Tài liệu RELIABILITY, MAINTAINABILITY AND RISK pptx

RELIABILITY, MAINTAINABILITY AND RISK

Also by the same author

Reliability Engineering, Pitman, 1972

Maintainability Engineering, Pitman, 1973 (with A. H. Babb)

Statistics Workshop, Technis, 1974, 1991

Achieving Quality Software, Chapman & Hall, 1995

Quality Procedures for Hardware and Software, Elsevier, 1990 (with J. S. Edge)

Reliability, Maintainability

and Risk

Practical methods for engineers

Sixth Edition

Dr David J Smith

BSc, PhD, CEng, FIEE, FIQA, HonFSaRS, MIGasE

OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI

Butterworth-Heinemann

Linacre House, Jordan Hill, Oxford OX2 8DP

225 Wildwood Avenue, Woburn, MA 01801-2041

A division of Reed Educational and Professional Publishing Ltd

A member of the Reed Elsevier group plc

First published by Macmillan Education Ltd 1981

Second edition 1985

Third edition 1988

Fourth edition published by Butterworth-Heinemann Ltd 1993

Reprinted 1994, 1996

Fifth edition 1997

Reprinted with revisions 1999

Sixth edition 2001

© David J. Smith 1993, 1997, 2001

All rights reserved. No part of this publication

may be reproduced in any material form (including

photocopying or storing in any medium by electronic

means and whether or not transiently or incidentally

to some other use of this publication) without the

written permission of the copyright holder except in

accordance with the provisions of the Copyright,

Designs and Patents Act 1988 or under the terms of a

licence issued by the Copyright Licensing Agency Ltd,

90 Tottenham Court Road, London, England W1P 9HE.

Applications for the copyright holder’s written permission

to reproduce any part of this publication should be addressed

to the publishers

British Library Cataloguing in Publication Data

Smith, David J. (David John), 1943 June 22–

Reliability, maintainability and risk. – 6th ed.

1 Reliability (Engineering) 2 Risk assessment

I Title

620'.00452

Library of Congress Cataloguing in Publication Data

Smith, David John, 1943–

Reliability, maintainability, and risk: practical methods for

engineers/David J Smith. – 6th ed.

p. cm.

Includes bibliographical references and index.

ISBN 0 7506 5168 7

1 Reliability (Engineering) 2 Maintainability (Engineering)

3 Engineering design I Title.

TA169.S64 2001

620'.00452–dc21 00–049380

ISBN 0 7506 5168 7

Composition by Genesis Typesetting, Laser Quay, Rochester, Kent

Printed and bound in Great Britain by Antony Rowe, Chippenham, Wiltshire

............................................................................. Preface

........................................................ Acknowledgements

Part One Understanding Reliability Parameters and

................................................................................Costs

1 The history of reliability and safety technology........................ 1

1.1 FAILURE DATA ................................................................................. 1

1.2 HAZARDOUS FAILURES .................................................................. 4

1.3 RELIABILITY AND RISK PREDICTION............................................. 5

1.4 ACHIEVING RELIABILITY AND SAFETY-INTEGRITY ..................... 6

1.5 THE RAMS-CYCLE ........................................................................... 7

1.6 CONTRACTUAL PRESSURES ......................................................... 9

............................................. 2 Understanding terms and jargon

2.1 DEFINING FAILURE AND FAILURE MODES ...................................

2.2 FAILURE RATE AND MEAN TIME BETWEEN FAILURES .............. 12

2.3 INTERRELATIONSHIPS OF TERMS ................................................ 14

2.4 THE BATHTUB DISTRIBUTION ........................................................ 16

2.5 DOWN TIME AND REPAIR TIME...................................................... 17

2.6 AVAILABILITY.................................................................................... 20

2.7 HAZARD AND RISK-RELATED TERMS ........................................... 20

2.8 CHOOSING THE APPROPRIATE PARAMETER ............................. 21

EXERCISES............................................................................................. 22

3 A cost-effective approach to quality, reliability and safety .......

................................................................... 3.1 THE COST OF QUALITY

3.2 RELIABILITY AND COST .................................................................. 26

3.3 COSTS AND SAFETY ....................................................................... 29

Part Two Interpreting Failure Rates ..............................

