature characteristics

Oil seal and gasket

263

(d) Good oil resistance (e) Good abrasion resistance Disadvantages (a) Lack of high heat resistance (b) Tendency to harden when used under continuous high temperature.

14.2.2 Polyacrylic compounds (ACM) These are recommended for application where the temperatures are between –18°C and +150°C. If the shaft run out is low, some compounds can be used at a temperature as low as –40°C. These are in the medium cost range of seal compounds. Advantages 1. Resistant to extreme pressure additives like phosphorous, etc. 2. Good performance at moderate temperature. 3. Good oil resistance.

14.2.3 Silicone compounds Silicones are recommended for application where the temperature is within the range –55°C to +200°C. The maximum usable temperature is limited by the decomposition temperature of the lubricant. Silicone rubbers are in the high cost range of seal compounds. Advantages 1. Good heat resistance. 2. Excellent low temperature properties. Disadvantage 1. 2. 3. 4.

High swell characteristics when used with some oils. Poor chemical resistance to oxidized oil and to some EP additives. Poor dry running characteristics. Get easily damaged during assembly.

14.2.4 Fluoroelastomer compounds (FPM) Fluoroelastomer are recommended for applications where temperature is within the range –40°C to 200°C. They have high cost.

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Modern approach to maintenance in spinning

Advantages 1. Excellent fluid resistance. 2. Fair dry running characteristics. 3. Excellent retention of original modulus and hardness in both dry heat and fluid service. Disadvantages 1. Used with caution in low temperature service. When subjected to temperatures low enough to cause compound stiffing, these may leak in high shaft run out conditions.

14.2.5 Metal case seal The principal function of metal case is to impart rigidity and strength to the seal. The case may comprise of two parts: the outer case and inner case or a single component – the bonded case. A rubber-covered case is known as a reinforcing metal insert. Seals comprising an outer and inner case are known as fully enclosed whereas the design in which case is a single component is known as open. A fully enclosed seal has good stability and simultaneously provides the sealing element and garter spring with a certain amount of physical protection. In order to ensure static sealing between the case and bore, seals are manufactured to H8 casing tolerance. A good surface finish is required to ensure the static sealing function. The metal case of seals has metal surface therefore normally centreless ground to a surface finish with maximum Rt of 15 mm. The case must not normally be exposed to any axial load.

Open Seal

Closed Seal

Reinforced Metal insert Seal

14.2 Types of metal seal.

These are made of CRCA steel sheets of deep drawn quality but sometimes they are made up of brass or of stainless steel depending upon the environmental requirement.

Oil seal and gasket

14.3

265

Why garter spring is needed?

Rubber is a visco-elastic material and therefore under goes static oxidation. After installation of an oil seal, the shaft produces a constant deformation in the inner diameter of rubber element. The stress generated during this deformation causes a gradually decay with time. As rubber is also a hydrocarbon material, it is susceptible to aging by heat, oxygen and ozone. Ageing diminishes the original radial load produced by the rubber element by increasing the stress relaxation process. In this event, the importance of garter spring is realized. The garter spring helps in maintaining a particular level of radial force needed for the satisfactory functioning of the oil seal. The total force exerted by the spring consists of the force required to overcome the initial tension and the force due to spring rate.

14.3 Garter spring.

Following advantages are gained by the use of garter spring with initial tension: 1. As the sealing element wears, the total radial force attributed to the initial tension will not change. 2. By eliminating some of the initial tension by heat treatment, the initial tension can be adjusted to achieve the level of radial force needed for the given shaft diameter. 3. The heat treatment of the spring takes place at a temperature above the operating temperature range of the seals, thus ensuring that the spring force is stabilized. This procedure eliminates the risk of the original spring force changing during service.

14.4

Shelf life

Seals and bearings are often stored as spare parts for prolonged periods. Most rubbers change in physical properties during storage and ultimately become unserviceable due to excessive hardening, softening, cracking, crazing or other surface degradation. These changes may be the result of particular factors or combination of factors, such as the action of

266

Modern approach to maintenance in spinning

deformation, oxygen, ozone, light, heat, humidity or oils and solvents. Considering few points while storing, we can increase the shelf life of these products. 1. Heat at the storing area The storage temperature should preferably be between +5°C and +25°C. Direct contact with sources of heat and sunlight should be avoided. 2. Humidity The relative humidity in the store room should be below 70%. Very moist or very dry conditions should be avoided. Condensation should not occur. 3. Light Elastomeric seals should be protected from light sources in particular direct sunlight or strong artificial light with an ultraviolet content. The individual storage bags offer the best protection as long as they are UV resistant. It is advisable to cover any windows of storage rooms with a red or orange coating or screen. 4. Deformation Elastomeric materials should, wherever possible, be stored in a relaxed condition free from tension, compression or other deformation.

14.5

Procedure for installation

The following procedure must be followed to ensure proper installation of an oil seal: 1. A light film of oil or grease should be applied to the shaft and the seal lip prior to the assembly of elastomeric seals, so as to decrease the probability of damage during assembly. 2. All surfaces over which the seal lip must slide over during assembly should be smooth and free from rough spots. 3. Assembly procedure should be carefully watched to ensure so that lips do not turned assembly. 4. The tension spring should not be tampered with or altered as it is accurately manufactured to give the correct loading. 5. An installation tool should always be used when installing an oil seal as shown in Figure 14.4.

Oil seal and gasket Minimum diameter 0.2 to 0.4 larger than seal outer diameter

Diameter 0.20 to 0.40 mm less than Bore diameter

Installation Tool

Installation Tool Surface Stop Tool

267

Housing

Housing

Tool stop against the support surface

14.4 Installation tool for oil seal.

6. A hydraulic or pneumatic press should be used to apply necessary force to install the seal. Use of the force improves the quality of installation and reduces the possibility of seal deformation. Precautions (a) Do not hit directly on the sides of the seal while fitting the seal. Use a proper adopter so that the load is uniformly distributed on the seal.

Deformed Seal Housing

14.5 Wrong method.

(b) Use a proper size of tool. Smaller Diameter Installation Tool

Housing

14.6 Seal may deform.

Seal

268

Modern approach to maintenance in spinning

(c) Align the tool properly. Installation tool

Outer diameter peeling

Housing

Misallignment Error 14.7 Misalignment error.

14.6

Reasons for seal failure

1. Excessively high temperature or excessively high peripheral speed. Increasing temperature accelerates the ageing of the rubber, the material becomes hard and brittle, the elongation decreases and the compression set increases. 2. The rubber is generally affected by the additives in the oil. This is the case with hypoid oil which contains sulphur. Since sulphur is used as vulcanizing agent for nitrile rubber, the sulphur additive in the oil acts as a vulcanizing agent at temperatures above +80°C. Nitrile rubber will rapidly become hard and brittle. Hydrogenated nitrile, acrylic and fluorinated rubbers which are not vulcanized with sulphur can therefore be used for this type of oil. Some of the oils are oxidized during operation and their properties will therefore change substantially. Such oils break down silicone rubber. 3. The shaft hardness plays an important role in increasing the life of oil seal. Normally seal contact area of shaft should be minimum of 45 Rockwell hardness. It is an important factor to prevent excessive wear deformation scratches in order to facilitate mounting. 4. The shaft surface roughness should be maximum 10–20 in. as it plays an important role in lip heating of seal. 5. Shaft should be properly chamfered otherwise the lip of the seal will damage. 6. Improper installation of seal.

14.7

Gasket

Gaskets are used to create a static seal between two stationary members of a mechanical assembly and to maintain that seal under operating conditions which may vary dependent upon changes in pressures and temperatures.

Oil seal and gasket

269

If it is possible to have perfectly mated flanges and possible to maintain an intimate contact of these perfectly mated flanges throughout the extremes of operating conditions, a gasket would not be required. But this is impossible due to the following reasons: 1. The difficulty in manufacturing such extremely smooth flanges. 2. Corrosion and erosion of the flange surfaces take place during operations. The gasket provides a seal by external forces flowing the gasket material into the imperfections between the mating surfaces. In order to get a proper sealing of the part, three major considerations must be taken into account. 1. Sufficient force must be available to initially seat the gasket. 2. Sufficient force must be available to maintain a residual stress on the gasket under operating conditions. 3. The selection of the gasket material must be such that it withstands the pressures exerted against the gasket and the temperature range to which part is exposed.

Mating part Gasket

14.8 Gasket.

14.8

Effecting a seal

A seal is affected by compressing the gasket material and causing it to flow into the imperfections on the gasket seating surfaces so that intimate contact is made between the gasket and the gasket seating surfaces preventing the escape of the confined fluid. Basically there are two different methods which are commonly used in the spinning mill: 1. Compression is the most common method of affecting a seal on a flange joint and the compression force is normally applied by bolting.

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Modern approach to maintenance in spinning

14.9 Compression.

2. Attrition is a combination of a dragging action combined with compression where the bolt is turned down on a gasket that is both compressed and screwed into the flange.

14.10 Attrition.

14.9

Installation of gasket

Following steps must be followed to install the gasket: 1. Inspect the gasket. It is important that the correct gasket has been chosen for the bolted flange connection. Verify that the material is as specified and visually inspect the gasket for any obvious defects or damage. 2. Inspect the gasket seating surfaces. Look for tool marks, cracks, scratches, or pitting by corrosion. 3. Use only new studs or bolts, nuts and washers. Make sure they are of good quality and appropriate for the application. 4. Lubricate all thread contact areas and nut facings. 5. Loosely install the stud bolts on the lower half of the flange. Insert the gasket between the flanges facing to allow the bolts to centre the gasket on the assembly. Install the remaining bolts and nuts and bring all to a hand-tight. 6. Torque all bolts one by one up to a maximum of 30% of the final torque value required.

Oil seal and gasket

271

7. Torque all bolts one by one up to a maximum of 60% of the final torque value required. 8. All studs should be re-torqued using a rotational pattern of re-torquing to the final value of torque until no further rotation of the nuts can be achieved.

References 1. Super Seal manual and catalogue. 2. Gasket hand book by Lasen gasket company. 3. Catalogue by PFE oil seal company.

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Modern approach to maintenance in spinning

15 Gears

15.1

Introduction

Like belts, ropes and chains, toothed gears are also used for transmitting power from one shaft to another. However, they are used only when the distance between the driving and driven shaft is relatively small. Gear is a component within a transmission device that transmits rotational force to another gear. A gear is different from a pulley in that a gear is a round wheel which has teeth that meshes with other gear teeth, allowing force to be fully transferred without slippage. Depending on their construction and arrangement, toothed gears are used to change the speed, the power and also in the direction of rotation between the input and the output shafts. Toothed gears are made in numerous sizes ranging from a tiny size in wrist watches to very large gears used in marine engines.

15.2

Spur gear

It is the simplest and most common type of gear that is used to connect two parallels and coplanar shafts, which rotate in opposite direction. Spur gear have teeth parallel to the axis of the shaft and is similar in profile through out. It can be observed that line of contact between corresponding teeth is always parallel to the axis of shaft. These gears can only mesh correctly if they are fitted to parallel axles. The major advantages of these gears are simplicity in design and economic to manufacture. These gears are used for slow speed but if run on high speed they create noise.

15.1 Spur gear.

272

Gears

273

Spur gears are further divided into three types: 1. External spur gears – In this system the gears of two shafts mesh externally with each other. The larger of these is called wheel and smaller one is called pinion. In this system the motion of two wheels is always opposite. Wheel

Pinon 15.2 External spur gears.

Internal gears – In internal spur gear the teeth is always cut on the inner diameter of ring while the outside diameter is kept smooth and they mesh with external spur wheel. The bigger wheel is called annular wheel and smaller one is called pinion. In internal gearing when gears move then shaft run in the same direction. Internal gears are hollow. The properties and teeth shape is similar as of external gears except that the internal gear had different addendum and dedendum values modified to prevent interference in internal meshes. When choosing a mating spur gear, always remember that the difference in the number of teeth between the internal gear and pinion should not be less than 15.

15.3 Internal gear.

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Modern approach to maintenance in spinning

2. Rack and pinion – It is the spur gear of infinite radius or zero curvature. The pitch line of gear moves in a straight path. The gear wheel transmitting rotary motion is called pinion. The motion of rack is ^ to the axis of rotation of pinion. The straight-line gear is called rack ad circular wheel is called pinion. Rack and pinion gears are used to convert rotation into linear motion or linear motion into rotation. The rack is the flat toothed part and the pinion is the gear. The diameter of the gear determines the speed that the rack moves as the pinion turns.

15.4 Rack and pinion.

15.2.1 Common terms used in spur gear Pitch circle It is an imaginary circle, which by pure rolling action would give the same motion as the actual gear. Pitch Circle

Pitch diameter

15.5 Pitch circle and pitch diameter.

Pitch circle diameter It is the diameter of pitch circle. The size of gear is usually specified by pitch circle diameter. It is also called a pitch diameter. Addendum It is the radial distance of a tooth from the pitch circle to the top of the tooth.

Gears

275

Dedendum It is the radial distance of a tooth from the pitch circle to the bottom of tooth. Circular pitch It is the distance measured on the circumference of pitch circle from one point of tooth to the corresponding point on next tooth. Circular Pitch =

D1 T

Where T is the no. of teeth and D is the diameter of the pitch circle. Addendum

Whole Depth

Working Clearance Dedendum 15.6 Terms used in spur gear.

Diametrical pitch It is ratio of number of teeth to pitch circle diameter in millimetre. T

Diametrical pitch = D Where T is the number of teeth and D is the diameter of pitch circle. 7. Module It is the ratio of pitch circle diameter in millimetre to the number of teeth. Module, m =

T D

Where T is the number of teeth and D is the diameter of pitch circle. The most common recommended modules are 1, 1.25, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 1012, 16, 20, 25. The most common module used in textile industry is 1, 1.25, 1.5, 2, 2.5. 8. Backlash It is the difference between the tooth space and tooth thickness as measured on pitch circle. It is 1/10th of module.

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Modern approach to maintenance in spinning

0.1 mm

15.7 Backlash.

9. Tooth space It is the width of space between the two adjacent teeth measured along the pitch circle. 10. Pressure angle Pressure angle (also referred to as ‘tooth shape’) is the angle at which the pressure from the tooth of one gear is passed on to the tooth of another gear. Spur gears come in two pressure angles: 14 1/2° and 20°. Normally 14 1/2° is commonly used.

15.2.2 Accuracy of gears The gears are rated according to which they are cut. Accuracy in cutting of the gear is essential for normal operation of drive. The degree of accuracy will depend upon the kind of service of the gear and demand it has to meet. The method for rating spur and helical gears is on the basis of accuracy. There is 1–12 degree of accuracy. The most common degree of accuracy used in textile industry is 4–8.

15.3

Helical gears

Helical gears are similar to spur gears except that their teeth are cut at an angle to the hole (axis) rather than straight and parallel to the hole like the teeth of a spur gear. The line of contact between two teeth is not parallel to the teeth but inclined. This ensures gradual engagement of teeth from one end of tooth to other rather than a sudden engagement as in case of spur gear. This gradual engagement makes the gears function smoothly without much noise. Pair of helical gears can be meshed in two ways: with shafts oriented at either the sum or the difference of the helix angles of the gears. These configurations are referred to as parallel or crossed, respectively.

Gears

277

15.8 Helical gear.

Right Hand Helical Gear

Left Hand Helical Gear

15.9 Types of helical gears.

1. Helical gears connecting parallel shafts Helical gears connecting parallel shafts will run more smoothly and quietly than spur gears, particularly when the helix angle is great enough to ensure that there is continuous contact from one tooth to the next. A pair of helical gears used to connect parallel shafts must have the same pitch, pressure angle and helix angle, but they will be opposite hand gears (i.e., one will be a left-hand gear and the other a right-hand gear). 2. Helical gears connecting non-parallel shafts Helical gears used to connect non-parallel shafts are commonly called spiral gears or crossed axis helical gears. If the shaft angle is 90 degrees,

15.10 Parallel crossed.

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Modern approach to maintenance in spinning

the gears will be of the same hand and the sum of the helix angles will be equal to the shaft angle (90 degrees). There is a point of contact between two gears where as there is a line contact in a helical gear. Because of point of contact which changes during action, there is considerable sliding between the teeth. Efficiency of spiral gear is very low.

15.3.1 Common terms used in helical gear 1. Outside circle – The outside circle is the distance around the outer edge of the gear’s teeth. The diameter of the outside circle is called the outside diameter.

Outside Diameter 15.11 Outside diameter in helical gear.

2. Pitch circle – The pitch circle is the imaginary circle found at the point where the teeth of two gears mesh. 3. Pitch diameter – The diameter of the pitch circle is called the pitch diameter. 4. Helix angle – The helix angle is the angle between the axis (bore) of a helical gear and an (imaginary) line tangent to the tooth. The helix angle will be between 0° and 90°.

Helix Angle

15.12 Helix angle.

Gears

15.4

279

Worm gears

A worm is a gear that resembles a screw. It is a species of helical gear, but its helix angle is usually somewhat large (i.e., somewhat close to 90 degrees) and its body is usually fairly long in the axial direction; and these attributes give it its screw-like qualities. A worm is usually meshed with an ordinary looking, disk-shaped gear, which is called the ‘gear’, the ‘wheel’, the ‘worm gear’, or the ‘worm wheel’. The prime feature of a worm-and-gear set is that it allows the attainment of a high gear ratio with few parts, in a small space. Helical gears are, in practice, limited to gear ratios of 10:1 and under; worm gear sets commonly have gear ratios between 10:1 and 100:1, and occasionally 500:1. The worm gear gives a line of contact between mating teeth unlike the point of contact. Note: Worm gears differ from spur gears in that their teeth are somewhat different in shape and are always formed on an angle to the hole (axis) in order to mate with worms. In order to transmit motion and power at various speeds and speed ratios, worms and worm gears work in sets, rotating on shafts at right angles to one another. The worm usually drives the worm gear. In worms and worm gear sets, both the worm and worm gear are of the same hand. Right-hand sets are considered standard.

Worm

Worm Gear

15.13 Worm gear.

This improves the load carrying capacity and also reduces the speed. Worm gear is always changed in a set, i.e. both worm and worm wheel needs replacement at the time of wear. A worm wheel of one diameter will not operate satisfactorily with a worm of different diameter even if thread pitch is same. The thread of worm may be single start, double start and so on. The velocity ratio depends whether the worm is one start or multiple start. To determine the number of threads on a worm, look at an end view so you can see the ‘start’ of each thread. One start means that you have a single thread, two starts a double thread, three starts a triple thread, and four starts a quadruple thread.

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Modern approach to maintenance in spinning

15.14 Single start thread.

15.4.1 Worm gear hand Worms and worm gears are manufactured with right or left-hand threads and teeth. The hand of a worm or worm gear may be determined by noting the direction in which the threads or teeth lean when the worm or worm gear is held with the hole facing up. In a worm gear set, the worm and gear must have the same hand, pitch, number of threads, and tooth dimensions. They also must have the same pressure angle and lead angle. Right hand worm and worm gear sets are considered standard.

15.15 Worm gear hand.

15.4.2 Most common terms used in worm gear 1. Axial pitch It is the distance from any point on one thread of worm to the corresponding point on the adjacent thread measured parallel to the worm axis. 2. Lead It is the distance travelled by thread when one complete revolution is given to the worm

Gears

281

L=P×N where P = axial pitch N = no. of start For single start, lead is equal to axial pitch but in case of double start it is twice the axial pitch. 3. Leading angle The lead angle is an important factor in determining the efficiency of a worm and worm gear set. The efficiency increases with lead angle increase. For a given pitch, the lead angle is controlled principally by two factors: (1) the number of threads and (2) the pitch diameter of the worm. Lead Angle

15.16 Lead angle.

15.4.3 How to calculate the velocity ratio? The linear velocity of worm is

Vw =

L × Nw 60

Velocity of worm gear is

Vg =

π dN g 60

where, N w = rev/min of worm d = pitch diameter of worm wheel N g = revolution of worm wheel Since Vw = Vg

LN w π dN g = 60 60

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Modern apprO!lch to maintenance in spinning

where LN. = miN,

N .. Velocity ratio (VR) = : N =

•

Hd

L

Now 1CdII - Zg x Pc

Z, _ no. of teeth in worm gear p. = circular pitch of gear L '"

z...xp.

z... = no. of Itart p. '" axial pitch Velocity Ratio(VR) =

Z~.. = Zw • lince P = P Z,P,

15.5

Z,

",

Bevel gell'"

These arc used to connect two shaft axes which arc intersecting and coplanar. They arc kincm.tica1ly cqlllll. to frustums of conc with their apices meeting at II point. The shaft angle may be of any value between 0° and 180" but one most common is 90". The teeth of bevel gcaI3 arc similar to thllt of spur gelll'll in that they make II line contact across the face of teeth. The teeth arc IQllllller at the front than at the back. There are two type. of bevel gear: 1. Straight tooth 1MI'd gCtJT$ In these gean the teeth of gear converge to the common point along Itraight Iinel. Thil point is called apex and allO point of intersection of geu axis. At high speed they give more noise.

16.17 Straight tooth bevel gear.

Gears

283

2. Spiral tooth bevel gears Spiral bevel gears have spiral angles, which give performance improvements. They are designed for an angle change of 90°, where the two axes are concurrent and in the same plane. These gears have a double function of being helical and beveled at the same time. The contact between the teeth starts at one end of the gear and then spreads across the whole tooth. In this type of gears the shaft must be perpendicular to each other and must be in the same plane. They are the most complex forms of bevel gears. The teeth are curved by cutting them obliquely, resulting in higher overall contact ratios. Because of higher contact ratio, these have better load carrying capacity and this allows them to be of smaller in size for a given load capacity than an equivalent gear. Thus, they can transmit more power with smaller gears. These gears have the following advantages over the straight gears: 1. Due to curvature there is an overlapping of mesh and teeth mesh with each other gradually resulting in smooth and quiet operation. 2. There is a gradual transfer of load from one tooth to another eliminating sudden impacts and change in tooth pressure. Note: Spiral bevel gears of the same hand will not operate together, a set of spiral bevel or spiral gears consists of one left-hand gear and one right-hand gear.

15.18 Spiral bevel gear.

Miter gear Miter gears are bevel gears put together with equal numbers of teeth and axes that are usually at right angles. Miter is the surface forming the beveled end or edge of a piece where a miter joint is made. Miter gears are cut with a generated tooth form that has a localized lengthwise tooth bearing. They are known for efficient power transfer and durability. They can carry heavy loads and can eliminate secondary operations that are useless during

284

Modern approach to maimenance in $piMing

the proC9l. They IIRI deUgned fm the efficient tnnamialion of powm: and motiOIl between intersecting Ihafts at right anglel. They can be of two types: stnUpt miter gear and IpUal miter gear. They give smoother and quieter operltiOIl. They hand1e higher llJleeda and Pliler torque load!. They proridc a l!cady ratio.

15.19 Mit« gelr.

15.11

Ge.r tNln.

Any c:ombiDatiOD of gears which employed. to trmlmit motion from one ahaft to IlKI1:her is called lear train. There Ire four more common type. of gear traiDI.

1. SiIIIp/e traU!. uf 8~tu6 ID simple par 1rIIin, two gean melh to form a simple train of wheeh. Out of the two wheeh, 0110 il driver and other is driven.

----W2 Wl

N2 Nl

n

T2

12 _ I11I!Ilbcr of teeth in gear DO. 2 T1 _ I11I!Ilbcr of teeth in Jear DO. 1

Nl_rpmof2 Nl_rpmofl

Hen: ;can rota!c in the oppomc dircc;tion. In the Figure 2 the third whael roUd:e in the lime direction II the lecond wheel has DO influence upoD. the velocity ratio. The lecond wheel il tnown

N3_TI.T2_TI Nt T2 T3 T3

Gears

285

as idle or idler wheel. Any number of idler wheels can be interposed between the first and last wheel without altering the speed ratio. The direction of rotation of last wheel depends upon whether total number of wheel is odd or even. Even number gives opposite rotation and odd number of wheel gives same direction.

Nn T1 = N1 Tn 2. Reverted gear train A reverted gear train is one where first and last gears are on the same axis.

2

3

1 4

15.20 Reverted gear train.

N1 T 2 * T 4 = N 4 T1 * T 3 3. Epicyclic gear train

C A B

15.21 Epicyclic gear train.

In an epicyclic gear train, B is fixed to frame while arm A revolve carrying with it wheel C.

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Modern approach to maintenance in spinning

For example, Calculation of differential gear box of card c1l3

,--23 _

!

I90 63

17

I-

Bm"

34

~

86

43

-

I

26

n ~

I

I

-

34

-

17

15.22 Differential gear box.

When the card is rotating at high speed, the disc is stationary.

23"'43·34 0.98 77"'17·26 When the card is moving at slow speed, disc

u not stationary.

n-a

e=--

m-a

e = differential ratio n = output speed m = input speed

a = differential ratio e = 43"34 17*26 m

3.307963

23 = 77 =0.2897012

(1)

Gears

287

23 * 90 = 0.3865545 63 * 85

a =

Put all the values in Eq. (1)

3.307962 =

n − 0.3865545 0.2897012 − 0.3865545

n = 0.0959629 The ratio of fast speed and slow speed is

0.98 = 10.2 0.095962

15.7

Black lash

Backlash, sometimes called lash or play, is clearance between mating components, sometimes described as the amount of lost motion due to clearance or slackness when movement is reversed and contact is reestablished. For example, in a pair of gears, backlash is the amount of clearance between mated gear teeth. This gap means that when a geartrain is reversed the driving gear must be turned a short distance before all the driven gears start to rotate. A similar effect is the taking up of slack when a train starts to pull away at the station and each car bumps as its link becomes tight. At low power outputs, backlash results in inaccurate calculation from the small errors introduced at each change of direction; at large power outputs backlash sends shocks through the whole system and can damage teeth and other components. It should be less than 1/10th of module.

Operating Pitch Circle

Backlash 15.23 Backlash.

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Modern approach to maintenance in spinning

15.8

Lubrication

1. Open gear Gears should be properly lubricated to: minimize wear, prevent the generation of excessive heat, improve efficiency through the reduction of friction between the mating tooth surfaces, reduce noise and inhibit the formation of rust. Good lubrication depends on the formation of a film thick enough to prevent contact between the mating surfaces. The relative motion between gear teeth helps to produce the necessary film from the small wedge formed adjacent to the area of contact. It is important that an adequate supply of the correct lubricant is properly applied. In open gears mostly extreme pressure grease are used. 2. Gear box lubrication I. Recommended oil In all machineries, a certain amount of power is required to overcome friction within the lubricating film itself. Friction of this kind is largely a function of the viscosity of the lubricant. To minimize power consumption, it is necessary to use oil with optimum viscosity compatible with satisfactory lubrication, while taking account of considerations like splashing and the rate of oil consumption. Oxidation tends to cause thickening of oil in service; therefore, it is advantageous to use lubricants with high oxidation stability. Such lubricants change less in viscosity with increase in temperature. II. Recommended oil level Industrial gears may be either of the enclosed type or of the open type. In the enclosed type a minimum level of oil is maintained. In the gearbox, teeth of the bottom gears are just dipped into the oil and gear are lubricated by means of splash. In case of splash lubrication it is necessary that oil level should not be too high. A high level results in churning of oil which in turn results in consequent rise in oil temperature and in power loss. The depth to which the bottom wheel is dipped is twice the tooth depth. This is sufficient for splash lubrication and to keep the churning effect to the minimum. Secondly, a pressure circulating system may be used in which oil is sprayed on the teeth close to the point of engagement. The oil is then recirculated either directly from the bottom of the gear box or by way of a separate tank with the help of oil pump.

Gears

15.9

289

Reasons for the failure of gear teeth

1. Fatigue – When two gears mesh with each other to transmit a load, the teeth of each gear are under bending action. The bending stress will be maximum at the root of tooth. Due to the periodical effect of the load, fatigue cracks may occur near the tooth base resulting in ultimate failure of tooth. 2. Wear – When some foreign material like dust particles deposited in between the mating teeth there will be wear of tooth surface. 3. Improper meshing.

References 1. 2. 3. 4.

Mechanical Engineering Design (1989) by JOSEPH EDWARD SHIGLEY. Mechanical Machine Design (1996) by DR. R . C. BEHL and V. K. GOEL. A Text Book of Machine Design by DR. P. C . SHARMA and DR. D. K. AGARWAL. Comprehensive Hand Book on Maintenance in Spinning (Part 3) by NEERAJ NIJHAWAN .

