Mechanical Fault Diagnosis and condition monitoring

504 Pages·1977·13.72 MB·English

by  R. A. Collacott B.Sc. (Eng), Ph.D., C.Eng., F.I.Mech.E., F.I.Mar.E. (auth.)

Mechanical Fault
Diagnosis
Mechanical Fault
Diagnosis
and condition monitoring
R. A. Collacott
B.Sc. (Eng), Ph.D., C.Eng., F.LMech.E., F.LMar.E.,
Director, U K. Mechanical Health Monitoring Group,
Leicester Polytechnic
S
Chapman and Hall
London
A Halstead Press Book
John Wiley & Sons, New York
First published in 1977
by Chapman and Hall, Ltd.,
11 New Fetter Lane,
London EC4P 4EE
© 1977 R.A. Collacott
Softcover reprint of the hardcover 1st edition 1977
Typeset by Alden Press Oxford, London & Northampton and
All rights reserved. No part of this book
may be reprinted, or reproduced or utilized in
any form or by any electronic, mechanical or
other means, now known or hereafter invented,
including photocopying and recording, or in
any information storage and retrieval system,
without permission in writing from the
Publisher.
Distributed in the U.S.A.
by Halsted Press, a Division
of John Wiley and Sons, Inc., New York
Library of Congress Cataloging in Publication Data
Collacott, Ralph Albert.
Mechanical fault diagnosis.
l. Machinery-Testing. 2. Machinery-Reliability.
I. Title
TJ148.C57 62l.8'028 77-397
ISBN-13: 978-94-009-5725-1 e-ISBN-13: 978-94-009-5723-7
001: 10.1 007/978-94-009-5723-7
Contents
Preface
1 Failure types, investigation and occurrences
1.1 Introduction 1
1.2 System failure and component failure 1
1.3 Failure decisions 1
1.4 Failure classifications 2
1.5 Types offailure 3
1.6 Failure investigations 5
1.7 Failure case studies 6
1.8 Human factors in failure incidents 13
2 Causes of failure 16
2.1 Introduction 16
2.2 Service failures 16
2.3 Fatigue 18
2.4 Excessive deformation 23
2.5 Wear 28
2.6 Co"osion 32
2. 7 Blockage, sludges 35
2.8 Blockage in cooling systems 35
2.9 Design, manufacturing and assembly causes of failure 37
3 Fault detection sensors 41
3.1 Introduction 41
3.2 Contaminant monitoring 41
3.3 Co"osion monitoring 41
3.4 Force monitoring 43
3.5 Gas leakage monitoring 45
3.6 Air pollution monitoring 47
3. 7 Liquid contamination monitoring 51
3.8 Non-destructive testing techniques 53
3.9 Optical examination 55
3.10 Temperature sensing 56
3.11 Particle testing 58
3.12 Proximity monitors 59
3.13 Sound monitoring 61
3.14 Vibration transducers 62
3.15 Telemetry 67
vi Contents
4 Data processing and analysis 76
4.1 Introduction 76
4.2 Fourier analysis 77
4.3 Frequency analysis techniques 87
4.4 Derived [unctions 88
5 Vibration analysis 100
5.1 Introduction 100
5.2 Vibration-simple harmonic motion concept 103
5.3 Vibration signature of active systems 105
5.4 Vibration monitoring equipment 107
5.5 System monitors and vibration limit detectors 113
5.6 Vibration monitoring experience 117
5.7 Critical vibration levels 132
6 Sound monitoring 142
6.1 Introduction 142
6.2 Sound frequencies 146
6.3 Sound loudness measurement 150
6.4 Acoustic power 151
6.5 Sound measurement 152
6.6 Magnetic tape recorders 153
6.7 Sound level meters 155
6.8 Sound analysers 156
6.9 Sound signal data processing 157
6.10 Sound monitoring 157
7 Discrete frequencies 179
7.1 Introduction 179
7.2 Simple vibrations 183
7.3 Transverse vibrations of bars - approximate frequency
calculations 188
7.4 More precise evaluations - overtones 192
7.5 Torsional oscillation off lywheel-bearing shafts 195
7.6 Belt drives 204
7.7 Whirling of marine line shafting 206
7.8 Gear excitation 209
7.9 Rolling element bearing 216
7.10 Blade vibration 220
7.11 Cam mechanism vibration 221