4 Realistic failure rates and prediction confidence .....................

............................................................................ 4.1 DATA ACCURACY

4.2 SOURCES OF DATA ......................................................................... 37

4.3 DATA RANGES ................................................................................. 41

4.4 CONFIDENCE LIMITS OF PREDICTION.......................................... 44

4.5 OVERALL CONCLUSIONS ............................................................... 46

5 Interpreting data and demonstrating reliability .........................

............................................................................ 5.1 THE FOUR CASES

5.2 INFERENCE AND CONFIDENCE LEVELS ......................................

5.3 THE CHI-SQUARE TEST .................................................................. 49

5.4 DOUBLE-SIDED CONFIDENCE LIMITS........................................... 50

5.5 SUMMARIZING THE CHI-SQUARE TEST........................................ 51

5.6 RELIABILITY DEMONSTRATION ..................................................... 52

5.7 SEQUENTIAL TESTING.................................................................... 56

5.8 SETTING UP DEMONSTRATION TESTS ........................................ 57

EXERCISES............................................................................................. 57

6 Variable failure rates and probability plotting ...........................

......................................................... 6.1 THE WEIBULL DISTRIBUTION

6.2 USING THE WEIBULL METHOD ...................................................... 60

6.3 MORE COMPLEX CASES OF THE WEIBULL DISTRIBUTION ....... 67

6.4 CONTINUOUS PROCESSES............................................................ 68

EXERCISES............................................................................................. 69

Part Three Predicting Reliability and Risk ....................

........................................................ 7 Essential reliability theory

..................................................................... 7.1 WHY PREDICT RAMS?

.................................................................... 7.2 PROBABILITY THEORY

7.3 RELIABILITY OF SERIES SYSTEMS ............................................... 76

7.4 REDUNDANCY RULES..................................................................... 77

7.5 GENERAL FEATURES OF REDUNDANCY ..................................... 83

EXERCISES............................................................................................. 86

.............................................................. 8 Methods of modelling

8.1 BLOCK DIAGRAM AND MARKOV ANALYSIS .................................

8.2 COMMON CAUSE (DEPENDENT) FAILURE ................................... 98

8.3 FAULT TREE ANALYSIS................................................................... 103

8.4 EVENT TREE DIAGRAMS ................................................................ 110

............................................. 9 Quantifying the reliability models

9.1 THE RELIABILITY PREDICTION METHOD ......................................

9.2 ALLOWING FOR DIAGNOSTIC INTERVALS ................................... 115

9.3 FMEA (FAILURE MODE AND EFFECT ANALYSIS)......................... 117

9.4 HUMAN FACTORS............................................................................ 118

9.5 SIMULATION ..................................................................................... 123

9.6 COMPARING PREDICTIONS WITH TARGETS ............................... 126

EXERCISES............................................................................................. 127

........................................................ 10 Risk assessment (QRA)

10.1 FREQUENCY AND CONSEQUENCE .............................................

10.2 PERCEPTION OF RISK AND ALARP............................................. 129

10.3 HAZARD IDENTIFICATION............................................................. 130

10.4 FACTORS TO QUANTIFY............................................................... 135

Part Four Achieving Reliability and Maintainability....

11 Design and assurance techniques ........................................

11.1 SPECIFYING AND ALLOCATING THE REQUIREMENT ...............

11.2 STRESS ANALYSIS ........................................................................ 145

11.3 ENVIRONMENTAL STRESS PROTECTION .................................. 148

11.4 FAILURE MECHANISMS................................................................. 148

11.5 COMPLEXITY AND PARTS ............................................................ 150

11.6 BURN-IN AND SCREENING ........................................................... 153

11.7 MAINTENANCE STRATEGIES ....................................................... 154

.......................................................... 12 Design review and test

.................................................................. 12.1 REVIEW TECHNIQUES

12.2 CATEGORIES OF TESTING........................................................... 156

12.3 RELIABILITY GROWTH MODELLING ............................................ 160

EXERCISES............................................................................................. 163

13 Field data collection and feedback ........................................

13.1 REASONS FOR DATA COLLECTION ............................................

13.2 INFORMATION AND DIFFICULTIES ..............................................

13.3 TIMES TO FAILURE........................................................................ 165

13.4 SPREADSHEETS AND DATABASES............................................. 166

13.5 BEST PRACTICE AND RECOMMENDATIONS.............................. 168

13.6 ANALYSIS AND PRESENTATION OF RESULTS .......................... 169

13.7 EXAMPLES OF FAILURE REPORT FORMS.................................. 170

............................................... 14 Factors influencing down time

...................................................................... 14.1 KEY DESIGN AREAS

14.2 MAINTENANCE STRATEGIES AND HANDBOOKS....................... 180

15 Predicting and demonstrating repair times ............................

................................................................ 15.1 PREDICTION METHODS

15.2 DEMONSTRATION PLANS............................................................. 201

16 Quantified reliability centred maintenance .............................

............................................................................ 16.1 WHAT IS QRCM?