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Modern approach to maintenance in spinning

16 Compressed air

16.1

Introduction

Compressed air is a potent form of energy that is used to get a mechanical energy output by linear motion through a pneumatic cylinder. This linear motion energy can in turn be used for various operations such as pushing, lifting, clamping, feeding, pressing and forming, etc. The linear movement is also used effectively to perform functions such as positioning, turning, bypassing, selecting segregating, index locating and ejecting in various mechanical devices. The advantages and disadvantages of the pneumatic system are given below: Advantages 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Air is available in plenty and free everywhere for compression and usage. Compressed air can be stored. It can be transported easily through pipes over long distance. Compressed air systems are cleaner as compared to the hydraulic system. For smaller output forces pneumatic are cheaper, simpler and can achieve high working speed. The speed and the force are infinitely variable. When overloaded a pneumatic tool will stop and so is safe as compared to electrical system. No fire hazard as in electrical systems so can be safely used in dangerous area like mines. Simple in construction, the pneumatic system components are easy to maintain and repair. The used air is dissipated into atmosphere so no return lines are needed as in hydraulic system.

Disadvantages 1. Extensive preparation is required for producing compressed air (by using regulator filter and lubricator), as otherwise the system would get worn out fast.

290

Compressed air

291

2. Smooth and uniform speeds against varying loads are not achievable as in the hydraulic system. 3. Beyond a certain load the compressed air system become cumbersome and expensive. 4. As the compressed air is exhausted into the atmosphere while doing its job, it produces an unpleasant noise. Even with a silencer, some noise will still emanates. 5. Dust and dirt are considered as the biggest enemies of the compressors. Therefore, Compressors must be installed where the environment is free from dirt and dust. In cases where the pollution in the environment is unavoidable, the manufacturers of compressor should be consulted for a cost effective solution. The location of installation must have good ventilation, be away from manufacturing departments and surrounded with trees, etc.

16.2

Compression of air

Atmospheric air has pressure, when measured at sea level the pressure is 760 mm as measured by mercury manometer. This pressure is called 1 atmosphere. In British units it is equal to 14.7 PSI (Pounds per square inch). So, 1 ATM = 14.7 PSI = 1.033 kg/cm2 1kg/cm 2 = 14.2 PSI When the one atmospheric pressure is measured by a dial type pressure gauge, it shows a reading of zero. The actual pneumatic absolute pressure = gauge pressure + 1 A PBs = Pg+1 The properties of compression of air is such that when volume V of air at a gauge pressure of P is compressed to a volume of V1 and the resultant increased pressure is P1 gauge. Then (P + 1) × V = (P1+1) × V1 assuming that the temperature remains constant. Similarly (P1 +1) × V1 = (P2 +1) × V2. From the above it is clear that when the volume become half the pressure become double. Converse is also true when compressed air expands.

16.3

Free air or atmospheric air

For all practical calculations in pneumatic application the volume of compressed air is always converted into free air, i.e. volume prevailing under the atmospheric condition.

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Modern approach to maintenance in spinning

Example If a tank of 400-litre capacity contains compressed air at 6 kg/cm2 and if the entire volume is exhausted to atmosphere, the following calculation arrives. P absolute = Pg +1 = 6 + 1 = 7 kg/cm2 V initial = 400 l. After expansion to atmospheric pressure P1 = Pg + 1= 0 + 1 =1 kg/cm2 V1 = to be found PV = P1V1 7 × 400 = 1 × V1 V1 = 2800 litres of free air The tank of 400 l. with 6 kg/cm2 actually contains 2800 l. of free air. This method of calculation is used to calculate the free air required for the operation of pneumatic cylinder. Example of calculation Calculate the free air required to operate a bore of 100 × 200 mm stroke actuating cylinder for one forward + one backward stroke (double stroke) at 5 kg/cm2. D = 10 cm l = 20 cm

2* *d *d *l 4 1000 2 * 3.14 *10 *10 * 20 1000

Double stroke volume of cylinder = 3.14 l. Operating pressure = 5 kg/cm2 Free air required to operate the cylinder for double stroke = 3.14 (5+1) = 18.84 l. of free air If the cylinder operate 10 times to and fro Total free air = 188.4 l/min. In this way, the free air requirement for any number of cylinders, and the required capacity of the compressor required.

Compressed air

16.4

293

Analyzing compressed air needs

Compressed air needs are defined by the air quality, quantity, and level of pressure required by the end uses in your plant. Analyzing needs carefully will ensure that a compressed air system is configured properly.

16.4.1 Air quality Quality is determined by the dryness and contaminant level required by the end uses, and is accomplished with filtering and drying equipment. The higher the quality, the more the air costs to produce. Higher quality air usually requires additional equipment, which not only increases initial capital investment, but also makes the overall system more expensive to operate in terms of energy consumption and maintenance costs. One of the main factors in determining air quality is whether or not lubricant-free air is required. Lubricant free air can be produced with either lubricantfree compressors, or with lubricant-injected compressors that have additional separation and filtration equipment. Lubricant-free rotary screw and reciprocating compressors usually have higher first costs, lower efficiency, and higher maintenance costs than lubricantinjected compressors. However, the additional separation and filtration equipment required by lubricant-injected compressors will cause some reduction in efficiency, particularly if systems are not properly maintained. Before selecting a lubricant-free or lubricant-injected compressor, careful consideration should be given to the specific end use for the lubricant free air, including the risk and cost associated with product contamination.

16.4.2 Air quantity–capacity Required compressed air system capacity can be determined by summing the requirements of the machine and process operations (taking into account load factors) in the spinning mill. The total air requirement is not the sum of the maximum requirements for each machine and process, but the sum of the average air consumption of each. High short-term demands should be met by air stored in an air receiver. Systems may need more than one air receiver. Strategically locating air receivers near sources of high demand can also be effective. In most cases, a thorough evaluation of system demand may result in a control strategy that will meet system demand with reduced overall compressor capacity. Oversized air compressors are extremely inefficient because most compressors use more energy per unit volume of air produced when operating at part-load. In many cases, it makes sense to use multiple, smaller compressors with sequencing controls to allow for efficient operation at times when demand is less than peak.

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Modern approach to maintenance in spinning

16.1 Flowchart of compressed air system.

16.4.3 Load profile Another key to properly designing and operating a compressed air system is analyzing a plant’s compressed air requirements over time, or load profile. The variation of demand for air over time is a major consideration in system design. Plants with wide variations in air demand need a system that operates efficiently under part-load. Multiple compressors with sequencing controls may provide more economical solution as shown in Fig. 16.1.

16.5

Production of compressed air

Air is available in plenty in the atmosphere and needs to be compressed and stored at high pressure for use in any pneumatic system. This is achieved by air compressor. Air compressors are available in two basic systems: reciprocating and screw. The reciprocating compressors are economical up to 20 HP capacity and are most commonly used. The screw compressors are advantageous beyond 30 HP. Each type of compressor is available in single stage, two stages and multistage version. The single stage compressor is used up to a max of 10 kg/cm2 and the two-stage compressor up to 15 kg/cm2. Beyond this pressure, multistage compressions are used. For a normal pneumatic system, the working pressure range is 4–7 kg/ cm2 so the compression with maximum pressure range of 10 kg/cm2 is normally selected.

Compressed air

295

16.5.1 Reciprocating compressor A reciprocating compressor is made up of cylinder and piston. The back and forth motion incorporated by a reciprocating compressor pulls gas in on the suction stroke and discharge it on other. Compression is accomplished by the change in volume as the piston moves toward the top end of the cylinder. The compression may be oil lubricated or, in some cases, it may require little or no lubrication in the cylinder. Spring loaded suction and discharge valves open/close automatically as the piston moves up and down in the cylinder chamber.

16.5.2 Rotary screw type compressor This type of compressor has one male rotor and a female rotor. The male rotor has four helical lobes 90° apart, which are like with the teeth of a helical gear. The female rotor has six matching flutes 60° apart that mesh with the lobes of the male rotor. When the four male rotor lobes rotate in mesh with six female rotor flutes, air gets trapped between the lobes and the flute and is gradually compressed until each pair of lobe and flutes reaches the outlet port. The meshing of rotor and the compression cycle in the compressor element are schematically illustrated in the following steps. Position 1 As the lobes/flute pair unmeshed, the interlobe volume increases and the interlobe pressure decreases. Atmospheric air gets sucked in the volume space between male and female rotor lobes. Direction of Rotation Female Rotor Male Rotor

Helical Lobes

16.2 Position (1) of lobes.

Position 2 As rotation continues, the interlobe space is sealed off from the atmosphere and the compression begins.

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Modern approach to maintenance in spinning

16.3 Position (2) of lobes.

Position 3 Compression continues as the inter-lobe space is reduced in volume by the pair of meshing lobe.

16.4 Position (3) of lobes.

Position 4 As the lobe/flute pair uncovers progressively larger area of the outlet port, the air compressed in the interlobe space is gradually released through the outlet port.

Outlet Port

16.5 Position (4) of lobes.

Compressed air

297

Because each lobe/flute pair reaches the outlet port before the previous pair has finished its compressed air, the compression cycles overlap and air is delivered without any major pulsation. The little pulsation that takes place has no practical importance.

16.5.3 Centrifugal compressors A centrifugal air compressor has a continuously flowing air stream which has velocity energy, or kinetic energy, imparted to it by an impeller, or impellers, which rotate at speeds that can exceed 50,000 revolutions per minute (rpm). Approximately one half of the pressure energy is developed in the impeller with the other half achieved by converting the velocity energy to pressure energy as the air speed is reduced in a diffuser and volute. The most common centrifugal air compressor is one with two to four stages for pressures in the range of 100–150 psig. A water-cooled intercooler and separator between each stage returns the air temperature to approximately ambient temperature and removes condensed moisture before entering the next stage. An after cooler cools the air from the final stage and a moisture separator removes the moisture prior to air delivery to distribution. The inherent characteristic of centrifugal air compressors is that as system pressure decreases, the compressor’s flow capacity increases. The steepness of the pressure head/capacity curve is dependent upon the impeller design. The more the impeller blades lean backwards from the true radial position, the steeper the curve. Centrifugal air compressors range from around 300 to more than 100000 cfm but the more common air compressors are from 1200 to 5000 cfm and with discharge pressures up to 125 psi. Centrifugal air compressors provide lubricant-free air delivery as there is no lubricant in the compression chambers. Lubrication for speed increasing gears and the special high-speed shaft bearings is kept away from the compression chambers by means of shaft seals, which may also have air purge and vent connections.

16.6

How to specify the right compressor type, capacity and pressure?

As a rule of thumb, the required HP of a compressor may be calculated as approximately 80 l. of free air per HP. If the entire pneumatic system requires 1000 l. of free air, the compressor capacity works out to be 12.5 HP. To select the right compressor, the following points must be considered.

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Modern approach to maintenance in spinning

16.6.1 The right pressure This depends upon the demand of the pneumatic equipment, which operates on the compressed air. Most of the pneumatic equipment is operated on a pressure of around 6 bar but there are also the pneumatic equipment which operate on the lower and higher pressure. One should select a compressor which is capable to generate of at least 1 bar above the pressure needed at the point of use. This is also to compensate for the pressure loss in pipelines, filters and other accessories, to ensure that at the point of use the needed pressure can be guaranteed. A too high pressure will unnecessarily increase the power consumption of the compressor about 5% for each pressure bar increase. Secondly, a too high pressure at the point of use will also increase the compressed air consumption of the pneumatic equipment and lead to more wear of the pneumatic equipment.

16.6.2 The capacity of compressor Pressure is not an indication of capacity; there are very small compressors available which supply very little air about at very high pressure. The opposite is also true that there are very large compressors for low pressures. The only relation between the capacity and pressure is that if high pressure is needed to produce a certain quantity then more power is required (about 5% extra power for each bar pressure increase). Capacity of a compressed air is always expressed in volume per time against certain pressure like m3/min, l/sec, m3/h or CFM (cubic feet per minute). The capacity is always expressed as free air delivery. This means the amount of compressed air can deliver recalculated to atmospheric pressure or the amount of atmospheric or the amount of atmospheric air compressor can compress to a certain pressure. Firstly, find out the compressed air requirement of each load point and its load factor. A sudden demand of air may upset the air supply for the entire plant. This would result in substantial pressure drops in the system at all load points affecting production and quality. Any such difficulties can be avoided by carefully estimating the air demand and then deciding the suitable size for the compressor. While determining the needed capacity, consider the following points: (a) Determine machine requirement. (b) Allot extra capacity to account for leakage and pressure drop and future expansion. (c) Give allowance for maintenance.

Compressed air

299

Example of spinning mill centralized compressor 1. First collect the requirement of compressed air of individual machine. 2. Calculate the requirement of each department by multiplying the requirement of one machine with number of machines. 3. Convert the requirement of each department from m3/h to C.F.M. 4. Calculate the requirement of whole plant by adding the requirement of individual department. 5. Add the following requirements: I. Add 10% for temperature difference II. Add 20% for cleaning III. Add5% for leakage 6. Consider the efficiency of compressor to be 95%. Example Department

Qty. of air in m3/h

Qty. of air in CFM

Blowroom Card Combing Roving Ringframe Autoconer Total Add 10% for temp difference Add 20% for cleaning Add 5% for leakage Total requirement

5.85 38.70 15.50 7 26 336 429 42.9 85.8 21.45 579.15

3.45 22.83 9.14 4.12 15.33 198.2 253 25.3 50.6 12.65 341.55

Proposal One can propose single stage rotary air compressor water cooled, lubricated type stationary, electrically operated capacity 200 × 3 = 600 CFM, working pressure = 10.5 kg/cm2. Air dryer capacity Total FAD = 341 × 1.1 = 375 Air dryer capacity = 200 We propose two dryers having capacity of 200 CFM. Air receiver capacity Total value = 600 Air receiver capacity = 600/80=7.5 m3

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Modern approach to maintenance in spinning

One can propose two number 4 m3 capacity as per specification given below 1. 2. 3. 4.

Capacity = 4m3 Working pressure range = 10.5 kg/cm2 Test pressure = 17.5 kg/cm 2 Material of construction = IS 2062

The altitude at which compressor has to be located also affects the compressor capacity, because the intake pressure decreases at higher altitude. To deliver air at same discharge rate as at sea level, it needs higher compression ratio; therefore the compressor would function with lower efficiency and lesser output capacity. According to thumb rule, at an altitude of 1000 m, air requirement increases by 10%. Note In a spinning mill the compressed air is used for cleaning the machine. It is advisable to install separate compressor and air distribution system for cleaning purpose. The system can operate only when it is needed may be 4 hours in day. It gives high installation cost but it helps in saving energy. If we do not put separate compressor for cleaning then we have to use bigger air compressors, i.e. 1.2 times the actual compressed air requirement. Oversized compressors are extremely inefficient because most compressors use more energy per unit volume of air produced when operating at partload. Secondly compressors consume 60% of energy in no-load condition.

16.6.3 Choice of compressor type Two basic options are available: one is to provide a centralized large compressor for all machines put together and other is to provide a number of separate compressors at suitable production stages. At each production stage – which contributes a load point for compressor – there exist a minimum and maximum consumption level for compressed air. The load factors of different machines are different. However, it becomes necessary to provide for the maximum consumption level. As a result if separate consumptions are to be provided, then total installed compressor capacity would become very high and would not be utilized most of the time. If a centralized compressor system is adopted, the actual total compressed air requirement is much less than the sum of maximum value needed for the compressor. However, the installation cost for the piping which carries the compressed air to different machines is high. Modern spinning mills prefer to opt for the centralized large compressor which

Compressed air

301

gives high efficiency. The installation costs as well as their maintenance costs are lower than those for separate compressor.

16.6.4 Operating cost These costs are recurring in nature consist of cost of power consumption, oil consumption, water cost of cooling arrangement and maintenance and repair cost of the complete system include the labour cost and down time for servicing, repair and overhauling.

16.7

Receiver or tank size for air compressor

Each air compressor is provided with an air receiver tank for the following reasons: 1. To dampen the pulsation of air. 2. To serve as a cooling chamber so that the moisture in the incoming air can be settled and drained. 3. To enable the fitment of pressure control devices such as pressure switches for automatic switching the compressor on–off operation so that running time of compressor is reduced. 4. It helps to store compressed air. This ensures the pneumatic control device connected to the system, which will result in neutral or safer operation in the event of any eventualities like power failure. 5. As a thumb rule for compressors with on–off operation the receiver capacity is normally equal to the free air capacity of the compressor. For example: a compressor with a free air delivery capacity of 500 l. is fitted with a tank of 500 l. However, several manufacturers supply tank as per their own specification. 6. For very large capacity compressors which are fitted with a special unloading device for continuous operation, the tank size is smaller than indicated by the thumb rule given above.

16.7.1 What is the best location for an air receiver tank? Normally the installation sequence is the compressor receiver dryer. The reason why receiver is advised to be installed upstream of the dryer, is to have more even flow over he dryer because the receiver will act as a pre cooler and pre water heater which will improve the effectiveness of the dryer. If air consumption fluctuates too strongly then in spite of reversing the installation sequence from compressor – receiver – dryer to compressor – dryer – receiver, then one should install a second receiver down stream to absorb the peak consumption. This second

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Modern approach to maintenance in spinning

receiver should not be located close to the dryer, but should be located as close as to the point of use. This avoids the air of this sudden peak has to travel a long way from the receiver all the way through the pipes to the point of use.

16.8

Moisture

Assume that the suction side of the compressor sucks the air with 32°C temperature and 50% relative humidity at 1 atmospheric pressure which is the average Indian condition. After compression to 6 atmospheric pressure, the volume of air reduces by 6 times resulting in an increase in humidity by 6 times. After compression the air temperature also becomes high. Therefore, this air must be passed through the water cooled after cooler to bring down its temperature to the level of ambient temperature. At this temperature air cannot possess more than 100% relative humidity. Thus the excess vapour gets condensed to liquid moisture which remains suspended in air and can be filtered out or be dried by a dryer. The atmospheric air contains certain amount of water vapour in it. When air is compressed and used, it carries water vapour also with it. This compressed air when used in pneumatic cylinder without removing the moisture entrapped in it, and can corrode the cylinder, and the valve, and reduce their life. The moisture can combine with lubricating oil and form an emulsion, which can cause sticking of moving component of electrovalves and other valves result in malfunctioning of the system. The problem gets more aggravated in the rainy season or in locations where the relative humidity is high. In coastal areas where the water is salty the problem of corrosion is severe. Moisture can corrode pneumatic components and cause costly replacement apart form loss due to machine down time. To overcome this problem, drier methods are used to separate the moisture from the compressed air effectively before it reaches the part/ components where it is to be used. Air can be called dry if it does not show liquid; however it contain certain amount of water vapour. The ability of air to absorb water vapour increases drastically at a high temperature and decreases at low temperature. It only depends upon the temperature and not on pressure. At each temperature there is a maximum amount of water vapour 1 m3 of air can absorb, anything more will become liquid. This temperature is called dew point.

Compressed air

303

Table 16.1 Relationship between temperature and water vapour Temperature of air (°C)

Amount of water vapour (1 m3 of air can contain in grams)

90 80 60 40 30 25 20 10 3 -15

417.935 290.017 129.020 50.673 30.078 22.830 17.148 9.359 5.953 1.380

Example 1 m3 of air any temperature containing 22.830 gram of air has a dew point of 25°C. At higher temperature this mean all the water will be vapour and at lower temperature a part will become liquid. This air will be dry as long as the temperature does not below 25°C. Two types of dryers are used in the industry: refrigerant dryers and desiccant dryers. The countries where there is no risk that compressed air temperature drops below 3°C a refrigerant dryer is the best choice. The working principles of both types are described below:

16.8.1 Chemical-type dryer This is also called drying by adsorption. Adsorbents are solids with a large number of micropores representing a large internal surface area. A continuously operating adsorption dryer works in accordance with the principle of dynamic adsorption. The air to be dried passes through the adsorbent bed. While the air passes through the bed, moisture is withdrawn from it. Since the absorbing capacity of any adsorbent is limited, the flow path needs to be changed prior to complete saturation. The continuous supply of dry absorbent as a drying medium is guaranteed by two alternatively operating absorber chambers while one absorber chamber is available for drying and the absorber in the second chamber is regenerated. The adsorption agent used in the spinning mills are activated almunia or silica gel.

304

Modern approach to maintenance in spinning Dry compressed air Open

Closed

Air Heater Absorber 2

Absorber 1 Regeneration

Drying

Fan

Open Hot air Closed

16.6 Chemical-type air dryer.

16.8.2 Refrigeration compressed air dryer The temperature of air reduces as its water holding capacity comes down drastically. This principle is employed in the refrigerated air dryer. Compressed air is cooled by refrigeration system thereby reducing its water holding capacity. Water vapour above the holding capacity at the reduced temp condenses into water droplets which are removed by using a water separator through centrifugal and demister action. Dry Compressed Air

Air from Compressor

Pre Heater

Referigeration Chamber

Moisture collector 16.7 Refrigeration-type air dryer.

Compressed air

305

The pipe lines are laid out in such a way that all vertical drop lines are taken upward from the horizontal line. Filters fitted in each machine separately collect whatever moisture can be separated by them. The pipelines should not end at the point where the connection to the machine is to be given. Its end should be somewhat at longer distance so that a drain valve can be fitted to separate the water. It is easier to separate the moisture from high-pressure air than from lowpressure air. This is because as the pressure increases the compressed air loses its capacity to retain moisture. This is the reason is why filters are provided on the high pressure side.

16.9

Quality of water required for compressor

Hard and unclean water supply to compressor causes scale/sludge formation in cylinder jackets in intercooler and oil cooler tubes and after cooler tubes etc. Sludge/scale formation does not permit heat transfer and causes the working part in the compressor to work at high temperature. This further reduces the life of working part of air compressor. Before installing a compressor, the water should be properly analyzed and if found hard, the water should be treated suitable to make it soft and clear.

16.9.1 Open re-circulating system water quality The recommended values are Temporary hardness Chlorides Sulphate (SO4) Total dissolved solids (residue at 105°C) Iron (Fe) Manganese (Mn)

50 mg/l 75 mg/l 50 mg/l 300 mg/l 0.2 mg/l 0.1 mg/l

16.9.2 Quality of re-circulating water The recommended water quality at equilibrium condition, which occurs at maximum temperature in the system are as follows: PH Permanent hardness Chlorides Sulphates Total dissolved solids Total suspended solids Iron (Fe) Manganese Free chlorine (Cl2) Organic components

6.8 400 mg/l (CaCo3) 300 mg/l 400mg/l 2500 mg/l 10 mg/l 0.2 mg/l 0.1 mg/l 4mg/l 25 mg/l (KMnO4)

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Modern approach to maintenance in spinning

16.10 What is oil free compressed air? Most of the people believe that air is 100% free from any type of hydrocarbon. But this is practically impossible because the ambient air inhaled by the compressor already contain lot of hydrocarbon and other pollutants. When the ambient air is compressed the concentration of all pollutant is increased with the ratio of final pressure. For example if we compress the air to a pressure of 6 bar the pressure ratio is 1:7. This means that 1 m3 of air with a pressure bar will have 7 times more pollutants and water vapour concentrated in this 1 m3 as was present in the ambient air. This shows that even with non-lubricated so-called oil free compressor the compressed air quality is always about 8 times more polluted than the ambient air. The best choice in the industry to use oil injected screw compressor than oil screw free compressor. First the complicated deign of dry screw compressor make it very expensive. It is better to use oil injected screw compressor equipped with an efficient oil separating system which can give the compressed the same air and often even better quality compared to oil free compressors. Even an oil free compressor will produce an air with an about 7 times higher concentration than ambient air due to the concentration effect of the compression. Note: In spinning mill where the air requirement is more than 500 CFM or more it is also advisable to use centrifugal compressor. These compressors may have several impellers in line on a single shaft or with separate impellers integrally geared. Centrifugal air compressors provide lubricant-free air delivery as there is no lubricant in the compression chambers. Lubrication for speed increasing gears and the special highspeed shaft bearings is kept away from the compression chambers by means of shaft seals, which may also have air purge and vent connections. But the centrifugal compressor is more expensive than oil injected screw compressor.

16.11 Air distribution systems The air distribution system links the various components of the compressed air system to deliver air to the points-of-use with minimal pressure loss. The specific configuration of a distribution system depends on the needs of the individual plant, but frequently consists of an extended network of main lines, branch lines, valves, and air hoses. The length of the network should be kept to a minimum to reduce pressure drop. Air distribution piping should be large enough in diameter to minimize pressure drop. A loop system is generally recommended, with all piping sloped to accessible drop legs and

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drain points. When designing an air distribution system layout, it is best to place the air compressor and its related accessories where temperature inside the plant is the lowest (but not below freezing). A projection of future demands and tie-ins to the existing distribution system should also be considered. Pneumatic systems are linked to air reservoir by pipes. A pipe, i.e. piping is subjected to shock load due to pressure changes inside the pipe. To avoid bursting of pipe good quality pipes are used, i.e. G.I. pipe. Piping must therefore be securely mounted and protected where there is danger from accidental damage. Line fittings such as valve and filter units have their own mounting and do not rely upon the support of pipe. Where flexibility is needed and working pressure is low. Nylon tubing or brass pipes are used. Pipe pieces are connected to get a longer length. The joining can be by means of welding, threaded connections and push type fitting. G.I. and steel pipes are connected by welding. Welded connections are leak-free and robust therefore these form the main choice for the fixed, main distribution pipe lines. However, threaded (elbow) connections are needed where a bend in a pipeline is desired or necessary. Plastic tubing is mainly connected by push type fitting and threaded connectors.

16.11.1 Lay out of pipeline While preparing the lay out for the pipe line, following points must be taken into consideration. 1. Use trench system. 2. Installed the pipe with a slope of 1% down from reservoir.

Slant 16.8 Slant.

3. Take every branch connection from top. TOP of pipe

16.9 Branch connection.

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4. Use proper sealant to avoid leakage. 5. Install moisture drain valve at the lowest point of the system so as to permit easy run off the condensation. 6. Do not finish the pipelines at the point of the connection to the machine. Extend it beyond the connection point and provide a drain valve at the end of pipeline.

16.10 Drain valve.

16.11.2 Importance of correct piping selection Selection of a proper size of the pipe is very important. In case the size is smaller than required, the compressor would discharge air at too high pressure than required (wasting power). In case the pipe size is larger installation cost would become unnecessarily high. An optimum size is that where the pressure drop is minimum between air reservoir of the compressor and workstation. Generally, such pressure drop in pipeline should not exceed 5–10 psig. Table 16.2 Pipe size corresponding to air flow Pipe inner diameter (mm) 10 15 20 25.4 32 40 50 65 80 100 125 150 200

Free air delivery (l/s) 3 5 10 17 34 50 115 200 330 500 900 1500 2000

Free air delivery (m3/min) 0.2 0.3 0.6 1 2 3 7 12 20 30 54 90 120

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Note If pipeline is more than 100 m, than use one size bigger than given in the Table 16.2. The graph in Fig. 16.11 shows the relationship between different parameters of pipelines and can be used to understand the way in which pressure drop can be kept to minimum.

16.11 Relationship between different parameters of pipelines.

16.12 Pneumatic cylinder It consists of five parts: two end caps (bearing cap and base cap) with port connection, a cylinder barrel, a piston and rod (Fig. 16.12). End caps can be secured to barrel by welding or brazing tie rod or by threaded connection. The inner surface of the barrel needs to be smooth to prevent wear and leakage. Generally, a seamless tube which machined to an

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accurate finish is used. The piston is usually made of cast iron. The piston not only transmits the force to the rod but also act as a sliding bearing in the barrel. A wiper seal is fitted to the end cap where the rod enters the cylinder, to remove the dust particles. End caps are generally made of cast iron and aluminum and incorporate the threaded entries for port. End caps have the capacity to withstand shock loads at extreme positions of piston travel. Piston seal

Extended Port

End Seal Port Wiper seal

End Cap Bearing Bush Barrel

Rod

Piston

16.12 Pneumatic cylinder.

The end of travel shock load can be reduced with the cushion valves built into the end caps. The exhaust flow route is now via de-acceleration valve, which reduces the speed and the end of travel impact. The deacceleration valve is adjustable to allow the de-acceleration rate.

Exhaust Port

Needle valve to set the decacceleration rate 16.13 De-acceleration valve.

16.12.1 Single acting cylinders These provide operating force/motion only in one direction; for the motion in other direction depend on a spring force or some external mechanical force. Normally, these cylinders have piston rod extension on one side only.

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Return Spring Extended port 16.14 Single acting cylinders.

16.12.2 Double acting cylinder They are capable of giving the operating force/motion in both the direction of the piston movement. These cylinders are available with or without end position to prevent mechanical damage. Retracted Port Extended port

16.15 Double acting cylinder.

16.12.3 Impact piston Pressure is initially applied to port X to restart the cylinder pressure. It is then applied to both port X and port Y but the cylinder remain in retracted state because area A is less than B.

Area A

Port Y

Port X

16.16 Impact piston.

Port X is vented properly. Since there is no pressure on side B side and A side experience full pressure due to which it accelerates rapidly at high velocity.

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16.12.4 Rotary cylinder Linear piston movement is converted to rotary motion by designing a rack and pinion arrangement, which allows the output shaft on actuator centre line rather than offset. Spring-loaded rack eliminates the backlash. Rotary cylinder has stroke adjustment at each end, which is combined with the adjustable, end position cushioning.

