1、BRITISH STANDARD BS 5760-2: 1994 Reliability of systems, equipment and components Part 2: Guide to the assessment of reliability UDC 006.015.7:62-192:658.562.012.7BS 5760-2:1994 This British Standard, having been prepared under the directionof the Quality Management and Statistics Standards Policy C
2、ommittee, waspublished under the authorityof the Standards Boardand comes into effect on 15October1994 BSI 04-1999 First published March 1981 Second edition October 1994 The following BSI references relate to the work on this standard: Committee reference QMS/23 Draft for comment 92/89922 DC ISBN 0
3、580 22808 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Quality Management and Statistics Standards Policy Committee (QMS/-) to Technical Committee QMS/23, upon which the following bodies were represented: AEA Technology Association
4、of Consulting Engineers Association of Project Managers British Gas plc British Railways Board British Telecommunications plc City University Civil Aviation Authority Consumers Association Cranfield Institute of Technology Department of Trade and Industry (Standards Policy Unit) Design Council Elect
5、ricity Association Electronic Components Industry Federation FEI (The Federation of the Electronics Industry) Federation of Small Businesses GAMBICA (BEAMA Ltd.) Institute of Quality Assurance Institute of Risk Management Institution of Electrical Engineers Institution of Mechanical Engineers Instit
6、ution of Plant Engineers Mercury Communications Limited Ministry of Defence National Computing Centre Ltd. Railway Industry Association of Great Britain Royal Institution of Chartered Surveyors Safety and Reliability Society Society of British Aerospace Companies Limited Society of Environmental Eng
7、ineers Society of Motor Manufacturers and Traders Limited University of Technology, Loughborough Amendments issued since publication Amd. No. Date CommentsBS 5760-2:1994 BSI 04-1999 i Contents Page Committees responsible Inside front cover Foreword vi Introduction 1 Section 1. General 1.1 Scope 1 1.
8、2 References 1 1.3 Definitions 1 1.4 Symbols 2 Section 2. Purposes and problems 2.1 Purposes 3 2.2 Costs versus benefits 3 2.3 Using and presenting the results 3 2.4 Basic concepts 3 2.5 Assessment problems 4 2.6 Failure classification 4 2.7 Accuracy of assessment and prediction 5 Section 3. Assessm
9、ent throughout the product life cycle 3.1 General 6 3.2 Definition phase 6 3.3 Design and development phase 8 3.4 Production phase 9 3.5 Installation and commissioning 9 3.6 Function and maintenance 9 Section 4. Fundamentals of reliability assessment 4.1 General 10 4.2 Function 10 4.3 Conditions of
10、use 10 4.4 Time interval 10 4.5 Probability 10 4.6 Reliability and safety 11 4.7 Principles of reliability modelling 11 4.8 Redundancy 11 4.9 Computer tools for reliability assessment 12 Section 5. Assessment techniques 5.1 Outlines of techniques 13 5.2 Assumptions 13 Section 6. Reliability block di
11、agram (RBD) technique 6.1 Application 15 6.2 Benefits 15 6.3 Limitations 15 6.4 Elementary models 15 6.5 More complex models 15 6.6 Extension to calculations of system availability 16 6.7 Typical RBD configurations and related formulae 16 6.8 Example of a block diagram analysis 21BS 5760-2:1994 ii B
12、SI 04-1999 Page Section 7. Reliability prediction 7.1 Application 23 7.2 Methods 23 7.3 System models 23 7.4 Similar equipment method 23 7.5 Extrapolation of reliability data from tests and trials 24 7.6 Reliability modelling 24 7.7 Generic parts methods 24 Section 8. Fault modes and effects analysi
13、s (FMEA) and fault modes, effects and criticality analysis (FMECA) 8.1 Application 26 8.2 Benefits 26 8.3 Limitations 26 8.4 Qualitative and quantitative analyses 26 8.5 Criticality matrices and histograms 27 8.6 Procedure 27 8.7 Results 28 8.8 Use of the analysis 28 8.9 Process FMEA 28 Section 9. F
14、ault tree analysis (FTA) 9.1 Application 29 9.2 Benefits 29 9.3 Limitations 29 9.4 Analysis 29 9.5 Minimal cut sets 29 9.6 Relationship with FMEA and FMECA 30 9.7 Results 30 Section 10. Monte-Carlo and other simulation techniques 10.1 Application 32 10.2 Benefits 33 10.3 Limitations 33 10.4 Outline
15、of procedure 33 10.5 Results 33 10.6 The Latin hypercube method 34 Section 11. Markov techniques 11.1 Application 35 11.2 Benefits 35 11.3 Limitations 35 11.4 System operation and environmental conditions 35 11.5 Representation of system failure definitions 36 11.6 Development of state diagrams 36 1
16、1.7 Evaluating the model 36 11.8 Example of the application of the Markov technique 38 Section 12. Reliability growth monitoring and testing 12.1 Application 40 12.2 Benefits 40 12.3 Limitations 40 12.4 Reliability growth monitoring techniques 41BS 5760-2:1994 BSI 04-1999 iii Page Section 13. Develo
17、pment reliability demonstration testing 13.1 Application 43 13.2 Benefits 43 13.3 Limitations 43 13.4 Interpretation of results 43 Section 14. Environmental stress screening (ESS), including burn-in, during production 14.1 Application 45 14.2 Benefits 45 14.3 Limitations 45 14.4 Inspection and testi
