BS 6548-6-1995 Maintainability of equipment - Guide to statistical methods in maintainability evaluation《设备的可维护性 可维护性评定统计方法指南》.pdf

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1、BRITISH STANDARD BS6548-6: 1995 IEC706-6: 1994 Maintainability of equipment Part 6: Guide to statistical methods in maintainability evaluationBS6548-6:1995 This British Standard, having been prepared under the directionof the Management Systems Sector Board, was published under the authority ofthe S

2、tandards Board and comesinto effect on 15May1995 BSI 06-1999 The following BSI references relate to the work on this standard: Committee reference QMS/23 Draft for comment90/97506 DC ISBN 0 580 24038 X Committees responsible for this British Standard The preparation of this British Standard was entr

3、usted to Technical Committee QMS/23, Reliability and maintainability systems upon which thefollowing bodies were represented: AEA Technology Association of Consulting Engineers Association of Project Managers British Gas plc British Railways Board British Telecommunications plc City University Civil

4、 Aviation Authority Consumers Association Cranfield University Design Council Electricity Association Federation of the Electronics Industry GAMBICA (BEAMA Ltd.) Institute of Quality Assurance Institute of Risk Management Institution of Electrical Engineers Institution of Mechanical Engineers Instit

5、ution of Plant Engineers London Underground Ltd. Mercury Communications Limited. Ministry of Defence National Computing Centre Ltd. Railtrack Railway Industry Association Royal Institution of Chartered Surveyors Royal Statistical Society Safety and Reliability Society Society of Environmental Engine

6、ers Society of Motor Manufacturers and Traders Limited University of Bradford University of Technology, Loughborough West Midlands Enterprise Board Amendments issued since publication Amd. No. Date CommentsBS6548-6:1995 BSI 06-1999 i Contents Page Committees responsible Inside front cover National f

7、oreword ii Introduction 1 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Mathematical back-up material 1 Annex A (informative) Maintainability allocation 3 Annex B (informative) Maintainability demonstration test methods 9 Annex C (informative) Kolmogorov-Smirnov distribution testing 15 Figure

8、 A.1 7 Figure A.2 Maintainability allocation to subitem level 8 Figure B.1 Test method 7: sequential test plan 14 Table A.1 Maintainability allocation to subitem level 6 Table B.1 Sampling plans for specified p 0 , p 1 , , (p 0 0,2) 13 Table B.2 Test method 7: acceptance and rejection numbers 14 Tab

9、le C.1 Critical values of d 15 List of references Inside back cover ACMT 50 MACMT -f ACMT 95 MACMT - =BS6548-6:1995 ii BSI 06-1999 National foreword This Part of BS6548 has been prepared by Technical Committee QMS/23. It is identical with IEC706-6:1994 Guide on maintainability of equipment Part6: Se

10、ction9: Statistical methods in maintainability evaluation, published by the International Electrotechnical Commission (IEC). Six Parts of this standard have been published and these may be summarized as follows. Part 1: Guide to specifying and contracting for maintainability. This Part introduces th

11、e concept of maintainability and provides guidance on the definition of maintainability requirements and on the programmes needed to achieve them. Part 2: Guide to maintainability studies during the design phase. This Part provides guidance on studies that should be carried out during the design pha

12、se and on the relationship of these studies to maintainability and maintenance support tasks. The purpose of the studies is to assist design decision making, to predict the quantitative maintainability characteristics of an item and to help in the evaluation of alternative design options. Part 3: Gu

13、ide to maintainability verification and the collection, analysis and presentation of maintainability data. This Part provides guidance on the various aspects of verification necessary to ensure that specified maintainability requirements have been met and outlines suitable procedures and test method

14、s. Guidance is also given on the collection, analysis and presentation of maintainability data. Part 4: Guide to the planning of maintenance and maintenance support. This Part provides guidance on the planning of maintenance and maintenance support during the system acquisition phase to ensure that

15、availability objectives are met in the operational phase. The interrelationships with reliability and maintainability programmes are also described. Part 5: Guide to diagnostic testing. This Part provides guidance on consideration of testability characteristics during the design and development of e