16.17 Rotary cylinder.

16.12.5 How to order pistons? The pneumatic cylinders are normally manufactured in bore size 12, 16, 25, 32, 40, 50, 60, 80, 100, 125, 150, 160 and 200 mm with a maximum stroke length of 100–1000 mm depending on the bore of cylinder for standard application. Different types of mountings are available in the market to mount the cylinder on the machine depending upon the space available and there need.

16.18 Cylinder mounting.

The following information must be given while ordering the piston. I. II. III. IV. V. VI.

Type of cylinder Size of piston diameter Cushion stroke Standard stroke working pressure range Type of cylinder mounting

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16.13 Regulator The main pressure in the machines is set higher than the required load pressure. Pressure regulation is performed at each machine to keep the pressure constant regardless of flow. Air pressure is regulated by mean of pressure regulator which simply restricts the air flow to the load. Regulators are of two types: non-relieving pressure regulator and relieving pressure regulator.

16.13.1 Non-relieving pressure regulator In this regulator, the outlet pressure is sensed by the diphagram which is pre-loaded by a pressure setting spring. If the outlet pressure is to low, then the spring forces the diphagram and poppet down, thus opening the valve to admit more air and raise the outlet pressure. If the air pressure is too high, it forces the diphagram up, reducing the air flow which causes a reduction in air pressure. In the steady state, the valve will balance the force on the diphagram from the outlet pressure against preset force on the spring. Addjusting screw

Pressure Setting Spring

Out

Inlet

Poppet 16.19 Non-relieving pressure regulator.

16.13.2 Relieving pressure regulator In the relieving regulator there are two diphagrams: main diphagram and pilot diphagram, which compares the outlet pressure with the adjusting pressure caused by setting the spring. Inlet pressure is applied to the main diphagram through a restriction and applied at the top of it. If outlet pressure is too low, the diphagram remains in the descended position and closes the ball valve. Due to this, the main diphagram descends downward to open the inlet valve and closes the vent to raise the pressure.

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If outlet pressure is too high, the pilot diphagram is raised above to open the ball valve and due to this the space above the main diphagram gets depressurized and raises the main diphagram. The main diphagram gets raised, causes the central vent valve to open and to allow the air to escape from load. The pressure thus gets reduced.

Adjusting screw

Pressure Setting spring Ball valve

Pilot Diphagaram Pressure Sensing line Main Diphagram Light spring Outlet

Inlet Inlet valve

Vent

Hollow Valve stem

16.20 Relieving pressure regulator.

The following information must be given while ordering a regulator of either type: 1. Pressure range 2. Port size 3. With filter or without filter

16.14 Lubricator It works on the principle of ventri, which creates a pressure difference between two surfaces. If the level of water in a capillary tube is to be raised then the pressure of water in the surface of container has to be increased. Lubricator in the pneumatic system works on the principle of the oil vapour lubricator, which mix the passing air with a very small percentage of oil atomized to microscopic fineness. This covers all the parts of succeeding system with oil film ensuring lubrication and rust proofing.

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y

R

P

T

X

C

Symbol for Lubricator

16.21 Lubricator.

Part of air entering inlet P is directed through the venturi R into the oil reservoir. The remaining air is diverted around an adjustable vane by pass. The air passing through venutri R creates a pressure difference, which causes the oil in the reservoir to flow up through the tube X to sight feed done Y. The action of air and oil creates finely divided oil fog in the upper part of the reservoir. All the oil particles larger than 2 m fall out returning to the oil reservoir and small particle remain air borne. The microfog represent about 5–10% of the oil which passes through the outlet to the air line then to the point of lubrication.

16.14.1 Setting The quantity of oil can be adjusted by turning the screw with a screw driver given on the top of lubricator. An arrow indicates the direction of rotation for increasing the amount of oil. If the amount of oil presented to air in the lubricator is less then there will be more friction inside the cylinder between the piston and cylinder wall, which would result in more heat, and would wear out the oil seal and o-ring, etc. If the oil amount presented to the air in the lubricator is more, then emulsification takes place, i.e. a sticky paste is formed which restricts the functioning of piston. If no specific guideline has been provided regarding oil lubrication then

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use the following setting provided. First open the outlet connection of lubricator. Place hand in the front of the outlet. If the oil is dropping from hand then reduce lubrication, as it is more. If hand remains dry then increase the lubrication.

16.14.2 How to order? The following information must be given while ordering I. II. III. IV.

Port size Flow rate in l/min Maximum supply pressure Bowl capacity

16.15 Moisture separator It works on the principle of centrifugal force, i.e. when a mixture of light and heavy particle move along the curved path. Centrifugal force would send the heavier particle towards the center. This lighter particle would continue to move with the same velocity and continue to move along a curve. In a moisture separator, the airflow through the unit is made to undergo a sudden reversal of direction and a deflector cone swirls the air. Since the air consists of light particles, it can bend easily but water particles are heavier. They are not able to keep to the curve and flung on to the wall of the separator. These water particles collect in the trap at the bottom from where the water can be drained.

inlet

Outlet

Symbol Glassbowl

Deflector Cone Filter Baffle

Swirl introduced by the deflector cone

Condensed Moisture Drain Plug 16.22 Moisture separator.

The water collected in separator should be drained out. It is advisable to check the separator after every 500 hours. If the fluid in the bowl of the

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separator has collected above the baffle disc, it has to be drained out. If it is not drained, then the separator would not function properly. The air will absorb moisture from the separator rather than removing it. In summer air will absorb more moisture; hence the separator must be checked before 500 hours. Maintenance 1. Clean the sight glass and inside fitting with soapy water. 2. Do not use solvent like petrol and CTC; they would decompose the plastic making it opaque. 3. Apply silicon grease to O-ring. 4. Replace the bowl immediately if the bowl is cracked, otherwise air would leak hence there will be a pressure fluctuation. A fine filter is provided to arrest all the impurities carried by the air. The filtration sleeve is made of sintered bronze with 25 micron pore size. It may clog up due to dust particles. To remove the clogged dust particles, unscrew the plastic container and take out the sintered insert; immersed it in a solvent then spin dry and leave to dry off. The filter insert should be re-fitted in dry state only.

16.16 Minimum pressure switch The switch prevents the machine from running without pressure or brings it to stop if the pressure falls due to any trouble in the pipe system or in compressor installation. The machine should stop when the pressure drops below t a certain minimum pressure which can be set on the switch. When the pressure rises above pressure set on the minimum pressure switch, then the machine re-starts. Operation The control signal pressure is applied to the bottom of the piston, and spring action is used for the reversed movement as shown in Fig. 16.23. The piston rod moves up against the spring pressure when the pressure is more than the preset value and moves down in case of pressure failure/ reduction. This downward movement actuates the control signal to stop the machine. Procedure for setting: 1. Set the regulator to the required pressure.

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Control signal

Spring

16.23 Minimum pressure switch.

2. Turn the nut no. 1 provided in the pressure switch clockwise until the pressure gauge reads minimum pressure to which it is to be set. 3. At this setting when pressure reaches the required value, the micro switch closes the circuit of machine. 4. Thereafter machine pressure can be set to the preset value for normal functioning of machine by regulator. 2

Control signal

16.24 Control signal.

16.17 Filters Filters are used to remove dirt and smoke particles before they can cause damage to the pneumatic equipment. Filters are classified according to the size of particles. Particle size is measured in micrometer. Dust particles are generally larger than 10 mm whereas smoke particles are around 1 mm. A filter can have normal rating (where it blocks 98% particles of specified size) or absolute rating (where it blocks 100% particles of specified size). Microfilters, with removable cartridge with air passing from the centre to outside of cartridge case, remove 99.9% of particles down to 0.01 mm. Coarse filters constructed out of wire mesh are called stainers, and are often used as inlet filters. They are usually specified in terms of mesh size, which approximates to the particle size in micrometer.

Compressed air Mesh size

Size (μm)

325 550 750

30 10 6

319

How to order? Following information must be given while ordering I. II. III. IV.

Port size Max supply pressure Filter size Bowl capacity

16.18 Safety valves The safety valve is set to blow off only when the pressure to the drafting arrangement increases more than the standard preset working pressure. As soon as discharge causes the pressure to drop below or equal to the working pressure, the safety valve seals tightly again. It is directly connected to the pressure regulator. A ball valve is closed by spring tension adjustable to required pressure. When the force due to air pressure exceeds the preset value of the spring force, then ball gets raised and valve opens and releases air thus reducing the pressure. A safety valve has a flow pressure relationship; therefore it self seals itself once the pressure falls below the cracking pressure. Adjustable screw Setting spring

Exhaust

Exhaust

16.25 Safety valve.

The following information must be given for ordering a safety valve: I. Port size II. Working pressure range

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16.19 Non-return valve It allows flow only in one direction. The simplest construction is the ball and seat arrangement. These valves are used normally where the system should not rapidly exhaust on removal of supply or to provide unidirectional flow in one signal line or supply line. They can be used in conjunction with a directional control valve to lock pneumatic cylinders in intermediate position. Ball

Light Spring

Free Flow Free Flow

16.26 Non-return valve.

The following information must be given to order this valve: 1. Working pressure range 2. Port size

16.20 Quick release valve It is used to vent cylinders quickly, i.e. cylinder speed can be increased by using these units. It is primarily used with spring return (single acting) pneumatic cylinder. The exhaust air is allowed to pass directly to the atmosphere instead (through the directional control valve) allowing the pressure on the exhaust side of the cylinder to decay much more rapidly. Port

Source

Port

Exhaust

Source

Exhaust

16.27 Quick release valve.

The following information must be given to order this valve: I. II.

Working pressure range Port size

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321

16.21 Micro valve It adjusts the rate at which air is admitted to or allowed out from a device that can control the speed of pneumatic cylinder. It allows full flow in one direction and restricted flow in other direction. Adjusting screw Needle valve Restricted flow Free Flow Air Blocked Flexible seal

Free Flow Free Flow Restricted flow

16.28 Micro valve.

The following information must be given to order this valve: I. Working pressure range II. Port size

16.22 Speed control device It is used to control the speed of an actuator. It determines the fluid flow rate and the actuator area. The physical dimension remains constant, so speed is controlled by adjusting the airflow. The two most common types of speed control devices are as follows: 1. Throttle disc 2. Throttle valve

16.22.1 Throttle disc It is the circular disc of brass with a hole of specific size. It is directly fitted on the orifice of input or output. Here speed is reduced by introducing simple restriction in the pipe that leads to the actuator. The restriction reduces the flow and allows speed to be reduced. It is used wherever constant lag time is required to build up the pressure.

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16.29 Throttle disc.

16.22.2 Throttle valve It is used where it is not practical to mount speed control fitting into the port of pneumatic cylinder. Therefore in line flow control, a regulator can be used to provide speed control. This valve operates by maintaining constant pressure drop across an orifice restriction in line and the rate being adjusted by altering the orifice. It is used in situations where the variation in lag time to build the pressure is needed. Adjusting screw

Restricted flow

inlet out let

16.30 Throttle valve.

The following information must be given to order this valve. I. Working pressure range II. Port size

16.23 Time delay valve They are used to delay the operation in a pneumatic system where a timebased sequence is required. Time delay control valve are available in two modes. 1. Normally closed timer gives pneumatic output a preset time after the supply of pneumatic input. 2. Normally open timer starts the application of pneumatic input and shut off the output after a preset time.

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The following information must be given to order this valve. I. Time delay amount II. Mode III. Adjustment method

16.24 Port flow control valve These fittings allow flow regulation for speed control and, at the same time greatly reduce the noise caused by exhausting air as the velocity of exhaust air jet is also reduced. These fittings are directly screwed into exhaust port of solenoid valve and these help in providing a safer working environment. The following information must be given while ordering. I. Port size II. Select flow rate III. Noise level permissible

16.25 Silencer This reduces the noise caused by exhausting air by reducing its velocity. The air velocity is reduced by diffusing the flow over a large area. This permits dealing with high flow rates hence no reduction in piston speed. This silencer is screwed into valve exhaust port, and provides a safe and more pleasant working environment. Only a port size needs to be mentioned for ordering a silencer.

16.26 Piping Pneumatic systems are linked to air reservoir by pipes. A pipe, i.e. piping is subjected to shock load due to pressure changes inside the pipe. To avoid bursting of pipe good quality pipes are used i.e. G.I. pipe. Piping must therefore be securely mounted and protected where there is danger from accidental damage. Line fittings such as valve and filter units have their own mounting and do not rely upon the support of pipe. Where flexibility is needed and working pressure is low. Nylon tubing or brass pipes are used. Pipe pieces are connected to get a longer length. The joining can be by means of welding, threaded connections and push type fitting. G.I. and steel pipes are connected by welding. Welded connections are leak-free and robust; therefore these form the main choice for the fixed, main distribution pipe lines. However, threaded (elbow) connections are needed where a bend in a pipeline is desired or necessary.

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Plastic tubing are mainly connected by push type fitting and threaded connectors.

16.27 Pressure hoses These are rubber hoses covered with canvas and are used for weighting the drafting rollers in different machines. For their proper maintenance, it should be ensured that the air is free from moisture and oil connectors should have proper sealing like tapes. These hoses become wet and sticky due to sweating. Therefore these should be removed from steel housing pipe once a year, cleaned, dried and refitted. While refitting, it should be ensure that pressure ledges do not act against the seam of hose

16.28 Push-type fitting These fittings are used as a connector of pipe and are also called touch fitting, since no tools are needed as in case of threaded fitting. The tube is connected to fitting by simple push and can be released by pressing a cap. Advantages of these types of fittings are 1. Full area of tube is available for full flow of air as holding is done by the outer part of the tube. 2. No tool is required for connecting and disconnecting. 3. Absolutely maintenance free for long time. Precautions to be taken while fitting the tube 1. 2. 3. 4.

Check outer diameter of the tube. Cut the tube ends using a proper cutting tool. Square the cut edge and free it from the burrs. When reconnecting the tube, cut the edge of the tube once again, square and burr free 10 mm away from the old edge of the tube to ensure leak proof joint.

How to order? 1. Name the type of connector. 2. Give the outer diameter of tube. 3. Give the detail of other side of connector.

16.28.1 How to use push-type fittings? 1. Opening the tube fitting

Compressed air

(a) (b)

325

Push the ring 1 in by using the right hand finger as shown in Figure 16.31. At the same time pull on the nylon tube 2 with the left hand. 1 a)

b)

2 16.31 Disconnecting a push-type fitting.

2. Connecting the tube (a) Push the tube 2 in. (b) Pull the tube 2 to check whether the connection is right.

2

16.32 Connecting a push-type fitting.

16.29 Threaded connector These metallic connectors have male part and female part on either side of pipe. The male part has an external threaded portion at one end and the female portion has an internal thread corresponding to the male threading. How to order? 1. Give the name of type of connector. 2. Size of both the threaded connector. Type of different connector are plug type connector, double nipple, pipe coupling, tee and elbow connector.

16.30 Barbed-type connectors These are made of brass or plastic and are used for connecting plastic pipes. Their ends are made taper and with several steps. This construction

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helps in tightening the fitting to piping. They are also provided with lock nuts which need to be ‘finger tight’ to ensure a pressure tight connection between the fitting and the tube. How to order? 1. Give the name of type of connector. 2. Give the internal diameter of tube to be connected.

16.31 Solenoid valve There are three types of solenoid valve that are made normally open, normally closed and universal valve.

16.31.1 Normally closed valve (NC) In normally closed valve the air is exhausted from the cylinder, i.e. no air is supplied and in the energized state air goes from inlet to cylinder. The spring used is longer and harder as it block the air at inlet. Top rubber in the plunger is softer while that at bottom is hard.

16.31.2 Normally open valve (NO) In normal state air goes from inlet to the cylinder in NO and in the energized state air goes from cylinder to exhaust. The spring is shorter and softer as magnetic flux has to overcome two forces one is spring and other is pressure. Top rubber plunger is hard. A soft rubber causes air leakage.

16.31.3 Universal valve It works like both NC and NO but it works in combination with NO and NC. How to check solenoid? Put the spring and the plunger in the coil and give electrical supply. If the plunger operates, it is in good condition. If it does not, it means that the coil is burnt. If electric supply is given without putting the plunger the coil will burnt.

16.32 Dial indicator It consists of a metal tube called bourdon tube oval in cross-section bent to form a circular segment of approximately 200–300 degrees. The tube is

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fixed in its position and is open at one end to which the pressure to be measured is applied. The other end of tube is closed but is free to allow displacement under the deforming action of pressure difference across the width. When pressure is applied then cross-section of tube tends to become circular. This makes the tube straighten itself out which results in an increase in its radius of curvature, i.e. free end moves away from the centre. The free end of the tube is connected to a spring load linkage which amplifies the displacement and transmits it as an angular rotation of a pointer over a calibrated scale. This gives a mechanical indication of the amount of pressure. A hair spring is used to fasten the spindle to the frame of the instrument to provide tension necessary for ensuring proper meshing of gear teeth. Thus the system is made free from blacklash. The reference point in the dial indicator containing the bourdon tube is usually the atmospheric pressure, so the pointer indicates the gauge pressure. Zero error sometimes occurs due to pointers becoming loose on the spindle. It remains constant for the entire pressure range. This error is rectified by repositioning the pointer in its correct position. Multiplication error can occur Where by the gauge tends to give progressively higher or lower readings. This error results from wrong setting in the multiplication mechanism between the bourdon tube and the spindle. To rectify this error, the multiplication screw is loosened and the connecting link is moved either a little inward (if the gauge reads low) or a little outward (if gauge reads high). Case Bourden tube

40 Quadrant 20 Endpiece Movement

Bezel Block Dial 16.33 Dial indicator.

Connecting link

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16.33 Compressed air system leaks Leaks can be a significant source of wasted energy in an industrial compressed air system, sometimes wasting 20–30 percent of a compressor’s output. A typical plant that has not been well-maintained will likely have a leak rate equal to 20 percent of total compressed air production capacity. On the other hand, proactive leak detection and repair can reduce leaks to less than 5 percent of compressor output. In addition to being a source of wasted energy, leaks can also contribute to other operating losses. Leaks cause a drop in system pressure, which can make air tools function less efficiently, adversely affecting production. In addition, by forcing the equipment to run longer, leaks shorten the life of almost all system equipment (including the compressor package itself). Increased running time can also lead to additional maintenance requirements and increased unscheduled downtime. Finally, leaks can lead to adding unnecessary compressor capacity. While leakage can come from any part of the system, the most common problem areas are as follows: ● Couplings, hoses, tubes, and fittings ● Pressure regulators ● Open condensate traps and shut-off valves ● Pipe joints, disconnects, and thread sealants

16.33.1 Estimating amount of leakage For compressors that have start/stop or load/unload controls, there is an easy way to estimate the amount of leakage in the system. This method involves starting the compressor when there are no demands on the system (when all the air-operated, end-use equipment is turned off). A number of measurements are taken to determine the average time it takes to load and unload the compressor. The compressor will load and unload because the air leaks will cause the compressor to cycle on and off as the pressure drops from air escaping through the leaks. Total leakage (percentage) can be calculated as follows: Leakage (%) = [(T × 100)/(T + t)] where, T = on-load time (minutes) t = off-load time (minutes) Leakage will be expressed in terms of the percentage of compressor capacity lost. The percentage lost to leakage should be 5% percent in a well-maintained system. Poorly maintained systems can have losses as high as 20–30 percent of air capacity and power.

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16.34 Leak detection Since air leaks are almost impossible to see, other methods must be used to locate them. The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize the high-frequency hissing sounds associated with air leaks. These portable units consist of directional microphones, amplifiers, and audio filters, and usually have either visual indicators or earphones to detect leaks. A simpler method is to apply soapy water with a paint brush to suspect areas. Although reliable, this method can be time consuming.

16.34.1 Ultrasonic leak detection Ultrasonic leak detection is probably the most versatile form of leak detection. Because of its capabilities, it is readily adapted to a variety of leak detection situations. The principle behind ultrasonic leak detection is simple. In a pressure or vacuum leak, the leak flows from a high-pressure laminar flow to a low-pressure turbulence. The turbulence generates a white noise which contains a broad spectrum of sound ranging from audible to inaudible frequencies. An ultrasonic sensor focuses in on the ultrasonic elements in the noise. Because ultrasound is a short wave signal, the sound level will be loudest at the leak site. Ultrasonic detectors are generally unaffected by background noises in the audible range because these signals are filtered out. Ultrasonic detectors can find mid- to large-sized leaks. The advantages of ultrasonic leak detection include versatility, speed, ease of use, the ability to perform tests while equipment is running, and the ability to find a wide variety of leaks.

16.34.2 How to fix leaks Leaks occur most often at joints and connections. Stopping leaks can be as simple as tightening a connection or as complex as replacing faulty equipment , such as couplings, fittings, pipe sections, hoses, joints, drains, and traps. In many cases, leaks are caused by failing to clean the threads or by bad or improperly applied thread sealant. Select high quality fittings, disconnects, hose, tubing, and install them properly with appropriate thread sealant. Non-operating equipment can be an additional source of leaks. Equipment no longer in use should be isolated with a valve in the distribution system. Another way to reduce leaks is to lower the air pressure of the system. The lower the pressure differential across an orifice or leak, the lower the rate of flow, so reduced system pressure will result in reduced

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leakage rates. Stabilizing the system header pressure at its lowest practical range will minimize the leakage rate for the system. Once leaks have been repaired, the compressor control system must be re-evaluated to realize the total savings potential.

16.34.3 Establishing a leak prevention program There are two basic types of leak repair programs: the leak tag program and the seek and repair program. The seek and repair is the simplest. As it states, you simply find the leak and repair it immediately. With the leak tag program, the leak is identified with a tag and logged for repair at a later time. This is often a two-part tag; one part stays on the leak and the other part is turned into the maintenance department, identifying the location, size, and description of the leak to be repaired. The best approach depends on the type, size, and the culture/work practices of the facility. It is more likely that the best solution will be a combination of the two.

16.35 Pressure drop and controlling system pressure Pressure drop is a term used to characterize the reduction in air pressure from the compressor discharge to the actual point-of-use. Pressure drop occurs as the compressed air travels through the treatment and distribution system. A properly designed system should have a pressure loss of much less than 10 percent of the compressor’s discharge pressure, measured from the receiver tank output to the point-of-use. Excessive pressure drop will result in poor system performance and excessive energy consumption. Flow restrictions of any type in a system require higher operating pressures than are needed, resulting in higher energy consumption.

16.35.1 What causes pressure drop? Any type of obstruction, restriction, or roughness in the system will cause resistance to air flow and cause pressure drop. In the distribution system, the highest pressure drops usually are found at the point-of-use, including undersized or leaking hoses, tubes, disconnects, filters, regulators and lubricators. On the supply side of the system, air/lubricant separators, after coolers, moisture separators, dryers and filters can be the main items causing significant pressure drops. The maximum pressure drop from the supply side to the points-of-use will occur when the compressed air flow rate and temperature are highest. System components should be selected based upon these conditions and the manufacturer of each component should be requested to supply pressure drop information under these conditions.

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331

16.35.2 Minimizing pressure drop Minimizing pressure drop requires a systems approach in design and maintenance of the system. Air treatment components, such as after coolers, moisture separators, dryers, and filters, should be selected with the lowest possible pressure drop at specified maximum operating conditions. When installed, the recommended maintenance procedures should be followed and documented. Additional ways to minimize pressure drop are as follows: ● ●

●

● ●

Properly design the distribution system. Operate and maintain air filtering and drying equipment to reduce the effects of moisture, such as pipe corrosion. Select after coolers, separators, dryers and filters having the lowest possible pressure drop for the rated conditions. Reduce the distance the air travels through the distribution system. Specify pressure regulators, lubricators, hoses, and connections having the best performance characteristics at the lowest pressure differential. These components must be sized based upon the actual rate of flow and not the average rate of flow.

16.36 Compressor air system economics In most spinning mills an interruption of compressed air supply means also an interruption of the production which can cause a big financial loss that is why most installations are equipped with a stand by compressor, because an even a short disruption of the compressed air supply can cause very costly production loss. Delivering compressed air in spinning mill is an expensive operation. Delivery requires costly compressed air manufacturing equipments, amount of electricity and needs frequent maintenance cost. To provide compressed air continuously with the lowest risk of interruption for the lowest possible cost is the major task of technician these days. To reduce the cost of compressed air one must analyze the factors which will contribute to the manufacturing cost of compressed air. 1. Electricity cost 2. Maintenance cost 3. Depreciation 1. Electricity cost – Compressor is a converter which converts one source of energy, i.e. electricity to another form of energy called compressed air. The most efficient this conversion is, lower the manufacturing cost. Electricity cost = compressor capacity × electricity consumption × electricity cost × operational hours.

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As a thumb rule 7 kW/h is required to produce 1m3/min air. 2. Depreciation cost = investment × depreciation, where as depreciation is normally 10% of capital investment. 3. Maintenance Cost includes all expenses required to run compressor like labour, spare parts, etc.

16.37 Maintenance of pneumatic system Table 16.3 Maintenance schedule for pneumatic systems Frequency

Items

Yearly Six Month

• • • • • • • • • •

Monthly Weekly

Daily

Check all pipe lines Check piston rod guides , guide bush , packing and sealing Check for leakage and performance of appliance Inspect and clean filters Inspect leaks in screw union, valves Inspect hoses for leaks links and fitness Check air gauges and pressure reducing valve Check lubricator for feed control and correct Drain condense water from filter Check oil level in lubricator

References 1. 2. 3. 4. 5. 6. 7.

Hydraulics and Pneumatics (1994) by ANDREW PARR. Festo Products 2002/2003 CD version 4/2002. Norgern product CD 98. Janatics Catalogue. Improving Compressed Air System Performance by U.S. Department of Energy. Compressed air engineering by Kaesar compressors. Pneumatic hand book by Antony Barber, published by Elsevier Advanced Technology. 8. Comprehensive Hand Book on Spinning Maintenance by NEERAJ NIJHAWAN. 9. Compressed Air manual by Atalas Copco.

17 Bearing and its maintenance

17.1

Introduction

During motion when two surfaces come in contact, the resistance generated is called friction. Two types of friction occurs when sliding friction and rolling friction. Sliding friction results when one surface slides over the other. In this type of motion the area of the contact between the two surfaces is large and hence the resistance is more. In rolling friction, the surface contact is less which results in less friction. Rolling friction is less than the sliding friction. Bearings are used to reduce friction and always work on the principle of rolling friction.

17.2

Bearing

1. Bearing consist of the following elements: inner ring rolling element, cage, outer ring and seal/shield.

Inner Ring Cage Rolling Element Outer Ring 17.1 Bearing.

17.2.1 Inner ring/outer ring The surface on which the rolling elements roll is referred to as the ‘raceway surface’. The load placed on the bearings is supported by this contact

333

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surface. The inner ring is used fitted on the shaft and the outer ring on the housing. These are made of high-grade carbon chromium steel with a high degree of cleanliness and surface finish. Both rings are made of different sizes and shapes depending upon the type of bearing. Both rings have a groove through out the circumference compatible to the size and type of rolling element. Each ring is given heat treatment so as to possess hardness between 59 and 65 HRC.

17.2 Rings of bearing.

17.2.2 Rolling element Rolling elements come in two general shapes: balls or rollers. Rollers come in four basic styles: cylindrical, needle, tapers and spherical. Rolling elements function to support the load while rolling on the bearing ring. The rolling element is held by the cage at a certain distance from each other between the inner ring and the outer ring. Rolling elements are made of carbon chromium steel, stainless steel or alloyed quality steel with hardness between58 and 65 HRC. Rolling elements are further classified depending upon their shape: 1. Ball is designated as RB available in the range 0.6–28 mm diameter.

17.3 Balls of bearing.

2. Roller are designated as RC and available in the range 4–70 mm diameter and 6–98 mm in length.

Bearing and its maintenance

Cylinderical

Taper

Spherical

335

Needle

17.4 Type of rollers.

17.2.3 Cage The main function of the cage is to keep the two successive rolling elements apart so that they will not come in contact with each other during movement. Use of the cage results in lower friction and lower heat generation. Secondly the cage helps in retaining the rolling elements during mounting and dismounting in case of separable bearings. Thirdly, it also acts as a reservoir for the lubricant since some grease always adheres to the cage. The cage is made from polyamide cage steel cage and brass cage. Polyamide cage Polyamide cage is used in small and medium sized bearing. It can be used up to working temperature of less than 120°C. When operating temperature is considerably above 120°C then bearing is fitted with metallic cage. Polyamide cage also is not suitable for temperature below –40°C as it loses elasticity.

17.5 Polyamide cage.

Steel cage Pressed cage made out of steel sheet are standard for many ball bearings, spherical bearings and most taper roller bearings. Steel can be used for temperature up to 300°C, and is not affected by organic solvent, synthetic and mineral based oils. There is a risk of corrosion due to presence of moisture.

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17.6 Steel cage.

