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1、BRITISH STANDARD BS 5760-5: 1991 Reliability of systems, equipment and components Part 5: Guide to failure modes, effects and criticality analysis (FMEA and FMECA) Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5760-5:1991 This British S
2、tandard, having been prepared under the direction of the Quality, Management and Statistics Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 20 December 1991 BSI 01-1999 The following BSI references relate to the work on this standard: Com
3、mittee reference QMS/23 Draft for comment 86/66800 DC ISBN 0 580 19660 7 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
4、following bodies were represented: Association for Consumer Research (ACRE) Association of Consulting Engineers British Gas plc British Railways Board British Telecommunications plc Cable and Wireless plc Cranfield Information Technology Institute Cranfield Institute of Technology EEA (the Associati
5、on of Electronics, Telecommunications and Business Equipment Industries) Electricity Supply Industry in United Kingdom Electronic Components Industry Federation Engineering Equipment and Materials Users Association GAMBICA (BEAMA Ltd.) Institute of Quality Assurance Institution of Electrical Enginee
6、rs Institution of Plant Engineers Ministry of Defence National Computing Centre Ltd. Railway Industry Association of Great Britain Society of British Aerospace Companies Limited United Kingdom Atomic Energy Authority Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun
7、 sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5760-5:1991 BSI 01-1999i Contents Page Committees responsibleInside front cover Forewordiii 0 Introduction1 Section 1. General 1.1Scope1 1.2Definitions1 Section 2. Failure modes and effects analysis 2.1Introduction2
8、2.2Procedure2 2.3Application6 2.4Supplementary information9 Section 3. Criticality analysis 3.1Introduction16 3.2Procedure17 3.3Supplementary information18 Appendix A Summary of procedure for FMEA and FMECA22 Appendix B Examples of analyses22 B.1Ranked contribution approach to criticality analysis22
9、 B.2FMECA Example 1. Fire protection system of an electric locomotive22 B.3FMECA Example 2. Sub-subsystem of a motor-generator set32 B.4Example of a process FMEA32 Appendix C Bibliography38 Figure 1 Example of the format of an FMEA worksheet 4 Figure 2 Relationship between failure modes and failure
10、effects in a system hierarchy5 Figure 3 Example of a criticality grid16 Figure 4 Example of a criticality matrix showing criticality bands21 Figure B.1.1 Example of an FMEA worksheet23 Figure B.1.2 Example of a frequency analysis24 Figure B.1.3 Bar chart of subsystem contributions to system failure2
11、6 Figure B.1.4 Analysis of contributions to system failure27 Figure B.1.5 Bar chart showing ranked contributions 29 Figure B.2 FMECA of the fire protection system of an electric locomotive30 Figure B.3.1 Block diagram of sybsystems of a motor-generator set33 Figure B.3.2 Block diagram of enclosure h
12、eating, ventilation and cooling systems34 Figure B.3.3 FMEA of subsystem including failure rate assessment35 Figure B.4 Part of a process or manufacturing FMECA for machined aluminium castings 36 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) B
13、SI BS 5760-5:1991 ii BSI 01-1999 Page Table 1 Example of a set of general failure modes10 Table 2 Example of an expanded list of failure modes10 Table 3 Possible failure causes11 Table 4 Example of a set of failure effects (for a motor vehicle starter)12 Table 5 Example of a failure effects summary
14、12 Table 6 Examples of failure effect severity scales 19 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5760-5:1991 BSI 01-1999iii Foreword This Part of BS 5760 has been prepared under the dire
15、ction of the Quality, Management and Statistics Standards Policy Committee. It is based on IEC 812 published by the International Electrotechnical Commission (IEC). In the preparation of this Part of BS 5760, the committee has modified and extended the text of IEC 812 to clarify the nature of failur
16、e modes and effects analysis and criticality analysis and to present, and place particular emphasis upon, procedures for carrying out these analyses. Seven Parts of this standard have now been published and these may be summarized as follows. Part 0: Introductory guide to reliability. This Part prov
17、ides guidance to directors of companies who need to know why reliability is important to them, to engineers not trained in quality and reliability to show how reliability should influence their technical decision making, and to middle management not specialized in engineering, to explain how measure
18、s to achieve reliability should be integrated with other aspects of project management to give optimum results. Part 1: Guide to reliability and maintainability programme management. This Part discusses the essential features of a comprehensive reliability and maintainability programme for the plann
19、ing, organization, direction and control of resources to produce systems, equipment and components which will be reliable and maintainable. It includes consideration of the specification and assessment of reliability and maintainability and of arrangements for the collection of reliability data. Par
20、t 2: Guide to the assessment of reliability. This Part recommends general procedures for the assessment of reliability of hardware systems and contains guidance for the reliability practitioner on the quantitative and statistical aspects of reliability, such as reliability modelling, the provision o
21、f data, and the concepts of redundancy and simulation. Part 3: Guide to reliability practices: examples. This Part contains authentic practical examples illustrating the principles established in Parts 1 and 2 of BS 5760. Part 4: Guide to specification clauses relating to the achievement and develop
22、ment of reliability in new and existing items. This Part provides more detailed guidance on the specification of reliability. Part 5: Guide to failure modes, effects and criticality analysis (FMEA and FMECA). This Part describes failure modes and effects analysis (FMEA) and failure modes, effects an
23、d criticality analysis (FMECA), and gives guidance on the application of these techniques. Part 6: Guide to programmes for reliability growth. This Part describes procedures to expose and remove weaknesses in hardware and software items in order to achieve acceptable reliability in a product. It exp
24、lains basic concepts, management and test procedures and describes techniques for analysis and correction of failures. Further Parts are envisaged in order to provide guidance on other techniques of reliability management. At present three further Parts are in the process of being drafted, and these
25、 are as follows. Part 7: Guide to fault tree analysis. Part 81): Guide to the assessment of reliability of systems containing software. This Part will provide guidance on the assessment of reliability of systems containing software. Part 9: Guide to reliability block diagrams. 1) Currently published