16.2 THE QRCM DECISION PROCESS................................................. 206

16.3 OPTIMUM REPLACEMENT (DISCARD)......................................... 207

16.4 OPTIMUM SPARES......................................................................... 209

16.4 OPTIMUM PROOF-TEST ................................................................ 210

16.6 CONDITION MONITORING............................................................. 211

...................................................... 17 Software quality/reliability

.......................................................... 17.1 PROGRAMMABLE DEVICES

17.2 SOFTWARE FAILURES .................................................................. 214

17.3 SOFTWARE FAILURE MODELLING .............................................. 215

17.4 SOFTWARE QUALITY ASSURANCE............................................. 217

17.5 MODERN/FORMAL METHODS ...................................................... 223

17.6 SOFTWARE CHECKLISTS ............................................................. 226

Part Five Legal, Management and Safety

................................................................ Considerations

............................................................. 18 Project management

18.1 SETTING OBJECTIVES AND SPECIFICATIONS ...........................

18.2 PLANNING, FEASIBILITY AND ALLOCATION ............................... 234

18.3 PROGRAMME ACTIVITIES............................................................. 234

18.4 RESPONSIBILITIES ........................................................................ 237

18.5 STANDARDS AND GUIDANCE DOCUMENTS .............................. 237

19 Contract clauses and their pitfalls ..........................................

........................................................................ 19.1 ESSENTIAL AREAS

19.2 OTHER AREAS ............................................................................... 241

19.3 PITFALLS......................................................................................... 242

19.4 PENALTIES ..................................................................................... 244

19.5 SUBCONTRACTED RELIABILITY ASSESSMENTS ...................... 246

19.6 EXAMPLE ........................................................................................ 247

20 Product liability and safety legislation ....................................

............................................................ 20.1 THE GENERAL SITUATION

20.2 STRICT LIABILITY........................................................................... 249

20.3 THE CONSUMER PROTECTION ACT 1987 .................................. 250

20.4 HEALTH AND SAFETY AT WORK ACT 1974 ................................ 251

20.5 INSURANCE AND PRODUCT RECALL.......................................... 252

....................................................... 21 Major incident legislation

21.1 HISTORY OF MAJOR INCIDENTS .................................................

21.2 DEVELOPMENT OF MAJOR INCIDENT LEGISLATION................ 255

21.3 CIMAH SAFETY REPORTS ............................................................ 256

21.4 OFFSHORE SAFETY CASES ......................................................... 259

21.5 PROBLEM AREAS .......................................................................... 261

21.6 THE COMAH DIRECTIVE (1999) .................................................... 262

22 Integrity of safety-related systems .........................................

22.1 SAFETY-RELATED OR SAFETY-CRITICAL? ................................

22.2 SAFETY-INTEGRITY LEVELS (SILs).............................................. 264

22.3 PROGRAMMABLE ELECTRONIC SYSTEMS (PESs).................... 266

22.4 CURRENT GUIDANCE.................................................................... 268

22.5 ACCREDITATION AND CONFORMITY OF ASSESSMENT .......... 272

23 A case study: The Datamet Project .......................................

.............................................................................. 23.1 INTRODUCTION

............................................................. 23.2 THE DATAMET CONCEPT

23.3 FORMATION OF THE PROJECT GROUP ..................................... 277

23.4 RELIABILITY REQUIREMENTS...................................................... 278

23.5 FIRST DESIGN REVIEW................................................................. 279

23.6 DESIGN AND DEVELOPMENT....................................................... 281

23.7 SYNDICATE STUDY ....................................................................... 282

23.8 HINTS .............................................................................................. 282

...................................................... Appendix 1 Glossary

A1 TERMS RELATED TO FAILURE ..........................................

A2 RELIABILITY TERMS ........................................................... 285

A3 MAINTAINABILITY TERMS .................................................. 286

A4 TERMS ASSOCIATED WITH SOFTWARE.......................... 287

A5 TERMS RELATED TO SAFETY ........................................... 289

A6 MISCELLANEOUS TERMS .................................................. 290

Appendix 2 Percentage points of the Chi- square

...................................................................... distribution

Appendix 3 Microelectronics failure rates ....................

Appendix 4 General failure rates ...................................

