EN 61649:2008

SLOVENSKI STANDARD
01-januar-2009
Weibullova analiza (IEC 61649:2008)
Weibull analysis (IEC 61649:2008)
Weibull-Analyse (IEC 61649:2008)
Analyse de Weibull (CEI 61649:2008)
Ta slovenski standard je istoveten z: EN 61649:2008
ICS:
03.120.30 8SRUDEDVWDWLVWLþQLKPHWRG Application of statistical
methods
29.020 Elektrotehnika na splošno Electrical engineering in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 61649
NORME EUROPÉENNE
November 2008
EUROPÄISCHE NORM
ICS 03.120.01; 03.120.30
English version
Weibull analysis
(IEC 61649:2008)
Analyse de Weibull Weibull-Analyse
(CEI 61649:2008) (IEC 61649:2008)

This European Standard was approved by CENELEC on 2008-10-01. 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, Bulgaria, 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

© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61649:2008 E
Foreword
The text of document 56/1269/FDIS, future edition 2 of IEC 61649, prepared by IEC TC 56,
Dependability, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 61649 on 2008-10-01.
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) 2009-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2011-10-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61649:2008 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60300-1 NOTE  Harmonized as EN 60300-1:2003 (not modified).
IEC 60300-2 NOTE  Harmonized as EN 60300-2:2004 (not modified).
IEC 60300-3-1 NOTE  Harmonized as EN 60300-3-1:2004 (not modified).
IEC 60300-3-2 NOTE  Harmonized as EN 60300-3-2:2005 (not modified).
IEC 60300-3-4 NOTE  Harmonized as EN 60300-3-4:2008 (not modified).
IEC 61703 NOTE  Harmonized as EN 61703:2002 (not modified).
__________
– 3 – EN 61649:2008
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
IEC 60300-3-5 2001 Dependability management - - -
Part 3-5: Application guide - Reliability test
conditions and statistical test principles

1) 2)
IEC 61810-2 - Electromechanical elementary relays - EN 61810-2 2005
Part 2: Reliability
ISO 2854 1976 Statistical interpretation of data - Techniques - -
of estimation and tests relating to means and
variances
ISO 3534-1 2006 Statistics - Vocabulary and symbols - - -
Part 1: General statistical terms and terms
used in probability
1)
Undated reference.
2)
Valid edition at date of issue.

IEC 61649
Edition 2.0 2008-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Weibull analysis
Analyse de Weibull
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XB
CODE PRIX
ICS 03.120.01; 03.120.30 ISBN 2-8318-9954-0
– 2 – 61649 © IEC:2008
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
2 Normative references .8
3 Terms, definitions, abbreviations and symbols.8
3.1 Terms and definitions .8
3.2 Abbreviations .10
3.3 Symbols .10
4 Application of the techniques.11
5 The Weibull distribution .11
5.1 The two-parameter Weibull distribution.11
5.2 The three-parameter Weibull distribution .13
6 Data considerations.13
6.1 Data types.13
6.2 Time to first failure .13
6.3 Material characteristics and the Weibull distribution .13
6.4 Sample size .13
6.5 Censored and suspended data .14
7 Graphical methods and goodness-of-fit .14
7.1 Overview .14
7.2 How to make the probability plot.14
7.2.1 Ranking.15
7.2.2 The Weibull probability plot .15
7.2.3 Dealing with suspensions or censored data .15
7.2.4 Probability plotting.17
7.2.5 Checking the fit .17
7.3 Hazard plotting.18
8 Interpreting the Weibull probability plot.19
8.1 The bathtub curve .19
8.1.1 General .19
8.1.2 β < 1 – Implies early failures.19
8.1.3 β = 1 – Implies constant instantaneous failure rate.20
8.1.4 > 1 – Implies wear-out.20
β
8.2 Unknown Weibull modes may be "masked".20
8.3 Small samples.21
8.4 Outliers .22
8.5 Interpretation of non-linear plots.22
8.5.1 Distributions other than the Weibull .25
8.5.2 Data inconsistencies and multimode failures .25
9 Computational methods and goodness-of-fit .25
9.1 Introduction .25
9.2 Assumptions and conditions .26
9.3 Limitations and accuracy .26
9.4 Input and output data .26

61649 © IEC:2008 – 3 –
9.5 Goodness-of-fit test.27
9.6 MLE – point estimates of the distribution parameters β and η .27
9.7 Point estimate of the mean time to failure.28
9.8 Point estimate of the fractile (10 %) of the time to failure.28
9.9 Point estimate of the reliability at time t (t ≤ T).28
9.10 Software programs .28
10 Confidence intervals.28
10.1 Interval estimation of β .28
10.2 Interval estimation of η .29
10.3 MRR Beta-binomial bounds .30
10.4 Fisher's Matrix bounds .30
10.5 Lower confidence limit for B .31
10.6 Lower confidence limit for R .31
11 Comparison of median rank regression (MRR) and maximum likelihood (MLE)
estimation methods .31
11.1 Graphical display.31
11.2 B life estimates sometimes known as B or L percentiles .31
11.3 Small samples.32
11.4 Shape parameter β.32
11.5 Confidence intervals.32
11.6 Single failure .32
11.7 Mathematical rigor.32
11.8 Presentation of results .32
12 WeiBayes approach.33
12.1 Description.33
12.2 Method.33
12.3 WeiBayes without failures .33
12.4 WeiBayes with failures .33
12.5 WeiBayes case study .34
13 Sudden death method .35
14 Other distributions .37
Annex A (informative) Examples and case studies .
...