18、ng 45 14.5 Environmental stress screening (ESS) 45 Section 15. Production reliability assurance testing (PRAT) 15.1 Application 47 15.2 Benefits 47 15.3 Limitations 47 15.4 Uncertainty of results 47 Section 16. In-service reliability demonstration 16.1 Application 48 16.2 Benefits 48 16.3 Limitation
19、s 48 Section 17. Life data analysis 17.1 Application 49 17.2 Data requirements 49 17.3 Quality of data 49 17.4 Quantity of data 50 17.5 Graphical analysis using Weibull 50 17.6 Example of two-parameter Weibull plot 50 17.7 Interpretation of Weibull analysis 51 17.8 Three-parameter Weibull distributi
20、ons 53 17.9 Plotting censored data 55 17.10 Graphical analysis using accumulated failures 55 Section 18. Sneak analysis (SA) 18.1 Application 58 18.2 Benefits 58 18.3 Limitations 58 Section 19. Assessment of software reliability 19.1 Application 59 19.2 Purposes 59 19.3 Benefits 59 19.4 Limitations
21、59 19.5 Concepts 60 19.6 Methods 62 Section 20. Human reliability assessment (HRA) 20.1 Application 65 20.2 The HRA process 65 20.3 Development of HRA 67BS 5760-2:1994 iv BSI 04-1999 Page Section 21. Data feedback and analysis 21.1 General 68 21.2 Relevance and applicability of data 68 21.3 Human in
22、fluences in data collection 68 21.4 Use of computerized databases 68 21.5 Data analysis 68 Section 22. Assessment of availability 22.1 Concepts 70 22.2 Mathematical representation 71 22.3 Forms of availability 71 22.4 Modelling principles 72 22.5 Operational and maintenance strategy 72 22.6 Availabi
23、lity assessment 72 Section 23. Reliability assessment of services 23.1 General 76 23.2 Reliability of services 76 23.3 Specification of services 76 23.4 Application of reliability modelling to the postal service 76 Section 24. Reliability assessment of one-shot devices 24.1 General 78 24.2 Failure o
24、f one-shot devices 78 Section 25. Common cause failure modelling and assessment 25.1 The importance of common cause failures 79 25.2 Coupling mechanisms 79 25.3 Assessment of common cause failures 79 Annex A (informative) Variation of failure rate with time: the bath-tub curve 80 Annex B (informativ
25、e) Failure distributions and goodness-of-fit 82 Annex C (informative) Simplified solutions for Markov diagrams and RBDs 97 Annex D (informative) Confidence intervals 102 Figure 1 Block diagrams of simple systems 17 Figure 2 A series/parallel arrangement 17 Figure 3 Another type of series/parallel ar
26、rangement 18 Figure 4 A series/parallel arrangement with a common block (D) 18 Figure 5 Another type of series/parallel arrangement with a common block (D) 18 Figure 6 A two-out-of-three system (at least two needed for system success) 18 Figure 7 A two-out-of-four system 18 Figure 8 A cold standby a
27、rrangement 19 Figure 9 Complex form of RBD 20 Figure 10 Another type of complex RBD 20 Figure 11 Alternative representation of the RBD shown in Figure 10 20 Figure 12 A two-out-of-five system 20 Figure 13 Examples of RBDs corresponding to a hi-fi system 22 Figure 14 Evaluation of system reliability
28、following RBD analysis 22 Figure 15 Example of simplified FTA of a calculator display 31 Figure 16 Two-unit active redundant system36 Figure 17 State diagram for non-identical units 37BS 5760-2:1994 BSI 04-1999 v Page Figure 18 Markov diagram modelling a one-out-of-three system 39 Figure 19 Example
29、of a two-parameter Weibull plot 52 Figure 20 Probability density function for a two-parameter distribution 54 Figure 21 Probability density function for a three-parameter distribution 54 Figure 22 Availability concept 73 Figure 23 Fault tree: system S unavailable 75 Figure 24 Example of RBD applied
30、to a postal service 77 Figure 25 RBD of a combined post and telephone service 77 Figure A.1 Bath-tub curve 81 Figure B.1 Histogram showing number of items failing within defined time intervals 83 Figure B.2 Probability density function 83 Figure B.3 Cumulative distribution function 83 Figure B.4 Nor
31、mal (Gaussian) distribution 85 Figure B.5 Exponential distribution 86 Figure B.6 Lognormal distributions 87 Figure B.7 Weibull distributions 89 Figure B.8 Gamma distribution 90 Figure B.9 Binomial distribution 91 Figure B.10 Poisson distribution 93 Figure B.11 Example of 2test: failure histogram 96
32、Figure C.1 Two-unit active redundant system 98 Figure C.2 Markov state diagram corresponding to Figure C.1 99 Figure C.3 RBD of a system with mixed redundancy 99 Figure C.4 RBD of system of three non-identical units, two-out-of-three needed 100 Figure C.5 Alternative representation of the RBD shown
33、in Figure C.4 101 Figure C.6 RBD of a more complex system with mixed redundancy 101 Figure D.1 One-sided 95% confidence interval 103 Figure D.2 Two-sided 95% confidence interval 103 Table 1 Application of some typical assessment techniques to product life cycle phases 7 Table 2 Basic events, undevel
