IEC_61511_.pdf

BRITISH STANDARDBS IEC 61511-3:2003Functional safety Safety instrumented systems for the process industry sector Part 3:Guidance for the determination of the required safety integrity levelsICS 25.040.01?Copyright British Standards Institution Provided by IHS under license with BSINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS IEC 61511-3:2003This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2003 BSI 30 April 2003ISBN 0 580 41752 2National forewordThis British Standard reproduces verbatim IEC 61511-3:2003 and implements it as the UK national standard.The UK participation in its preparation was entrusted by Technical Committee GEL/65,Measurement and control,to Subcommittee GEL/65/1,Systems considerations,which has the responsibility to:A list of organizations represented on this subcommittee can be obtained on request to its secretary.Cross-referencesThe British Standards which implement international 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 of 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.aid enquirers to understand the text;present to the responsible international/European committee any enquiries on the interpretation,or proposals for change,and keep the UK interests informed;monitor related international and European developments and promulgate them in the UK.Summary of pagesThis document comprises a front cover,an inside front cover,the IEC title page,pages 2 to 53 and a back cover.The BSI copyright date displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd.No.DateCommentsCopyright British Standards Institution Provided by IHS under license with BSINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTERNATIONALSTANDARDIEC61511-3First edition2003-03Functional safety Safety instrumented systemsfor the process industry sector Part 3:Guidance for the determination of the requiredsafety integrity levelsScurit fonctionnelle-Systmes instruments de scurit pour le secteurdes industries de transformationPartie 3:Conseils pour la dtermination des niveaux dintgritde scurit requisReference numberIEC 61511-3:2003(E)BS IEC 615113:2003Copyright British Standards Institution Provided by IHS under license with BSINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CONTENTSFOREWORD.4INTRODUCTION.61Scope.92Terms,definitions and abbreviations.103Risk and safety integrity general guidance.103.1General.103.2Necessary risk reduction.113.3Role of safety instrumented systems.113.4Safety integrity.113.5Risk and safety integrity.133.6Allocation of safety requirements.143.7Safety integrity levels.143.8Selection of the method for determining the required safety integrity level.15Annex A(informative)As Low As Reasonably Practicable(ALARP)and tolerablerisk concepts.16Annex B(informative)Semi-quantitative method.19Annex C(informative)The safety layer matrix method.27Annex D(informative)Determination of the required safety integrity levels a semi-qualitative method:calibrated risk graph.33Annex E(informative)Determination of the required safety integrity levels a qualitative method:risk graph.41Annex F(informative)Layer of protection analysis(LOPA).46Figure 1 Overall framework of this standard.8Figure 2 Typical risk reduction methods found in process plants.10Figure 3 Risk reduction:general concepts.13Figure 4 Risk and safety integrity concepts.13Figure 5 Allocation of safety requirements to the Safety Instrumented Systems,non-SIS prevention/mitigation protection layers and other protection layers.14Figure A.1 Tolerable risk and ALARP.17Figure B.1 Pressurized Vessel with Existing Safety Systems.20Figure B.2 Fault Tree for Overpressure of the Vessel.23Figure B.3 Hazardous Events with Existing Safety Systems.24Figure B.4 Hazardous Events with Redundant Protection Layer.25Figure B.5 Hazardous Events with SIL 2 SIS Safety Function.26Figure C.1 Protection Layers.27Figure C.2 Example Safety Layer Matrix.31Figure D.1 Risk graph:general scheme.37Figure D.2 Risk Graph:Environmental Loss.39Figure E.1 DIN V 19250 Risk graph personnel protection(see Table E.1).44Figure E.2 Relationship IEC 61511,DIN 19250 and VDI/VDE 2180.45Figure F.1 Layer of Protection Analysis(LOPA)Report.47BS IEC 615113:20032Copyright British Standards Institution Provided by IHS under license with BSINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Table A.1 Example of risk classification of incidents.18Table A.2 Interpretation of risk classes.18T