Brass cage Pressed brass cage are used for small and medium size bearings. Brass cage cannot be used in case of 300°C. The use of alkaline cleaning agents is not recommend because ammonia causes season cracking in brass cage so brass cages are unsuitable where we use alkaline cleaning agent.

17.7 Brass cage.

17.2.4 Seal/shield Bearings which are equipped with a seal/shield contain optimum quantity of grease. Hence there is no need to grease these bearings after mounting. Shelf-life of shield bearings is less as compared to bearing without seals. The quality of grease deteriorates after the period of 2–3 year. They must be used on the principle of FIFO (first in first out).

17.8 Seal.

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Table 17.1 Difference between seal and shield Seal

Shield

Made of steel Gap between seal and inner ring Cannot prevent the dirt and foreign matter from entering inside the bearing Cheap Friction is less

Made of rubber No gap Prevents from foreign matter Costly Friction is more

17.2.5 Materials for bearing Steel used for any element of a bearing must possess the following properties: appropriate hardness, high fatigue strength, wear resistance and high stability at high temperature. Bearings are mostly made of either through hardened steel and case hardening steel. The through hardening steel has some carbon and 1.0–1.5% of chromium. This steel is fully alloyed with manganese and molybdenum to attain through hardening properties. The case hardening steel consists of chromium nickel and manganese with a carbon content of 0.15%. The bearings made from such steel can be used up to 125°C. If the bearings are required to operate at a temperature above 125°C then they need special heat treatment process.

17.3

Types of bearing

Bearings can be classified based on the nature of their rolling element or the load acting or the nature of application. On the basis of rolling element, bearings are divided into two categories: ball bearing and roller bearing.

17.3.1 Ball bearing The ball bearings provide a point contact, and so the friction is less. Ball bearing can be run at high speed but can carry less load. Ball bearings are further divided into three categories suitable for the type of load and applications: deep groove ball bearing, self aligning bearing and angular contact ball bearing.

17.3.2 Deep groove ball bearing These are the most common bearings used in the textile industry especially in spinning mill. These bearings can carry both radial and axial load. The bearing contains one row of ball bearing with a flat raceway in the inner

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ring and outer ring. These bearings are available in the market with seal or shield; and without seal or shield. Both radial and axial load simultaneously

Radial load

Width of bearing Ball

Bore Diameter

Outer Diameter

Axial Load

Cage

Inner Ring Outer Ring 17.9 Deep groove ball bearing.

17.3.3 Self-aligning bearing A self-aligning ball bearing has two rows of balls with common spherical raceways in the outer ring. This feature endows them with the self aligning Radial load

Ball

Outer diameter

Inner diameter

Inner Ring Outer Ring Width of bearing 17.10 Self-aligning cylindrical bore ball bearing.

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339

properties and permits them to work properly even with a slight misalignment of shaft relative to the housing. They are particularly suitable for application where misalignment can arise from errors in mounting or shaft deflection. These bearings are made with seal or without seal. They are also available with tapered bore and adapter sleeve.

Outer diameter

Inner diameter

Width of bearing 17.11 Self-aligning bearing with taper bore.

17.3.4 Angular contact ball bearing An angular ball bearing has the raceways of the inner ring and of the outer ring, displaced with respect to each other in the direction of bearing axis. This means they are suitable for accommodation of both radial and axial load. This axial load carrying capacity of an angular contact ball bearing increases with increasing contact angle a as shown in Fig. 17.12. This is defined as the angle between the line joining the point of contact between the ball and raceways in the radial plane (along which the load is transmitted from one raceway to another) and line ⊥ to the bearing axis.

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α

17.12 Angular contact ball bearing.

17.3.5 Single row angular contact ball bearing A single row angular contact ball bearing can accommodate axial loading in one direction only. This ball bearing has one high shoulder on each row enabling a large no of balls to be incorporated. This gives them very high loading capacity. Width of bearing

Inner Diameter

Outer Diameter

17.13 Single row angular contact ball bearing.

To counteract the axial load, these bearings are must be fitted in pairs. Normally three types of pairs are made: face to face, and tandem and back to back.

Bearing and its maintenance

Back to Back arrangement

Face to Face arrangement

341

Tandom arrangement

17.14 Arranged in pairs.

1. Back-to-back arrangement It can accommodate radial loads and axial loads in either direction. As it has a large distance between the acting load centre of the bearing, and therefore a large momentary force load capacity. Allowable misalignment angle is small. 2. Face-to-face arrangement It can accommodate radial loads and axial loads in either direction.. As it has a smaller distance between the acting load centre of the bearing, and therefore a smaller momentary force load capacity. But it can be used where more misalignment angle is required 3. Tandom arrangement It can accommodate radial loads and single direction axial loads. Axial loads are received by both bearings as a set, and therefore it can handle heavy axial loads.

17.3.6 Double row angular contact ball bearing These ball bearings are similar to two single angular contact ball bearing arranged back to back but they are narrower than that double width. They can accommodate both radial and axial loads in both directions and having a contact angle of 30°.

17.15 Double row angular contact ball bearing.

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17.3.7 Four point contact ball bearing These are single angular contact ball bearings with raceways, designed to take the axial load in both the directions and possess a contact angle of 35°. These bearings are made separable by design, i.e. the inner ring and the outer ring with ball and cage can be mounted individually/ separately. When the inner and outer rings receive a radial load the ball bearings contact the inner and outer rings at four points. This construction enables a single bearing to accommodate axial loads from either direction.

17.16 Four point contact ball bearing.

17.4

Roller bearings

These bearings provide a line contact at the roller element so they can function well at higher load and speeds. These bearings are further classified depending upon the shape of roller: cylindrical, spherical roller, taper roller and needle bearings.

17.4.1 Cylindrical roller bearing These are of four types: NU, N, NJ and NUP as shown in Fig. 17.17. The NU type has two internal flanges on the outer rings and an inner ring without internal flange. N type has an inner ring with two internal flanges and an outer ring with two flanges. Due to this arrangement some axial displacement of the shaft is permitted in both directions within certain limit, i.e. any change in length which take place due to as thermal expansion can be accommodated. Therefore these bearings are called non-locating bearings.

Bearing and its maintenance

343

Radial Load

width of bearing

Inner Diameter

Outer Diameter

NU

NJ

NUP

N

17.17 Four types of cylindrical bearing.

The NJ type bearing has two internal flanges on the outer ring and one internal flange on the inner ring so axial location can be provided for the shaft only in one direction. The NUP cylindrical bearing has two flanges on the outer ring, while the inner ring has an internal flange and one loose flange which permit the bearing to locate itself axially in both the directions.

17.4.2 Spherical roller bearings These bearings have two rows of rollers with a common spherical raceway in the outer ring. Two inner raceway rings are inclined at an angle to the bearing axis. The bearings are self-aligning and can accommodate slight errors of alignment of shaft relative to the housing. The bearing can accommodate axial load in both the directions.

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Modern approach to maintenance in spinning Both radial Load and axial laod simultaneously

Radial Load Width of bearing

Inside Diameter

Inside Diameter

Outside Diameter

Axial Load

Spherical roller bearing with cylinderical Bore

Spherical roller bearing with tapered bore

17.18 Spherical roller bearings.

17.4.3 Tapered roller bearings Taper roller bearings have tapered inner and outer ring raceways between which the tapered rollers are arranged. If extended, the tapered surface would Radial Load

Both radial load and axial load simultaneously

17.19 Tapered roller bearings.

Inside Diameter

Outside Diameter

Axial Load

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345

converge towards a single point on the bearing axis. This means the rolling conditions are optimum. Their axial load carrying capacity is largely determined by the contact angle, a which corresponds to the angle of outer ring raceway. The larger the angle the larger is the load carrying capacity.

17.4.4 Needle bearing This is one type of cylindrical roller bearing. A cylindrical roller bearing is called needle bearing when the ratio l/d of roller is greater than 2.5. Here l is the length of roller and d is the diameter of roller in mm. These bearings are used where there is a space limitation and the load is high. Radial Load

Inner Diameter

Outer Diameter

Width of Bearing 17.20 Needle bearing.

Mostly four types of needle bearings are used as shown in Fig. 17.21. 1. Cage needle bearing 2. Machined ring needle bearing 3. Drawn cup needle bearing

Cage Needle Bearing

Machined Ring Needle bearing

17.21 Types of needle bearing.

Drawn cup Needle bearing

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Modern approach to maintenance in spinning

17.4.5 Thrust bearings These bearings are used where heavy axial loads and intensive shocks to be borne are required. These are mostly single direction bearings and can accommodate the axial loads in one direction only. Only spherical roller thrust bearing can accommodate radial load in addition to axial load as the load is transmitted from one raceway to another at an angle to the bearing axis. They are also classified on the basis of type of roller element: thrust ball bearing, cylindrical roller bearing, needle roller thrust bearing, and spherical roller thrust bearing. Inner Diameter

Height of Bearing

Outer Diameter 17.22 Thrust bearings.

17.5

Bearing designation

Bearing designation describes the type of bearing, its load carrying capacity, and the diameter of shaft on which it is to be mounted. The first digit represents the type of bearing, second and third digits represent the load carrying capacity, i.e. width and outer diameter of bearing. The last two digits represent the diameter of the shaft on which the bearing is to be mounted. The bore diameter is obtained by multiplying the last two digits by 5. This is applicable only if last two digits are 4 and above. For less than 4, the bearing diameter is fixed as given in Table 17.2. Table 17.2 Inner diameter of the bearing Last two digits

Bearing inner diameter

00 01 02 03

10 12 15 17

The first digit position represents the type of bearing as given in Table 17.3.

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347

Table 17.3 Type of bearing First digit

Type of bearing

0 1 2 4 6 7 N 5 3 8 QJ

Angular contact ball bearing double row Self-aligning bearing Spherical roller bearing Deep groove ball bearing double row Deep groove ball bearing single row Angular contact ball bearing single row Cylindrical bearing Thrust ball bearing Taper roller bearing Cylindrical roller thrust bearing Four point angular contact ball bearing

Second and third digits represent the load carrying capacity. Table 17.4 Load levels Second digit

Type of load

o 1 2 3 4

Extra light load Light load Medium load Heavy load Extra heavy load

Example of bearing no. 6206 1. First digit ‘6’ represents that it is deep groove single row ball bearing. 2. Second digit ‘2’ represents medium size load bearing. 3. Last two digits ‘06’ represent 06 × 5 = 30 mm, the diameter of shaft on which bearing has to be mounted. If the bearing specification is not given or known, then its type is seen from its construction itself. The three useful dimension to be measured are the outer diameter D, inner diameter d, width or height if it is a thurst bearing. W

d

D

17.23 Measurements for cylindrical bearing.

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Modern approach to maintenance in spinning

For cylindrical bearing D = outer diameter d = inner diameter W = width of the bearing Thrust bearing D

H

d 17.24 Measurements for thrust bearing.

D = outer diameter d = inner diameter H = height of the bearing

17.6

Internal clearance

It is the distance through which the inner ring can move relatively to another and vice versa under no load, as shown in Fig. 17.25. There are two types of internal clearance: radial or axial. β

17.25 Internal clearance.

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349

17.6.1 Reasons for internal clearance. 1. The internal diameter of the bearing is always less than the diameter of the shaft on which the bearing has to be mounted. After the bearing is mounted, the inner ring expands and the internal clearance compensates for the expansion. 2. The diameter of the housing is made less than the outer ring diameter of the bearing, which results in interference fit of the bearing. The outer ring thus gets compressed thereby reducing the space available for b the rolling element. Internal clearance compensates for the above compression. 3. During running the temperature of various part of the bearing increases due to friction and heat generation. Steel will expand with rise in temperature leading to expansion of various parts of the bearing. Internal clearance is provided to compensate for such expansion.

17.6.2 Type of internal clearance Six different levels of internal clearance are provided in the bearings and are designated by suffix ‘c’ with an integer. Table 17.5 Bearing designation for internal clearance. Designation

Amount of clearance

C1 C2 Nil C3 C4 C5

Smaller Smaller Normal Greater Greater Greater

than C 2 than normal than normal than C 3 than C 4

Note: Normal clearance is not designated by any suffix. Example 6206 C3 it means the bearing has internal clearance greater than normal. If the bearing no. is only 6206, it means the bearing has a normal clearance. In case the bearing of recommended clearance is not available, then the bearing of the next higher clearance can be used so that various expansions can be compensated very easily.

17.7

Withdrawal sleeves with nut and locking washer

These are used to secure bearings with a tapered bore on cylindrical seats. Bearings are easier to mount and dismount using the withdrawal sleeves.

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Modern approach to maintenance in spinning

Use of sleeve permits locating the bearing at any position on the shaft. These sleeves are supplied in a complete set, with locking nuts and washers of the appropriate size. They are slotted and have an external taper of 1:12. Lock nuts have four or eight equally spaced slots around the periphery to take the hook and impact spanner. These facilitate mounting and dismounting on the withdrawal sleeve. Locking washers are engaged to a groove in the sleeve and lock the nut in position.

17.26 Withdrawal sleeve.

17.8

Bearing characteristics

17.8.1 Friction One characteristic of rolling bearings is that they produce less friction than sliding bearings, particularly starting friction. Friction of rolling bearings involves a variety of factors: 1. Friction that accompanies rolling (load). 2. Sliding friction between cage and rolling elements, and cage and guide surface. 3. Sliding friction between roller end faces and guide rib. 4. Friction of lubricant or sealing device. Table 17.6 Friction Factor for various bearing. Type of bearing

Friction factor ()

Deep groove ball bearing Angular contact ball bearing Self-aligning ball bearing Cylindrical roller bearing Needle roller bearing Tapered roller bearing Thrust roller bearing

1.0–1.5 1.2–1.8 0.8–1.2 1.0–1.5 2.0–3.0 1.7–2.6 2.0–3.0

Bearing and its maintenance

351

17.8.2 Temperature Almost all friction loss is converted to heat inside the bearing, causing the temperature of the bearing itself to rise. Bearing temperature is determined by the balance of the amount of heat produced and the amount of heat released. In most cases temperature rises sharply during the initial stages of operation, and then stabilizes to a somewhat lower temperature after a certain amount of time elapses. The amount of time it takes to reach this constant temperature differs according to various conditions such as bearing size, type, rotational speed, load, lubrication, and heat release of the housing. If constant temperature is never reached, it is assumed that there is something wrong. Possible causes are as follows: 1. Insufficient bearing internal clearance or excessive preload. 2. Bearing is mounted improperly. 3. Excessive axial load due to heat expansion or improper mounting of the bearing. 4. Excess/lack of lubricant, improper lubricant. 5. Heat is being generated from the sealing device.

17.8.3 Sound When the inner or outer ring of the bearing turns, the rolling elements roll along the raceway surface accompanying the cage, thus producing various sounds and vibrations. In other words, vibration and sound is produced according to shape and roughness of the rolling surface and sliding parts, and the lubrication status.

17.9

Lubrication of bearing

The objective of lubricating a bearing is to form a film of oil on the rolling and sliding surfaces to prevent metal parts from making direct contact with each other. Lubrication provides the following effects: 1. 2. 3. 4. 5.

Reduces friction and wear, Discharges friction heat, Extends bearing life, Prevents rust and Prevents foreign material from getting inside.

In order to get the most from the lubricant, one must choose a lubricant and lubrication method that suits your usage conditions, and must make use of sealing devices for preventing dirt from getting in and lubricant from leaking out.

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Modern approach to maintenance in spinning

Grease is widely used because it is easy to handle, it facilitates sealing device design, and is the most economical lubricant. The technique of varies lubrication according to whether bearings are either separable or non separable and whether their housing are split type or one piece.

17.9.1 Sealed bearing Sealed bearings where the grease is sealed inside the bearing. These sealed bearings do not need any re-lubrication. It is not advisable to open the seal/shield for lubrication, as the seal/shield will not fit tight properly again.

17.9.2 Non-separable bearing The deep groove and angular contact ball bearing are non-separable bearings. These should be filled with grease from both ends. In self-aligning and spherical roller bearings, the outer ring can be swivelled so that rolling elements are accessible. Grease can be then injected into all free spaces between them.

17.9.3 Separable bearing These include cylindrical, taper roller and all types of thrust bearings. These bearings are greased in separate steps, the same order to determine by mounting sequence. After mounting the first ring, if this ring has a non-separable ball/roller and cage assembly attached to it then grease the ring and fill the internal space with grease. If the ring is separate, it is sufficient to grease it lightly so that it will not get damaged when the outer ring with cage and ball/ roller is pushed on it.

17.9.4 Ball bearing in housing When ball bearings are contained in housing with removable cover and no grease nipple, they are managed with long-greasing intervals. Before regreasing, these bearings are to be dismounted and flushed out thoroughly. When fitting the bearing again the bearing and its housing is to be filled with grease, about one-third for shafts running at more than 500 rip. If the bearings are packed full then balls have no room to turn and the bearing gets hot. Slow running bearings may be packed full.

17.9.5 Bearing with grease nipple These bearings are lubricated with a grease gun as per schedule. These bearing require a very little quantity of grease (one or two strokes of the

Bearing and its maintenance

353

grease gun). Bearings in housing equipped with grease nipple require 10– 15 stroke of grease gun (10–15 g) of grease at every re-lubricating interval).

17.9.6 Precautions while lubricating a bearing 1. Use only the recommended grade of grease. If a higher grade of grease is used, it would become stiff at very low temperature results in poor lubrication. The rolling elements of the bearing rotate with difficulty and may slow down or stop completely in unloaded zone. When the elements pass back into the loaded zone, they are immediately forced to accelerate under load which results in heavy sliding. Lower grade grease is used then at high temperature, there is a risk of leakage of grease. At extremely high temperatures, the lubricate grease particularly metallic soap grease oxidize rapidly and then grease hardens and bleeding oil stops completely. 2. When a bearing is to be lubricated then first clean the grease nipple and area around the fitting to avoid any combination. 3. Never mix the grease of different thickener then resulting mixture will be either softer or sometime even much stiffer.

17.10 Mounting of different bearings The following precautions should be taken while mounting the bearings: 1. Clean the shaft and abutment shoulders and check the seating with regard to the diameter tolerance and accuracy. 2. Do not remove the bearing from packaging till mounting. 3. Protect the new bearing from dirt to the extent possible. 4. Leave the rust inhibiting compound intact except in the bearing bore and on the outer ring’s outside surface. Wash these surfaces with a petroleum-based solvent and dry. Four different methods are used to mount different types of bearings: mechanical, hydraulic, oil injection and heating method. Textile mills need only small size bearings and use only the mechanical methods to mount bearings.

17.10.1 Mounting a bearing on cylindrical seating by press method 1. Apply a light oil to the shaft and to the bearing bore. 2. Put the bearing square on the shaft. 3. Use the mechanical press (Fig. 17.27) to mount the bearing.

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Modern approach to maintenance in spinning

4. Placed a sleeve in between the press and the bearing abutting the ring of bearing. 5. Apply pressure till bearing reaches the seating area. Force

Force Tube

Tube Pressed into Inner Ring

Tube Washer Pressing against both the righs

17.27 Mounting press.

17.10.2 Mounting a bearing on cylindrical seating with hammer and matching sleeve 1. Apply a light oil on the shaft and the bearing bore. 2. Put the bearing square on the shaft so that bearing is mounted at right angle to the shaft. 3. Use an ordinary hammer or press and sleeve with impact ring to mount the bearing. 4. The sleeve should be made of one piece to moderate the blows. 5. Hammer the sleeve till the bearing reaches the seating area. Impact Ring Bearing

Impact sleeve

Shaft

Nylon Hammer 17.28 Mounting a bearing on cylindrical seating.

The precautions to be taken are as follows: 1. Never apply pressure in order to mount. 2. Never directly strike a bearing ring while mounting.

Bearing and its maintenance

355

Wrong 17.29 Hammering on ring.

3. Never use a soft hammer on breakage of such a hammer, fragments of soft material may go in the bearing while mounting.

17.10.3 Mounting a self-aligning bearing on the adapter sleeve 1. Wipe the preservative from the sleeve and from the bearing bore; then oil the outer surface of the sleeve lightly with mineral oil.

17.30 Wipe the preservative.

2. Apply oil to the threads and side face of the nut which is to abut the ring.

17.31 Applying oil.

3. Open the sleeve slightly with the help of a screw drive and slide it to the correct position on the shaft.

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17.32 Position the sleeve on the shaft.

4. Place the bearing on the sleeve and screw the nut. Tighten the nut just enough to ensure that bearing and shaft make contact with the sleeve. But do not tighten to drive the bearing further up on the sleeve. 5. Tighten the nut with a hook spanner to achieve the right fit. Turn the nut through 70–80°. Then reposition the spanner and tighten a few degrees more by tapping on the spanner with hammer. 6. To check the bearing for correct drive up, rotate the outer ring of the bearing. It should rotate easily but should resist swiveling. 7. Unscrew the nut, place the locking washer in position and then tighten the nut firmly again making sure that bearing is not further drawn up.

17.33 Unscrew and tighten.

8. Lock the nut by bending one of the tab from the locking washer down in the slot; but do not slacken the nut to get the tab to fit.

17.34 Bending a tab.

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357

A loose adapter sleeve can lead to the inner ring turning on the adapter sleeve and the adapter sleeve turning on the shaft. To ensure that the nut is not excessively tightened, make sure that that outer ring of the bearing rotates freely.

17.10.4 Mounting a spherical bearing on the adapter sleeve 1. Wipe the preservative from the sleeve and from the bearing bore; then oil the outer surface of the sleeve lightly with mineral oil.

17.35 Wipe the preservative.

2. Apply oil to the threads and side face of the nut which is to abut the ring.

17.36 Applying oil.

3. Open the sleeve slightly with the help of screw drive and slide it to the correct position on the shaft.

17.37 Position the sleeve.

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4. Before mounting the bearing, measure the radial internal clearance with a feeler gauge. The reduction of internal clearance is used as a measure of interference fit. 5. Use a feeler blade slightly thinner than the minimum value of clearance before mounting. 6. Insert it over the roller next to the upper most roller. In that position measure with an increasingly thicker blade until, when attempting to pull out the blade, there is a slight resistance.

17.38 Checking internal clearance.

7. Push the bearing up on the sleeve and check the reduction in internal clearance during the drive up under the lowest roller

17.39 Checking clearance after mounting.

8. Place the locking washer in position and tighten the nut firmly, making sure that the bearing is not driven up further. 9. Lock the nut by bending one of the tabs from the locking washer down in the nut slot but do not slacken the nut to get the tab to fit.

17.40 Bending a tab.

Bearing and its maintenance

359

17.10.5 Mounting double row angular contact and four point contact ball bearings of split type 1. Wipe the inner ring and outer ring of the bearing with dry cloth. 2. Put oil on the shaft and the seating of the bearing. 3. When the bearing is with split inner ring mount the inner half of the inner ring first. 4. Mount the outer ring with ball and cage. 5. Mount the outer half of the inner ring.

17.10.6 Mounting of old bearing Dismount the old bearing. It can be reused after cleaning. There are two methods of cleaning the bearing: hot and cold. Cold cleaning involves washing the bearing in petroleum-based solvents. Always use a clean solvent and clean tools: use one bowl for the first wash, and another one for the rinse. Dry the bearing and grease or oil it immediately after drying. Protect it from dirt till mounting. In textile industry mostly cold cleaning method is used. Hot cleaning needs thin oil with a flash point of at least 250°C. Heat the oil to about 120°C for washing the bearing. Hot cleaning is generally effective and the residual oil provides temporary protection against rust. Never wash the seal bearings; just clean their outer surface. Replace the bearing if it appears to be damaged. Before mounting, examine the bearing closely to determine whether it is re-usable. Inspect raceways, cage and rolling element for scratch marks and so on. Spin the bearing and listen to the sound. An undamaged bearing is one that has no marks or other defects and run evenly without abnormally large radial internal clearance and without any sound. If the dismounted old bearing is found to be very dirty or its lubricant is highly carbonized, it is generally not worth cleaning. It is economical and safer to install new bearing.

17.11

Dismounting method of different bearing

Four different types of methods are used to dismount the different types of bearing: mechanical, hydraulic, oil injection and heating method. Since spinning mills mostly use small size bearings, only mechanical methods are followed to dismount the bearings.

17.11.1 Dismounting method for cylindrical bearing 1. A bearing which has to be re-used should always be remounted in

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Modern approach to maintenance in spinning

the same relative position as before. It is therefore advisable to mark the position of the bearing before dismounting. 2. A small bearing can be dismounted using a conventional puller since the bearing is mounted with interference fit on the shaft. The puller should preferably engage the inner ring. 3. To avoid any damage to the bearing seating, the puller must be accurately centred.

17.41 Puller placed on the inner ring.

Only in cases where it is impossible to engage the inner ring, apply the puller to the outer ring. But it is very important that the outer ring be rotated during dismounting so that no part of the bearing is damaged by the dismounting force. This can be done by locking the screw and turning the puller continually until the bearing becomes free.

17.42 Rotating the puller.

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361

17.11.2 Dismounting a bearing mounted on adapter sleeve 1. Mark the adapter sleeve position on the shaft so that it can be remounted in the same position. 2. Disengage the tab of locking screw. 3. Loosen the lock nut a few turn. 4. Place a suitable dismounting sleeve against the lock nut and give a couple of sharp blows so that the bearing becomes loose. 5. Loosen the screw completely. 6. Take out the bearing. 7. Open the sleeve slightly with the help of screw drive and slide it from the shaft.

17.12 Reason for failure of bearings 1. When properly used, the only reason for the failure of bearing should be fatigue generated owing to long year of usage. However, relatively early failures can occur and do take place in spinning mills due to contamination, faulty mounting and dismounting method, improper lubrication, misalignment of shaft and careless handling. Bearing failures not only increase the cost of replacement and also cause excessive machine stoppage. Therefore, these five different factors that can cause undue early failures must be carefully eliminated from work practices.

17.12.1 Fatigue This type of bearing failure is due to the age of the bearing. With the passage of time, this failure mostly occurs owing to development of cracks under the load carrying surface due to the shear stress. These cracks gradually increase and extend up to the surface. When the rolling element pass over these cracks the edges of the cracks break due to pressure. This results in bigger cracks and leads to the failure of the bearing. This is natural process and is expected to occur after long period of several years.

17.12.2 Contamination Dirt is the main reason for contamination. Dirt is essentially silicon dioxide. It is the second hardest particle after diamond in nature. When a dirt particle ³ 5 mm gets forced through the gap between the ring and ball, it deforms the bearing permanently.

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Modern approach to maintenance in spinning

17.12.3 Lubrication of bearing Observation in industrial practice shows that most of the early failure of bearings due to poor lubrication. Therefore, it is vital to use the right lubricant, in the right amount, at the right place, in the right time and with the right method.

17.12.4 Misalignment of shaft Misaligned shafts leads to the following consequences: 1. Increased bearing load, which reduces the life of the bearing. 2. Increased wear of seals, which lead to contamination and or the leakage of lubricant. 3. Increased vibration and noise. 4. Increased energy consumption. Carefully inspect the misalignment of the shaft and ensure it is removed.

17.12.5 Careless handling Careless handling also leads to the early failure of bearings. The following precautions must be taken to ensure proper handling of bearings. 1. Bearings are coated with a rust inhibiting compound before packaging and can be stored in the original package for several years. 2. Keep the bearings in a vibration free lace 3. The seal and shield bearings have a limited time of storage as lubricating properties of grease have deteriorated with time, and result in high starting torque. Therefore follow the principle FIFO.

17.13

Examinations of bearing in service

The bearings can be easily examined in running condition and corrective action taken for reducing/eliminating defective working.

17.13.1 Checking for the noise of bearing Any noise from the bearing can be easily detected by placing the blade of a Stethoscope on the bearing housing and then listening carefully to the noise which is generated transmitted. If bearing is ok then soft purring sound will be heard. A squeaking noise may be caused by inadequate lubrication. A metallic tone possibly indicates that the clearance is not sufficient. A smooth but clear tone may be produced by a damaged outer ring. When the sound intensity varies regularly with each revolution it

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363

indicates that the inner ring is damaged. Noise can arise due to following reasons: foreign particles like dirt, cage failure, corrosion and/or indention caused by balls. If the defect is found to be severe, replace the bearing.

17.13.2 Checking the bearing temperature The bearing temperature should be checked at regular intervals in order to avoid possible future damaged to the bearing. If the temperature is high then the bearing must be running in poor condition. High temperature of the bearing could be due to following reasons: I. II. III. IV. V.

Over lubrication Under lubrication Mounting of bearing of wrong clearance Due to poor mounting Excessive load

17.13.3 Vibration Vibration can be detected by placing hand on the bearing or by using frequency or amplitude analyser. Any excessive vibration indicates that the bearing is running in abnormal condition. Vibration may be caused by unbalanced load due to wear, excessive internal clearance, corrosion, and foreign particles.

