IEC 61511-3:2016
(Main)Functional safety - Safety instrumented systems for the process industry sector - Part 3: Guidance for the determination of the required safety integrity levels
Functional safety - Safety instrumented systems for the process industry sector - Part 3: Guidance for the determination of the required safety integrity levels
IEC 61511-3:2016 applies when functional safety is achieved using one or more SIF for the protection of either personnel, the general public, or the environment; may be applied in non-safety applications such as asset protection; illustrates typical hazard and risk assessment methods that may be carried out to define the safety functional requirements and SIL of each SIF; illustrates techniques/measures available for determining the required SIL; provides a framework for establishing SIL but does not specify the SIL required for specific applications; does not give examples of determining the requirements for other methods of risk reduction. This second edition cancels and replaces the first edition published in 2003. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: Additional H&RA example(s) and quantitative analysis consideration annexes are provided.
Sécurité fonctionnelle - Systèmes instrumentés de sécurité pour le secteur des industries de transformation - Partie 3: Conseils pour la détermination des niveaux exigés d'intégrité de sécurité
L'IEC 61511-3:2016 s'applique lorsque la sécurité fonctionnelle est obtenue en utilisant une ou plusieurs SIF pour la protection du personnel, du grand public ou de l'environnement; peut s'appliquer dans des applications non liées à la sécurité (notamment la protection des biens); présente les méthodes d'analyse de danger et de risque qui peuvent être réalisées pour définir les exigences fonctionnelles de sécurité et le SIL de chaque SIF; identifie des techniques et mesures disponibles pour déterminer le SIL exigé; fournit un cadre pour la détermination du SIL, mais ne spécifie pas le SIL exigé pour des applications spécifiques; ne donne aucun exemple de détermination des exigences relatives à d'autres méthodes de réduction de risque. Cette deuxième édition annule et remplace la première édition parue en 2003. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: Réalisation d'exemples additionnels H&RA et d'annexes sur la considération d'analyse quantitative.
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IEC 61511-3 ®
Edition 2.0 2016-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Functional safety – Safety instrumented systems for the process industry
sector –
Part 3: Guidance for the determination of the required safety integrity levels
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
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IEC 61511-3 ®
Edition 2.0 2016-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Functional safety – Safety instrumented systems for the process industry
sector –
Part 3: Guidance for the determination of the required safety integrity levels
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.110; 25.040.01 ISBN 978-2-8322-3545-4
– 2 – IEC 61511-3:2016 RLV IEC 2016
CONTENTS
FOREWORD. 7
INTRODUCTION . 9
1 Scope . 12
2 Normative references . 13
3 Terms, definitions and abbreviations . 14
Annex A (informative) Risk and safety integrity – general guidance . 15
A.1 General . 15
A.2 Necessary risk reduction . 15
A.3 Role of safety instrumented systems . 15
3.4 Safety integrity .
A.4 Risk and safety integrity . 17
A.5 Allocation of safety requirements . 18
A.6 Hazardous event, hazardous situation and harmful event . 18
A.7 Safety integrity levels . 19
A.8 Selection of the method for determining the required safety integrity level . 19
Annex B (informative) Semi-quantitative method – event tree analysis . 22
B.1 General Overview . 22
B.2 Compliance with IEC 61511-1:2016 . 22
B.3 Example . 23
B.3.1 General . 23
B.3.2 Process safety target level . 24
B.3.3 Hazard analysis . 24
B.3.4 Semi-quantitative risk analysis technique. 25
B.3.5 Risk analysis of existing process . 26
B.3.6 Events that do not meet the process safety target level . 29
B.3.7 Risk reduction using other protection layers . 30
B.3.8 Risk reduction using a safety instrumented function . 30
Annex C (informative) The safety layer matrix method . 34
C.1 Introduction Overview . 34
C.2 Process safety target . 35
C.3 Hazard analysis . 36
C.4 Risk analysis technique . 36
C.5 Safety layer matrix . 37
C.6 General procedure . 38
Annex D (informative) Determination of the required safety integrity levels – A semi-
qualitative method: calibrated risk graph . 40
D.1 Introduction Overview . 40
D.2 Risk graph synthesis . 40
D.3 Calibration . 41
D.4 Membership and organization of the team undertaking the SIL assessment . 42
D.5 Documentation of results of SIL determination . 43
D.6 Example calibration based on typical criteria . 43
D.7 Using risk graphs where the consequences are environmental damage . 46
D.8 Using risk graphs where the consequences are asset loss . 47
D.9 Determining the integrity level of instrument protection function where the
consequences of failure involve more than one type of loss . 47
Annex E (informative) Determination of the required safety integrity levels – A
qualitative method: risk graph . 48
E.1 General . 48
E.2 Typical implementation of instrumented functions . 48
E.3 Risk graph synthesis . 49
E.4 Risk graph implementation: personnel protection . 50
E.5 Relevant issues to be considered during application of risk graphs . 53
Annex F (informative) Layer of protection analysis (LOPA) . 54
F.1 Introduction Overview . 54
F.2 Layer of protection analysis .
