EN 61078:2006

SLOVENSKI STANDARD
01-januar-2007
1DGRPHãþD
SIST EN 61078:2002
Analizne tehnike za zagotovljivost – Zanesljivost, blokovni diagram in Boolove
metode (IEC 61078:2006)
Analysis techniques for dependability - Reliability block diagram and boolean methods
Techniken für die Analyse der Zuverlässigkeit - Verfahren mit dem
Zuverlässigkeitsblockdiagramm und Boole'sche Verfahren
Techniques d'analyse pour la sûreté de fonctionnement - Bloc-diagramme de fiabilité et
méthodes booléennes
Ta slovenski standard je istoveten z: EN 61078:2006
ICS:
21.020 =QDþLOQRVWLLQQDþUWRYDQMH Characteristics and design of
VWURMHYDSDUDWRYRSUHPH machines, apparatus,
equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 61078
NORME EUROPÉENNE
May 2006
EUROPÄISCHE NORM
ICS 03.120.01; 03.120.99 Supersedes EN 61078:1993

English version
Analysis techniques for dependability -
Reliability block diagram and boolean methods
(IEC 61078:2006)
Techniques d'analyse  Techniken für die Analyse
pour la sûreté de fonctionnement - der Zuverlässigkeit -
Bloc-diagramme de fiabilité Verfahren mit dem
et méthodes booléennes Zuverlässigkeitsblockdiagramm
(CEI 61078:2006) und Boole'sche Verfahren
(IEC 61078:2006)
This European Standard was approved 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 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 into 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, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 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
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 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 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 of the International Standard IEC 61078:2006 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60812 NOTE Harmonized as EN 60812:2006 (not modified).
__________
- 3 - EN 61078:2006
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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 the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

IEC 60050-191 1990 International Electrotechnical Vocabulary - -
(IEV)
Chapter 191: Dependability and quality of
service
1) 2)
IEC 61025 Fault tree analysis (FTA) HD 617 S1
- 1992
ISO 3534-1 1993 Statistics - Vocabulary and symbols - -
Part 1: Probability and general statistical
terms
1)
Undated reference.
2)
Valid edition at date of issue.

NORME CEI
INTERNATIONALE
IEC
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2006-01
Techniques d'analyse pour la sûreté
de fonctionnement –
Bloc-diagramme de fiabilité et
méthodes booléennes
Analysis techniques for dependability –
Reliability block diagram and
boolean methods
 IEC 2006 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
W
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

61078  IEC:2006 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11

1 Scope.13
2 Normative references .13
3 Terms and definitions .13
4 Symbols and abbreviated terms.15
5 Assumptions and limitations .17
5.1 Independence of events .17
5.2 Sequential events.17
5.3 Distribution of times to failure .17
6 Establishment of system success/failure definitions.17
6.1 General considerations.17
6.2 Detailed considerations .19
7 Elementary models.21
7.1 Developing the model.21
7.2 Evaluating the model.25
8 More complex models.31
8.1 General procedures.31
8.2 Models with common blocks .41
8.3 m out of n models (non-identical items) .45
8.4 Method of reduction.45
9 Extension of reliability block diagram methods to availability calculations .47

Annex A (informative) Summary of formulæ .51
Annex B (informative) Boolean disjointing methods.59

Bibliography.71

Figure 1 – Series reliability block diagram.21
Figure 2 – Duplicated (or parallel) series reliability block diagram.21
Figure 3 – Series duplicated (or parallel) reliability block diagram .23
Figure 4 – Mixed redundancy reliability block diagram .23
Figure 5 – Another type of mixed redundancy reliability block diagram.23
Figure 6 – 2/3 redundancy .23
Figure 7 – 2/4 redundancy .23
Figure 8 – Diagram not easily represented by series/parallel arrangement of blocks.25
Figure 9 – Parallel arrangement of blocks .27
Figure 10 – Standby redundancy .29
Figure 11 – Representation of Figure 8 when item A has failed.33
Figure 12 – Representation of Figure 8 when item A is working .33

61078  IEC:2006 – 5 –
Figure 13 – One-out-of-three parallel arrangement .35
Figure 14 – Reliability block diagram using an arrow to help define system success .41
Figure 15 – Alternative representation of Figure 14 using common blocks .41
Figure 16 – 2-out-of-5 non-identical system .45
Figure 17 – Illustrating grouping of blocks before reduction .47
Figure 18 – Reduced reliability block diagrams .47

Table 1 – Application of truth table to the example of Figure 13 .37
Table 2 – Application of truth table to the example of Figure 8 .39
Table 3 – Application of truth table to the examples of Figures 14 and 15 .43

61078  IEC:2006 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ANALYSIS TECHNIQUES FOR DEPENDABILITY –
RELIABILITY BLOCK DIAGRAM AND BOOLEAN METHODS

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardisation comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardisation in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including
...