16、quipment. It will assist in determining effective test procedures as an integral part of operation and maintenance. Part 6: Guide to statistical methods in maintainability evaluation. This Part provides guidance on statistical methods for use when allocating maintainability requirements to the vario

17、us parts of a system, and when carrying out maintainability demonstrations and evaluations. Guidance on many studies closely related to maintainability is also contained in the various Parts of BS5760 Reliability of systems, equipment and components. Many terms used in this standard are defined in B

18、S4778 Quality vocabulary Section3.1 Guide to Concepts and related definitions. Cross-references International standard Corresponding British Standard IEC50 (191) BS4778 Quality vocabulary Section3.2:1991 Glossary of international terms (Identical) ISO3534-1:1993 BSISO3534-1 Statistics Vocabulary and

19、 symbols Part1:1993 Probability and general statistical terms (Identical)BS6548-6:1995 BSI 06-1999 iii Reference to sections of IEC706 The various Parts of IEC706 each contain one or more sections. References to these sections are sometimes made in the text. The sections are reproduced in the Parts

20、of BS6548 as follows. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. IEC706 section numb

21、er and title Corresponding Part of BS6548 Section 1 Introduction to maintainability BS6548-1:1984 Section 2 Maintainability requirements in specifications and contracts BS6548-1:1984 Section 3 Maintainability programme BS6548-1:1984 Section 4 Diagnostic testing BS6548-5:1995 Section 5 Maintainabilit

22、y studies during the design phase BS6548-2:1992 Section 6 Maintainability verification BS6548-3:1992 Section 7 Collection, analysis and presentation of data related to maintainability BS6548-3:1992 Section 8 Maintenance and maintenance support planning BS6548-4:1993 Summary of pages This document co

23、mprises a front cover, an inside front cover, pagesi toiv, pages1to16, an inside back cover and a back cover. This standard 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.iv blankBS6548-6:1995 BS

24、I 06-1999 1 Introduction Maintainability engineering is the technical discipline directed towards enhancement of the ease of maintenance of equipment. In the preceding parts of this guide, important methods and techniques are presented which can be used to achieve this objective. Many of them are of

25、 a qualitative nature; some, however, include also quantitative aspects, especially for: allocating maintainability target values to subitems; verifying the fulfilment of quantitative maintainability requirements; evaluating maintainability data. For a complete understanding of these methods and tec

26、hniques, it is necessary to provide some mathematical explanation to enable the user to apply them more generally. 1 Scope This part of IEC706 is being issued as section9 of the guide on maintainability of equipment. It specifies techniques covering some quantitative aspects of maintainability engin

27、eering in various phases of the system life cycle. This part of IEC706 is applicable to the tasks of maintainability allocation, maintainability demonstration and maintainability data evaluation, as described in sections 5, 6 and 7, respectively, of the guide (IEC706-2 andIEC 706-3). In the informat

28、ive Annex A, Annex B and Annex C, mathematical methods and procedures for performing these tasks are presented in corresponding order. The document is intended to serve as an addendum, for specific maintainability topics, to existing statistical textbooks. 2 Normative references The following normat

29、ive documents contain provisions which, through reference in this text, constitute provisions of this part of IEC706. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC706 are encouraged

30、to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC50(191):1990, International Electrotechnical Vocabulary (IEV) Chapter191: Dependability and quality

31、 of service. IEC706-2:1990, Guide on maintainability of equipment Part2: Section 5 Maintainability studies during the design phase. IEC706-3:1987, Guide on maintainability of equipment Part3: Sections 6 and 7 Verification and collection, analysis and presentation of data. ISO3534-1:1993, Statistics

32、Vocabulary and symbols Part1: Probability and general statistical terms. 3 Definitions For the purpose of this part of IEC706, the terms and definitions of IEC50(191), ISO3534-1 and of preceding sections apply. Additional terms, symbols and acronyms which are used in some of the annexes are defined

