1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58diagram and boolean methods The European Standard EN 61078:2006 has the status of a British Standar
2、dICS 03.120.01; 03.120.99Analysis techniques for dependability Reliability block BRITISH STANDARDBS EN 61078:2006BS EN 61078:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2006 BSI 2006ISBN 0 580 48700 8request to its secretary.C
3、ross-referencesThe 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 “Search” facility of the BSI Electronic Catalogue or o
4、f 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 legal obligations.Summary of pagesThis document comprises
5、a front cover, an inside front cover, the EN title page, pages 2 to 37 and a back cover.The BSI copyright notice displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd. No. Date CommentsA list of organizations represented on this committee can b
6、e obtained on present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK.National forewordThis British Standard is the
7、official English language version of EN 61078:2006. It is identical with IEC 61078:2006. It supersedes BS EN 61078:1994 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee DS/1, Dependability and terotechnology, which has the responsibility to: aid enquire
8、rs to understand the text;EUROPEAN STANDARD EN 61078 NORME EUROPENNE EUROPISCHE NORM May 2006 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B -
9、1050 Brussels 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61078:2006 E ICS 03.120.01; 03.120.99 Supersedes EN 61078:1993English version Analysis techniques for dependability - Reliability block diagram and boolean methods
10、 (IEC 61078:2006) Techniques danalyse pour la sret de fonctionnement - Bloc-diagramme de fiabilit et mthodes boolennes (CEI 61078:2006) Techniken fr die Analyse der Zuverlssigkeit - Verfahren mit dem Zuverlssigkeitsblockdiagramm und Boolesche Verfahren (IEC 61078:2006) This European Standard was app
11、roved by CENELEC on 2006-03-01. 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 concerning such nat
12、ional 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 into its own langua
13、ge and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuan
14、ia, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Foreword The text of document 56/1071/FDIS, future edition 2 of IEC 61078, prepared by IEC TC 56, Dependability, was submitted to the IEC-CENELEC parallel
15、 vote and was approved by CENELEC as EN 61078 on 2006-03-01. This European Standard supersedes EN 61078:1993. The major change with respect to EN 61078:1993 is that an additional clause on Boolean disjointing methods (Annex B) has been added. The following dates were fixed: latest date by which the
16、EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2006-12-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2009-03-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text o
17、f the International Standard IEC 61078:2006 was approved by CENELEC as a European Standard without any modification. _ EN 61078:2006 2 3 EN 61078:2006 CONTENTS INTRODUCTION.5 1 Scope 6 2 Normative references .6 3 Terms and definitions .6 4 Symbols and abbreviated terms 7 5 Assumptions and limitation
18、s8 5.1 Independence of events.8 5.2 Sequential events8 5.3 Distribution of times to failure 8 6 Establishment of system success/failure definitions.8 6.1 General considerations 8 6.2 Detailed considerations .9 7 Elementary models.10 7.1 Developing the model 10 7.2 Evaluating the model .12 8 More com
19、plex models.15 8.1 General procedures .15 8.2 Models with common blocks.20 8.3 m out of n models (non-identical items) 22 8.4 Method of reduction.22 9 Extension of reliability block diagram methods to availability calculations.23 Annex A (informative) Summary of formul25 Annex B (informative) Boolea
20、n disjointing methods.29 Annex ZA (normative) Normative references to international publications with their corresponding European publications37 Bibliography .35 Figure 1 Series reliability block diagram .10 Figure 2 Duplicated (or parallel) series reliability block diagram 10 Figure 3 Series dupli
21、cated (or parallel) reliability block diagram 11 Figure 4 Mixed redundancy reliability block diagram .11 Figure 5 Another type of mixed redundancy reliability block diagram .11 Figure 6 2/3 redundancy 11 Figure 7 2/4 redundancy 11 Figure 8 Diagram not easily represented by series/parallel arrangemen
22、t of blocks.12 Figure 9 Parallel arrangement of blocks13 Figure 10 Standby redundancy.14 Figure 11 Representation of Figure 8 when item A has failed 16 Figure 12 Representation of Figure 8 when item A is working16 EN 61078:2006 4 Figure 13 One-out-of-three parallel arrangement 17Figure 14 Reliabilit
23、y block diagram using an arrow to help define system success.20 Figure 15 Alternative representation of Figure 14 using common blocks 20 Figure 16 2-out-of-5 non-identical system.22 Figure 17 Illustrating grouping of blocks before reduction23 Figure 18 Reduced reliability block diagrams23 Table 1 Ap
24、plication of truth table to the example of Figure 13 .18 Table 2 Application of truth table to the example of Figure 8 .19 Table 3 Application of truth table to the examples of Figures 14 and 15.21 5 EN 61078:2006 INTRODUCTION Different analytical methods of dependability analysis are available, of
25、which the reliability block diagram (RBD) is one. The purpose of each method and their individual or combined applicability in evaluating the reliability and availability of a given system or component should be examined by the analyst prior to starting work on the RBD. Consideration should also be
26、given to the results obtainable from each method, data required to perform the analysis, complexity of analysis and other factors identified in this standard. A reliability block diagram (RBD) is a pictorial representation of a systems reliability perform-ance. It shows the logical connection of (fu
27、nctioning) components needed for successful operation of the system (hereafter referred to as “system success”). EN 61078:2006 6 ANALYSIS TECHNIQUES FOR DEPENDABILITY RELIABILITY BLOCK DIAGRAM AND BOOLEAN METHODS 1 Scope This International Standard describes procedures for modelling the dependabilit
