AN INTRODUCTION TO PREDICTIVE MAINTENANCE Second Edition AN INTRODUCTION TO PREDICTIVE MAINTENANCE Second Edition R. Keith Mobley Amsterdam London New York Oxford Paris Tokyo Boston San Diego San Francisco Singapore Sydney Butterworth-Heinemann is an imprint of Elsevier Science. Copyright © 2002, Elsevier Science (USA). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Recognizing the importance of preserving what has been written, Elsevier-Science prints its books on acid-free paper whenever possible. Library of Congress Cataloging-in-Publication Data Mobley, R. Keith, 1943–. An introduction to predictive maintenance / R. Keith Mobley.—2nd ed. p. cm. Includes index. ISBN 0-7506-7531-4 (alk. paper) 1. Plant maintenance—Management. I. Title. 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For information, please contact: Manager of Special Sales Elsevier Science 225 Wildwood Avenue Woburn, MA 01801-2041 Tel: 781-904-2500 Fax: 781-904-2620 For information on all Butterworth-Heinemann publications available, contact our World Wide Web home page at: http://www.bh.com 10987654321 Printed in the United States of America 1 Impact of Maintenance 1 1.1 Maintenance management methods 2 1.2 Optimizing predictive maintenance 10 2 Financial Implications and Cost Justification 23 2.1 Assessing the need for condition monitoring 24 2.2 Cost justification 25 2.3 Justifying predictive maintenance 29 2.4 Economics of preventive maintenance 32 3 Role of Maintenance Organization 43 3.1 Maintenance mission 43 3.2 Evaluation of the maintenance organization 44 3.3 Designing a predictive maintenance program 50 4 Benefits of Predictive Maintenance 60 4.1 Primary uses of predictive maintenance 61 5 Machine-Train Monitoring Parameters 74 5.1 Drivers 75 5.2 Intermediate drives 78 5.3 Driven components 86 6 Predictive Maintenance Techniques 99 6.1 Vibration monitoring 99 6.2 Themography 105 6.3 Tribology 108 6.4 Visual inspections 111 6.5 Ultrasonics 111 6.6 Other techniques 112 7 Vibration Monitoring and Analysis 114 7.1 Vibration analysis applications 114 7.2 Vibration analysis overview 117 7.3 Vibration sources 122 7.4 Vibration theory 125 7.5 Machine dynamics 132 7.6 Vibration data types and formats 146 7.7 Data acquisition 152 7.8 Vibration analyses techniques 161 Appendix 7.1 Abbreviations 165 Appendix 7.2 Glossary 166 Appendix 7.3 References 171 8 Thermography 172 8.1 Infrared basics 172 8.2 Types of infrared instruments 174 8.3 Training 175 8.4 Basic infrared theory 176 8.5 Infrared equipment 178 8.6 Infrared thermography safety 179 8.7 Infrared thermography procedures 179 8.8 Types of infrared problems 179 Appendix 8.1 Abbreviations 183 Appendix 8.2 Glossary 183 Appendix 8.3 Electrical terminology 187 Appendix 8.4 Materials list 193 9 Tribology 202 9.1 Lubricating oil analysis 203 9.2 Setting up an effective program 208 10 Process Parameters 217 10.1 Pumps 218 10.2 Fans, blowers, and fluidizers 225 10.3 Conveyors 229 10.4 Compressors 229 10.5 Mixers and agitators 240 10.6 Dust collectors 240 10.7 Process rolls 241 10.8 Gearboxes/reducers 242 10.9 Steam traps 249 10.10 Inverters 249 10.11 Control valves 249 10.12 Seals and packing 251 11 Ultrasonics 256 11.1 Ultrasonic applications 256 11.2 Types of ultrasonic systems 257 11.3 Limitations 258 12 Visual Inspection 259 12.1 Visual inspection methods 260 12.2 Thresholds 263 13 Operating Dynamics Analysis 267 13.1 It’s not predictive maintenance 267 14 Failure-Mode Analysis 285 14.1 Common general failure modes 286 14.2 Failure modes by machine-train component 301 15 Establishing A Predictive Maintenance Program 325 15.1 Goals, objectives, and benefits 325 15.2 Functional requirements 326 15.3 Selling predictive maintenance programs 330 15.4 Selecting a predictive maintenance system 334 15.5 Database development 343 15.6 Getting started 348 16 A Total-Plant Predictive Maintenance Program 352 16.1 The optimum predictive maintenance program 353 16.2 Predictive is not enough 356 17 Maintaining the Program 389 17.1 Trending techniques 389 17.2 Analysis techniques 390 17.4 Additional training 392 17.5 Technical support 393 17.6 Contract predictive maintenance programs 393 18 World-Class Maintenance 394 18.1 What is world-class maintenance? 394 18.2 Five fundamentals of world-class performance 395 18.3 Competitive advantage 396 18.4 Focus on quality 397 18.5 Focus on maintenance 398 18.6 Overall equimpment effectiveness 402 18.7 Elements of effective maintenance 406 18.8 Responsibilities 412 18.9 Three types of maintenance 413 18.10 Supervision 419 18.11 Standard procedures 424 18.12 Workforce development 426 Index 435 Maintenance costs are a major part of the total operating costs of all manufacturing or production plants. Depending on the specific industry, maintenance costs can rep- resent between 15 and 60 percent of the cost of goods produced. For example, in food- related industries, average maintenance costs represent about 15 percent of the cost of goods produced, whereas maintenance costs for iron and steel, pulp and paper, and other heavy industries represent up to 60 percent of the total production costs. These percentages may be misleading. In most American plants, reported maintenance costs include many nonmaintenance-related expenditures. For example, many plants include modifications to existing capital systems that are driven by market-related factors, such as new products. These expenses are not truly maintenance and should be allocated to nonmaintenance cost