17.13.4 Condition of seals A seal not only takes care that no dirt particles enter the beating but also retains the lubricant in the bearing housing. Any leakage of seal should be eliminated immediately. The only reasons for such leakage are wear out seal, poor mounting of seal and breakdown of grease resulting in release of oil.

17.13.5 Checking the lubricant Grease – If the grease has hardened it should be replaced. If the grease has become brown or dark, it is an indication of oxidation. Take a little grease between fingers and rub it to check for lubricity and abraded particle. Replace the grease if found unsatisfactory on any item above. Oil – Take a small quantity of oil and compare it with the new unused oil. It is darker or thicker then it has become carbonized; replace it.

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References 1. SKF Bearing Maintenance Hand Book (1992). 2. SKF Bearing Catalogue (1992). 3. A Text Book of Machine Design by DR. P. C . SHARMA and DR. D. K . AGARWAL . 4. Technical catalogue NBC Bearing (2001). 5. SKF Needle roller bearing catalogue 4001, e-reg. 471-170001991-09.

18 Tools

18.1

Open-ended spanner

These can be single-ended or double-ended. Single-ended spanners are provided with holding mouth at one end only and the size of mouth is different according to the size of the bolt and/or the nut. In double-ended spanner, openings are provided on both ends and are of different considerable sizes. These spanners are forged from chrome vanadium steel and heat treated. The size of the opening between the jaws determines the size of the open end wrench. The length of the wrench is determined by the size of the opening since the lever advantage of the wrench is proportional to its length; spanners with larger openings are made longer and heavier to increase leverage and strength.

18.1 Double-ended spanner.

Double open-end spanners are available in following sizes: 6 × 7, 8 × 9, 10 × 11, 12 × 13, 14 × 15, 16 × 17, 18 × 19, 20 × 22, 21 × 23, 24 × 27, 25 × 28 and 30 × 32.

18.1.1 How to use? It is important for a spanner to be a snug fit on a nut or bolt head. If it is too loose, the spanner will slip and round the corners. Make certain that the spanner fits squarely on the sides of the nut or bolt head. Turn the spanner over after each swing so that the opposite face is down and the angle of the spanner opening is reversed. Always place yourself so that you can pull on the spanner to turn the work in the desired direction.

365

366

Modern approach to maintenance in spinning Wrench is snug fit

Right

Wrench is too large

Wrong

18.2 Ways to fit wrench.

18.2

Ring spanner

Ring spanners are so named because they completely surround or box the bolt head or nut. The opening in a box spanner contains 6 or 12 notches, called points, arranged in a circle. The box spanner is a safer tool than the open end spanner since it will not slip off the work. They can be singleended as well as double-ended. These are used only where it is not possible to use the open end spanner. These rings are made in different size to suit different sizes of nuts and bolts. They are double-ended spanners. They are designated by the inner diameter (mm) of the ring.

18.3 Ring spanner.

Ring spanners are available in sizes (mm): 6 × 7, 8 × 9, 10 × 11, 12 × 13, 14 × 15, 16 × 17, 18 × 19, 20 × 22, 21 × 23, 24 × 27, 25 × 28 and 30 × 32.

18.2.1 How to use? Always select the size of wrench that fits the nut or bolt head. Box wrenches will not slip off and are preferably used before open end wrenches. A swing through an arc of 15° is sufficient to continuously loosen or tighten a nut or bolt. Unless there is room to swing a box wrench in a full circle, lift it completely off the nut when it comes to the limit of its swing and place it in a new position which will permit it to be swung again. Since a box wrench cannot slip off a nut, it is ideal for loosening tight nuts and bolts and for setting them up.

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367

Sockets and accessories

The common socket wrench is box-like and made as a detachable socket for various types of handles. A socket wrench set usually consists of various sized sockets, a ratchet, sliding bar tee, speeder, speed tee, ratchet adapter, nut spinner, 3/8-inch drive handle, and extensions. Socket wrenches have two openings: one a square hole which fits the handles and the other a circular hole with notched sides to fit the bolt or screw head or nut to be turned. The handle has a retractable ball, which allows locking and releasing of the socket. Square opening of socket is available in four sizes 3/8", 1/2", 3/4", 1” and handles are available in the same four sizes and made in different shapes. Sockets are available in sizes which range from 10 to 32 mm.

Swivel handle

Sliding T Bar Extension Ratchet Speed Brace

Speed Tee

Universal joint socket

Deep Socket

Socket

18.4 Different sockets and accessories.

18.4

Torque wrench sockets

Sockets are also available with torque spanners. The torque wrench is a device which exerts only a pre-determined level of force while tightening. If greater force is applied, it does not get conveyed to the nut or the bolt, the wrench simply ‘slips’ after the predetermined force is applied. When assembled, two component parts are held together by a screw or by a nut and bolt. Therefore, each tightened nut-bolt is subjected to three major forces: over-tightening, vibrations and temperature changes. 1. Over tightening – When any part to be fixed, it may get subjected to

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Modern approach to maintenance in spinning

excessive force. Then the body of the nut or the screw has a tendency to stretch till the elastic limit is reached. Such nut or a screw would get permanently deformation or even may break completely if stretch beyond limits. Therefore, while tightening by using any kind of spanner, one should take into account also the strength of the component parts, which are usually not as strong as nut or bolt. Overtightening should be avoided. The fact that different people tend to exert more or less force than others needs to be considered. 2. Vibration – A large majority of equipments and machine in any industry have some motor or engine to operate it. Consequently, vibrations set in and often can cause loosening of parts that have been insufficiently tightened. 3. Temperature changes – When items have been assembled at normal temperature and then operate at different temperatures, i.e. mostly higher. They tend to loose due to expansion. Use of torque spanner avoids over-tightening while ensuring enough tightening to protect against vibration and temperature changes.

18.5

Allen key

An allen key is used for tightening or loosening set-screws. The allen key is made of steel in hexagonal cross-section through out its length. It is mostly made in L-shape, and in different shapes and sizes to suit the different sizes of set-screws. These are also available in sets, ranges from 1 to 18 mm.

Allen Key

18.5 Allen key.

18.5.1 How to use? Select the proper type and size that fits the recess of the screw being worked on. The short end of the wrench is used to give a final tightening or break

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369

loose tight screws. The long end of the wrench is used to turn the screw rapidly when very little leverage is needed.

18.6

Try square

Better known as engineering try square, this is a very common tool used for subscribing straight lines at right angle to any true surface, or for testing the trueness of mutually normal surfaces. It consists of a steel blade fitted into a steel stock of rectangular cross-section. They are well-hardened and tempered to suit to ensure rigidity and low wear. Try squares are made in different sizes. More accurate types of try squares are made with blades with bevelled edge properly ground and finished square. Both inner and outer surfaces of the blade are kept at right angles to the corresponding surface of the stock. In order to maintain this trueness, this tool should be handled with care and should never be used as a striking tool or supporting tool. Try squares are available in sizes 100 × 70 mm, 125 ×80 mm, 150 × 100 mm, 200 × 130 mm, 250 × 160 mm and 300 × 180 mm. The stock is simple or of magnetic type for ease of positioning it firmly at different places.

Blade Stock

18.6 Try square.

The accuracy of this tool should be checked frequently to ensure its ‘trueness’ it affects the accuracy of the finished job to the corresponding extent. The most commonly used method for testing the try square is showed in Fig. 18.6. In this method, the blade of try square is made to lie flat on the top surface of a surface plate with the stock touching the machine edge of the plate. A straight line is marked along the outer edge of the blade, and the try square is then shifted to take a new position, as shown by dotted lines in Figure 18.7. If both the lines coincide with each other, i.e. they appear as one line only, then the try square is confirmed to be true (angles equal 90° exactly) and accurate. If these lines do not coincide

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Modern approach to maintenance in spinning

with each other, the try square is inaccurate. An angle formed between the two lines as shown in the Fig. 18.7 would indicate that the square block and stock are fixed at an angle less than 90° to each other. However, if these lines appear in the reverse position, i.e. firm line in the place of dotted line then it would indicate an angle of more than 90° between the square blade and stock.

Plate

Surface

18.7 Testing the angle of try square for exact 90º.

18.6.1 How to use? To check a square joint, place the stock (1) against a horizontal section and the blade (2) against a vertical section. Light must not be seen around blade edge. If light is seen, the work is not square.

2

No Light

1 Vertical

Horizontal No Light 18.8 Measurements of try square.

18.7

Steel rule

This is the simplest and commonly known measuring instrument used in inspection. It works on the basic measuring technique consists of comparing unknown length to one previously calibrated. It is made of a hardened steel or wood or plastic and has line graduation engraved at interval of

Tools

371

fractions of a standard unit length which is in mm or in inches. Different combinations of a scale are found depending upon whether the scale is graduated on both sides or only on one side. The scale is generally of 150 mm or 300 mm.

18.9 Steel rule.

How to use a scale? To get good results, it is very necessary to follow the right technique when using a scale. (a) Generally, scales are worn out at the ends; so it is difficult to line up the end of a scale accurately with the edge of the part to be measured. Therefore, the scale must never be set with the edge of part to be measured.

18.10 Way to use scale.

(b) The scale should never be laid flat on the part to be measured because the graduation on the scale would not be in direct contact with the surface of the part, and it would be very difficult to read the correct dimension.

18.7.1 Folding box wood scale It is generally one meter long and is folded at three to six places and it is marked with inches and millimetres. They are available in two sizes 1 m and 2 m.

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Modern approach to maintenance in spinning Pivot

Catch Figure 18.11 Folding scale

18.7.2 Measuring tape The tape is a thin flexible steel strip. It is folded around a centre pin attached with a small handle. It is marked with inches and millimetres. It is available in different lengths from 1 to 100 m. The tape is spring loaded, so that as soon as it is released it will automatically return to the case. On some cases a lock is provided to hold the tape when extended.

Lock Tape Hook

18.12 Coiled-up tape.

18.7.3 How to use? A hook is placed at the end of the work piece to be measured so that long dimension can be measured single handed. Hook is loosely riveted on the tape and it is free to move in and out for a fixed distance when hooked over an object it extends by its own thickness so that measurement can be accurately taken from end.

18.8

Feeler gauge

These are used to measure the width of the gap between two parallel flat surfaces. A feeler gauge is a narrow strip of steel sheet of a given thickness.

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373

A complete set consists of number of gauging blades of different thickness from 0.03 to 1 mm assembled together and fulcrum med at one end. Their use depends entirely upon the sense of feel of the user.

18.13 Feeler gauges.

The blades are made of heat treated bright polished steel with tensile strength of 70 kg/cm2. Generally, the blades are 100 mm long and 12 mm wide at heel (fulcrum end) and tapered from the outer half of their length so that the width of the tip is approximately 6 mm (Fig 18.13). These are hinged in a sheath on a screw and a nut of such a design that each blade is removable. The nut is in the form of bush passing through both sides of the sheath and forms an hinge or a fulcrum upon which the blades can rotate. The sheath is so designed as to fully protect the blades when not in use. The different blades should be assembled in such a way that each thin blade is given maximum protection by interleaving it between two thicker blades. The maximum deviation in thickness of blade should not exceed 0.004 mm for blades up to 0.3 mm thick, and 0.006 mm for blades over 0.3 mm thick.

18.8.1 How to use? It is used to check the gap between the two matting surfaces. The feeler blade should neither have to be forced between surface nor should it slide freely. The correct thickness of blade will give a characteristic ‘gauge fits’ type of feel. If necessary two blades may be taken together for matching any dimension.

18.9

Hammers

A hammer is the main principle-striking tool and is made of forged steel. Their classification depends largely upon the size and the weight of the

374

Modern approach to maintenance in spinning

hammer. Factors which affect the working of hammer: size and shape of hammer, falling weight of hammer and height of falling hammer. A hammer is divided into four parts: pein, eye, cheeks and face. The pein is the top part made slightly tapered from the cheeks and rounded at the top. This top portion is given the shape of ball, and the portion between the ball and the cheeks is reduced in size by fullering, it gets a particular form known as ball pein hammer. The face is hardened and polished well and is given a slight rounding along the circular edge so that any metal surface is not spoiled by the sharp edge when the surface hit with the hammer. The eye is normally made oval or elliptical in shape to accommodate a handle or shaft. The straight pein hammer is one, which carries a pein parallel to the axis at one end and flat face at other end. The cross pein is similar in construction to the straight pein except the pein runs at right angle to the axis of the eye. Ball Face

Eye

Flat Face 18.14 Ball pein hammer.

Ball Pein Hammer Straight Pein sledge Cross Pein Sledge Double Ended Hammer hammer sledge hammer 18.15 Types of hammer.

If the hammer has no pein formation, but carries flat faces at both ends, it is known as double-ended hammer.

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The ball pein hammer is the most commonly used hammer in the spinning mills. These are available in sizes 200 g, 500g, 600 g and 800 g.

18.10 Soft hammers These hammers are double-ended hammers with ends made of nylon, which are replaceable. These are used whenever lighter force is required. There nylon heads are available in sizes of 250 and 500 g.

18.16 Soft hammers.

18.11 Dial gauge Dial gauges are used for checking flatness of surfaces; parallelism of bar and rods; and detecting small differences if any in linear measurement of identical objects. A dial gauge is also used for measuring concentricity of round objects. These are available in inches as well as in millimetre. Inch dial gauges of 0.001 “measuring accuracy is in general use, but gauges are available up to the accuracy of 0.0001”. The commonly used metric dial gauge has an accuracy of 0.01 mm.

18.11.1 Construction The clock-like graduated dial of dial gauge (Fig. 18.17) carries two pointer arms A1 and A2. The dial is divided into 100 equal divisions where each division represents spindle movement through 0.01 mm. In 1 mm movement of the spindle, the arm A1 makes one complete turn on the dial. The smaller arm A2 registers the number of full turns made by the longer arm A1. Figure 18.17 shows that the spindle carries a rack cut in its body along its length. It meshes with pinion P1, mounted on the same spindle as gears G1, G2 and the pointer arm A1. The gear G2 meshes with gear G3 carrying a helical spring. The pinion P1 also meshes with gear G4 mounted on the same spindle as pointer arm A2. When the instrument is not in use, the spindle projects a definite length outside the instrument under contact pressure of helical spring through

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Modern approach to maintenance in spinning

gear G3, G2, pinion P2, gear G1 and pinion P1 and the rack. To test a surface, the tip end of the spindle is brought in contact with the surface and readings of arm A1 and A2 are noted. Then either the dial gauge is moved over the surface or the surface is moved under the spindle. A clockwise deviation indicates deviation of arm A1 from the initial position indicated the convexity, and an anticlockwise deviation indicates concavity in 100th of millimetre; and that of arm A2 in full millimetre. Case

1 100

Spindle

Rack

A1 mm

G1

A2

A1

P1

G2

Graduated Dial A2 Spindle

P2

G3

Helical spring G4

18.17 Dial gauge.

18.12 Spirit level These are used for measuring any small angle or inclination and also for determining the position of any surface with respect to horizontal. A spirit

10

5

2

8

9

1

18.18 Spirit level.

7

6

4

3

Tools

377

level consists of a sealed glass tube ground on its inside surface to a convex form with a large radius of curvature. A scale is engraved on the glass at the top of tube. The tube is filled with ether to such an extent that only a small volume remains at the top part of the tube. This top part contains ether vapor in the form of a bubble. The spirit level consists of a body with a flat base surface and glass tube mounted on the upper part of the body. The side edge of the frame level is made strictly square with the base. A glass tube with ether enclosed mounted in the base. 1. Spirit level body with a highly machined location having flat and prismatic measuring faces 2. Level tube with main level 3. Adjusting cylinder 4. Positioning key 5. Zero adjustment screw 6. Twist stability adjusting screw 7. Adjusting cylinder locking device 8. Level cover 9. Transverse level 10. Transverse level adjusting screw The glass tube set in the base is adjusted in such a way that when the base is horizontal the bubble rests at the centre of the scale (which is engraved) on the glass. If the base level is not perfectly horizontal, the bubble tries to remain at the highest point of the tube and thus moves along the scale. Table 18.1 Availability of spirit levels in 6 sizes

Length (mm)

Sensitivity (mm/m)

100 150 200 250 300 500

0.02 0.01 0.01 0.01 0.01 0.01

18.12.1 How to use? Place the level on a flat horizontal surface. Check the horizontal dial (1). The bubble should be between the two etched lines on the dial. If it is not, the surface is not horizontal.

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Modern approach to maintenance in spinning

Place the level against a flat vertical surface. Check the vertical dial (3). The bubble should be between the two etched lines on the dial. If it is not, the surface is not vertical.

18.13 Vernier calliper The instrument is widely used for precision measurement of length, thickness, width, depth and inside of inner and outside diameters. The metric callipers are manufactured with a measuring accuracy or least count of 0.1, 0.02 and 0.05 mm. The vernier calliper having least count of 0.02 mm is the most commonly used. The ‘inches’ vernier calliper has least of 0.001 inch. A vernier calliper consists of a beam engraved with scale, inside and outside measuring jaws, depth gauge bar and an adjustable vernier head (slider) which can be moved along the beam. 2 7

6

9

4 8

10

5

3

1 18.19 Vernier calliper.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Outside jaw jaws for measuring outer diameter Inside jaws for measuring inside diameter Depth bar Step surface Main beam Slider Main scale Vernier scale Clamp screw Reference surface

Principle of vernier calliper consists of dividing a known length (main scale) into a certain number of equal divisions and then comparing length of one such division with length of one division marked with another line

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of one unit less or more length but divided into same number of divisions (vernier scale). The difference between the single divisions of these two scales is the smallest distance that can be measured (least count).

18.13.1 Metric vernier calliper of 0.1 mm accuracy In this vernier scale is 9 mm long and is divided into 10 equal divisions. Each division on the main scale measures 1 mm. From the above data Division of vernier scale =

9 10

One division of Vernier scale is shorter than the division of main scale by 1.0 – 0.9 = 0.1 mm. That is what is known as the least count of measurement.

18.13.2 Metric vernier calliper with 0.02 mm accuracy In this the vernier scale is 49 mm long and is divided into 50 equal divisions. The main scale as usual carries small division of 1 mm length each. 1 division of vernier scale =

98 49 = = 0.98 mm 50 100

It is shorter than 1 main scale division by 1 – 0.98 = 0.02 mm.

18.13.3 Metric vernier calliper with 0.05 mm accuracy In this the vernier scale is 39 mm long divided into 20 equal divisions.

39 = 1.95 mm 20 So it’s each division is smaller than 2 mm by 0.05 mm. Therefore, each vernier division is of

18.13.4 Reading the vernier calliper Before commencing any measurement, it should be ensured that the zero marks on the vernier scale and the main scale coincide with each other. If they do not, then the difference should be carefully noted and duly accounted for in the final reading. The method of reading vernier is as follows: Metric vernier has 0.1 mm accuracy. 1. Note the number of divisions of the main scale crossed by zero mark on vernier scale.

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Modern approach to maintenance in spinning

2. Note which vernier division is coinciding with any of main scale division. 3. Multiply the reading 2 by the least count and add to reading 1.

18.14 Digital vernier calliper Digital vernier callipers with a least count of 0.01 mm are employed for quick and free measurement. The benefit of using digitalized vernier calliper is that one can measure the size of any object without having to do steps 1, 2, 3 described above in section 1.11.4. In fact one can use the digital without knowing how to use the conventional vernier calliper. While using the conventional vernier calliper one has to keep track of a number of working parameters such as millimetres reading on the main scale, coinciding point of vernier scale as well as the least count of the instrument to arrive at the end result. This tedious process has to be eliminated by digitalizing the vernier callipers.

18.14.1 Working of digital calliper 1. Reference point setting – The measuring faces are closed gently and the clear button is pressed. Power is then switched on and zero is set. 2. Absolute value measurement – After zero setting as in 1, the instrument can measure the absolute value of inside, outside depth and step dimensions. 3. Comparative measurement – Press the ‘Clear button’ at a required dimensional value. The display will be set to 0.00 mm at that value, and the readings taken thereafter are for comparative measurements. 4. Inch/metric conversion instantaneous – Inch/metric conversion of any measurement can be obtained by pressing the mode selection button. Inch or mm is shown on the display along with reading. Inside Measurement jaw LCD Display Mode Button

Clear Button Outside Measurement jaw

Sliding jaw

18.20 Digital vernier calliper.

Main Scale

Depth Measurement Blade

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381

18.15 File This is a hand tool used by fitters. All the files irrespective of their shape, size and grade essentially consist of five main parts, i.e. point, edge, face, heel and tang which is fitted into the wooden handle. Files are generally forged out of high carbon steel or tungsten steel followed by cutting of teeth, hardening and tempering, etc. The files are manufactured in different varities and their classification is done based on effective length, shape or cross-section and depth spacing and cut of teeth. Face

Point

Heel

Handle

Ferrule

Tang

Edge 18.21 A typical file.

The length of a file is different according to the need, but the most commonly used length usually ranges from 10 to 40 cm. This range covers almost all sorts of filing work to be done by hand. Lengths between 10 cm and 15 cm are generally used for fine work, between 15 cm and 25 cm for medium work and 25 cm and above for all general and large size work.

1

5

4

3

2

6 7

18.22 Cross-section of files.

18.15.1 Cross-section Files are manufactured with shapes of different cross-sections (Fig. 18.22) to suit the nature of jobs for which they are to be worked on. 1. Square file – It carries double cut teeth on all the four faces (two faces and two edges) and is normally made tapered for about one

382

2.

3.

4. 5.

6.

Modern approach to maintenance in spinning

third of its length near the end opposite to tang. Square files without taper length are also available. Triangular file – This file normally carries single cut teeth on all faces and is tapered towards the end about two third of its length near the tip. The cross-section is an equilateral triangle. Round file – It has a circular cross-section and carries single cut teeth on all around its surface. It is normally made tapered towards the tip. Half round file – It has single teeth on curved surface and double cut teeth on flat surface. Flat file and hand file – Both these files have a rectangular crosssection (no. 5 and 6 in Fig. 18.23) and difference between them lies in the way they are tapered. A flat file is tapered towards the tip in length as well as in thickness, whereas the hand file is tapered in thickness only. The former carries double teeth on both the faces and single cut on the edges. In a hand file the flat faces carry double cut teeth and one of the edges carries single teeth. Knife edge file – The cross-section of knife edge file carries double cut teeth on broad faces and single cut teeth on the edge. It is specifically used in filing narrow and intricate sharp corners having an inclined angle of less than 90°.

18.15.2 Teeth The type of teeth and the spacing between teeth (known as pitch) play an important role in the selection of a file for particular work. Single cut – In single cut, the teeth are cut in parallel rows inclined at an angle of 60° with the centre line of faces. These are particularly suitable for filling hard metal. These give better finish as compared to double cut teeth but remove material at a comparatively at a low rate. 60

18.23 Single cut.

Double cut – There are two sets of teeth, one set similar to those of single cut; and the other running diagonally across the first set and inclined at an angle of about 10° to the centre line of faces on which teeth are cut.

Tools

383

All these teeth have a negative rake, i.e. sloping backward. Therefore these teeth thus cut only in the forward stroke.

18.24 Double cut.

Designation of teeth These files are designated as rough or smooth depending upon the pitch of the teeth. The smaller the pitch, the smoother is the file and the finer is its effect. The designations commonly used are as follows: Designation

Number of teeth per cm

Rough Middle or Coarse Bastard Second cut Smooth Dead smooth

8 10 12 16 20 40

18.15.3 Use and care of files The file should be held in perfect horizontal position. Most of the files have their teeth pointing forward, so pressure should be applied in the forward stroke only. The item to be filed-work is marked for filing and then is held in vice. Keeping the right hand on the front end, the file is moved firmly to and fro by the left hand with a speed of 15–20 strokes per minute. Rough files are used where more metal is to be removed, more and fine files are used for finishing.

18.15.4 How to use? 1. Clamp the work securely so that the area to be filed is horizontal and is parallel to and projecting slightly above the jaws. 2. Hold the file handle in one hand, thumb on top, and hold the end of the file with the fingers of the other hand. 3. When filing hard metals, apply pressure on the forward stroke only. Unless the file is lifted from the work on the return stroke, it will become dull much sooner than it should be.

384

Modern approach to maintenance in spinning

4. When filing soft metals, using pressure on the return stroke helps keep the cuts in the file clean. 5. Use a rocking motion when filing round surfaces. 6. When using a new file, applying too much pressure will cause the teeth to break off. Do not force the file. File slowly, lightly, and steadily. Too much speed and too much pressure cause the file to rock, rounding off the corners of the work.

18.16 Chisels These are used for chipping away some material from a work piece. Some very commonly used chisels are flat, cross cut and round. All chisel are 150 cm and 200 cm long are forged from the carbon steel and usually possess octagonal or hexagonal cross-section. After the desired shape is given to chisel during its manufacturing, the process of a annealing, hardening and tempering to follow make hardened finished chisel. The full length of chisel is never hardened; only a small portion above the cutting edge (20 to 30 mm.) is subjected to above treatment so that remaining length is left tough and comparatively softer, and therefore not brittle. The hardness of the cutting edge of chisel is kept about 70–75° for hard material, about 60° for medium hard material, and about 40° for soft material.

Flat Chisel

Cross cut chisel

Round Chisel

Point Chisel

18.25 Types of chisel.

18.17 Screw driver It is very useful tool for rotating screw with line slots on their head. It consists of a wooden or plastic handle, and a steel blade shaped at the end. The flat end of the tool is inserted into the slot provided on the head of the screw for rotating it. Screw drivers are made in various sizes to suit the corresponding

Tools

385

sizes of slot on the screw head and made of different lengths to tighten and to open screws with different torque. These are available in sizes 5 × 75, 6.5 × 80, 6.5 × 100, 8 × 125, 8 × 150, 11 × 200 and 13 × 250 mm.

Slot End Handle 18.26 Screw driver.

18.17.1 Star screw driver For rotating screw with star shape at the head, it is necessary to use a star shaped driver. It is also made in different sizes to suit the corresponding star shape on the screw head. These are available in sizes in 5 × 100, 6.5 × 125, 8 × 150, 4 × 75 and 5 × 75. It is important not to use a simple screw driver to open or close a star headed screw so as to avoid damage to screw head. Handle Star Shape

18.27 Star screw driver.

18.17.2 How to use? Choose a screwdriver which is correctly ground and the right size to fit snugly in the screw head. A rounded, chipped or undersized tip will slip and damage either the screw slot or the work itself. Similarly avoid using a tip that is too large and projects from either side of the countersunk screw. This will damage the screw. Rotate the screwdriver to open the screw.

Wrong 18.28 Correct way to use.

Right

386

Modern approach to maintenance in spinning

18.18 Vices Vices are the most suitable and widely used tool for gripping and holding firmly different job in position during various operations such as filing and drilling, etc, carried out in the maintenance department. These are available in different sizes and the selection of suitable sizes will depend upon the max. size of work it is expected to grip. The width of jaws determines the size of a vice. Different types of vices are used for different type of work like parallel jaw vice, pipe vice, etc. Jaw

Handle

Collar

A square threaded screw

18.29 A simple vice. Machinist Bench Vise

Bench and Pipe Vise

18.30 Different types of vices.

Clamp Bench Vise

Pipe Vise

Tools

387

The vice is fixed on a bench with the help of two bolts passing through the plank of wood and holes in the base of the vice. These bolts are tightened by means of nuts. The jaws of the vice are always kept over hanging the edge of bench. The vice is made of cast steel body with one fixed and another moveable steel jaw, and square threaded screw, and a fixed nut under the moveable jaw piece. The threaded screw is made to pass through the moveable jaw at the outer end. It carries a handle at the outer end and a collar inside so as to prevent it from coming out of the jaw when revolved. The threaded screw runs through the fixed nut longitudinally under the moveable jaw. Separate cast steel plates known as jaw plates are fixed to the jaw by means of set screws which are set finish with the working face of these plates so as not to protrude. The holding faces of these plates are provided with serrations to increase the gripping power of jaws.

18.18.1 Working For gripping any work piece in the vice the jaws are opened out by withdrawing the moveable jaw by rotating the screw. The work is held between the jaw by one hand and the screw tightened by rotating the handle by the other hand. This brings the jaw closer and ultimately the work is gripped between the jaws. The desired pressure on the work is attained by tightening or loosening the screw depending upon the need. The work to be held in the vice may be of regular or irregular shape and desired amount of grip can be applied. On account of serrations on the gripping jaw plates, there is always a likelihood of the working surface get damaged when gripped too tightly between the jaws. To avoid this soft plates made of copper or tin are placed between the work and jaw. This prevents the work surface coming in direct contact with the jaws. All these vices are available in sizes 3, 3.5, 4, 5, 6, 8 inches.

18.19 Punch The punch is a primary tool. One end of this tool is flat for hammering and other end is pointed having an angle of 60°. It is used for making round indentation on a metal surface for providing a specific location for making further operations such as drilling.

