1、BRITISH STANDARD BS EN 61703:2002 Incorporating Amendment No. 1 to BS IEC 61703:2001 (renumbers the BS IEC as BS EN 61703:2002) and incorporating Amendment No. 1 to BS EN 61703:2002 Mathematical expressions for reliability, availability, maintainability and maintenance support terms ICS 21.020 BS EN
2、 61703:2002 This British Standard, having been prepared under the direction of the Management Systems Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 28 November 2001 BSI 27 August 2002 ISBN 0 580 38729 1 National foreword Thi
3、s British Standard is the official English language version of EN 61703:2002. It is identical with IEC 61703:2001. The UK participation in its preparation was entrusted to Technical Committee DS/1, Dependability and terotechnology, which has the responsibility to: A list of organizations represented
4、 on this committee can be obtained on request to its secretary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publ
5、ications may contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the
6、“Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from leg
7、al obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. S
8、ummary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 52, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comm
9、ents 13690 27 August 2002 Implements European StandardEUROPEAN STANDARD EN 61703 NORME EUROPENNE EUROPISCHE NORM January 2002 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secre
10、tariat: rue de Stassart 35, B - 1050 Brussels 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61703:2002 E ICS 03.120.30;21.020 English version Mathematical expressions for reliability, availability, maintainability and maint
11、enance support terms (IEC 61703:2001) Expressions mathmatiques pour les termes de fiabilit, de disponibilit, de maintenabilit et de logistique de maintenance (CEI 61703:2001) Mathematische Ausdrcke fr Begriffe der Funktionsfhigkeit, Instandhaltbarkeit und Verfgbarkeit (IEC 61703:2001) This European
12、Standard was approved by CENELEC on 2001-12-04. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references con
13、cerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member int
14、o its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherland
15、s, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.CONTENTS 1 Scope.5 2 Normative references .5 3 Definitions 6 4 Glossary of symbols and abbreviations.7 4.1 Non-repaired items7 4.2 Repaired items with zero time to restoration8 4.3 Repaired items with non-zero time to restoration.9 5
16、 Assumptions.12 5.1 General remarks12 5.2 Assumptions for non-repaired items 12 5.3 Assumptions for repaired items .13 6 Mathematical expressions 16 6.1 Non-repaired items16 6.1.1 Presentation16 6.1.2 Reliability 191-12-0116 6.1.3 Instantaneous failure rate 191-12-02 .17 6.1.4 Mean failure rate 191-
17、12-03.18 6.1.5 Mean time to failure 191-12-07 19 6.2 Repaired items with zero time to restoration20 6.2.1 Presentation20 6.2.2 Reliability 191-12-0120 6.2.3 Instantaneous failure intensity 191-12-04 21 6.2.4 Mean failure intensity 191-12-0522 6.2.5 Mean time to failure 191-12-07 23 6.2.6 Mean time b
18、etween failures 191-12-08 23 6.2.7 Mean operating time between failures 191-12-09.24 6.2.8 Mean up time 191-11-1124 6.3 Repaired items with non-zero time to restoration.24 6.3.1 Presentation24 6.3.2 Reliability 191-12-0125 6.3.3 Instantaneous failure intensity 191-12-04 26 6.3.4 Mean failure intensi
19、ty 191-12-0529 6.3.5 Mean time to failure 191-12-07 30 6.3.6 Mean time between failures 191-12-08 31 6.3.7 Mean operating time between failures 191-12-09.31 6.3.8 Instantaneous availability 191-11-0132 6.3.9 Instantaneous unavailability 191-11-0233 Page2 EN61703:20026.3.10 Mean availability 191-11-0
20、3.34 6.3.11 Mean unavailability 191-11-04.35 6.3.12 Asymptotic availability 191-11-05 36 6.3.13 Asymptotic unavailability 191-11-07.37 6.3.14 Mean up time 191-11-1137 6.3.15 Mean down time 191-11-12 .38 6.3.16 Maintainability 191-13-01.39 6.3.17 Mean repair rate 191-13-03 .40 6.3.18 Mean repair time