centers; however, true maintenance costs are substantial and do represent a short-term improvement that can directly impact plant profitability. Recent surveys of maintenance management effectiveness indicate that one-third—33 cents out of every dollar—of all maintenance costs is wasted as the result of unnec- essary or improperly carried out maintenance. When you consider that U.S. industry spends more than $200 billion each year on maintenance of plant equipment and facil- ities, the impact on productivity and profit that is represented by the maintenance oper- ation becomes clear. The result of ineffective maintenance management represents a loss of more than $60 billion each year. Perhaps more important is the fact that ineffective maintenance management significantly affects the ability to manufacture quality products that are competitive in the world market. The losses of production time and product quality that result from poor or inadequate maintenance management have had a dramatic impact on U.S. industries’ ability to compete with Japan and other countries 1 IMPACT OF MAINTENANCE 1 [...]...2 An Introduction to Predictive Maintenance that have implemented more advanced manufacturing and maintenance management philosophies The dominant reason for this ineffective management is the lack of factual data to quantify the actual need for repair or maintenance of plant machinery, equipment, and systems Maintenance scheduling has been, and in many instances still is, predicated... Improving maintenance efficiency and effectiveness In most TPM plans, though, the operator is directly involved in some level of maintenance This effort involves better planning and scheduling better preventive maintenance, predictive maintenance, reliability-centered maintenance, spare parts equipment stores, and tool locations—the collective domain of the maintenance department and the maintenance technologies... catastrophic failures and the need for corrective maintenance These methods will also extend the useful life and minimize the life cycle cost of critical production systems 16 An Introduction to Predictive Maintenance Predictive Maintenance Is More Than Maintenance Traditionally, predictive maintenance is used solely as a maintenance management tool In most cases, this use is limited to preventing unscheduled... maintenance (TPM) and reliability-centered maintenance (RCM), have been developed and touted as the panacea for ineffective maintenance Many domestic plants have partially adopted one of these quick-fix methods in an attempt to compensate for perceived maintenance shortcomings Total Productive Maintenance Touted as the Japanese approach to effective maintenance management, the TPM concept was developed... production plants 1.1 MAINTENANCE MANAGEMENT METHODS To understand a predictive maintenance management program, traditional management techniques should first be considered Industrial and process plants typically employ two types of maintenance management: run -to- failure or preventive maintenance 1.1.1 Run -to- Failure Management The logic of run -to- failure management is simple and straightforward: When... cost of maintenance It also improves the product quality, productivity, and profitability of manufacturing and production plants Predictive maintenance is a condition-driven preventive maintenance program Instead of relying on industrial or in-plant average-life statistics (i.e., mean-time -to- failure) to schedule maintenance activities, predictive maintenance uses direct monitoring of the mechanical... unscheduled downtime and/or catastrophic failures Although this function is important, predictive maintenance can provide substantially more benefits by expanding the scope or mission of the program As a maintenance management tool, predictive maintenance can and should be used as a maintenance optimization tool The program’s focus should be on eliminating unnecessary downtime, both scheduled and unscheduled;... preventive maintenance downtime, or delays Maintenance prevention, not quick-fixes of breakdowns, should be the objective Maintenance planning and scheduling are essential parts of effective maintenance Planners must develop and implement both preventive and corrective maintenance tasks that achieve maximum use of maintenance resources and the production capacity of plant systems Good planning is not an option... means to 22 An Introduction to Predictive Maintenance effectively communicate and coordinate the integrated functions, such as sales, production, maintenance, and procurement, into an effective unit Large plants must also exercise caution The tendency is to become excessive when implementing continuous improvement programs Features are added to the information management system, predictive maintenance. .. their interest to try, however, because without financial data there can be no satisfactory cost justification for CM, and hence no will or investment to improve the maintenance situation Ultimately, their department and the company will be the losers if poor maintenance leads to an uncompetitive marketplace position Some of the factors relevant to maintenance engineering that can have an adverse effect . AN INTRODUCTION TO PREDICTIVE MAINTENANCE Second Edition AN INTRODUCTION TO PREDICTIVE MAINTENANCE Second Edition R. Keith Mobley Amsterdam. of manufacturing and pro- duction plants. 1.1 MAINTENANCE MANAGEMENT METHODS To understand a predictive maintenance management program, traditional manage- ment