18.31 Punch.

388

Modern approach to maintenance in spinning

18.20 Hacksaw It is used to cut bar stock, rods, tubes, iron flats, etc, for desired lengths. It consists of a metal frame with a wooden handle carrying metal clips with a wing nut at its one end to hold and stretch a metal blade called hexa blade. The clip carrying the fly nut is threaded so as to accommodate and stretch the blade to the desired extent. The frame can be either of fixed type or adjustable type. In the fixed type, a blade of a given length only can be accommodated while in the adjustable type, blade of different length can be accommodated.

Adjustable Metal frame

Tension Rod Fly Nut

Pin

Blade

Handle

18.32 Hexa blade.

The hexa blade which is the main part is a push type blade which cuts only during its forward stroke. The hexa blade is a thin narrow steel band 12 mm or 16 mm wide and 0.65 and 0.8 mm thick and 250-300 mm long with saw teeth. These teeth always point away from the operator. The teeth of the blade are cut in such a way as to make the width of the cut slightly larger than the blade thickness. This facilitates the operation making it smoother, and also easier removal of saw dust. For a blade with 1 mm pitch, one tooth is set to the right, one tooth is set to the left and one is unset, i.e. it does not protrude beyond the width of blade. For blades with higher pitch, each tooth is set alternatively. For smaller pitch blades, every two teeth are bent to opposite side. Such setting of teeth increases the thickness of blade by 0.28–0.65 mm. from each end of the blade a length of 30mm is left unset.

18.33 Setting of teeth for 1 mm pitch.

The pitch of teeth to be used for different kinds of different cutting operation is given in Table 18.2.

Tools

389

Table 18.2 Pitch of teeth used for different cutting operations No. of teeth per cm 6 7 10

Type of metal Rolled and structural steel with thick section General cutting Brass and copper etc

18.20.1 Cutting operation While cutting, the hacksaw must be moved strictly in a horizontal plane. The cutting force is mainly exerted by the left hand while the right hand imparts reciprocate movement to frame. The cutting operation consists of two motions: a forward stroke, i.e. cutting stroke and a return stroke, i.e. non-cutting stroke. During the forward stroke both hands slightly press the saw downward to ensure its straight movement. In the return stroke, no pressure is applied, and the teeth just slide back along the cut. The blade should be run along the cut to ensure that its entire length is in action. Hacksaw blades are manufactured in two different categories: hard and flexible. The former are hardened all over while the flexible are hardened only along the teeth. The remaining portion is tempered to make it tough and comparatively soft. The latter type is most widely used and former type is used for cutting hard metal like steel.

18.20.2 Precautions to be taken during cutting operation The precautions to be taken during the cutting operation are as follows: 1. Reduce the pressure on the saw when the cutting operation is about to be over, i.e. when only 1.5 mm to 1 mm thick material remains to be cut. Otherwise blade under pressure may break. 2. Always use a new blade for cutting brass and bronze because even slightly worn out teeth result in slipping over material rather than in cutting. 3. Replace the blade if one tooth is broken in the entire blade. 4. Check and adjust the blade tension. 5. If any saw tooth breaks in the work while cutting, it is better to start the new blade on other point. This is to be done because the older cut is narrower than the blade thickness since the teeth of the teeth of old blade are slightly worn.

18.21 Taps Hand-operated taps are used for cutting internal threads in machine part or cleaning damaged thread. A tap consists of two parts: a toothed body

390

Modern approach to maintenance in spinning

and a shank. The toothed body has helical axial flute. These flutes are provided for the same purpose as in the case of a twist drill. For removal of chips taps having cutting edge slanting 6–10° to axis at the chamfer. The direction of slant is opposite to that of the thread, i.e. the slant is left hand for right hand thread and vice versa. The body consists of round shank and square formation at the end of shank which premises a firm grip by tapping handle called tap wrench. Hand taps of different sizes are available in three types known as taper, second, and plug tap (Fig. 18.34). In each threading operation they are used in the same order as first taper next second and last plug. The taper tap cuts a rough thread and removes up to 60 % of material. The second tap removes up to 30 % of material, and the plug tap removes the last 10 % of material. In the taper tap, the last five or six threads are ground out to produce a tapered surface. Thus, diameter of tap becomes slightly less or equal than the diameter of the hole to be tapped. This helps in advancing the tap without any difficulty into the hole. Each successive tooth increases the depth of the thread until the entire threaded portion of the tap has entered the hole. The tap wrench is a tool to hold the tap while cutting the thread. It is available in three sizes that are designated by the capacity to hold taps of different sizes i.e. 2–6m, 4.0–12.5 mm and 9–25 mm. Square shaft Fits in wrench

Shank Body

Toothed Body

18.34 Tapered tap.

18.21.1 Tapping procedure Select the right drill for drilling a hole before tapping

Tools

391

D=d–p D = hole diameter in mm d = major diameter of thread in mm P = thread pitch in mm After drilling the hole, insert the taper tap into the hole. Then press the tap wrench by the left hand and rotate it by right hand in clockwise direction till it cuts a few threads. After each clockwise revolution, rotate the tap by half revolution in anticlockwise direction. By doing so, chip breaks into small pieces and the cutting process become easier. When the thread cutting is complete, unscrew the tap completely and repeat the above process by using the second and last plug tap.

First

Second

Plug

Tapn wrench 18.35 Taps of different kinds.

18.22 Die and die stock Hand-operated threading die is the main tool used for cutting cylindrical thread on cylindrical parts such as bolts and studs. Whether it is made in two pieces or single piece, its steel hardened nut carries flutes cut along

392

Modern approach to maintenance in spinning

its inside surface that forms the cutting edge. Flexible dies have a slit ranging from 0.5 to 0.15 mm which allows the thread to be adjusted within the range of 0.1–0.25 mm. These split dies produce a thread of less accurate size as compared to the solid dies. A die stock is the frame work which is recessed in order to accommodate the die. The die is either made in one piece or consists of two halves. The frame work has a handle at each end of the centre piece, and guides on which the die pieces can slide along when placed in position. The stock is made in such a manner that several sizes of die can be accommodated.

18.36 Solid die and die stock.

Table 18.3 Availability of sizes of die and die stock Internal diameter (mm) 3–9 10–20 22–24 27–30

Outer diameter (mm) 25.4 38.1 50.8 63.5

Table 18.4 Availability of sizes of die stock Internal diameter (mm)

Length (mm)

25.4 38.1 50.8 63.5

215 350 490 600

18.22.1 Use of dies 1. Choose a proper diameter of the bar for cutting threads. 2. Make sure that that work piece to be threaded is clean and free from burrs. 3. Secure the work firmly in a vice.

Tools

393

4. Ensure that the die is held firmly in the die stock. 5. Apply cutting oil on the work and the die, and position the chamfer of the front face of the die squarely on the work. 6. Rotate the die slowly and firmly until the thread formation takes place. After cutting a few thread, check the die for square ness. 7. Turn the die back, a quarter turn, after each forward push to prevent teeth from breaking off and for ease of threading. 8. Back the die of newly cut thread carefully and check the cut thread with a proper screw gauge.

18.23 Grinding wheels A grinding wheel is metal cutting tool in which the tool has thousands of cutting edges instead of few large edges possessed by other rotary cutters. A grinding wheel is made up of grinding material which are a particles of a hard substance called abrasive embedded in a rough way as bricks and mortar. The abrasive grains constitute the bricks, and the bond holding them together is the mortar. There are thousands of edges of these grains are projecting from the surface of the grinding wheel. When applied to work, these grains act in the same way as tiny cutting tools.

18.23.1 Abrasives Earlier, two minerals are used as grinding material in grinding wheels were emery and corundum. Both of these are pure forms of aluminous oxide: emery consists of crystals of oxide embedded in a matrix form of oxide while corundum consists of aluminous oxide associated with varying amounts of impurities. Emery is about 60% pure and corundum is about 90% pure. Modern grinding wheels are made with artificial abrasives called silicon carbide and aluminous oxide. Silicon carbide is a chemical combination of carbon and silicon, whereas aluminous oxide is made from bauxite (hydrated aluminous oxide). Both abrasives are graded by sieving through screens having holes or meshes o different sizes. The grit signifies the number of mesh used to grade any particular size. Screens from 200 to 46 are generally made of silk, while those from 46 to 8 are made of wire.

18.23.2 Bonds The bond is a substance which when mixed with the abrasive grains holds them together permitting the mixture to be shaped in the form of a wheel; and after suitable treatment, to take on the necessary mechanical strength for its function. The degree of hardness possessed by the bond is called

394

Modern approach to maintenance in spinning

the grade of the wheel, which also signifies the ability of the bond to hold the abrasive gains in the wheel. A soft bond permits the grain to break away more readily than a hard one and should be used where the abrasive becomes more readily dulled, i.e. when grinding any hard material. A hard bond retains the abrasive longer and should be used on soft material. Several types of bonding materials are in use vitrified, silicate, shellac, rubber and synthetic resin.

18.23.3 Wheel specification The abrasive industries associations the world over/in India have adopted the British standardized marking system for grinding wheels. For example, wA46K5V specifications as shown in the chart below

18.24

Pliers

Circlips are spring circular retaining clips which are designed to engage in the internal and external groove, special pliers are needed to fit them. There is a small hole at the each end of circlip. Circlip pliers have cylindrical tips to fit into these holes. Pliers consist of a pair of jaws designed for holding the internal and external circlips before being located. They are made in two shapes straight or bent to suit the nature of jobs. The size is determined by the overall length of the jaw. Available sizes are tabulated here for pliers to be used for internal as well as external pliers. Straight nose

18.37 Different type of internal circlip plier.

Tools

395

Table 18.5 Different type of internal circlip plier Jaws

Circlip size (mm)

Straight Straight Straight Straight

or or or or

bent bent bent bent

8–25 19–60 40–100 85–250

Length L Length (mm) (mm) 24 39 42.5 73

135 170 210 280

Bent Nose

Return Spring

18.38 Different types of outer circlip plier. Table 18.6 Different types of outer circlip plier Jaws Straight Straight Straight Straight Straight

or or or or or

bent bent bent bent bent

Circlip size (mm)

Length L1 Length (mm) (mm)

3–9 10–25 19–60 40–100 85–250

31 31 48 57 75

135 135 175 215 280

18.25 Stud extractor Screw extractors are used to remove broken screws without damaging the surrounding material or the threaded hole. Screw extractors can be used only when a hole can be drilled in the centre of the thread of the stud to be extracted. Screw extractors are straight, have flutes from end to end. The stud extractor is used with twist drill, drill guide and turn nut. These are available in different sizes to remove screws with different outer diameter.

396

Modern approach to maintenance in spinning

Spiral Extractor

Hole drill in brokenscrew

Broken screw

18.39 Stud extractor.

Table 18.7 Size of the stud extractor Stud extractor diameter (mm) 4 5 6 8 11

Length (mm)

Drill (mm)

Diameter of stud (mm)

55 60 65 75 85

2.8 3.5 4.2 5.5 7.5

3–6 6–8 8–11 11–14 14–18

18.25.1 How to use an extractor? 1. Select the right size of drill and stud extractor to suit the diameter of stud of the broken screw. 2. Before using the extractor, make a sure that metal chips of the broken screw, if any are removed from the hole. 3. Drill a hole of the recommended diameter in the broken stud. 4. Drive the extractor into the hole. Slip the turn nut over the extractor and turn it clockwise, and thus turn the broken unit anticlockwise. The flutes grip the walls of drilled unit and remove it without damaging the threads of the tapped hole.

18.26 Kit for mounting of bearing Bearings are precision components and need proper tools for accurate mounting. It is estimated that 30–40 % of service life of bearing gets

Tools

397

reduced because proper tools are not used for mounting life and also due to improper mounting procedure. While mounting a bearing due care must be taken that the load is uniformly distributed on the outer ring or inner ring of the bearing. In case any un-even load comes on the bearing during its mounting, serious damage can take place within the rolling element and rings. This would lead to premature failure of the bearing. Bearing kit is a simple, convenient and versatile tool to mount any bearing correctly and systematically without causing any damage to the bearing and to the shaft. The tool consists of impact rings and impact sleeves. These are stored in a box. All impact rings /sleeves are made of alloy steel; machined, hardened and blackened for corrosion prevention, and individually numbered for easy identification. Each ring has a rubber –O-ring that keeps the ring joined to the sleeve during usage and also permits one sleeve to cover many rings. The commonly used kit comprises 33 rings, 05 sleeves covering bearing from 10 mm to 50 mm inner diameter. As generally bearing larger than 50 mm should be fitted by heating.

18.40 Bearing mounting kit: sleeve and rings.

18.26.1 How to use this kit? Apply some oil on the shaft on which the bearing is to be mounted. Using the selection chart given in the kit box, select the impact ring and impact sleeve suitable for the particular bearing. Place the bearing on to the shaft and place impact ring of the same on the bearing. Ensure that it covers the full face of the bearing; and then insert impact sleeve gently on the ring. Using a iron hammer and give gentle blow on the sleeve so that impact

398

Modern approach to maintenance in spinning

ring exerts uniform force on the bearing making it to move straight on the shaft up to the desired position. Bearing

Impact Ring Impact sleeve

Hammer 18.41 Mounting a bearing on a shaft.

18.27 Pullers Care should be always taken while dismounting machine elements like gears, pulleys etc to ensure that these are not damaged during dismounting. The job of extracting any machine element becomes very easy and safe with the help of a puller. The puller consists of two/three jaws. These jaws are usually made of heat-treated alloy steel. These jaws are made in one piece or two pieces depending upon the design of the puller. A puller with jaws made in two pieces consists of the main arm having Tee section on which a female Tee-section slides and is held by high tensile screws. An alloy steel spindle is placed at the centre of three arms. To reduce the load/fatigue on an operator, the spindle is provided with a fine pitch. At one end of the spindle there is a hardened/ground rotating centre provided with puller. The other end of the spindle is made square on which a tommy can be fixed. The rotating centre not only reduces the fatigue on the operator but also ensures that no damage is done to the shaft. The tommy facilitates positive rotation to spindle by offering a greater leverage. Pipe Jaw Main Arm

Tommy Holder 18.42 A typical puller.

Tools

399

18.27.1 How to use puller? 1. Check puller for smooth motion. Apply some oil on the moving parts to get smooth motion. 2. Centralize the male centre of the spindle of the puller on the female centre of the shaft. shaft

Center

Spindle

18.43 Centralizing the spindle on shaft.

In case the female centre of the shaft is bigger than male centre of the puller then n additional centre can be used as shown in Fig. 18.44.

shaft

Center

Spindle

18.44 Centralizing using an extra centre.

3. Adjust the jaw of the puller on the machine element and centralize these jaws. Keep equal gap or no gap between jaws and machine elements as shown in Fig. 18.45. Gap

Gap

Bearing 18.45 Jaw adjustment.

jaw

jaw

Bearing

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Modern approach to maintenance in spinning

4. Ensure full grip of jaw on machine element (Figure 18.46). jaw

Bearing

Jaw

Bearing Not Correct

18.46 Correct adjustment of puller jaws.

5. Insert tommy on the spindle and apply force on tommy. If the entire puller starts rotating then hold the jaws with hand to lock the rotation of the puller (Fig. 18.47).

18.47 Puller ready for extraction.

6. The puller is now ready for extracting the machine element. Rotate the spindle till the machine element is extracted.

18.28 Micrometer The micrometer is an accurate length/thickness measuring instrument which is based on the principle of lateral movement of a screw in each revolution, i.e. its lead. It consists of a screw with twenty threads per cm which revolves in a fixed nut. The end of the screw forms one measuring face and the other measuring face is a fixed one and is mounted in the base of the frame. The lead of the micrometer is 0.5 mm and can read 100th of mm. The barrel graduations on the outer sleeve are half millimetre and the millimetre, each 5mm being numbered. The thimble is divided into 50 equal divisions along its circumference. Thus one division on the thimble represent 0.01 mm which is the least count of micrometer.

Tools

401

The anvil and spindle end must be clean and the micrometer should be held truly square with the job while taking readings. The thimble by ratchet stud to ensure uniform grip at each measurement. Ratchet stop

Thumble

Spindle Anvil

Barrel Lock nut

Frame

18.48 Micrometer.

Thimble Outer sleeve 18.49 Reading a micrometer.

Graduations = 0.01 mm An outer sleeve reading of 7.00, and thimble reading of 37 means (7 + 37 × 0.01) = 7.37 mm since the least count is 0.01 mm.

18.29 Drill Drilling is an important operation carried out during maintenance work for producing different types and sizes of holes in different materials. The most important form of drill is a fluted twist drill. This drill is a thin, long cylindrical body carrying a spiral flute cut on its surface. Twist drills are usually made of high speed steel. The twist drill generally consist of two main parts, a shank which is gripped in the chuck of drilling machine and the body which forms the main cutting unit. Body is the entire cone shaped

402

Modern approach to maintenance in spinning

surface at the cutting end of drill. The drills are made in different forms to suit the work. The most commonly used type of drills are those with parallel or tapered shank. Parallel shank is provided on small drills (say up to 12.7 mm in diameter) and above sizes are provided with tapered shank which normally carries the morse taper. Tapered shank drills are provided with a tang at the end of shank to ensure positive grip. This tang position fit into the slot provided in the socket of the drilling machine. Advantages of using twist drills are as follows: 1. The chips and the cut metal are automatically driven out of the hole being drilled through the spiral flute of the body. 2. The cutting edges in good condition for a fairly long period, thus avoiding frequent grinding. 3. Heavier feeds and speed can be safely employed. 4. For any given size and depth of the hole they need less power as compared to other forms of drills.

Tang

Length of flute

Flute

18.50 Twist drill

18.30 Step ladder Step ladders, made of metal, are self supporting, having a frame hinged to the back of the ladder. Ladder has wide steps which lie horizontally when the ladder is fully opened. The hinged sections are fitted with folding stays to prevent them sliding open further than the optimum position. A platform at the top of the ladder carries tools.

Tools

403

Precautions Inspect step ladders before use paying particular attention to the condition of the steps, stays and hinges. Make sure that the steps are fully opened and on even ground before climbing on them.

18.51 Step ladder.

18.31 Oil cans Oil cans made from tinplate containers which pump the oil through the spout by squeezing the base of the container, to cans which incorporate a thumb-operated pump. Pumped oil cans are more suitable for lubricating machines as they can be used at various angles and incorporate long spouts which ran into confined spaces.

Handle

Delivery Tube

Thumb Operated Lever

Oil Reservior

18.52 Thumb-operated pump.

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Modern approach to maintenance in spinning

18.32 Grease gun Larger guns are used for greasing the bearing and are operated by lever or trigger. The grease is loaded into the grease reservoir from a grease container. The nozzle of grease gun fit into the nipple which has spring loaded seal. The trigger is pressed to force the grease into the bearing or housing through nipple. Trigger Nozzle for grease Nipple Delivery Tube

Pull Knob Grease reservoir 18.53 Grease gun.

18.33 Chalk line A chalk line is used to draw straight line on the floor. The line is contained in a case with coloured chalk powder. As the line is drawn from the casing a felt gasket distributes an even coating. The line has a hook and ring at one end for attaching to a nail or catching between floor boards. Hook Line Folding Rewind Crank

Case 18.54 Chalk line.

Tools

405

18.34 Knife Knife is used for cutting the lapping on bottom roll. It consists of a blade and retracting button which is use to retract the blade after use. Retracting Button

Blade

18.55 Knife.

18.35 Plumb bob The plumb bob is a pointed weight attached to a length of line which is contained in the bob itself and fastens in a slot in the cap. If the hardened point on the bob end becomes bent it will no longer give a true reading, so must be replaced. Hold the end of the line at the required point and allow it to settle out of its natural swing. Make sure that it is hanging free, and mark the point below the plumb bob.

Line

18.56 Plumb bob.

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Modern approach to maintenance in spinning

18.36 Requirement of tool for erection, installation and maintenance General requirement 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

Chain block with wire rope – 3 ton capacity – 2 no. Pallet truck – 2 ton capacity – 2 no. Floor drilling machine with 10, 12, 14, 16 mm drill bit – 1 no. Ladder with top working platform and castors 3 m height – 2 no. Ladder with top working platform and castors half meter height – 2 no. Crow bar – 4 no. ½” round bar – 1 meter height – 6 no. 2" G.I. pipe – 1 meter length – 6 no. Hand drilling machine with 2 mm to 12 mm drill bit – 1 no. each Bench drilling machine with 2 mm to 20 mm drill bit – 1 no. each Bench grinder – 1 no. Torch light for cell – 2 no. Fluorescent inspection lamp – 1 no. Extension reel with 25 m electric cable Forklift of 5 ton capacity – 1 no. Vertical spirit level 0.3 mm/m – 2 no. Horizontal spirit level 0.3 mm/m Prismatic calliper – 2 no. Digital vernier calliper – 1 no. Vernier calliper 150 mm and 300 mm least count 0.1 mm – 2 no. Dial gauge with magnetic stand – 1 no. Soldering iron 500 W – 1 no. Plumb bob – 4 no. Fish net nylon thread for lining – 50 m continuous length – 2 set Fish net nylon thread for lining – 10 m continuous length – 2 set Dyeing ink for marking on floor – 0.5 l. Measuring tape 50 m – 2 no. Marking pen –12 Chalk line size – 30 m

Tools 1. Nylon hammer – 0.5 kg and 1 kg each – 1 no. each of each department 2. Steel hammer –1/2 kg and 1kg each – 1 no. each of each department 3. Circlip plier (a) Inner – small and big – one no. each for each department (b) Outer – small and big – one no. each for each department

Tools

4. 5. 6. 7.

8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

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Bearing assembly tool kit – 1 no. each for each department Tap set – 3, 4, 5, 6, 8, 10, 12 – 1 no. each for each department Drill bit – 3, 4, 5, 6, 8, 10, 12 – 1 no. each for each department Spanner (a) Open end spanner set – 6–32 mm – 1 no. each for each department (b) Ring spanner set – 6–32 mm – 1 no. each for each department (c) Socket spanner set – 6–32 mm – 1 no. each for each department Allen key set – 1–18 mm – 1 no. each for each department Tri-square – 150 mm – 1 no. each for each department Feeler gauge – 1 no. each for each department Screw driver Star screw driver Chisel File rough of fine length 150 mm and 300 mm Hacksaw Steel scale – 300 mm Steel measuring tape – 3 m Bench vice Grease gun 0.5 kg Chisel flat end length 150 mm.

References 1. Workshop Practice Manual by V. KAPOOR . 2. Workshop Technology (1971) by W . A. J. CHAPMAN . 3. Workshop Technology (1982) by S . K. H. CHOUDHARY and DR . S . C . BHATTACHARYA. All the photographs and tables are sourced from above references.

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19 Tips to fine tune the spinning machinery

19.1

Introduction

In earlier days, the objective of maintenance was just to prevent mechanical breakdown but now-a-days the concept of maintenance has totally changed, i.e. good maintenance is supposed to prevent mechanical as well quality breakdown. The main objective of maintenance is to ensure high quality in the product, i.e. to make the products free from defect and faults. Quality breakdown does not mean that the mill is not able to achieve the required average quality parameters. Breakdowns refer to the rejection of lots due to only a few spindles that are producing faulty yarn. To avoid formation of such faulty yarn, it is very necessary that the spindle to spindle variation at ringframes and on winding machines, and machine to machine variation in pre-spinning. This is possible only when the maintenance teams must also act as quality teams and work with statistical quality control (SQC) department to provide the required result. Hence, the maintenance engineer must be capable of understanding and analyzing quality reports. The SQC reports normally show only the average values of the quality parameters, not the number or quality of the defectives. The numbers of the defectives need to be found out by the analyzing raw data on yarn tests and then noting down the abnormal readings or the outliers. The outliers are those readings which fall outside the normal limit of variability given in percentage by ±3 CV on both sides of the average value (e.g., if the average count is 30.4 and lea count CV is 2% then the normal variability is 30.4 ±6%, i.e. from 28.6 to 32.2. All readings falling beyond these limits are ‘outliers’ which should not more than 3 in 1000. If the outliers are more, preventive measures need to be taken to correct the defective spinning positions that cause an outlier to occur. In this way, the maintenance engineer and his team helps to reduce the numbers of defective by ensuring good mechanical conditions uniformly from spindle to spindle.

19.2

Blow room

Cotton reaches in the industry in the form of bales after ginning. These bales contain cotton in the compressed form and contain foreign matter

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which are used to deposit during the natural growth of cotton and during picking, ginning and transport. The foreign particles which find their way into cotton are as follows: Vegetable matter 1. Husk portion 2. Seed fragmen 3. Stem fragmen 4. Leaf fragmen 5. Wood fragments Mineral material 1. Earth 2. Sand 3. ore dust picked up in the transpor 4. Coal dust picked up in the transpor Other foreign matter 1. Metal fragmen 2. Cloth fragmen 3. Packing material The foreign matter leads to extreme disturbance during process. Metal parts can cause fire or damage card clothing. Cloth fragment and packing material can lead to foreign fibre in the yarn which is unsuitable for further processing. Trash can lead to drafting disturbances, yarn breaks and filling up of card clothing. Trash deposit can cause high wear rate in machines. The continuous research in the industry comes out with the conclusion that good yarn quality such as evenness, single yarn strength, breakage rate at different stage of spinning process and fabric appearance depends on the initial opening, cleaning and blending in blowroom. Hence main function of blowroom is opening, cleaning and blending of fibre without damaging the fibre, minimum fibre loss and with minimum nep generation. Today yarn purchaser not only demand the best possible yarn value but also consistent yarn value, so it is very important that one should pay more importance to opening, cleaning and blending technologies, i.e. right type of blowroom in your spinning mill. Basic operations in the blowroom: 1. Opening 2. Cleaning 3. Mixing or blending 4. Microdust removal

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5. Uniform feed to the carding machine 6. Recycling the waste Today, yarn purchaser demand not only the best possible yarn value but also consistent yarn value so it is very important that one should pay more importance to opening, cleaning and blending technologies, i.e. right type of blowroom in your spinning mill. The performance of blowroom can be checked by checking the following points in blowroom: 1. 2. 3. 4. 5. 6. 7.

Cleaning efficiency of blowroom Nep generation in blowroom Fibre rupture Control of CV% in airfeed CV% (lap to lap and within lap in case of lap feed) Width-wise variation in lap in case of lap feed Lap formation in case of lap feed

19.2.1 Reasons for high nep generation at blowroom Normally 100–150 % of increase in blowroom is considered as normal. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Low maturity in fibre Low micronaire fibre Blunt point of beaters Blunt point of grids Rough surface of conveying pipes Rough surface of vanes of transport fans High velocity of air Sharp bend in conveying pipes and more no. of bends Rough surface of covers where fibres come in contact Poor condition of spiked lattice Higher speed and too close setting More no of fans and beating points

19.2.2 Reasons for rich dropping Normally the lint percent should be less than 40% in the waste under any beater. 1. Amount of trash present in mixing. 2. Type of trash present. 3. Too close grid bar setting to beater with high beater speed give more waste. 4. Too wide feed roll to beater setting may give white waste.

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5. Feed roller weighing should be proper to avoid plucking of material. 6. If the angle between grids is too open white waste will be more or waste plate setting is high. 7. Running efficiency should be between than 85–90%. 8. Type of waste plate short waste plate give more waste and long plate give less waste.

19.2.3 Reasons for fibre rupture Fibres are considered to be ruptured at blowroom only if the span length 2.5 % drop by 4 % and/or the uniformity ratio drops more than 5%. 1. 2. 3. 4. 5. 6.

Low maturity Low micronaire Higher beater speeds at each stage Feed roll to beater setting to close Running efficiency at each stage is less Grid bar to beater setting is too close

19.2.4 Reasons for low blowroom cleaning efficiency Generally, cleaning efficiency of the blowroom ranges from 50–60%. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Type of trash present in mixing. Amount of trash present in mixing. Moisture percent of cotton. To reduce the feed at every stage. Increase the beater speed. Reduce feed roll to beater gauge. Increase the condenser speed but maintain the pressure by keeping the windows in pipe. Keeps the grid bar setting to minimum. Poor condition of beater. Less than the required no of beating points. The condition of air current should be proper. Excessive humidity in blowroom.

19.2.5 Reasons for ineffective suction in ducts 1. 2. 3. 4. 5.

Air leakages. Low Fan speed: check for belt slippage. High resistance to air flow due to chock ups, etc. Too long pipelines and sharp bends. Wrong direction of rotation of the fan.

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19.2.6 How to adjust the feed weight? 1. 2. 3. 4.

By By By By

adjusting the chute width. altering the opening roller speed. controlling the material level in chute. changing the draft between trio rollers to card feed roller.

19.2.7 How to control feed variability in chute feed line? 1. Ensure the uniform filling of all chute. 2. The proportion of the running time and idle time of the feeding machine should be about 90 % and 10 % respectively. 3. Adjust the exhaust opening for proper filling. 4. The feed roller in any chute feed should be run for the maximum time possible. 5. The differential pressure switch should be adjusted in such a way that as soon as the material is filled in the chute, the feeding machine is switched off. 6. Any material/dust accumulation on the perforated sheet should be cleaned. 7. Avoid lapping in the card feed rollers.