21、 191-13-05.41 6.3.19 Mean active corrective maintenance time 191-13-0742 6.3.20 Mean time to restoration 191-13-08 .43 6.3.21 Mean administrative delay 191-13-11 44 6.3.22 Mean logistic delay 191-13-13 .44 Annex A (informative) Performance aspects and descriptors46 Annex B (informative) Summary of m
22、easures related to time to failure.47 Annex C (informative) Comparison of some dependability measures for continuously operating items.49 Annex D (informative) Software dependability aspects.50 Annex ZA (normative) Normative references to international publications with their corresponding European
23、publications .51 Bibliography52 Figure 1 Sample realization of a non-repaired item 13 Figure 2 Sample realization of a repaired item with zero time to restoration .14 Figure 3 Sample realization of a repaired item with non-zero time to restoration 15 Figure 4 Comparison of an up time for a COI and a
24、n IOI16 Figure A.1 Performance aspects and descriptors .46 Table B.1 Relations among functional measures of time to failure of continuously operating items.47 Table B.2 Summary of measures for some probability distributions of time to failure of continuously operating items.48 Table C.1 Comparison o
25、f some dependability measures of continuously operating items with constant failure rate and restoration rate R .49 Page3 EN61703:2002Foreword 1A tnemdnema ot The text of document 56/747/FDIS, future edition 1 of IEC 61703, prepared by IEC TC 56, Dependability, was submitted to the IEC-CENELEC paral
26、lel vote and was approved by CENELEC as EN 61703 on 2001-12-04. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2002-09-01 latest date by which the national standards conflict
27、ing with the EN have to be withdrawn (dow) 2004-12-01 Annexes designated “normative“ are part of the body of the standard. Annexes designated “informative“ are given for information only. In this standard, annex ZA is normative and annexes A, B, C and D are informative. Annex ZA has been added by CE
28、NELEC. _ Endorsement notice The text of the International Standard IEC 61703:2001 was approved by CENELEC as a European Standard without any modification. _ Foreword Txet eht fo codmu7/65 tneF/74DISf ,rutue deitino 1 fo CEI 167,30 rpperade by IEC TC ,65 epeDadnibtily, saw smbut dettiht oI eE-CNECELE
29、C rapaelll tova edn saw rppavob dey CENELEsa C 16 NE07no 3 02-10-210.4 Teh followisetad gn rewe fix:de lsetatad te by whcih tNE eh hsa mi eb otmelpdetne an taoitnal level by uplbcioitafo n na ditnecila itananos ltaradnd ro by erodnsmetne ()pod -2002-9010 lsetat tadb ey whcit hn ehitanos lataradnsd c
30、fnocilitgn ah NE eht htiwev to bw eirdhtawn (odw) -4002-2110 nnAxese sediangdet n“romevitara “e rapfo t htob edy fo s ehttaradn.d nnAxese sediangdet “ifnrom“evita rag eivf nero ifnromnoita lnoy. ht nIsi stdnaraa ,dnnxe ZA si ronmevita dna naxense A, B, na CD d rai efnromevita. nnAxe ZA hsa ebne ddab
31、 dey CENELE.C _ odnEnemesrt noteci Txet eht fo nI ehtretantoianS ltnaradI dEC 61072:3100 saw arppovde by CEENCEL sa a ruEoaepn natSradd tiwtuoh nay mfidoicoita.n _ Page4 EN61703:200261703 IEC:2001 6 MATHEMATICAL EXPRESSIONS FOR RELIABILITY, AVAILABILITY, MAINTAINABILITY AND MAINTENANCE SUPPORT TERMS
32、 1 Scope This International Standard provides mathematical expressions for reliability, availability, maintainability and maintenance support measures defined in IEC 60050-191. The following classes of items are considered separately in this standard: non-repaired items; repaired items with zero tim
33、e to restoration; repaired items with non-zero time to restoration. In order to keep the mathematical formulae as simple as possible, the following basic mathematical models are used to quantify dependability measures: random variable (time to failure) for non-repaired items; simple (ordinary) renew
34、al process for repaired items with zero time to restoration; simple (ordinary) alternating renewal process for repaired items with non-zero time to restoration. To facilitate location of the full definition, the IEC 60050-191 reference for each term is shown (in parenthesis) immediately following ea