28、y of a system and for using the model in order to calculate reliability and availability measures. The RBD modelling technique is intended to be applied primarily to systems without repair and where the order in which failures occur does not matter. For systems where the order of failures is to be t
29、aken into account or where repairs are to be carried out, other modelling techniques, such as Markov analysis, are more suitable. It should be noted that although the word “repair” is frequently used in this standard, the word “restore” is equally applicable. Note also that the words “item” and “blo
30、ck” are used extensively throughout this standard: in most instances interchangeably. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of
31、the referenced document (including any amendments) applies. IEC 60050-191:1990, International Electrotechnical Vocabulary (IEV) Chapter 191: Depend-ability and quality of service IEC 61025, Fault tree analysis (FTA) ISO 3534-1:1993, Statistics Vocabulary and symbols Part 1: Probability and general s
32、tatistical terms 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60050-191 and ISO 3534-1 apply. 7 EN 61078:2006 4 Symbols and abbreviated terms A B Symbol/Abbreviation Meaning , CBA When used in Boolean expressions, these symbols indicate that items
33、 A, B, C, . are in up states , CBA When used in Boolean expressions, these symbols indicate that items A, B, C, . are in down states SF Probability of system failure )(tfAProbability density function of block A. The term “block” is used to denote a group of one or more components Pr(SS|X failed) Con
34、ditional probability of system success, given that item X is failed R , , )(tR )(StRReliability probability that an item can perform a required function under given conditions for a given time interval (0,t) AR , , BRReliability of blocks A, B, . SR System reliability SWR Reliability of switching an
35、d sensing mechanism SF System failure (used in the Boolean expressions) SS System success (used in the Boolean expressions) t Mission time or time period of interest CBA, Failure rate (constant) of blocks A, B and C dB Dormant failure rate of block B CBA, Repair rates (constant) of blocks A, B and C
36、 ( )nrNumber of ways of selecting r items from n items 0, 1 These symbols are used in truth tables to denote down and up states and apply to whichever item is the column heading Boolean symbols denoting AND logic, e.g. AB, A.B (intersection) Boolean symbols denoting OR logic, e.g. A B, A+B (union) A
37、ctive (parallel) redundancy Standby redundancy O I OA B I EN 61078:2006 8 Symbol/Abbreviation Meaning m/n is symbol used to show m-out-of-n items needed for system success in an active redundant configuration I O indicates input indicates output Such indications are used for convenience. They are no
38、t mandatory, but may be useful where connections have a directional significance Grouping of equipment, components, units or other system elements m/n I I I I I O A I O 5 Assumptions and limitations 5.1 Independence of events One of the most fundamental assumptions on which the procedures described
39、in this standard are based, is the assumption that components (or blocks representing them) can exist in only two states: working (“up” state) or failed (“down” state). Another important assumption is that failure (or repair) of any block must not affect the probability of failure of (or repair to)
40、ANY other block within the system being modelled. This implies that there should be available, in effect, sufficient repair resources to service those blocks needing repair and that when two or more persons are repairing a particular block at the same time, neither gets in the others way. Thus failu
41、res of and repairs to individual blocks are considered to be statistically independent events. 5.2 Sequential events RBDs are not suitable for modelling order-dependent or time-dependent events. In such instances, other methods such as Markov analysis or Petri nets should be used. 5.3 Distribution o
42、f times to failure Provided the assumptions noted in 5.1 are valid, there is no restriction, other than mathematical tractability, on the distribution that may be used to describe the times to failure or repair. 6 Establishment of system success/failure definitions 6.1 General considerations A prere
43、quisite for constructing system reliability models is a sound understanding of the ways in which the system can operate. Systems often require more than one success/failure definition. These should be defined and listed. An RBD diagram can be made on different levels: system level, sub-system (modul
44、e) level or assembly level. When an RBD is made for further analysis (for example for FMEA analysis), a level suitable for such analysis has to be chosen. 9 EN 61078:2006 In addition, there should be clear statements concerning functions to be performed, performance parameters and permissible limits
45、 on such parameters, environmental and operating conditions. Various qualitative analysis techniques may be employed in the construction of an RBD. Therefore the systems success/failure definition has to be established. For each system success/failure definition the next step is to divide the system
46、 into logical blocks appropriate to the purpose of the reliability analysis. Particular blocks may represent system substructures, which in turn may be represented by other RBDs (system reduction see 8.4). For the quantitative evaluation of an RBD, various methods are available. Depending on the typ
47、e of structure, simple Boolean techniques (see 8.1.3) and/or path and cut set analyses may be employed. For a definition of cut set see IEC 61025 (FTA). Calculations may be made using basic component reliability/availability methods and analytical methods or Monte Carlo simulation. An advantage with
48、 Monte Carlo simulation is that the events in the RBD do not have to be combined analytically since the simulation itself takes into account whether each block is failed or functional (see 8.1). Since the reliability block diagram describes the logical relations needed for system function, the block
49、 diagram does not necessarily represent the way the hardware is physically connected, although an RBD generally follows, as far as possible, the physical system connections. 6.2 Detailed considerations 6.2.1 System operation It may be possible to use a system in more than one functional mode. If separate systems were used for each mode, such modes should be treated independently of other mo