19.2.8 Reasons for patchy lap in case of lap feed 1. The tension draft between the calendar roller and the shell roller is too high. 2. Too low fan speed at cages. 3. Damaged grid bars. 4. Less opening of cotton flocks should be ensured. 5. Dust accumulation between the pedals (affects the sensitivity of the pedal levers). 6. Too high weight/metre of lap which will cause the reduction of beats per inch. 7. Too sticky tint which deposited in the hood and grids will obstruct the movement of fibre and cause lumps.

19.2.9 Reasons for lap licking 1. Improper deposition of the material on the cage across the width: the maximum variation allowed is ±8%. 2. Low calendar roll pressure. 3. High rack pressure. 4. Material in damp condition.

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5. 6. 7. 8. 9.

Spin finish not used while processing synthetics. Reduce fan and beater speeds. Maintain a RH% of about 50–55%. High gap between calendar roll to finger plate. The sticky nature of raw material and type of spin finish used in raw material. 10. More lap weight. 11. More soft waste %.

19.2.10 Reasons for conical laps 1. Calendar roll pressure non uniform across the width. 2. Rack pressure non uniform. 3. Non uniform suction at the sides of cage.

19.2.11 Reasons for bulky laps 1. 2. 3. 4.

In sufficient pressure for calendar rolls and rack. Tension draft not 1.0. High soft waste in mixing should be avoided. Low relative humidity .

19.2.12 Ring traveller on calendar roller 1. Introduce magnetic rollers. 2. Fix ‘magnetic track’ in the pipe lines.

19.3

Card

The proverbs of the experts ‘The Card is the heart of the Spinning Mill’ and ‘Well-Carded is half spun’ demonstrate the immense significance of carding for final result of the spinning operation. There is a strong relationship between increase in production and reduction in quality: the higher the performance, the more sensitive becomes the carding operation and the greater the danger of a negative influence on quality. The tasks of the card are given below: 1. Opening to individual fibres enables elimination of impurities and performance of other operations. 2. Elimination of impurities occurs mainly in the region of the taker-in. The degree of cleaning achieved by modern card is very high, in the range 90–95%. Thus, the overall degree of cleaning achieved by the blowroom and carding room together is as high as 95–99%. Card sliver still contains 0.05–0.03% of foreign matter.

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3. Elimination of dust is bound to the fibres. Significant fibre/metal and/or fibre friction is needed in order to loosen such particles, this are available in carding operation. 4. Disentangling of neps. The number of neps increases from machine to machine in the blow-room, the card reduces the remaining number to a small fraction, they are mostly opened out. Improvement in disentangling of neps is obtained by closer spacing between clothing; sharper clothing; optimal speed of taker-in; low doffer speeds; lower throughput. 5. Elimination of short fibres may occur at flats. Long fibres have more contact with the clothing of the main cylinder than the short fibres. Thus longer fibres are continuously caught and carried along the main cylinder, where the short fibres stay caught in the flats clothing, press into it and leave the machine in the flat stripping. The card eliminates very small percentage of short fibres about 1%. 6. Fibre blending or transverse blending occurs because the card is the only machine to process individual fibres. In formation the web, and with repeated rotation of the fibres on the main cylinder, intimate fibre with fibre mixing is achieved. 7. Fibre orientation. The card is often attributed the effect of paralyzing. A parallel condition is achieved on main cylinder, but it disappears during web formation between cylinder and doffer. 8. Sliver formation for further processing. Generally the hank lies between 4 and 5. The performance of card can be checked by checking following parameters: 1 2 3 4 5 6

Nep reduction Trash in sliver Waste percentage Uneveness of sliver Fibre rupture Sliver breakage

19.3.1 Reasons for low nep removal efficiency Normally 70–85% of nep removal efficiency is considered as normal. 1. Ensure that waste in mixing should not exceed more than 3.5% for carded count and 1.5% for combed count. 2. Flat in poor condition. 3. Cylinder, doffer and lickerin wires in poor condition. 4. Improper flat setting. 5. Improper speed of cylinder, lickerin and fla

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Poor transfer of fibre between cylinder and doffer wire. Flat loading problem. Improper lickerin to feed roll gauge. Improper cylinder to doffer gauge. Poor condition of stationary flats.

19.3.2 Reasons for fibre rupture in card 1. 2. 3. 4. 5. 6.

Flat gauge is too tight. Too narrow setting of feed plate to lickerin. High cylinder speed. High lickerin speed. Low micronaire cotton. Low maturity of fibre.

19.3.3 Reasons for poor cleaning efficiency Normally 90–95 % of cleaning efficiency in card is considered as normal. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Amount of trash in the feed. Type of trash. Poor condition of flat. Improper speed of cylinder, lickerin and flat. Cylinder, doffer and lickerin wires in poor condition. Improper flat setting. Poor transfer of fibre between cylinder and doffer wire. Flat load. Improper lickerin to feed roll gauge. Improper cylinder to doffer gauge. Poor condition of stationary flats. Humidity condition is not proper.

19.3.4 Reasons for high sliver unevenness Card sliver unevenness more than 3–4% is considered to be higher. 1. 2. 3. 4. 5. 6. 7. 8.

Too high tension draft. Worn out bearings. Worn out clothings. Size of coiler trumpet not adjusted to proper hank. Worn out belts. Transfer of fibre between cylinder and doffer wire poor. Good fibres going in the suction box. Auto-leveller not working properly.

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19.3.5 Reasons for more sliver breakage in card More than 2–3 sliver breaks/shift/card are not accepted. 1. 2. 3. 4. 5. 6. 7. 8. 9.

Cut in the web. Material falling from doffer. Narrow trumpets. Tension drafts high. Poor transfer of fibre between cylinder and doffer wire. Running efficiency of blowroom less than 90%. Auto-leveller not set correctly. Variation in the feed is too high. Worn out gear or belt.

19.3.6 Reasons for undercasing side fly at cylinder 1. 2. 3. 4.

Low micronaire. Squaring of cylinder undercasing not done correctly. Scratches on undercasing. Gauge not slightly loose in the middle of the undercasing compared to the left and right side edges. 5. Undercasing tongue setting improper. 6. Poor condition of cylinder and doffer wire.

19.3.7 Reasons for feed roll lapping 1. 2. 3. 4.

Pneumafil box choked. Very close setting between the feed roller and lickerin. Worn out feed roller and feed roller wire. Rubber flap on the feed roller is in poor condition and not in touch with the feed roller. 5. Feed roller loading is not in perfect condition.

19.4

Drawframe

Quality of the drawframe sliver determines the yarn quality. Drawing is the final process of quality improvement in the spinning mill. The function of drawframe sliver is given below: 1. 2. 3. 4. 5. 6.

Through doubling the slivers are made even. Doubling results in homogenization (blending). Through draft fibres get parallelised. Hooks created in the card are straightened. Through the suction, intensive dust removal is achieved. Auto-leveller maintains absolute sliver fineness.

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The performance of drawframe can be judged by checking. 1. Evenness of the sliver 2. CV% of sliver

19.4.1 Reasons for high sliver unevenness Drawframe sliver unevenness more than 2.0–2.5% is considered to be higher. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Improper roller setting. Improper total draft. Slivers from the creel roller should over riding each other. Eccentricity of drafting rollers high. Poor top rollers conditions. Under size cots. Incorrect pressure bar setting. Incorrect trumpet condenser. Tension draft too high. Auto-leveller not set perfectly. Worn out bearings and belt.

19.4.2 Reasons for high CV% 1. 2. 3. 4. 5. 6.

Improper setting of auto-leveller. Improper roller setting. Improper total draft. Slivers from the creel roller should over riding each other. Eccentricity of drafting rollers high. Poor top rollers conditions.

19.5

Comber

Combing is the process which is used to upgrade the raw material. It influences the following yarn quality: 1. 2. 3. 4. 5.

Yarn evenness Strength Cleanness Smoothness Visual appearance

In addition to the above, combed cotton needs less twist than a carded yarn. To produce an improvement in yarn quality, the comber must perform the following operations.

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1. Elimination of short fibres 2. Elimination of remaining impurities 3. Elimination of neps Following parameters must be checked to judge the performance of comber machine: 1. Combing efficiency 2. Nep removal efficiency 3. Evenness of sliver

19.5.1 Reasons for variation in waste% between head and machine The waste at combers needs to be checked regularly as 1. Higher waste than nominal result in financial loss. 2. Less waste than nominal leads to poor yarn quality and also result in count variation between bobbins. Reasons for variation in waste % between head and machine are as follows: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Variation in mixing from time to time. Variation in blending of different cotton. Variation in unsuitable and unproportional mixing of soft waste. Variation lap weight. Insufficient draft in lap preparation. Bad mechanical condition of lap machine like bent weighting hooks, defective top rollers and variation in top roller pressure. Bad condition of comber machine parts like brush, unicomb and top comb. Differences in top comb penetration from head to head. Poor nipper grip and bent nipper on some of the heads. Difference in ratchet gear, count change gears and tension change gears between combers working on given mixing.

The head-to-head variation can be controlled to the level of ±1.5%. The comber-to-comber variation can be controlled to the level of ±0.5%.

19.5.2 Reasons for high comber sliver unevenness Comber sliver unevenness more than 2.5–3.5% is considered to be higher. 1. Top rollers eccentric, too small diameter of top roller, uneven load.

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2. Dirty lap tension roller, nipper, fluted roller, table top rollers, fleece guide, trumpets etc. 3. Non uniform, inadequate nipper grip. 4. Higher gap between nipper and unicomb. 5. Dirty half lap needles in unicomb. 6. Unicomb too much backward. 7. Too wide setting in drafting. 8. Top detaching roller eccentric.

19.5.3 Reasons for low nep removal efficiency The nep removal efficiency at comber should be 50–60%. 1. Lap weight – there should be around 5 lakhs fibre in lap for new combers and 4 lakhs fibre in lap for old combers. 2. Lap preparation – the pre-comber draft should not be more than 10. It is better if it lies between 6 and 7. 3. Top comb penetration insufficient. 4. Unicomb to nipper gap too wide. 5. Lap weight excessive. 6. Lap preparation with insufficient total draft. 7. Uncleanliness of unicomb. 8. Unicomb too less backward. 9. Poor condition of brush and improper setting.

19.6

Speedframe

Roving machine is complicated, liable to faults, causes defects, adds to production costs and delivers a product that is sensitive in both winding and unwinding. This machine is forced to use by the spinner for the following two reasons. 1. Sliver is thick, untwisted strand that tends to be hairy and to create fly. The draft needed to convert this is around 300–500. Drafting arrangements of ringframes are not capable of processing. This strand in a single drafting operation to create a yarn that meets all the normal demands on such yarns. 2. Drawframe cans represent the worst conceivable mode of transport and presentation of feed material to the ring spinning frame. The speedframe perform following functions: 1. Attenuation-drafting the sliver into roving. 2. Twisting the drafted strand. 3. Winding the twisted roving on a bobbin.

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The performance of speedframe can be judged by checking the following parameters: 1. Roving end breakage 2. CV% of roving

19.6.1 Reasons for more roving end breakage Roving breaks less than 1 per spindle hours are considered acceptable. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

Groove cut or improperly buffed top rollers. Bottom rollers with burrs, greasy materials. Thick places in sliver resulting in undrafting ends. Singles present in the sliver. More tension in the creel or creel rollers not rotating. Hard piecing in the sliver. Clearers fully covered with waste. Choking inside flyers. Improper tension in the roving. Mix up of bobbin of different diameter. Low top arm loading not proper on some spindles. Different number of wraps on the pressure finger. Poor condition of bottom and top apron is not proper. Saddle gauge differs from spindle to spindle. Poor condition of false twister. More number of skived bottom aprons. Weak broken end suction. Spacer too narrow and less break draft. Pressure fingers worn out. Low twist in roving.

19.6.2 Causes of high variation in CV% of roving 1. 2. 3. 4. 5. 6. 7.

Stretching of sliver at feed. High variation in bare bobbin diameter. Improper choice of ratchet wheel and lifter wheel. Load variation between top arms. Choking of flyers. Number of wraps on the pressure finger not same on all spindles. Improper bobbin built up.

19.6.3 Reasons for load variation between top arms 1. Bent pressure ledge.

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2. Poor condition of hose. 3. Non uniform air pressure or diameter of top roller. 4. Poor condition of arms.

19.6.4 Reasons for slough off of roving 1. Improper fitting of empty bobbin on the bobbin driving wheel pin. 2. Broken roving end not pieced immediately (reduction in bobbin diameter may leads to slough off). 3. Bobbin trough not well-balanced and not traversing up and down freely. 4. The joint key in the carriage shaft not sufficiently tightened. 5. Adjustment of the compensating rail and setting of the initial position of the cone belt on the cone drum not correct. 6. Wraps around the pressure finger not same on all positions. 7. Bent pressure finger on some spindle positions. 8. Taper angle of the bobbin between 40° and 45°.

19.7

Ringframe

Ringframe is the final stage of producing yarn. Ringframe performs the following functions: ● ● ●

To draft the roving until the required fineness is achieved. To impart strength to the fibre, by inserting twist. To wind up the twisted strand (yarn) in a form suitable for storage, transportation and further processing.

The performance of ringframe can be judged by the checking the following parameters: 1. 2. 3. 4.

End breaks in ringframe Yarn imperfection Yarn hairiness Yarn CV%

19.7.1 Reasons for more end breaks Following precautions/measure should be taken to avoid more end break. End breaks more than 3 per 100 spindle hour. 1. Creel breaks due to low roving T.M. 2. Excess friction in some bobbin holders. 3. Improper spacer size.

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Non uniform top roller pressure. Improper ring traveller and ring combination. Poor Condition of cots on some spindle positions. Non-centred spindle-ring and lappet hook on some spindles. Ring rail not balanced properly. Improper fly catcher gauge. Poor condition of rings and lappet hook. Worn out gear. Wear of traveller. Too quick change over from Slow to fast spindle speed. Bad condition of some separator.

19.7.2 Reasons for higher imperfections When some bobbins are seen to give more than 100% increase over the average number of thick places or neps, or more than 300 in thin places, the corresponding spindle positions would have one or more of the following deficiencies. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Eccentric top roller. Eccentric bottom roller. Misalignment of top roller w.r.t. Bottom rollers. Improper draft field setting. Jerky bottom apron movement. Faulty bottom roll drive. Non-uniform top arm loading. Excessive cot hardness. Poor condition of cot. Poor condition of top apron. Poor condition of bottom apron. Faulty traverse motion. Uneven roving stretch at creel. Damaged cradles. Different size of distance clips. Top rollers contaminated by grease. Fluff accumulation in the drafting zone.

19.7.3 Reasons for high yarn hairiness If a few rings or travellers or any surface in contact with the yarn during its travel from front rollers to bobbins is rough or cut, excessive hairiness is generated in yarn spun on those spindle position. Cop hairiness is the excessive hair protruding from the full diameter of

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a cop. These protruding fibres result in real snouts by adhering with other fibres. A large portion of this protrusion falls away during the subsequent winding process winding yarn. Yarn spun on faulty spindle positions with high degree of hairiness always develops cop hairiness also. An important consideration is the occurrence of excessive hairiness within a cop or on full cops among the lot of same yarn. Such excessive hairiness can lead to the problem of barre by producing stripiness in the fabric. In fabric like denim, the hairiness becomes visible even on single picks. Hairiness value of some bobbin showing greater than 50–60% needs investigation. 1. Anti-balloon rings and yarn guide badly centred or with roughened surface. 2. Cop diameter too large. Fibres protruding from cop get caught by traveller. 3. Cut and roughened yarn passage on traveller. 4. Improper profile of traveller: tend to catch the yarn. 5. Excessive Yarn tension owing to traveller (wrong number) or due heavy worn traveller. 6. Low yarn tension due to lighter traveller causes : (a) Poor binding at the spinning triangle. (b) Greater friction at anti-balloon ring. (c) Inadequate twist transmission to the spinning triangle. 7. Excessively dry atmosphere result in high static charges. 8. Deformed cops. 9. Some rings worn out. 10. Some rings improperly centred. 11. Missing condensers in front zone of drafting.

19.7.4 Reasons for high lea count variation The norm for lea count variation is 1.5–1.8 %. 1. Reasons for the count variation within bobbin (a) High sliver U% at finisher drawframe. (b) Stretch in the roving. 2. Reasons for count variation ‘between bobbin’ (a) Hank sliver difference between finisher drawframes. (b) Non-optimum role for changing the draft pinion: high unnecessary changes. (c) Excessive hank differences within roving bobbins after large number of layers due to stretch during poor tension setting at roving frame.

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19.7.5 Reasons for high yarn faul If the reduction in the average number of faults of different types is desired, check the following controllable items. Short length thick fault (A and B type) 1. Presence of large amount of trash (more than 5%) or high proportion of seed fragments (more than 1.5%) in mixing. 2. Insufficient nep removal at combing. 3. Poor opening and cleaning in blowroom and card. 4. Use of higher total draft at ringframes. 5. Use of too wide or too narrow setting of spacers at ringframes. Long length faul 1. Poor condition of drafting at ringframes. 2. Poor house keeping in spinning room (spun in fly, loose fly, long collection of fly and cork screw faults). 3. Hard roving piecing and poor yarn spinning piecing. 4. Poor mechanical conditions at combers therefore insufficient removal of fibre cluster. Guidelines for trouble shooting 1. Fly accumulation at traveller A3 and A4. 2. Foreign matter: A3 and A4. 3. Wrong Spacer A and B type or A4, B2, C2. 4. Smaller cage length and tight cage setting: B4, C4, D3 and D4. 5. Fused fibre in synthetic: B3, C3 and C2 6. Piecing at ringframe: C3 and C4 7. Defects in drafting elements defect at roving frame: C3, C4, D2, D3 and D4. 8. Cracked aprons n ringframe: B2 and C2. 9. Roving stretch: H1. 10. Apron felting: F.

19.7.6 Reasons for low cop content 1. 2. 3. 4.

Cop diameter less than the ring diameter by more than 3 mm. More chase length. The dog not adjusted properly. Selection of actuating pins and the number of teeth in the ratchet lower/higher for needed yarn count. 5. Improper balancing of ring rail and lappet.

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19.7.7 Reasons for excessive slough off during unwinding The number of slough off per 100 bobbins at auto-winding more than 2 is considered unacceptable. 1. 2. 3. 4.

Less compact bobbin. Too low chase length and high winding length per cam revolution. Too light traveller. Ring rail movement jerky.

19.7.8 Reasons for excessive unevenness When the bobbins show abnormally high value of U%, the cause could be any one or more from the listed below. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Top roller eccentric. Bottom roller Eccentric. Misalignment of top roller w.r.t. Bottom rollers. Improper draft field setting. Jerky bottom apron movement. Faulty bottom roll drive. Low top arm loading. High cot hard ness. Poor condition of cot. Poor condition of top apron. Poor condition of bottom apron. Faulty traverse motion. Uneven roving stretch at creel. Damaged cradles. Wrong size of distance clips. Top roller contaminated by grease. Fluff accumulation in the drafting zone.

19.7.9 Reasons for twist variation Twist per unit length reduces owing to unwanted reduction in ‘spindle/ bobbin’ speed in some spinning positions 1. 2. 3. 4. 5. 6.

Poor condition of spindle tape. Jockey pulley condition is not good. Condition of spindle bolster is poor. One or more of the spindle driven by tape is idle. Partial brake applied on running spindle. Cotton sticking to spindle tape causing slippage.

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19.7.10 Reasons for top apron damage 1. Channelling grooves formed due to defective traverse motion, or excessive top arm pressure or high twist of material. 2. Accumulation of fluff. 3. Stickiness caused by materials used for colour coding. 4. Wrong and/or defective cradle. 5. Defective spacer. 6. Top roll lapping.

19.7.11 Reasons for bottom apron damage 1. 2. 3. 4. 5. 6.

Tension pulley jammed. Top apron cradle not sitting properly. Inadequate or too high arm pressure. Defective traverse motion. Defective spacer. Bottom roll lapping.

19.7.12 Reasons for spindle tape breakage 1. 2. 3. 4. 5. 6.

Bobbin sitting very tight on spindle. Spindle tape elongation. Condition of spindle lock is very poor. Hard waste entangled on spindle. Spindle tape joint is not proper. Jockey pulley alignment is not perfect.

19.8

Automatic cone winder

Automatic cone winder winds yarn onto one package unwound from several bobbins, testing and improving its quality during the process .This package is directly send to the package department for packing then to market for further process Performance of automatic cone winder can be judge by 1. The package quality and 2. Efficiency of winding machine.

19.8.1 Reasons for lapping on winding drum 1. Drum is cut by excessive yarn tension (Optimum tension is 8–12% of the single yarn strength).

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2. 3. 4. 5.

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Uneven contact of the drum brush with the drum. Winding at a low humidity. Any flaws on the drum. When winding dyed yarn, the quality and type of dye could cause a problem.

19.8.2 Reasons for increase of imperfection during winding Winding increases the number of neps and thick place by 20–30%. 1. 2. 3. 4. 5. 6. 7.

Tension setting is not proper. Tensor disc does not rotate smoothly. Yarn path not free from flaws. Pre-clearer setting is not between 5 to 7 times the diameter of yarn. Winding speed to high. Unwinding accelerator is not placed at proper height. Excessive contact pressure between cone and drum.

19.8.3 Reasons for excessive yarn breakage If the yarn breaks without actuation of the knife blade of electronic yarn clearer more than 10% of total breaks, then the reason could be: 1. Tension setting is too high, tensor disc does not rotate smoothly or yarn path is not free from flaws. 2. Pre-clearer setting smaller than 5– 7 times the yarn diameter. 3. Waste yarn sticking on drum brush due to flaw on drum nose. 4. Unwinding accelerator not properly aligned with bobbin and or not positioned at correct height. 5. Yarn clearer faulty. Frequent ‘clearer cuts’ on some spindle .No clearer cut at all. Check the spindle by inserting a sheet of paper into the slit of detection head. 6. Spinning bobbin too soft, broken yarn in bottom cop, excessive pick yarn due to miss-winding at ringframes, excessive loosening on chase when doffing at ringframes.

19.8.4 Frequent pick failure on bobbin side If the pick failure is more than 1–2%, the reasons to be searched are as follows: 1. Retie pipe – Yarn is being caught by the retie pipe, insufficient stroke adjustment, insufficient stroke due to twisting of retie pipe due to excessive wear of retie opener cam, and improper clamping.

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2. Magazine suction – no suction, weak suction, yarn tail too low in magazine vacuum nozzle, in sufficient residual back wind removed from the cop. 3. Tension cutters are blunt.

19.8.5 Reasons for pick failure on package side If the pick failure is more than 1–2%, the reasons to be searched are as follows: 1. Drum brake shoe wear out. 2. Suction mouth package set far away from package, comb is catching the yarn or low suction pressure. 3. Reverse rotation of drum: Oil remains on the surface of reverse roll, reverse roll worn out or drum belt worn out. 4. Reverse rotation of the package: rotation of cone holder is sluggish or package brake is not working properly.

19.8.6 Reasons for frequent missed splicing When missed slice is more than 1%, investigate the following: 1. Low opening and splicing pressure. 2. Wide/loose settings of the yarn holding lever or feeder arm. 3. Poor untwisting.

19.8.7 Reasons for low splice strength If the average splice strength is lower than 70 % of yarn strength, check the following to improve splicing: 1. 2. 3. 4.

Splicing pressure is too low. Air blasting time is too short. Splice length is too long. Untwisting of yarn end is not sufficient.

19.8.8 Reasons for yarn not accepted by splicing nozzle 1. Abnormal high tension. 2. Yarn caught by suction mouth.

19.8.9 Reasons for splice being thick at one side only 1. Yarn cutter is dull. 2. Insufficient clamping of upper and lower end. 3. Inadequate setting of untwisting nozzle.

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19.8.10 Reasons for package faul Packages are inspected 100%, for visible faulty cone need to be segregated and rewound etc, and actions taken to reduce incidence of such faults. 1. Stitch The yarn drops off the edge of the package.

19.1 Cradle of yarn.

1. 2. 3. 4. 5. 6. 7. 8.

Inadequate tension or variation in tension. Flaw near the drum nose. Improper rotation of the cradle bearing centre. Loose cradle. Improper position of drum to cone holder. Due to ribbon formation. Due to yarn sloughing. Due to low contact pressure of cone at high yarn tension.

2. End missing At the winding end of the spinning bobbin or at the yarn breakage, yarn end is wound on the either end of the take up tube or wound on to the package layer. 1. 2. 3. 4. 5.

Improper gap between the drum cover and package. Excessive sloughing. Excessive surface cut of spinning bobbin. Winding speed too high. Due to static charge.

3. Ribbon winding It occurs when the ratio of the drum diameter to package diameter is an integer.

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19.2 Ribbon winding.

1. 2. 3. 4. 5.

Improper setting of ribbon breaker. Excessive contact pressure. Improper rotation of cradle. Excessive moisture in spinning bobbin. Spinning bobbin is too soft.

4. Bulge winding The internal compression gets increased as the winding diameter is increased.

19.3 Bulge winding.

1. Winding angle is too large. 2. Winding tension is excessive. 3. Contact pressure is too high. 5. Wrinkles These occur due to short traverse at the starting.

19.4 Wrinkles.

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1. 2. 3. 4.

431

Inadequate tension. Inadequate contact pressure. Deflection of take up tube centre. Poor alignment of contact surface of take up tube and drum.

6. Scramble

19.5 Scramble.

1. 2. 3. 4. 5. 6.

Drum does not stop at yarn breakage. Joining motion repeats several times. Suction mouth comes in contact with package. Contact pressure is too low. Ribbon comes off. Weak starting force of drum.

7. Stepped winding

19.6 Stepped winding.

1. 2. 3. 4.

Flaw on drum. Flaw on drum cover. Low yarn tension. Disengaged yarn from the yarn path after machine maintenance or cleaning.

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8. Saddle back package

19.7 Saddle back package.

1. Excess tension. 2. Low contact pressure. 3. Low increase. 9. Reasons for swelled package

19.8 Swelled package.

1. No tension is applied due to improper guiding of yarn on tensor, foreign substance staying on tensor disc and improper movement of tension disc. 2. Due to ribbon winding. 3. Improper movement of wax.

19.9

Two-for-one twister

19.9.1 Reasons for over-twisted yarn lengths 1. 2. 3. 4. 5. 6. 7. 8.

Wrong change gear combination. Wrong primary combination. Damaged gear toothed belt. Take up tube not aligned with the package drive roll. Centring disc rubs against the package drive roll. Centring disc not turning freely. Package drive roll loose on the shaft. Cradle pressure too low.

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9. Traverse thread touches the take up package. 10. Yarn take up tension too high causes package to slip.

19.9.2 Reasons for slack twist 1. 2. 3. 4. 5.

Wrong change gear combination. Yarn lap around spindle. Spindle brake shoe binding on whorl. Spindle pot or spindle bearing defective. Spindle speed too low on some spindles.

19.9.3 Reasons for loss of tensile strength in yarn 1. Yarn balloon touches the rim of spindle pot or yarn balloon bulges over the rim of balloon limiter. 2. Erratic yarn balloon. 3. Loops or kink in ply twisted yarn. 4. Damaged yarn guide element.

19.9.4 Reasons for defective package formation 1. 2. 3. 4. 5.

Improper position of take up tube against package drive roll. Too high or too low cradle pressure. Improper pre take up roll pressure. Improper position and slot width of traverse guide. Ribbon functioning is not working properly.

19.9.5 Reasons for variation in package density 1. 2. 3. 4.

Wrap angle is not equal on all the spindles. Cradle is not equal on all the spindles. Improper rotation of deflection rolls. Lapping of pre take up roll.

19.9.6 Reasons for excessive ends down More ends down than 2 per 100 drum/spindle is considered excessive 1. Yarn reserve incorrectly set at full cheese. 2. Flyer rubs against feed package on rim of spindle pot or yarn balloon during starting. 3. Take up tension too high. 4. Yarn balloon touches the upper rim of spindle pot.

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5. Yarn guide elements damaged. 6. Yarn waste accumulates underneath labyrinth ring on the spindle rotor. 7. Traverse yarn guide too narrow 8. Traverse guide touches take up package.