35、ch term, for example: mean time to restoration 191-13-08 The application of each dependability measure is illustrated by means of a simple example. NOTE This standard is mainly applicable to hardware dependability, but many terms and their definitions may be applied to items containing software. Som
36、e of the software dependability aspects are explained in annex D. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of,
37、any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative docum
38、ent referred to applies. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 60050-191:1990, International Electrotechnical Vocabulary (IEV) Chapter 191: Dependability and quality of service ISO 3534-1:1993, Statistics Vocabulary and symbols Part 1: Probability
39、and general statistical terms BSIEC61703:2001 1002rebmevoN82ISB 6 Page5 EN61703:200261703 IEC:2001 7 3 Definitions For the purpose of this International Standard, the terms and definitions of IEC 60050-191 and ISO 3534-1 apply. In addition, the following terms and definitions are used. 3.1 instantan
40、eous restoration intensity v(t) limit, if it exists, of the quotient of the mean number of restorations of a repaired item in the time interval (t, t + t) and the duration of this interval, t, when the duration of the time interval tends to zero NOTE The instantaneous restoration intensity is expres
41、sed by the formula as t t N t t N E t t v ) ( ) ( 0 lim ) ( R R where N R (t) is the number of restorations in the time interval (0, t); E denotes the expectation. 3.2 asymptotic failure intensity z( ) for modelling purposes, limit, if it exists, of the instantaneous failure intensity z(t), when tim
42、e t tends to infinity 3.3 up-time distribution function F U (t) function giving, for every value of t, the probability that an up time will be less than, or equal to, t 3.4 complement to the up-time distribution function R U (t) function giving, for every value of t, the probability that an up time
43、will be greater than t For convenience, this function is referred to as the up-time survival function in this standard. NOTE 1 R U(t) = 1 F U(t). NOTE 2 If the up time is exponentially distributed, then R U(t) = exp( t/MUT) where MUT is the mean up time. In this case, the reciprocal of MUT is denote
44、d by U: U = 1/MUT BSIEC61703:2001 1002rebmevoN82ISB 7 Page6 EN61703:200261703 IEC:2001 8 4 Glossary of symbols and abbreviations NOTE The symbols given below are widely used and recommended but are not mandatory. 4.1 Non-repaired items COI Continuously operating item IOI Intermittently operating ite
45、m MTTF Mean time to failure MTTF Point estimate of the mean time to failure R(t) Reliability function, i.e. the probability of survival until time t: R(t) = R(t 1 , t 2 ) for t 1= 0 and t 2= t () Rt Point estimate of the reliability function at time t R(t 1 , t 2 ) Reliability for the time interval
46、(t 1 , t 2 ) ) | , ( t x t t R Conditional reliability for the time interval (t, t + x), assuming that the item survived to time t TTF i Observed time to failure of item i f(t) Probability density function of the (operating) time to failure ) ( t f Point estimate of the probability density function
47、of the (operating) time to failure at time t n Number of (non-repaired) items in the population that are operational at the instant of time t = 0 n S (t) Number of (non-repaired) items that are still operational at the instant of time t (n S (0) = n) n S (t) n S (t + t) Number of items that fail in
48、the time interval (t, t + t) Constant failure rate, i.e. the reciprocal of the mean time to failure (MTTF) when the times to failure are exponentially distributed Point estimate of the constant failure rate (t) Instantaneous failure rate ) ( t Point estimate of the instantaneous failure rate at time t ) , ( 2 1 t t Mean failure rate for the time interval (t 1 , t 2 ) BSIEC61703:2001 1002rebmevoN82ISB 8 Page7 EN61703:200261703 IEC:2001 9 4.2 Repaired items with zero time to restoration COI Continuously operating item IOI