Appendix 5 Failure mode percentages .........................

Appendix 6 Human error rates ......................................

............................................... Appendix 7 Fatality rates

Appendix 8 Answers to exercises .................................

................................................ Appendix 9 Bibliography

.......................................................................................BOOKS

............................................................ OTHER PUBLICATIONS

.............................................. STANDARDS AND GUIDELINES

................................................................................ JOURNALS

Appendix 10 Scoring criteria for BETAPLUS

.................................................... common cause model

1 CHECKLIST AND SCORING FOR EQUIPMENT

CONTAINING PROGRAMMABLE ELECTRONICS ...................

2 CHECKLIST AND SCORING FOR

NON-PROGRAMMABLE EQUIPMENT .....................................

Appendix 11 Example of HAZOP ...................................

.............................................................. EQUIPMENT DETAILS

............................................................. HAZOP WORKSHEETS

................................................ POTENTIAL CONSEQUENCES

........................................ Appendix 12 HAZID checklist

................................................................................. Index

Preface

After three editions Reliability, Maintainability in Perspective became Reliability, Main￾tainability and Risk and has now, after just 20 years, reached its 6th edition. In such a fast

moving subject, the time has come, yet again, to expand and update the material particularly

with the results of my recent studies into common cause failure and into the correlation between

predicted and achieved field reliability.

The techniques which are explained apply to both reliability and safety engineering and are

also applied to optimizing maintenance strategies. The collection of techniques concerned with

reliability, availability, maintainability and safety are often referred to as RAMS.

A single defect can easily cost £100 in diagnosis and repair if it is detected early in production

whereas the same defect in the field may well cost £1000 to rectify. If it transpires that the failure

is a design fault then the cost of redesign, documentation and retest may well be in tens or even

hundreds of thousands of pounds. This book emphasizes the importance of using reliability

techniques to discover and remove potential failures early in the design cycle. Compared with

such losses the cost of these activities is easily justified.

It is the combination of reliability and maintainability which dictates the proportion of time

that any item is available for use or, for that matter, is operating in a safe state. The key

parameters are failure rate and down time, both of which determine the failure costs. As a result,

techniques for optimizing maintenance intervals and spares holdings have become popular since

they lead to major cost savings.

‘RAMS’ clauses in contracts, and in invitations to tender, are now commonplace. In defence,

telecommunications, oil and gas, and aerospace these requirements have been specified for

many years. More recently the transport, medical and consumer industries have followed suit.

Furthermore, recent legislation in the liability and safety areas provides further motivation for

this type of assessment. Much of the activity in this area is the result of European standards and

these are described where relevant.

Software tools have been in use for RAMS assessments for many years and only the simplest

of calculations are performed manually. This sixth edition mentions a number of such packages.

Not only are computers of use in carrying out reliability analysis but are, themselves, the subject

of concern. The application of programmable devices in control equipment, and in particular

safety-related equipment, has widened dramatically since the mid-1980s. The reliability/quality

of the software and the ways in which it could cause failures and hazards is of considerable

interest. Chapters 17 and 22 cover this area.

Quantifying the predicted RAMS, although important in pinpointing areas for redesign,

does not of itself create more reliable, safer or more easily repaired equipment. Too often, the

author has to discourage efforts to refine the ‘accuracy’ of a reliability prediction when an

order of magnitude assessment would have been adequate. In any engineering discipline the

ability to recognize the degree of accuracy required is of the essence. It happens that RAMS

parameters are of wide tolerance and thus judgements must be made on the basis of one- or,

at best, two-figure accuracy. Benefit is only obtained from the judgement and subsequent

follow-up action, not from refining the calculation.

A feature of the last four editions has been the data ranges in Appendices 3 and 4. These were

current for the fourth edition but the full ‘up to date’ database is available in FARADIP.THREE

(see last 4 pages of the book).

DJS

xii Preface

Acknowledgements

I would particularly like to thank the following friends and colleagues for their help and

encouragement:

Peter Joyce for his considerable help with the section on Markov modelling;

‘Sam’ Samuel for his very thorough comments and assistance on a number of chapters.

I would also like to thank:

The British Standards Institution for permission to reproduce the lightning map of the UK

from BS 6651;

The Institution of Gas Engineers for permission to make use of examples from their guidance

document (SR/24, Risk Assessment Techniques).

ITT Europe for permission to reproduce their failure report form and the US Department of

Defense for permission to quote from MIL Handbooks.

Part One

Understanding Reliability

Parameters and Costs