prEN IEC 61025:2023
(Main)Fault tree analysis (FTA)
Fault tree analysis (FTA)
Fehlzustandsbaumanalyse
Analyse par arbre de panne (AAP)
Analiza drevesa okvar (FTA)
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2023
Analiza drevesa okvar (FTA)
Fault tree analysis (FTA)
Fehlzustandsbaumanalyse
Analyse par arbre de panne (AAP)
Ta slovenski standard je istoveten z: prEN IEC 61025:2023
ICS:
03.120.01 Kakovost na splošno Quality in general
21.020 Značilnosti in načrtovanje Characteristics and design of
strojev, aparatov, opreme machines, apparatus,
equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
56/1999/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61025 ED3
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2023-09-08 2023-12-01
SUPERSEDES DOCUMENTS:
56/1916/CD, 56/1922A/CC
IEC TC 56 : DEPENDABILITY
SECRETARIAT: SECRETARY:
United Kingdom Ms Stephanie Lavy
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
Other TC/SCs are requested to indicate their interest, if
any, in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
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the final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).
TITLE:
Fault tree analysis (FTA)
PROPOSED STABILITY DATE: 2024
NOTE FROM TC/SC OFFICERS:
Copy right © 2023 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
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– 2 – IEC CDV 61025 IEC:2023
1 CONTENTS
3 FOREWORD . 7
4 INTRODUCTION . 9
5 1 Scope . 10
6 2 Normative references . 10
7 3 Terms and definitions . 11
8 3.1 Definitions directly relating to a fault tree . 11
9 3.2 Dependability related definitions . 14
10 4 Symbols and abbreviated terms . 17
11 5 General aspects of FTA . 24
12 5.1 Fault tree description and structure . 24
13 5.2 Objectives and purpose . 25
14 5.3 Applications . 26
15 5.4 Limitations . 26
16 6 Development of an FT . 27
17 6.1 Steps in performing an FTA . 27
18 6.2 Defining objectives, scope and context . 27
19 6.3 Information required for performing FTA . 28
20 6.4 Understanding how the system works and potential failure modes . 29
21 6.5 Identifying and specifying the top event . 29
22 6.6 Developing the FT . 30
23 6.6.1 Modelling the system . 30
24 6.6.2 Identification and labelling . 31
25 6.7 Qualitative and quantitative analysis . 31
26 6.8 Assessment of results, sensitivity and uncertainty analysis . 32
27 6.9 Report . 33
28 7 Mathematical representation of logic gates . 34
29 7.1 General . 34
30 7.2 OR Gate . 34
31 7.3 AND Gate . 35
32 7.4 Voting gate . 36
33 7.5 NOT, NOR and NAND gates . 37
34 7.6 Subtrees and transfer symbols . 37
35 8 Qualitative analysis . 38
36 8.1 Identification of minimal cut sets of an FT . 38
37 8.2 Qualitative analysis with minimal cut sets . 40
38 8.3 Common cause failure analysis . 40
39 9 Quantitative analysis . 41
40 9.1 Constant probabilities . 41
41 9.1.1 General . 41
42 9.1.2 Use of cut sets . 41
43 9.1.3 Probability of the top event using Sylvester-Poincaré formula . 42
44 9.1.4 Quantitative analysis with disjointed terms . 43
45 9.1.5 Importance factors . 43
46 9.2 Analysis of FTs involving events with time-dependent probabilities . 44
IEC CDV 61025 IEC:2023– 3 –
47 9.2.1 General . 44
48 9.3 Boolean techniques for quantitative analysis of large models . 46
49 9.4 Time dependent analysis for systems consisting of non-repaired components . 47
50 9.4.1 Failure rates . 47
51 9.4.2 Small sub trees related to non-repaired items . 47
52 9.4.3 Preventive replacement strategies and MTTF . 49
53 9.5 Time-dependent analysis for systems that include repaired components . 49
54 9.5.1 General . 49
55 9.5.2 Small sub trees related to repaired items . 50
56 9.5.3 FTs involving failures of periodically tested components . 51
57 9.5.4 Average and asymptotic unavailability calculations . 52
58 9.5.5 Frequency calculations and METBF . 53
59 9.5.6 Unreliability calculations . 54
60 9.5.7 Composition of two independent items – Practical examples using rates . 56
61 10 Extension of fault tree technique. 57
62 10.1 XOR gates and non-coherent fault trees . 57
63 10.1.1 Example of probabilistic calculation for a non-coherent fault tree . 58
64 10.2 Dynamic fault trees . 59
65 10.2.1 General . 59
66 10.2.2 Local interactions . 59
67 10.2.3 Systemic dynamic interactions . 61
68 10.2.4 Graphical representations of dynamic interactions . 61
69 10.2.5 Probabilistic calculations . 64
70 Annex A (informative) Relationship with other dependability and risk assessment
71 techniques . 66
72 A.1 Reliability block diagrams . 66
73 A.1.1 Introduction . 66
74 A.1.2 Series structure . 66
75 A.1.3 Parallel structure . 67
76 A.1.4 Mix of series and parallel structures . 67
77 A.2 Combination of FTA and failure modes and effects analysis (FMEA) . 68
78 A.3 Combination of FTA and event tree analysis (ETA) or cause-consequence
79 analysis (CCA) . 68
80 A.4 Combination of FTA and Markov analysis . 70
81 Annex B (informative) Automated fault tree construction . 71
82 Annex C (informative) Use of Monte Carlo analysis for analysing uncertainty . 72
83 Annex D (informative) Procedure for disjointing minimal cut sets . 75
84 Annex E (informative) Shannon decomposition and BDDs. 77
85 E.1 Shannon decomposition . 77
86 E.2 Binary decision diagram (BDD) . 79
87 E.2.1 Building of BDDs . 79
88 E.2.2 Minimal cut sets identification . 79
89 E.2.3 Probabilistic calculations with BDDs . 80
90 E.2.4 Conditional probability calculations with BDD . 81
91 Annex F (informative) Importance factors . 83
92 F.1 General . 83
93 F.2 Vesely-Fussell importance factor . 83
94 F.3 Birnbaum importance factor or marginal importance factor . 83
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95 F.4 Lambert importance factor or critical importance factor . 84
96 F.5 Diagnostic importance factor . 85
97 F.6 Risk achievement worth . 85
98 F.7 Risk reduction worth . 85
99 F.8 Differential importance measure . 85
100 F.9 Remarks about importance factors . 86
101 Annex G (informative) FT driven Petri nets . 87
102 G.1 General . 87
103 G.2 Example of sub-PN to be used within FT driven P
...
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