34、oped events and probabilities during expected calculator lifetime of 10 years 30 Table 3 Minimal cut set probability during expected calculator lifetime of 10 years 30 Table 4 Results from simulations of a system of two components 32 Table 5 Approximate expressions for system failure rates (repairab
35、le systems) 37 Table 6 Example of a Weibull plot: arrangement of the raw data 51 Table 7 Weibull plot of multiply censored data 57 Table 8 Generic human error probabilities 66 Table B.1 Example of 2test: steering mechanism failures 94 Table B.2 Example of 2test: observed and expected values 94 Table
36、 B.3 Example of KS test: failures of valves 95 Table B.4 Example of KS test: observed and expected values 95 Table C.1 Contribution of failure combinations to total system failure rate 100 Table D.1 Relationship between confidence level and k value 102 List of references 104BS 5760-2:1994 vi BSI 04-
37、1999 Foreword This Part of BS 5760 has been prepared under the direction of the Quality, Management and Statistics Standards Policy Committee. It supersedes BS 5760-2:1981, which is withdrawn. This revision of BS 5760-2 has a wider scope than BS 5760-2:1981. The text has been restructured with the o
38、bject of providing more guidance to the practitioner on the extensive range of techniques available for reliability assessment. Some of the important pitfalls and limitations that may be encountered are identified. Many new topics are addressed but some of the mathematical treatment of the1981 editi
39、on has been retained in the annexes. References are given to standards that provide more detailed guidance on individual assessment techniques. A standardized systematic approach is essential to ensure that statements are consistent and unambiguous in all communications concerning reliability progra
40、mmes. As well as providing a basis for the preparation of reliability programmes this British Standard can be used in preparing documents concerned with the specification of reliability or the reporting of reliability data or tests. It is vital that reliability is recognized and treated as an import
41、ant characteristic of a system (equipment or component) from design conception to the end of its working life, and that the reliability experience of one generation of products, engineers or technology is used by the next. This means that each factor that affects reliability at any stage in the life
42、 of an item has to be identified and considered in its relationship to the other factors. This procedure can be formalized into a reliability programme. It may be necessary to divide such a programme into two parts, one of which may be the concern of the designer and manufacturer, and the other the
43、concern of the user. It is most important that consideration be given to the reliability of items or parts that are used by one manufacturer but produced by another, i.e. subcontractor evaluation and vendor appraisal (see BS EN ISO 9000). BS 5760 provides comprehensive guidance on many aspects of re
44、liability management. Thirteen Parts of this standard have been published and these may be summarized as follows: Part 0: Introductory guide to reliability. This Part provides guidance for senior management and non-specialists on the importance of reliability and explains how measures to achieve rel
45、iability should be integrated with other aspects of project management. Part 1: Guide to reliability and maintainability programme management. This Part discusses the essential features of a comprehensive reliability and maintainability programme to produce reliable and maintainable products. Part 2
46、: Guide to the assessment of reliability. This Part explains the purpose and problems of assessing reliability. A range of available assessment techniques is reviewed and the principal advantages and limitations are outlined. Sections are included on the assessment of software reliability, human rel
47、iability and one-shot devices. The extension of these techniques to the assessment of availability and to the assessment of reliability of services is considered. The use of a range of statistical distributions to analyse reliability data is described. Part 3: Guide to reliability practices: example
48、s. This Part contains authentic practical examples illustrating the principles established in BS5760-1 and BS5760-2. Part 4: Guide to specification clauses relating to the achievement and development of reliability in new and existing items. This Part provides detailed guidance on the specification
49、of reliability. Part 5: Guide to failure modes, effects, and criticality analysis (FMEA and FMECA). This Part gives guidance on the application of these techniques.BS 5760-2:1994 BSI 04-1999 vii Part 6: Guide to programmes for reliability growth. This Part describes procedures for exposing and removing weaknesses in hardware and software items in order to achieve acceptable reliability in a product. It explains basic concepts, management