33、in Annex A. 4 Mathematical back-up material The material under this heading is presented in the order of the related sections of the guide. For each of these sections, the problems to be solved by mathematical means are indicated; the mathematical material itself is then given in an annex. 4.1 Mater

34、ial related to Section 5 Section 5 of the guide on maintainability of equipment deals with maintainability studies in the design phase. One of the tasks considered is the allocation of item maintainability requirements to subitems/lower indenture levels. This is an iterative process starting early i

35、n the item life cycle on the basis of preliminary design information, and later on updated when more detailed data and information becomes available. An example of the early type of maintainability allocation is given in Annex A of section 5; the underlying assumption in this case is that the subite

36、m maintainability requirement is inversely proportional to the subitems complexity.BS6548-6:1995 2 BSI 06-1999 Annex A presents the method recommended for the updating of the early maintainability allocation. This method should be used when additional design data become available, so that the functi

37、onal breakdown of the item can be carried down to lower subitem levels, with failure rate values allocated to all subitems. The method is applicable to all systems where the assumption of a log-normal distribution of the corrective maintenance time is satisfied, and where sufficiently detailed desig

38、n information is available, for example, in or at the end of the definition phase. For application of the method, it needs specification of a maximum allowable time for active corrective maintenance. 4.2 Material related to Section 6 In Appendix A of Section 6 of the guide, statistical test methods

39、are identified, which should be applied to verify the fulfilment of quantitative maintainability requirements. Details of these test methods are described in Annex B. They may be applied to all maintainability demonstrations, when the maintenance events are statistically independent. The test condit

40、ions should be representative of the actual conditions of use. 4.3 Material related to Section 7 In Section 7 of the guide, aspects of the analysis of maintainability related data which could beobtained from relevant sources (e.g.historical sources, development or demonstration tests, production,ass

41、embly, or field operations), and which should be used for maintainability compliance/determination testing, are briefly described. One important part of this analysis is the determination of the data distribution. In Annex C, the most frequently used method for distribution testing, the Kolmogorov-S

42、mirnov test (alsoknown as d-test), is presented. This test is applicable for alltypes of data and for all distribution forms. For other possible methods (chi-square test, graphical procedures), pertinent statistical textbooks should be consulted.BS6548-6:1995 BSI 06-1999 3 Annex A (informative) Main

43、tainability allocation A.1 Definitions and abbreviations All definitions in clause3 also apply to this annex. In addition, the terms, definitions and abbreviations determined in the following subclauses are used: A.1.1 Definitions A.1.1.1 active corrective maintenance time that part of the active ma

44、intenance time during which actions of corrective maintenance are performed on an item IEV191-08-07 A.1.1.2 line replaceable unit functional item which is suited and intended to be removed from the system as part of a single maintenance action on the first (field) line of maintenance A.1.1.3 maximum

45、 active corrective maintenance time by convention, the0,95 fractile of the active corrective maintenance time distribution, i.e.that part of the active corrective maintenance time during which95% of all actions of corrective maintenance on an item can be accomplished A.1.1.4 median active corrective

46、 maintenance time that part of the active corrective maintenance time during which50% of all actions of corrective maintenance on an item can be accomplished A.1.1.5 mean active corrective maintenance time the expectation of the active corrective maintenance time A.1.2 Acronyms A.2 Maintainability a

47、llocation requirements and method A.2.1 Requirements The maintainability allocation method described below should be applied when sufficient design information is available to carry the functional subdivision of the item considered down to lower indenture levels. It is essential to provide the follo

48、wing information: a required or preliminarily predicted value of the items failure rate2; allocated failure rate values 2 ifor all n subitems, such that a specified value of the items mean active corrective maintenance time MACMT (alternatively, the value2MACMT may be specified, i.e.the mean active

49、corrective maintenance time multiplied by the items failure rate2. 2MACMT is thus the mean active corrective maintenance time per operational time unit); a specified value of the maximum active corrective maintenance time ACMT 95 . On this basis, required values ACMT ishould be allocated to each subitem i. ACMT active corrective maintenance time ACMT 95 maximum active corrective maintenance time ACMT 50 median active corrective maintenance time LRU line replace