Newnes Boston Oxford Auckland Johannesburg Melbourne New Delhi Newnes is an imprint of Butterworth-Heinemann. Copyright 0 1999 by Butterworth-Heinemann -& A member of the Reed Elsevier group 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, Butterworth-Heinemann prints its books on acid-free paper whenever possible. Library of Congress Cataloging-in-PublicationD ata Mobley, R. Keith, 1943- Vibration fundamentals /by R. Keith Mobley. p. cm. - (Plant engineering maintenance series) Includes index. ISBN 0-7506-7150-5 (alk. paper) 1. Plant maintenance. 2. Vibration. 3. Machinery-Vibration. I. Title. 11. Series. TS192.M626 1999 621.8’ 16-dc21 98-32098 CIP British Library Cataloguing-in-PublicationD ata A catalogue record for this book is available from the British Library. The publisher offers special discounts on bulk orders of this book. For information, please contact: Manager of Special Sales Butterworth-Heinemann 225 Wildwood Avenue Wobum, MA 01801-2041 Tel: 78 1-904-2500 Fax: 781-904-2620 For information on all Butterworth-Heinemann publications available, contact our World Wide Web home page at: http://www.bh.com 10 9 8 7 6 5 4 3 2 1 Printed in the United States ofAmerica PLANTE NGINEERINGM AINTENANCSEE RIES Vibration Fundamentals R. Keith Mobley Root Cause Failure Analysis R. Keith Mobley Maintenance Fundamentals R. Keith Mobley CONTENTS Part I Theory: Introduction to Vibration Analysis 1 Chapter 1 Introduction 2 Chapter 2 Vibration Analysis Applications 3 Chapter 3 Vibration Analysis Overview 6 Chapter 4 Vibration Sources 13 Chapter 5 Vibration Theory 17 Chapter 6 Machine Dynamics 26 Chapter 7 Vibration Data Types and Formats 42 Chapter 8 Data Acquisition 49 Chapter 9 Analysis Techniques 60 Part I1 Frequency-DomainV ibration Analysis 65 Chapter 10 Overview 66 Chapter 11 Machine-Train Monitoring Parameters 71 Chapter 12 Database Development 97 Chapter 13 Vibration Data Acquisition 112 Chapter 14 Trending Analysis 125 Chapter 15 Failure-Mode Analysis 138 Chapter 16 Signature Analysis 181 Chapter 17 Root-Cause Analysis 189 Part I11 Resonance and Critical Speed Analysis 200 Chapter 18 Introduction 20 1 Chapter 19 Types of Resonance 202 Chapter 20 Examples of Resonance 208 Chapter 21 Testing for Resonance 213 Chapter 22 Mode Shape 222 Part IV Real-Time Analysis 224 Chapter 23 Overview 225 Chapter 24 Applications 230 Chapter 25 Data Acquisition 235 V vi Contents Chapter 26 Analysis Setup 246 Chapter 27 Transient (Waterfall) Analysis 255 Chapter 28 Synchronous Time Averaging 259 Chapter 29 Zoom analysis 265 Chapter 30 Torsional Analysis 267 Glossary 286 List of Abbreviations 29 1 Index 293 Part I THEORY: INTRODUCTION TO VIBRATION ANALYSIS Part I is an introduction to vibration analysis that covers basic vibration theory. All mechanical equipment in motion generates a vibration profile, or signature, that reflects its operating condition. This is true regardless of speed or whether the mode of operation is rotation, reciprocation, or linear motion. Vibration analysis is applica- ble to all mechanical equipment, although a common-yet invalid-assumption is that it is limited to simple rotating machinery with running speeds above 600 revolu- tions per minute (rpm). Vibration profile analysis is a useful tool for predictive main- tenance, diagnostics, and many other uses. 1 Chapter 1 INTRODUCTION Several predictive maintenance techniques are used to monitor and analyze critical machines, equipment, and systems in a typical plant. These include vibration analysis, ultrasonics, thermography, tribology, process monitoring, visual inspection, and other nondestructive analysis techniques. Of these techniques, vibration analysis is the dominant predictive maintenance technique used with maintenance management pro- grams. Predictive maintenance has become synonymous with monitoring vibration character- istics of rotating machinery to detect budding problems and to head off catastrophic failure. However, vibration analysis does not provide the data required to analyze electrical equipment, areas of heat loss, the condition of lubricating oil, or other parameters typically evaluated in a maintenance management program. Therefore, a total plant predictive maintenance program must include several techniques, each designed to provide specific information on plant equipment. 2 Chapter 2 VIBRATION ANALYSIS APPLICATIONS The use of vibration analysis is not restricted to predictive maintenance. This tech- nique is useful for diagnostic applications as well. Vibration monitoring and analysis are the primary diagnostic tools for most mechanical systems that are used to manu- facture products. When used properly, vibration data provide the means to maintain optimum operating conditions and efficiency of critical plant systems. Vibration anal- ysis can be used to evaluate fluid flow through pipes or vessels, to detect leaks, and to perform a variety of nondestructive testing functions that improve the reliability and performance of critical plant systems. Some of the applications that are discussed briefly in this chapter are predictive main- tenance, acceptance testing, quality control, loose part detection, noise control, leak detection, aircraft engine analyzers, and machine design and engineering. Table 2.1 lists rotating, or centrifugal, and nonrotating equipment, machine-trains, and continu- ous processes typically monitored by vibration analysis. Table 2.1 Equipment and Processes Typical0 Monitored by Viiration Analysis Centrifugal Reciprocating Continuous Process Pumps Pumps Continuous casters Compressors Compressors Hot and cold strip lines Blowers Diesel engines Annealing lines Fans Gasoline engines Plating lines Motorigenerators Cylinders Paper machines Ball mills Other machines Can manufacturing lines Chillers Pickle lines continued 3 4 Vibration Fundamentals Table 2.1 Equipment and Processes Typically Monitored by VZrationA nalysis Centrifugal Machine-Tkains Continuous Process Product rolls Boring machines Printing Mixers Hobbing machines Dyeing and finishing Gearboxes Machining centers Roofing manufacturing lines Centrifuges Temper mills Chemical production lines Transmissions Metal-working machines Petroleum production lines Turbines Rolling mills, and most Neoprene production lines Generators machining equipment Polyester production lines Rotary dryers Nylon production lines Electric motors Flooring production lines All rotating machinery Continuous process lines Source: Integrated Systems, Inc. PREDICTIVEM AINTENANCE The fact that vibration profiles can be obtained for all machinery that has rotating or moving elements allows vibration-based analysis techniques to be used for predic- tive maintenance. Vibration analysis is one of several predictive maintenance tech- niques used to monitor and analyze critical machines, equipment, and systems in a typical plant. However, as indicated before, the use of vibration analysis to monitor rotating machinery to detect budding problems and to head off catastrophic failure is the dominant predictive maintenance technique used with maintenance management programs. ACCEPTANCET ESTING Vibration analysis is a proven means of verifying the actual performance versus design parameters of new mechanical, process, and manufacturing equipment. Preac- ceptance tests performed at the factory and immediately following installation can be used to ensure that new equipment performs at optimum efficiency and expected life- cycle cost. Design problems as well as possible damage during shipment or installa- tion can be corrected before long-term damage and/or unexpected costs occur. QUALITY CONTROL Production-line vibration checks are an effective method of ensuring product qual- ity where machine tools are involved. Such checks can provide advanced warning that the surface finish on parts is nearing the rejection level. On continuous pro- cess lines such as paper machines, steel-finishing lines, or rolling mills, vibration