Modern Approach to Maintenance in Spinning (Woodhead Publishing India)

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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


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


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


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


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


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


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.

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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


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

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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

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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

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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.

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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.

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22


3.2


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.


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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.

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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


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

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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.


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.

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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


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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.

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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


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.

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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.


3.3.9

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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

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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.


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


450–1000

5.

Flat tops repla cement


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


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.


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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.

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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.


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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.

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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


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


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


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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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

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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


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.

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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


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

56


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.


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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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


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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


Preparatory Foreman

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.

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

Maintenance Clerk


Preparatory Foreman

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.


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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

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7.

8. 9. 10.


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.


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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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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.


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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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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.


6.7.1

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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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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

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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

70


Department – Ringframe Acti vity


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


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

72


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.


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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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


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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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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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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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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

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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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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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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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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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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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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

90


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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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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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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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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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


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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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


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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


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


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


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


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


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.


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


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


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


59.

Flat speed


60.

Aero feed beater speed


Belts and pulley 61.

Condition of belts

62.

Belts are properly aligned

63.

Condition of pulleys

R.H.

M

107 L.H.

108


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


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.


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


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


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


Fitter

Cleaning

18. Scanning roll

Its size must suits the weight of feeding sliver.

Fitter

Cleaning


Fitter

Cleaning

Actual report

10. Trumpet

110


S. Activity no.


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.


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



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


S. Activity no.


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



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


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


Fitter

Cleaning


Fitter

Cleaning

Check for oil leakage

Fitter

Cleaning

Use only servo spin 32 no.

Fitter

Cleaning


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


S. Activity no.


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



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


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



Date

117


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


S. Activity no.


Date


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


Fitter

Cleaning

Alignment

Fitter

Cleaning

Tension of the belt is proper or not.

Fitter

Cleaning


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


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


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

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