References 1. Operating Instruction for the high production card C1/3 issued in November 1987. 2. Trutzschler Card DK 903 instruction manual second edition year 1999. 3. Rieter CardC-61 instruction manual year 2002. 4. Murata Machconer /Linkconer No. 7 instruction manual revised May 1988. 5. Kirloskar Toyada Ringframe RXI240 instruction manual year 1999. 6. Rieter Ingolstadt Drawframe RSB 951 year 1996. 7. Rieter Unilap E32 operating instruction manual10055921. 8. Rieter Comber E62 operating instruction manual 10013753. 9. Lakshmi Speedframe LF 1400 operating instruction manual year 1990. 10. Lakshmi Ringframe G5/1 operating instruction manual year 1990. 11. Roving Frame Instruction Manual FL-16 by Toyada Automatic Loom Works edition 1997, Toyada FL 100 Roving Frame Instruction manual seventh edition August 2001. 12. Prerna Leewha Two-for-One Twister for spun yarn PRN –140- LW Instruction manual. 13. Texmaco zinser ringframe instruction manual issued in January 1969 reprinted April 1973. Zinser Speedframe 660 instruction manual year 1990, Zinser Drawframe 720 instruction manual year 1990, Zinser Ringframe 321 instruction manual year 1990. 14. High Speed Simplex Fly Frame instruction manual RME Howa Machinery Limited Edition august 1993 15. Drawframe Cherry DX –500 – E2 instruction manual, Drawframe Cherry D – 400 MT instruction manual 16. Savio Orion instruction manual, manual code 11645.0004.1/0 revision index :01 date of issue : 06.01 17. Two for one Twister instruction manual Leewha LW 560 SA 18. Rieter Unifloc A11 instruction manual edition 2000, Ringframe G33 instruction manual year 2001,CardC-61 instruction manual year 2002. 19. Murata Process Coner 21-C instruction manual revised October 2002, 20. Schlaforst Autoconer 338 instruction manual year 2003. 21. Volkman VTS 05/07/08/09 operating Instruction manual. 22. Application manual of Off Line UT-4 year 2001 23. Lakshmi Ringtraveller catalogue. 24. Bracker Ringtraveller catalogue.

20 Tips to improve energy saving in spinning mills

20.1

Energy

Energy is defined as ‘the ability to do work’. In this sense, examples of work include moving something, lifting something, warming something, or lighting something. The following is an example of the transformation of different types of energy into heat and power. Oil burns to make heat Heat boils water Water turns to steam Steam pressure turns a turbine Turbine turns an electric generator Generator produces electricity Electricity powers light bulbs Light bulbs give off light and heat It is difficult to imagine spending an entire day without using energy. We use energy to light our cities and homes, to power machinery in factories, cook our food, play music, and operate televisions.

20.1.1 Energy loss Heat transfer occurs through conduction, convection and radiation. Conduction is affected by conductivity of material through which heat is transferred. Convection is transfer of heat by flow of material. It depends

435

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upon the physical properties like area and temperature. Convective heat transfer occurs when surface of hot material is displaced by cool air. Radiation is transfer of heat energy by electromagnetic means between two materials whose surfaces face each other and is generally governed by the absolute temperatures and positions of two surfaces.

20.1.2 Energy discharge It depends upon the composition, discharge rate and temperature of each out flow from process unit.

20.2

Textile production process

The textile industry produces a wide range of products. The production process includes four main activities: spinning, weaving and knitting, wet processing and stitching (sewing). The production from fibers to spun yarn takes place through the spinning process and constitutes the first stage. Then the yarn is weaved to make fabrics in looms. Most woven fabrics retain the natural color of the fibers from which they are made and are called ‘grey fabrics’ at this stage. These fabrics then undergo several different processes including bleaching, printing, dyeing and finishing; these are grouped under the category of wet processing. Finally, the stage from fabrics to garments is done by stitching. The industry uses cotton, jute, wool, silk, man-made and synthetic fibers as raw material. In this chapter we will talk about ring spinning only.

20.2.1 Spinning Spinning involves opening/blending, carding, combing, drawing, drafting and spinning. It uses four types of technologies: ring spinning, rotor spinning, air jet spinning and friction spinning. Ring spinning is the most used in the world with its main advantage being its wide adaptability for spinning different types of yarn.

20.3

Energy consumption in spinning mill

Energy availability and its cost play a significant role in the profitability of any industry. With energy cost escalating day by day and its availability becoming more and more scarce, there is an urgent need for the textile industry to manage energy by ensuring its effective usage and conservation. Energy consumption in the spinning industry has augmented with increased mechanization. Energy consumption per unit of output is higher in modern spinning units due to technological development, which tends to replace

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manual labor by electric power. However, technological development also offers better productivity and quality that can overcome the efficiency measure. Energy costs vary from 9 to 14% of total manufacturing costs according to the type of process involved, cost of the power and type of machines involved. Raw material Packing cost Interest 1% 2%

2%

Wages overhead expenses

Power Maintenance cost

8%

10% 5%

72%

20.1 Distribution of manufacturing cost of yarn.

Major consumption of power in spinning plant is 1. 2. 3. 4. 5.

Ringframe Humidification plant Chiller Winding Card

Ringframe using 35% of the total power consumed in the spinning mill. Humidification plant, chiller and winding consume 16%, 15% and 10% of the total power consumption. Blowroom Ringframe

Card Winding

Others

Chiller 15%

Drawframe Humidification 4%

3% 5%

16%

7%

Speedframe Compressor

2% 3%

35% 10%

20.2 Distribution of power in spinning mill.

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20.4

Maximum cost effectiveness in energy use

Maximum cost effectiveness in energy used is achieved when maximum production is achieved at least energy cost. Maximum cost effectiveness in energy use is determined by two most important components. (a) Energy cost per unit of production (b) Cost for implementing energy conservation ideas 1. Energy costs – Taking conservation measures to reduce energy use or to reduce wastage of energy (at constant energy prices) decreases the per unit energy cost. Less energy is required for each unit of production which means that the process become thermodynamically more efficient. 2. Cost effectiveness – This is measured by the ratio of benefits due to conservation over the cost of conservation. Every means of conservation which gives benefit to installation cost ratio of more than 3 must be implemented with highest priority and those giving ratio 1.2–3.0 with appropriate lower priority. Even when the annual saving are nearly equal the one time cost of implementation, it is worth to implement the measure.

20.5

Energy conservation measures

The implementation of energy conservation program in spinning mill is widely accepted due to rising cost of energy everyday. The three major factors for energy conservation in the textile industry are high capacity utilization, fine tuning of equipment and technology upgradation. An exhaustive list of all measures of energy conservation found useful by spinning mill in India is given here. Each mill should check whether they have implemented each item and then consider implementing those which they have not.

20.5.1 Ringframe 1. Individual pulley drives on ringframe saves energy compare to tin roller drive. The mills are advised to convert it to single where they can. The lighter the pulley the more is the saving. 2. The spinning mills which were installed before 1993 may have ringframes conventional, heavy spindles. Lighter spindles save energy. Spindles of 280 g or more should be replaced with light weight spindles of 250 g. 3. Less wharve diameter spindles should be used. When going for lighter spindles use 18.5–19 mm wharve diameter in place of the 25mm to 20mm. The advantage is indirect. For the same horse power motor,

Tips to improve energy saving in spinning mills

4.

5.

6. 7. 8. 9.

10. 11. 12.

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these spindles have a better drive ratio for the same diameter driving pulley. When spindle weight and individual pulley weight is reduced, then the horsepower of motor can be reduced for the given spindle rpm. Use Servo Spin 12 oil instead of Servo Spin 22 oil. The life of oil would reduce but saving in power consumption is much higher than the increased cost of oil replacement. Synthetic oil saves topping and saves about 0.9–1.0% energy. Synthetic oil cost is very high so one must think of viability – benefit to cost ratio before switching over to synthetic oil. A lighter and concentric bobbin helps to save energy. Use of lighter drum pulley in ringframe results in energy saving. Use of hollow main shaft instead of solid main shaft in ring frame results in energy saving. The VPS drives themselves consume more power and therefore are not economical. The mills need not plan for VPS drive in for ring frame in future. Use energy efficient impellers in ringframe suction fan in order to consume less power. Use of energy efficient impellers in overhead traveling cleaners results in less power consumption. If high efficiency motors are to be installed on ringframes then either HP of motors can be stepped down by 10% or the mill can operate at 5% higher spindle speed, whichever is more advantageous to mill.

20.5.2 Humidification plant Several design aspects of humidification plant installed in mills have been found to be non-optimum and these can be rectified to give saving in power costs. 1. When two supply fans are coupled, they must be isolated. Otherwise the stationary fan will rotate in the opposite direction and act as a supply fan to the working fan and thus create a local circulation rather than humidifying the machine shed. 2. The humidification duct should not be exposed to outside atmospheric conditions. If done so on warm days, the exposed duct should be warmed up and the supply air would be heated up and thus the humidification effect would be considerably reduced. 3. In some installations, the supply ducts are integrated into the concrete roof itself to save additional ducting space. However, the humidification effect gets spoiled owing to the conductivity of reinforcing steel bars, which results in warming up of the supply air, by conduction.

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4. Centrifugal fans are better supply fans and axial fans are better exhaust fan, 5. False ceilings not only prevent radiation from the top but also help in reducing the volume of space to be humidified. 6. Exhaust grills must be located near the motors, which are one of the important heat sources. 7. The pneumafil air must be collected in a separate duct, and a positive exhaust must be provided for it. 8. The exhaust ducts from the pneumafil into the trench must have a tapered design so that a nozzle effect is created and air is drained properly into the exhaust trench. Experience has shown that several items of maintenance are not done properly. The checklist below should be used to check whether mill practice is satisfactory. 1. The trenches should not be used as place to dump waste material. 2. The supply and exhaust ducts should be cleaned periodically; all obstructions should be removed. All supply and exhaust grills must be clean. The air distribution should be properly ratified. Uniform air flow would be available only if the supply and exhaust air duct are properly cleaned and maintained. 3. Outside ambient conditions should be effectively used. When the conditions are favorable the use of humidification plant should be minimized. 4. The humidification area must always be isolated. The windows and door must always be closed. 5. The air supply should be 25% more than exhaust. Then the supply air would always maintain a positive pressure in the humidified area and thus prevent the entry of outside air into the humidified area. 6. The air supply ducts above the false ceiling should be well-insulated. 7. Water used for humidification should be periodically removed and replaced always rather than level made up by topping. Making up of the water level increases salt concentration, which in turn corrodes the baffles and nozzle. 8. Periodic measurement of air velocities in the supply exhaust baffles should be made so that any defect in the system can be immediately noted and corrections made. 9. If the air velocity is felt to be low it may be due to choked grills and ducts. They must be cleaned. 10. Periodic cleaning of nozzles and baffles must be carried out as per maintenance schedule.

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20.5.3 Winding The use of invertors in the suction fan in automatic winding machines results in less power consumption. This helps to maintain the optimum suction constantly.

20.5.4 Blowroom Air velocities or static pressure in supply and exhaust duct in blowroom should be periodically measured. Any defect in the system should be immediately noted and corrections made. Seal all duct joints properly with a suitable adhesive solutions to avoid suction of fresh air through joints.

20.5.5 Speedframe Use receiver and emitter to stop the speedframe at roving breaks instead of using the pneumatic stop motion. This helps in eliminating the suction fan from speedframe.

20.5.6 Carding 1. Time motion interlocking between doffer drive and main cylinder drive. 2. Use of fluid coupling saves energy in old card and on old speedframes.

20.5.7 Electrical 1. AVR failure and RAR diode failure are due to leading current situations encountered at the time of switching on, when the capacitor functions as short circuit. A provision must be made to isolate the capacitors at the time of putting captive load in action or time delay switches must be incorporated on line. 2. Check at least once every month the capacitance of all capacitors to find out how many are out of order and to replace them. 3. Installation of automatic power factor correction system with capacitors. The power factor must be maintained around 0.95. This would give sufficient margin to avoid leading current situations, which can cause motor burnouts or an AVR failure. Higher value of power factor can sometimes leads to cable rupture and/or to fire in cable trench. 4. The power cables should never be laid along the penumafil trench. From penumafil trenches hot air will heat the cable and increase the heat losses.

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5. A separate trench with the exhaust fan at the one end always helps to keep the cables cool. A cool cables always less energy loses. 6. To reduce the cable losses, the rated current carrying capacity of the cable should be de-rated. If any specific situation warrants higher current density, then either the cable rating has to be increased or one more cable has to be laid. We should never use different cable size for the same load centre. 7. Replacement of old high losses transformers with new energy efficient low loss transformers. It helps to save 10% of power loss.

20.5.8 Electrical motors 1.

2. 3. 4. 5. 6.

7.

8.

Motors must be mounted in such a way that they are vibration free. A vibrating motor consumes more energy and, therefore, the available energy for use gets that much reduced. Motors must be well-ventilated and must not be mounted where hot air bathes them. Exhaust trenches must be located near the working area of motors. In rewinding use the same class of insulation as used in the original motor. After every rewinding, the motor should be dynamically balanced. After every rewinding, the motor efficiency should be checked. If efficiency falls by just 2% for a 20 HP motor the loss of energy is 1800 units during 8000 hours of operations. After three burns, it is always better to replace the old motor with a new one instead of rewinding. Each mill must maintain a record on the motors. Each motor must be numbered and its history must be recorded. This would enable the maintenance engineer to identify whether the trouble is due to the motor or due to the machine. The cause of motor burn out should be analysed after every burn out to determine why not a burnout has occurred and then to take steps for avoiding reoccurrence.

20.5.9 Lighting 1. Fluorescent tubes are better for indoor lighting. Slim tubes save energy, and are cost-effective. 2. When lamp and tubes level are at low levels, the illumination is better. If a lamp of a given power were to be mounted at 2 m and 4 m heights, the lamp at 2 m height will throw 4 times more light on the floor than the one at 4 m height.

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3. Though each tube holder has two tube lights, switch control on alternate tube would be better. Depending upon the needed light level, alternate tubes can be switched on. 4. The illumination level must be appropriate only at working area and tubes must be mounted appropriately. 5. It is always advantageous to have separate transformers for lighting. Under low voltage conditions, the transformer tapping needs to be raised to run the motor. If the lamp and tubes are in the circuit under high voltage level, they burn out faster. When a separate transformer is used, the tapping can be adjusted in such a way that both the lamp and tube life, and the power factor can be maintained. 6. Use always electronic choke instead of copper blast choke and Electronic choke consumes 2–3 watt whereas copper choke consumes 7–10 watt. 7. Outside lighting is better done by low pressure sodium vapour lamps. 8. Clean the reflective shades so they throw all the light down by total reflection. 9. Light should be switched off when not required in offices and elsewhere. We should use no motion sensor for effective use of power in office installations.

20.5.10 Compressors 1. In a spinning mill the compressed air is used for cleaning the machine. It is advisable to install separate compressor and air distribution system for cleaning purpose. The system can operate only when it is needed may be 4 hours in day. It gives high installation cost but it helps in saving energy. If we do not put separate compressor for cleaning then we have to use bigger air compressors i.e. 1.2 times the actual compressed air requirement. Oversized compressors are extremely inefficient because most compressors use more energy per unit volume of air produced when operating at part-load. Secondly, compressors consume 60% of energy in no load condition. 2. One should select a compressor which is capable to generate of at least 1 bar above the pressure needed at the point of use. This is also to compensate for the pressure loss in pipelines, filters and other accessories, to ensure that at the point of use the needed pressure can be guaranteed. A too high pressure will unnecessarily increase the power consumption of the compressor about 5% for each pressure bar increase. 3. Leaks can be a significant source of wasted energy in an industrial compressed air system, sometimes wasting 20–30 percent of a

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compressor’s output. A typical plant that has not been well maintained will likely have a leak rate equal to 20 percent of total compressed air production capacity. On the other hand, proactive leak detection and repair can reduce leaks to less than 5 percent of compressor output.

20.5 .11 General recommendation for spinning plant 1. Belts 1. Flat belts saves energy, so V belts must be converted to flat belts wherever possible (like TFO main drive of Vijay Lakshmi machine). Care has to be taken that flat belts do not slacken by use. 2. Lesser the weight of flat belts and the accessories used, the better it is for energy saving. Light weight flat belts are superior to heavy weight flat belts. Belts must be thin and must have very low elongation. Engineering precautions must be taken to ensure that the belt does not slip. 3. The flat belt system so used in the place of a V belt system should not have more weight than the V belt system. 4. Bearing wear out can be reduced considerably by avoiding excessive belt tension, vibrating foundation and pulley eccentricity. 5. On a multiple V belt drive always replace the entire set of belts if one or more belt breaks. Replacement of only the broken belt results in undue stretching of the new belt, and it moves with a different velocity. Secondly, matched V belts should be used. Otherwise energy transfer would take place through a few V belts while the others would be simply running and consuming energy. 6. Correct belt tension should be provided by measuring the belt tension with the help of tension measuring equipment. 2. Pulley 1. One should take care of the following points for better energy transfer and less power consumption while handling V pulleys. (a) Check the dimension of the groove of the pulley if belts are to be mounted on new pulley. (b) The grooves should be free from burr, rust, oil, dirt or grease. The V grooves of pulleys wear out during use so worn out pulleys should be replaced immediately. 3. Gear box lubrication

Tips to improve energy saving in spinning mills

445

Recommended oil In all machinery a certain amount of power is required to overcome friction within the lubricating film itself. Friction of this kind is largely a function of the viscosity of the lubricant. To minimize power consumption, it is necessary to use an oil with optimum viscosity compatible with satisfactory lubrication, while taking account of considerations like splashing and the rate of oil consumption. Oxidation tends to cause thickening of oil in service, therefore it is advantageous to use lubricants with high oxidation stability. Such lubricants change less in viscosity with increase in temperature. Recommended oil level Industrial gears may be either of the enclosed type or of the open type. In the enclosed type a minimum level of oil is maintained. In the gearbox, teeth of the bottom gears are just dipped into the oil and gear are lubricated by means of splash. In case of splash lubrication it is necessary that oil level should not be too high. A high level results in churning of oil which in turn results in consequent rise in oil temperature and in power loss. The depth to which the bottom wheel is dipped is twice the tooth depth. This is sufficient for splash lubrication and to keep the churning effect to the minimum. Secondly a pressure circulating system may be used in which oil is sprayed on the teeth close to the point of engagement. The oil is then recirculated either directly from the bottom of the gear box, or by way of a separate tank with the help of an oil pump.

References 1. Pollution Prevention (P2) Education Toolbox Tools for Helping Teachers Integrate P2 Concepts in the Classroom United States Environmental Protection Agency EPA-905-F-97-011 August 1997. 2. Energy Competence Developed in Medium Spinning Mill by Jim Trade .com. 3. ‘Energy Management in Spinning Mills’ by SITRA in Nov October 9, 2007. 4. Comprehensive Hand Book on Spinning Maintenance Part-1 by NEERAJ NIJHAWAN.

Index

ABC analysis, 73, 74 Abrasion, 227 Abrasive wear, 3 Abrasives, 393 Absenteeism, 57 Accident losses, 134 Additives, 162, 167 Adhesive wear, 3 Adhesive, application of, 191 Adjustable pitch pulley, 212 Air distribution system, 306 Air line oilers, 174 Allen key, 368 Analysis, 17 Angular ball bearing, 339 Aniline point, 165 Animal oils, 160 Antiwear additives, 163 Aquadag, 172 Aromatic hydrocarbons, 165 Asset register, 91 Automatic cone winder, 426 Backlash, 287 Ball bearings, 337 Barbed-typed connector, 325 Base oil, 167, 168 Bearing characteristics, 350 Bearing designation, 346 Bearings, 333 types of, 333 Belt drive with idler pulley, 186 Belt drives, 183 types of, 183 Belt length, 190 Belts, 183 Bevel gears, 282 Bleed rate, 168 Blended oils, 161

446

Blow room, 408 Bonds, 393 Boundary lubrication, 157 Box spanner, 366 Brass cage, 336 Breakdown history register, 95 Breakdowns, 408

Cage, 335 Calcium grease, 167 Carbon residue, 165 Card, 413 Careless handling, 362 Carriage bolt, 248 Carrying costs, 72 Castle nut, 253 Cavitation, 6 Centralized pump, 174 Centrifugal compressor, 297 Chain installation, 231 Chain lubrication, 230 Chains, 225 construction of, 229 designation of, 229 maintenance of, 232 Chalk line, 404 Chemical-type dryer, 303 Chisels, 384 Chuck nut, 252 Circlip, 256 Cleaning fitter, 65 Cleaning schedule, 93 Cloud point, 164 Combing, 417 Common gang, 59 Component history register, 95 Compound drive, 186 Compressed air, 290

Index Computer-managed maintenance system, 16, 89 benefits of, 90 components of, 90 Condition monitoring, 103 Condition-based maintenance, 103 Condition-based monitoring, 24 benefits of, 34 principle of, 25 Cone drive, 186 Consistency, 168 Consumable items, 79 Consumption, rate of, 74 Contamination, 361 Contingency, 85 Continuous improvement, 17 Control limits, 74 Corrective action register, 94 Corrosion, 6, 63, 228 Crew size, 68 Cross belt drive, 185 Cylindrical roller bearing, 342 Daily report, 100 Deep groove ball bearing, 337 Defoamants, 163 Dial gauges, 375 Dial indicator, 326 Die stock, 391 Digital vernier callipers, 380 Direct accidental loss, 134 Dirt, 361 Double V section belts, 202 Double-ended spanner, 365 Double-sided polyurethane belts, 218 Drawframe, 416 Duplex chain, 234 dimension of, 234 Dynamic sealing, 261 Ear protection, 140 Elasto hydrodynamic lubrication, 159 Electrical safety, 144 Electrical shock, 144 Engineer’s weekly report, 104 Erosion, 6 Expenditure budget, 83, 84 procedure for, 84 Extreme pressure additives, 163 Extreme pressure greases, 170

Eye and face protection, 139 Failure statistics, 76 Fast moving spares, 84 Fatigue, 5, 227, 361 Feeler gauge, 372 Files, 381 types of, 381, 382 Filters, 318 Fire point, 165 FISPO, 73, 76 Fitter, 65 Fixed oils, 160 Flash point, 165 Flat belt drive, 183, 184 types of, 184 Flat belt joints, 189 types of, 189 Flat belts, installation of, 188 Flat Pulleys, 197 Fluoroelastomer, 263 Foot protection, 142 Foreman, 64 Garter spring, 265 Gaskets, 268 installation of, 270 Gear train, 284 Gears, 272 General protection, 143 Good lighting, 138 Graphite, 172 Grease guns, 404 Grease, 166, 169 characteristics of, 168 composition of, 166 working of, 168 Grinding wheels, 393 Hacksaw, 388 Hammers, 373 types of, 373 Hand gloves, 142 Hands and arm protection, 142 Head protection, 141 Helical gears, 276 High torque timing belt, 216 High-temperature greases, 170 History registers, 95 Hot press, 191

447

448

Modern approach to maintenance in spinning

House keeping, 144, 145 Human error, 66 reasons for, 67 types of, 66 Humidification plant, 439 Hydrodynamic lubrication, 158 Hydroperoxides, 163 Impact piston, 311 Impact wear, 4 Indirect accidental loss, 135 Industrial accident, 133 causes of, 135 effects of, 134 preventions of, 135 technical causes of, 135 Industrial gear, 173 Industrial safety, 133 Insurance items, 77 Internal clearance, 348 Inventory carrying cost, 72 Inventory, 71 types of, 71 Key, 254 types of, 254 Kinematic viscosity, 164 Knife, 405 Leaf chains, 237 Leak detection, 329 Leakage, 30 Liquid lubricants, 160 properties of, 164 Lithium grease, 167 Locking device, 252 Low-friction coefficients, 172 Low-temperature greases, 170 Lubricants, 157 conservation of, 177 functions of, 160 handling of, 177 types of, 157 Lubricating oil, 161 Lubrication, 157, 226 Lubricator, 314 Machine cleaner, 65 Machine guarding, 147 Machine joints, 242

Machinery audit, 50 Maintenance audit report, 53 Maintenance audit, 50 Maintenance budget, 85 review of, 85 Maintenance clerk, 64 Maintenance cost, 102 Maintenance engineer, 63 Maintenance information systems, 89 Maintenance management, 89 Maintenance manuals, 92 Maintenance organization structure, 58 Maintenance schedule, 44 Maintenance scheduler, 93 Maintenance, role of, 8 Maintenance, types of, 12 Manpower norms, 57 Manpower planning, 55 Manual lubrication, 174 Material costs, 72 Material handling safety, 148 Measuring tape, 372 Mechanical overload, 7 Medium-temperature greases, 170 Metal case seal, 264 types of, 264 Micro valve, 321 Micrometer, 400 Minimum pressure switch, 317 Misaligned shafts, 362 Miter gear, 283 Moisture separator, 316 Molybdenum disulphide, 172

Naphthalenic oil, 161 Needle bearing, 345 types of, 345 Neutralization number, 165 Nitrile compounds, 262 Non-return valve, 320 Non-separable bearing, 352 Normally closed valve, 326 Normally open valve, 326 Nut, 252 types of, 252 Oil cans, 403 Oil seal, 261 Oil separation, 169

Index Oildag, 172 Open belt drive, 184 Ordering costs, 72 Overhauling items, 83 Overtime maintenance record, 101 Oxidation inhibitors, 163 Oxidation, 169 Ozone, 7 Paraffinic oil, 161 Peroxy radicals, 163 Personal protective equipments, 139 Petroleum oil, 161 Pins, 256 Piping, 323 Pitch, 215 Planned maintenance, 12 Planned replacement items, 79–83 Planning, 37 principles of, 37, 38 procedure of, 38 Pliers, 394 Plumb bob, 405 Pneumatic cylinder, 309 Pneumatic systems, 307 Poisson distribution, 76 Polyacrylic compounds, 263 Polyamide cage, 335 Polyurethane synchro-power belts, 218 Port flow control valve, 323 Pour point depressants, 162 Pour point, 164 Predictive maintenance, 14 Pressure drop, 330 Pressure hoses, 324 Preventive maintenance checklist, 104 Preventive maintenance, 13 Preventive maintenance, 22 Proactive maintenance, 15, 21 Procurement lead-time, 74 Product mix, 55, 56 Pullers, 398 Punch, 387 Push-type fitting, 324 Quad power V belt, 202 Quality-based maintenance, 18 Quick release valve, 320 Reciprocating compressor, 295

449

Regulators, 313 types of, 313 Re-lubricating interval, 171 Repair inventory, 73 Repairable spares, 83 Respiratory protection, 142 Ring spanners, 366 Roller bearings, 342 Rolling elements, 334 Rolling friction, 333 Rotary cylinder, 312 RPP polyurethane belts, 219 Running fitter, 65 Rust inhibitors, 163 Safety belts, 143 Safety helmets, 141 Safety tags, 155 Safety valve, 319 Sawn nut, 253 Scheduling, 40 Screw clamps, 259 Screw driver, 384 Screw extractors, 395, 396 Screw, 242 Screwed joint, 242 Seal materials, 262 Sealed bearings, 352 Seals, condition of, 363 Self-aligning bearing, 338 Self-lubrication properties, 172 Semisolid lubricant, 166 Separable bearing, 352 Set screw, 248 Sheave, 226 Shifting material safety, 151 Silencer, 323 Silent chains, 238 Silicones, 263 Simple chain, 233 dimension of, 233 Single row angular ball bearing, 340 Single-ended spanners, 365 Sliding friction, 333 Socket wrench, 367 Sodium grease, 167 Soft hammers, 375 Solenoid valve, 326 Solid lubricants, 172 Spare part catalogue, 92

450

Modern approach to maintenance in spinning

Spare parts management, 73, 75 implementation of, 83 Spherical roller bearings, 343 Spindle tapes, 192 Spiral bevel gears, 283 Spirit level, 377 Splice laps, 190 Spur gear, 272 Star screw driver, 385 Static sealing, 261 Steel cage, 335 Steel rule, 370 Steel wire rope, 223, 224 classification of, 225 Step ladders, 402 Stepped pulley drive, 185 Structural stability, see also mechanical stability, 168 Stud, 248 Synthetic oil, 161 Synthetic-based grease, 167 Tap bolt, 249 Taper lock, 257 Taper roller bearings, 344 Taps, 390 Technical file, 91 Teeth, 382 Temporary fastening, 242 Tension element, 255 Tension rollers, see also jockey pulleys, 214, 215 Thermofix, 189 Thickener, 167, 168 Thread nomenclature, 244 Threaded connector, 325 Throttle disc, 321 Throttle valve, 321, 322 Through bolt, 247 Thrust bearing, 346 Time delay control valve, 322 Timing belt, 183, 213, 215

Torque spanners, 367 Triplex chain, 234 Triplex chain, dimension of, 235 Try square, 369 Twin power belts, 217 Twist drills, 401 Ultrasonic leak detection, 329 Universal joint, 258 Universal valve, 326 Unpacking and cleaning safety, 152 Unplanned maintenance, 17 Unsafe actions, 135 Utilization loss, 103 V belt, 199 construction of, 199 installation of, 204 types of, 200 V pulleys, 211 V-belt drive, 183 VED classification, 73, 75 Vegetable oils, 160 Vernier calliper, 378 Vibration, 363 Vices, 386 types of, 386 Viscosity index improvers, 162 Viscosity index, 164 Washer, 251 types of, 251 Wear debris, 32 Wear, 1, 2 Wedge belts, 201 Winding, 441 Worker dress, 139 Workshop, 147 Worm gear, 279 Zero error, 327