Reliability, Maintainability and Risk (eBook)

Cover 1
Contents 6
Preface 12
Acknowledgements 14
Part One Understanding Reliability Parameters and Costs 16
The history of reliability and safety technology 18
Failure data 18
Hazardous failures 19
Reliability and risk prediction 20
Achieving reliability and safety-integrity 22
The RAMS-cycle 23
Contractual pressures 25
Understanding terms and jargon 26
Defining failure and failure modes 26
Failure Rate and Mean Time Between Failures 27
Interrelationships of terms 30
The Bathtub Distribution 32
Down Time and Repair Time 33
Availability, Unavailability and Probability of Failure on Demand 36
Hazard and risk-related terms 36
Choosing the appropriate parameter 37
Exercises 38
A cost-effective approach to quality, reliability and safety 39
Reliability and cost 39
Costs and safety 42
The cost of quality 45
Part Two Interpreting Failure Rates 50
Realistic failure rates and prediction confidence 52
Data accuracy 52
Sources of data 54
Data ranges 58
Confidence limits of prediction 61
Overall conclusions 64
Interpreting data and demonstrating reliability 65
The four cases 65
Inference and confidence levels 65
The Chi-square Test 66
Double-sided confidence limits 68
Summarizing the Chi-square Test 69
Reliability demonstration 69
Sequential testing 72
Setting up demonstration tests 74
Exercises 75
Variable failure rates and probability plotting 76
The Weibull Distribution 76
Using the Weibull Method 78
More complex cases of the Weibull Distribution 84
Continuous processes 85
Exercises 86
Part Three Predicting Reliability and Risk 88
Basic reliability prediction theory 90
Why predict RAMS? 90
Probability theory 90
Reliability of series systems 93
Redundancy rules 94
General features of redundancy 100
Exercises 103
Methods of modelling 104
Block Diagrams and Repairable Systems 104
Common cause (dependent) failure 111
Fault Tree Analysis 116
Event Tree Diagrams 124
Quantifying the reliability models 128
The reliability prediction method 128
Allowing for diagnostic intervals 129
FMEA (Failure Mode and Effect Analysis) 131
Human factors 133
Simulation 138
Comparing predictions with targets 143
Exercises 144
Risk assessment (QRA) 145
Frequency and consequence 145
Perception of risk and ALARP 145
Hazard identification 147
Factors to quantify 152
Part Four Achieving Reliability and Maintainability 158
Design and assurance techniques 160
Specifying and allocating the requirement 160
Stress analysis 162
Environmental stress protection 165
Failure mechanisms 165
Complexity and parts 168
Burn-in and screening 170
Maintenance strategies 171
Design review and test 172
Review techniques 172
Categories of testing 173
Reliability growth modelling 178
Exercises 181
Field data collection and feedback 182
Reasons for data collection 182
Information and difficulties 182
Times to failure 183
Spreadsheets and databases 184
Best practice and recommendations 186
Analysis and presentation of results 187
Examples of failure report forms 188
Factors influencing down time 191
Key design areas 191
Maintenance strategies and handbooks 198
Predicting and demonstrating repair times 211
Prediction methods 211
Demonstration plans 219
Quantified reliability centred maintenance 223
What is QRCM? 223
The QRCM decision process 224
Optimum replacement (discard) 225
Optimum spares 227
Optimum proof test 227
Condition monitoring 229
Systematic failures, especially software 230
Programmable devices 230
Software-related failures 232
Software failure modelling 233
Software quality assurance 234
Modern/formal methods 240
Software checklists 243
Part Five Legal, Management and Safety Considerations 248
Project management 250
Setting objectives and specifications 250
Planning, feasibility and allocation 251
Programme activities 251
Responsibilities 253
Functional safety capability 254
Standards and guidance documents 255
Contract clauses and their pitfalls 256
Essential areas 256
Other areas 259
Pitfalls 261
Penalties 262
Subcontracted reliability assessments 264
Examples 265
Product liability and safety legislation 266
The general situation 266
Strict liability 267
The Consumer Protection Act 1987 268
Health and Safety at Work Act 1974 268
Insurance and product recall 270
Major incident legislation 272
History of major incidents 272
Development of major incident legislation 273
CIMAH safety reports 274
Offshore safety cases 277
Problem areas 278
The COMAH directive (1999) 279
Rail 280
Integrity of safety-related systems 281
Safety-related or safety-critical? 281
Safety-integrity levels (SILs) 282
Programmable electronic systems (PESs) 285
Current guidance 287
Framework for certification 289
A case study: The Datamet Project 291
Introduction 291
The DATAMET concept 291
The contract 294
Detailed design 295
Syndicate study 295
Hints 295
A case study: Gas Detection System 297
Safety-integrity target 297
Random hardware failures 298
ALARP 300
Architectures 300
Life-cycle activities 300
Functional safety capability 300
Glossary 301
Percentage points of the Chi-square distribution 309
Microelectronics failure rates 313
General failure rates 315
Failure mode percentages 322
Human error rates 325
Fatality rates 327
Answers to exercises 329
Bibliography 335
Scoring criteria for BETAPLUS common cause model 338
Example of HAZOP 345
HAZID checklist 349
Markov analysis of redundant systems 352
Index 358