Vibration Fundamentals

299 Pages·1999·12.1 MB·English

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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
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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