F.2 Impact event . 55
F.3 Severity level . 55
F.4 Initiating cause . 56
F.5 Initiation likelihood . 57
F.6 Protection layers . 57
F.7 Additional mitigation . 58
F.8 Independent protection layers (IPL) . 58
F.9 Intermediate event likelihood . 59
F.10 SIF integrity level . 59
F.11 Mitigated event likelihood . 59
F.12 Total risk . 59
F.13 Example . 60
F.13.1 General . 60
F.13.2 Impact event and severity level . 60
F.13.3 Initiating cause . 60
F.13.4 Initiating likelihood . 60
F.13.5 Protection layers General process design . 60
F.13.6 BPCS . 60
F.13.7 Alarms . 60
F.13.8 Additional mitigation . 61
F.13.9 Independent protection level layer(s) (IPL) . 61
F.13.10 Intermediate event likelihood . 61
F.13.11 SIS . 61
F.13.12 Next SIF . 61
Annex G (informative) Layer of protection analysis using a risk matrix . 63
G.1 Overview . 63
G.2 Procedure . 65
G.2.1 General . 65
G.2.2 Step 1: General Information and node definition . 65
G.2.3 Step 2: Describe hazardous event . 66
G.2.4 Step 3: Evaluate initiating event frequency . 69
G.2.5 Step 4: Determine hazardous event consequence severity and risk
reduction factor . 70
G.2.6 Step 5: Identify independent protection layers and risk reduction factor . 71
G.2.7 Step 6: Identify consequence mitigation systems and risk reduction
factor . 72
G.2.8 Step 7: Determine CMS risk gap . 73
G.2.9 Step 8: Determine scenario risk gap . 76
G.2.10 Step 9: Make recommendations when needed . 76
– 4 – IEC 61511-3:2016 RLV IEC 2016
Annex H (informative) A qualita
...
IEC 61511-3 ®
Edition 2.0 2016-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Functional safety – Safety instrumented systems for the process industry
sector –
Part 3: Guidance for the determination of the required safety integrity levels
Sécurité fonctionnelle – Systèmes instrumentés de sécurité pour le secteur des
industries de transformation –
Partie 3: Conseils pour la détermination des niveaux exigés d'intégrité de
sécurité
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
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Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
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bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 15 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.
IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and
CISPR.
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IEC 61511-3 ®
Edition 2.0 2016-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Functional safety – Safety instrumented systems for the process industry
sector –
Part 3: Guidance for the determination of the required safety integrity levels
Sécurité fonctionnelle – Systèmes instrumentés de sécurité pour le secteur des
industries de transformation –
Partie 3: Conseils pour la détermination des niveaux exigés d'intégrité de
sécurité
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.110; 25.040.01 ISBN 978-2-8322-3212-5
– 2 – IEC 61511-3:2016 IEC 2016
CONTENTS
FOREWORD. 7
INTRODUCTION . 9
1 Scope . 12
2 Normative references . 13
3 Terms, definitions and abbreviations . 13
Annex A (informative) Risk and safety integrity – general guidance . 14
A.1 General . 14
A.2 Necessary risk reduction . 14
A.3 Role of safety instrumented systems . 14
A.4 Risk and safety integrity . 16
A.5 Allocation of safety requirements . 17
A.6 Hazardous event, hazardous situation and harmful event . 17
A.7 Safety integrity levels . 18
A.8 Selection of the method for determining the required safety integrity level . 18
Annex B (informative) Semi-quantitative method – event tree analysis . 20
B.1 Overview . 20
B.2 Compliance with IEC 61511-1:2016 . 20
B.3 Example . 20
B.3.1 General . 20
B.3.2 Process safety target . 21
B.3.3 Hazard analysis . 21
B.3.4 Semi-quantitative risk analysis technique. 22
B.3.5 Risk analysis of existing process . 23
B.3.6 Events that do not meet the process safety target . 25
B.3.7 Risk reduction using other protection layers . 26
B.3.8 Risk reduction using a safety instrumented function . 26
Annex C (informative) The safety layer matrix method . 28
C.1 Overview . 28
C.2 Process safety target . 29
C.3 Hazard analysis . 29
C.4 Risk analysis technique . 30
C.5 Safety layer matrix . 31
C.6 General procedure . 32
Annex D (informative) A semi-qualitative method: calibrated risk graph . 34
D.1 Overview . 34
D.2 Risk graph synthesis . 34
D.3 Calibration . 35
D.4 Membership and organization of the team undertaking the SIL assessment . 36
D.5 Documentation of results of SIL determination . 37
D.6 Example calibration based on typical criteria . 37
D.7 Using risk graphs where the consequences are environmental damage . 40
D.8 Using risk graphs where the consequences are asset loss . 41
D.9 Determining the integrity level of instrument protection function where the
consequences of failure involve more than one type of loss . 41
Annex E (informative) A qualitative method: risk graph . 42
E.1 General . 42
E.2 Typical implementation of instrumented functions . 42
E.3 Risk graph synthesis . 43
E.4 Risk graph implementation: personnel protection . 43
E.5 Relevant issues to be considered during application of risk graphs . 45
Annex F (informative) Layer of protection analysis (LOPA) . 47
F.1 Overview . 47
F.2 Impact event . 48
F.3 Severity level . 48
F.4 Initiating cause . 49
F.5 Initiation likelihood . 50
F.6 Protection layers . 50
F.7 Additional mitigation . 51
F.8 Independent protection layers (IPL) . 51
F.9 Intermediate event likelihood . 52
F.10 SIF integrity level . 52
F.11 Mitigated event likelihood . 52
F.12 Total risk . 52
F.13 Example . 53
F.13.1 General . 53
F.13.2 Impact event and severity level . 53
F.13.3 Initiating cause .
...
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