8 Contaminant analysis 231
8.1 Introduction 231
Contents vii
8.2 Contaminants in used lubricating oils 231
8.3 Carrier fluid degradation 235
8.4 Contaminant monitoring techniques (wear processes) 237
8.5 Oil degradation analysis 238
8.6 Abrasive particles in lubricating oil 240
8.7 Abrasive particles in bearings 240
8.8 Abrasive particles in hydraulic systems 241
8.9 Dissolved gas fault monitoring 245
9 SOAP and other contaminant monitoring techniques 250
9.1 Introduction 250
9.2 Spectrometric oil analysis procedure 250
9.3 Magnetic chip detectors 260
9.4 'Ferrograph' particle precipitation 270
9.5 STM control kit 274
9.6 Used oil blotter test 275
9.7 Thin-layer chromatography 276
9.8 Capacitative oil debris monitor 276
9.9 X-ray fluorescence detection of contamination (XRF) 277
9.10 X-ray photoelectron spectrometry 277
9.11 Particle classification 278
10 Perfonnance trend monitoring 284
10.1 Primary monitoring --performance 284
10.2 Primary and secondary performance parameters 290
10.3 Performance trend analysis 298
10.4 Turbine gas path performance monitoring thermodynamics 301
10.5 Steam turbine performance analysis 310
10.6 Case studies in performance monitoring 313
10.7 Performance monitoring systems 323
11 Static testing 331
11.1 Introduction 331
11.2 Visual testing 331
11.3 Liquid penetrant inspection 337
11.4 Thermal methods 338
11.5 X-ray photography 338
11.6 Sonics 344
11. 7 Ultrasonics 344
11.8 Stress wave emission 348
11.9 Magnetic testing methods 351
11.10 Electrical NDT techniques 356
11.11 Eddy current testing 357
11.12 NDT selection 357
viii Contents
12 Monitoring systems in operation 367
12.1 Introduction 367
12.2 Marine monitoring systems 367
12.3 Marine condition monitoring requirements 370
12.4 . Marine diesel engine monitoring 372
12.5 Marine turbine monitoring systems 379
12.6 Shipboard vibration monitoring 382
12.7 Spectrometric oil analysis programme - marine 384
12.8 Monitoring integrity verification 384
12.9 Aircraft condition monitoring 386
12.10 Condition monitoring - generating plant 395
12.11 Automotive diagnostic equipment 395
12.12 Systematic fault monitor selection 399
13 Fault analysis planning and system availability 404
13.1 Introduction 404
13.2 Availability 423
13.3 Failure prediction/reliability assessment 428
13.4 Hazard rate curve 433
13.5 Complex system reliability - Monte Carlo simulation 438
13.6 Hazardous chemical plants - high integrity protective 439
systems (HIPS)
14 Reliability/failure concepts 443
14.1 Introduction 443
14.2 Probability of reliability and failure 444
14.3 Failure pattern-exponential distribution 448
14.4 Load and strength - statistical distribution 454
14.5 Reliability assurance - BS 9000 system 457
15 Reliability data sources 459
15.1 Introduction 459
15.2 Systems Reliability Service (SRS) 461
15.3 Failure data 469
15.4 Environmental influences on instrument failure rates 475
15.5 Failure data-confidence level 476
Index 479
Preface
Although the most sophisticated fault diagnosis and condition monitoring systems
have their origin in the aerospace and nuclear energy industries, their use is by no
means restricted to such areas of 'high technology'. Modern machinery in most
industrial plants is now so complex and expensive that mechanics find it increas
ingly difficult to detect failure by, for instance, recognising changes in sound
'signatures', and few plants can afford the luxury of regular 'stripping down'.
Increasingly, therefore, eady-warning devices are being employed in an effort to
prevent catastrophic breakdown.