26、 as a Draft for Development, DD 198:1991. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5760-5:1991 iv BSI 01-1999 NOTE 1This British Standard makes reference to BS 4778, the Quality Vocabulary, and in particular to BS 4778-3, a glossar
27、y which contains definitions relating to reliability concepts applicable to the guide and it is essential that these definitions and concepts should be fully understood if this guide is to be interpreted correctly. For this reason it is recommended that BS 4778 should be read in conjunction with BS
28、5760. NOTE 2 Chapter 191 of IEC 50, the International Electrotechnical Vocabulary, now deprecates the use of the terms “failure modes and effects analysis” and “failure modes, effects and criticality analysis” and favours the use of “fault modes and effects analysis” and “fault modes, effects and cr
29、iticality analysis” respectively. However, the older terms have been retained in this standard in order to align it with the current version of IEC 812 which has been adopted by CEN. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards
30、 are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 38, an inside back cover and a back cover. This stand
31、ard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5760-5:1991 BSI 01-19991 Section
32、1. General 0 Introduction Failure modes and effects analysis (FMEA) and failure modes, effects and criticality analysis (FMECA) are methods of reliability analysis intended to identify failures which have consequences affecting the functioning of a system within the limits of a given application, th
33、us enabling priorities for action to be set. Generally, failures or failure modes of any component will affect system performance adversely. In the study of system reliability, safety and availability, both qualitative and quantitative analyses are needed and these complement one another. Quantitati
34、ve analysis methods allow the calculation or prediction of performance measures of the system while fulfulling a specific task or in long-term operation under specific conditions. Typical measures denote reliability, safety, availability, failure rates, and mean time to failure (MTTF). FMEA begins a
35、t the item or subassembly level for which the basic failure criteria (primary failure modes) are available. Starting from the basic failure characteristics of the elements and the functional structure of the system, the FMEA indicates the relationship between element failures and failures, malfuncti
36、ons, operational constraints and degradation of performance or integrity of the system.To evaluate secondary and higher-order system and subsystem failures, the sequences of events in time may also need to be considered. In a narrow sense, FMEA is limited to a qualitative analysis of failure modes o
37、f hardware, and does not include human errors and software errors, despite the fact that current systems are usually subject to both. In a wider sense, these factors should be included. Criticality is a measure which combines the concepts of severity of consequences of failure and rate of occurrence
38、 or probability of occurrence of failure in a defined period. Severity is usually measured by placing a failure mode in one of a number of categories according to the consequences. Probability or rate of occurrence may also need to be dealt with in this way if numerical data are not available. Criti
39、cality is then measured by combining these indices in a defined manner. 1.1 Scope This Part of BS 5760 describes failure modes and effects analysis (FMEA) and failure modes, effects and criticality analysis (FMECA), and gives guidance as to how they may be applied to achieve various objectives conne
40、cted with the development of reliable designs, as follows: a) by describing the procedural steps necessary to perform an analysis (these are summarized in Appendix A); b) by identifying appropriate terms, assumptions, failure modes and criticality measures; c) by determining basic principles; d) by
41、providing examples of the necessary worksheets; e) by providing recommendations for applications of FMEA and FMECA. All the general qualitative considerations presented for FMEA also apply to FMECA. However, FMEA and FMECA are different in the sense that FMEA can be performed on its own, whereas cri
42、ticality analysis has to be carried out in conjunction with an FMEA. FMECA also differs from FMEA in that the former is quantitative. For these reasons the two methods of analysis are dealt with separately in this standard. Examples of FMECA and FMEA are given in Appendix B. While this Part of BS 57
43、60 is concerned with the use of FMEA and FMECA for the pursuit of reliable designs, both FMEA and FMECA can also be used in the development of reliable processes. An example of this application is also given in Appendix B. (See example in B.4.) NOTE 1The titles of the publications referred to in thi
44、s standard are listed on the inside back cover. NOTE 2Additional relevant publications are listed in Appendix C for information. 1.2 Definitions For the purposes of this British Standard the definitions given in BS 4778-1, BS 4778-2 and BS 4778-3 apply, together with the following. 1.2.1 failure eff
45、ect the consequence of a failure mode in terms of the operation, function or status of a system 1.2.2 failure mode the effect by which a failure is observed 1.2.3 criticality a combination of the severity of an effect and the probability (or expected frequency) of its occurrence Licensed Copy: sheff
46、ieldun sheffieldun, na, Fri Dec 01 13:41:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5760-5:1991 2 BSI 01-1999 Section 2. Failure modes and effects analysis 2.1 Introduction 2.1.1 General FMEA and FMECA (see section 3) are important techniques for a reliability assurance programme. They can be
47、applied to a wide range of problems which may occur in technical systems, and can be carried out in varying degrees of depth, or modified, to suit a particular purpose. The analysis is carried out in a limited way during the conception, planning, and definition phases and more fully in the design an
48、d development phase. It is however important to remember that the FMEA is only part of a reliability and maintainability programme which requires many different tasks and activities. FMEA is an inductive method of performing a qualitative system reliability or safety analysis from a low to a high le
49、vel. A thorough understanding of the system under analysis is essential prior to undertaking FMEA. Functional diagrams and other system drawings are normally necessary for this understanding. Reliability block diagrams, fault trees and/or state diagrams are then usually derived from these in order to carry out the analysis. In many instances the block diagram descriptions and block diagram failure descriptions are included in the FMEA format. Separate diagrams will be needed for the following: a) the way in which different criteria for s