This book provides the first co-ordinated compilation of fault diagnosis and con
dition monitoring devices. It proceeds in three logical steps. The eady chapters deal
with those conditions which contribute to deterioration and the consequent likely
development of faults. The middle part of the book considers the various tech
niques of monitoring and discusses the criteria for their selection in different situ
ations. The final chapters provide a guide to the interpretation of the information
signals deriving from monitoring, relating to reliability science and the mathematics
of probability, and thus providing decision data on which management can act.
Through establishing the UK Mechanical Health Monitoring Group, I have
appreciated the enormously wide industrial interest in this field. It is my hope that
this book will serve the needs of both plant engineers and senior executives in
providing a quick source of reference to those devices most suited to their require
ments. It should also prove valuable to mechanical materials and control engineers
whose particular interests include manufacture and maintenance of complex
machinery.
1976 R. A. Collacott
I Failure types, investigation
and occurrences
1.1 Introduction
Failure is defined in the BS Maintenance Glossary as 'The termination of the ability
of an item to perform its required function.' This can involve such failure cate
gories as follows:
(l) Catastrophic failures which result in an immediate inability of a system to
achieve its function;
(2) Performance failures associated with a reducing performance of the equip
ment.
(3) When the operator deliberately takes the equipment out of service, even
though it is producing, at that time, its specified output.
1.2 System failure and component failure
The extent to which any particular system failure or component failure has an effect
on the 'normal function' or 'mission' depends on the function. There is a great dif
ference between the failure of a pump on a machine tool and on an aeroplane or
space-craft.
When considering the failure of a ship's machinery, Bridges [1] stated that cer
tain systems and equipment may only be required during part of the mission. If,
during the passage of a ship to the main mission area, systems or equipments which
are required in the main mission fail, and they cannot be repaired before passage
completion, then the mission is deemed to have failed.
Typically, consider a mission by a fishing vessel. It might have two shafts both of
which are needed during fishing but only one shaft is needed for the passage to or
from the fishing grounds. Therefore if one shaft set of propulsion equipment failed
during the passage to the fishing grounds, and it could be repaired before fishing
commenced, the mission would still continue. If, however, the failure could not be
repaired, then the whole mission for the purpose of the analysis would be assumed
to be aborted. Similarly if a propulsion system failure occurred during the fishing
phase the mission would then be deemed to have failed.
1.3 Failure decisions
The events which lead up to a plant or system failure do not fall into a neat sequence
and the planning network is very complex. A typical planning network based on a
nuclear plant operation involves the following steps:
(l) Knowledge of the plant characteristics;
2 Mechanical fault diagnosis
(2) Analysis of methods of operation (steady-rate and transient);
(3) Establishment of safety limits for all plant characteristics;
(4) Consideration of the available signals;
(5) Setting control trips (allowing for instrumentation inaccuracies);
(6) Design of operation interlocks;
(7) Selection of automatic control and operation overrides;
(8) Survey protection systems, involving (a) automatic shutdown, (b) restriction
of plant operation, (c) use of auxiliary protection systems;
(9) Formulate recovery methods based on the consequences of the protection
systems;
(10) Establish the cause of the operation of the protective systems.
1.4 Failure classifications
The terms 'failure' or 'fault' may be viewed from different angles according to the
effect which the lack of performance has on the overall functional capability. Such
aspects as economic viability, safety, engineering complexity, speed, causal influen
ces all provide classifications leading to a description of failure.
1.4.1 Engineering failure classifications
There are two distinct classes of failure:
(l) Intermittent failure: failures which result in a lack of some function of the
component only for a very short period of time, the component reverting to its full
operational standard immediately after failure;
(2) Permanent failure: failures which result in a lack of some function which will
continue until some part of the component is replaced.
1.4.2 Degree offailure classification
Permanent failures may be further subdivided into the following two types:
(1) Complete failure: failure which causes the complete lack of a required func
tion. (It should be noted that in certain cases the limit when a lack of function is
said to be complete is open to interpretation, which depends upon the application);
(2) Partial failure: failure which leads to a lack of some function but not such as
to cause a complete lack of the required function.
1.4.3 Speed off ailure classification
Both complete and partial permanent failure may be further classified according to
the suddenness with which the failure occurs:
(1) Sudden failure: failure which could not be forecast by prior testing or exam
ination;
(2) Gradual failure: failure which could have been forecast by testing or examin
ation.