BS-EN-61511-3-2004.pdf

BRITISH STANDARD BS EN 61511-3:2004 Incorporating Amendment No. 1 to BS IEC 61511-3:2003 (renumbers the BS IEC as BS EN 61511-3:2004) Functional safety Safety instrumented systems for the process industry sector Part 3: Guidance for the determination of the required safety integrity levels The European Standard EN 61511-3:2004 has the status of a British Standard ICS 25.040.01 ? Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 61511-3:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2003 © BSI 16 May 2005 ISBN 0 580 41752 2 National foreword This British Standard is the official English language version of EN 61511-3:2004. It was derived by CENELEC from IEC 61511-3:2003, including Corrigendum October 2004. 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-references The British Standards which implement international or European 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 pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 52, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments 1557816 May 2005Implementation of the European Standard Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD EN 61511-3 NORME EUROPÉENNE EUROPÄISCHE NORM December 2004 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 © 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61511-3:2004 E ICS 25.040.01 English version Functional safety Safety instrumented systems for the process industry sector Part 3: Guidance for the determination of the required safety integrity levels (IEC 61511-3:2003 + corrigendum 2004) Sécurité fonctionnelle Systèmes instrumentés de sécurité pour le secteur des industries de transformation Partie 3: Conseils pour la détermination des niveaux d'intégrité de sécurité (CEI 61511-3:2003) Funktionale Sicherheit - Sicherheitstechnische Systeme für die Prozessindustrie Teil 3: Anleitung für die Bestimmung der erforderlichen Sicherheits- Integritätslevel (IEC 61511-3:2003 + Corrigendum 2004) This European Standard was approved by CENELEC on 2004-10-01. 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Foreword The text of the International Standard IEC 61511-3:2003, prepared by SC 65A, System aspects, of IEC TC 65, Industrial-process measurement and control, was submitted to the Unique Acceptance Procedure and was approved by CENELEC as EN 61511-3 on 2004-10-01 without any modification. 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) 2005-10-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2007-10-01 _ Endorsement notice The text of the International Standard IEC 61511-3:2003 + corrigendum October 2004 was approved by CENELEC as a European Standard without any modification. _ Page 2 EN 615113:2004 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CONTENTS INTRODUCTION. 5 1 Scope . 8 2 Terms, definitions and abbreviations9 3 Risk and safety integrity general guidance9 3.1 General 9 3.2 Necessary risk reduction10 3.3 Role of safety instrumented systems .10 3.4 Safety integrity 10 3.5 Risk and safety integrity 12 3.6 Allocation of safety requirements.13 3.7 Safety integrity levels 13 3.8 Selection of the method for determining the required safety integrity level.14 Annex A (informative) As Low As Reasonably Practicable (ALARP) and tolerable risk concepts.15 Annex B (informative) Semi-quantitative method 18 Annex C (informative) The safety layer matrix method26 Annex D (informative) Determination of the required safety integrity levels a semi- qualitative method: calibrated risk graph .32 Annex E (informative) Determination of the required safety integrity levels a qualitative method: risk graph.40 Annex F (informative) Layer of protection analysis (LOPA).45 Figure 1 Overall framework of this standard . 7 Figure 2 Typical risk reduction methods found in process plants .9 Figure 3 Risk reduction: general concepts12 Figure 4 Risk and safety integrity concepts 12 Figure 5 Allocation of safety requirements to the Safety Instrumented Systems, non-SIS prevention/mitigation protection layers and other protection layers 13 Figure A.1 Tolerable risk and ALARP .16 Figure B.1 Pressurized Vessel with Existing Safety Systems19 Figure B.2 Fault Tree for Overpressure of the Vessel.22 Figure B.3 Hazardous Events with Existing Safety Systems .23 Figure B.4 Hazardous Events with Redundant Protection Layer .24 Figure B.5 Hazardous Events with SIL 2 SIS Safety Function.25 Figure C.1 Protection Layers26 Figure C.2 Example Safety Layer Matrix.30 Figure D.1 Risk graph: general scheme33 Figure D.2 Risk Graph: Environmental Loss .38 Figure E.1 DIN V 19250 Risk graph personnel protection (see Table E.1) .43 Figure E.2 Relationship IEC 61511, DIN 19250 and VDI/VDE 218044 Figure F.1 Layer of Protection Analysis (LOPA) Report 46 BS IEC 615113:2003 2 Page 3 EN 615113:2004 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Table A.1 Example of risk classification of incidents.17 Table A.2 Interpretation of risk classes.17 Table B.1 HAZOP analysis results20 Table C.1 Frequency of hazardous event likelihood (without considering PLs) .29 Table C.2 Criteria for rating the severity of impact of hazardous events 29 Table D.1 Descriptions of process industry risk graph parameters33 Table D.2 Example calibration of the general purpose risk graph .36 Table D.3 General environmental consequences38 Table E.1 Data relating to risk graph (see Figure E.1) 43 Table F.1 HAZOP developed data for LOPA.46 Table F.2 Impact event severity levels47 Table F.3 Typical protection layer (prevention and mitigation) PFDs 47 Table F.4 Initiation Likelihood.48 BS IEC 615113:2003 3 Page 4 EN 615113:2004 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTRODUCTION Safety instrumented systems have been used for many years to perform safety instrumented functions in the process industries. If instrumentation is to be effectively used for safety instrumented functions, it is essential that this instrumentation achieves certain minimum standards and performance levels. This International Standard addresses the application of safety instrumented systems for the Process Industries. It also requires a process hazard and risk assessment to be carried out to enable the specification for safety instrumented systems to be derived. Other safety systems are only considered so that their contribution can be taken into account when considering the performance requirements for the safety instrumented systems. The safety instrumented system includes all components and subsystems necessary to carry out the safety instrumented function from sensor(s) to final element(s). This International Standard has two concepts which are fundamental to its application; safety lifecycle and safety integrity levels. This International Standard addresses safety instrumented systems which are based on the use of Electrical (E)/Electronic (E)/Programmable Electronic (PE) technology. Where other technologies are used for logic solvers, the basic principles of this standard should be applied. This standard also addresses the safety instrumented system sensors and final elements regardless of the technology used. This International Standard is process industry specific within the framework of IEC 61508 (see Annex A of IEC 61511-1). This International Standard sets out an approach for safety lifecycle activities to achieve these minimum standards. This approach has been adopted in order that a rational and consistent technical policy be used. In most situations, safety is best achieved by an inherently safe process design. If necessary, this may be combined with a protective system or systems to address any residual identified risk. Protective systems can rely on different technologies (chemical, mechanical, hydraulic, pneumatic, electrical, electronic, programmable electronic). Any safety strategy should consider each individual safety instrumented system in the context of the other protective systems. To facilitate this approach, this standard requires that a hazard and risk assessment is carried out to identify the overall safety requirements; requires that an allocation of the safety requirements to the safety instrumented system(s) is carried out; works within a framework which is applicable to all instrumented methods of achieving functional safety; details the use of certain activities, such as safety management, which may be applicable to all methods of achieving functional safety. This International Standard on safety instrumented systems for the process industry: addresses all safety life cycle phases from initial concept, design, implementation, operation and maintenance through to decommissioning; enables existing or new country specific process industry standards to be harmonized with this standard. This standard is intended to lead to a high level of consistency (for example, of underlying principles, terminology, information) within the process industries. This should have both safety and economic benefits. BS IEC 615113:2003 6 Page 5 EN 615113:2004 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI In jurisdictions where the governing authorities (for example national, federal, state, province, county, city) have established process safety design, process safety management, or other requirements, these take precedence over the requirements defined in this standard. This standard deals with guidance in the area of determining the required SIL in hazards and risk analysis (H the determination of tolerable risk, see Annex A; a number of different methods that enable the safety integrity levels for the safety instru- mented functions to be determined, see Annexes B, C, D, E, and F. In particular, this part a) applies when functional safety is achieved using one or more safety instrumented functions for the protection of either personnel, the general public, or the environment; b) may be applied in non-safety applications such as asset protection; c) illustrates typical hazard and risk assessment methods that may be carried out to define the safety functional requirements and safety integrity levels of each safety instrumented function; d) illustrates techniques/measures available for determining the required safety integrity levels; e) provides a framework for establishing safety integrity levels but does not specify the safety integrity levels required for specific applications; f)does not give examples of determining the requirements for other methods of risk reduction. 1.2 Annexes B, C, D, E, and F illustrate quantitative and qualitative approaches and have been simplified in order to illustrate the underlying principles. These annexes have been included to illustrate the general principles of a number of methods but do not provide a definitive account. NOTE Those intending to apply the methods indicated in these annexes should consult the source material referenced in each annex. 1.3 Figure 1 shows the overall framework for IEC 61511-1, IEC 61511-2 and IEC 61511-3 and indicates the role that this standard plays in the achievement of functional safety for safety instrumented systems. Figure 2 gives an overview of risk reduction methods. BS IEC 615113:2003 9 Page 8 EN 615113:2004 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 01:35:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Figure 2 Typical risk reduction methods found in process plants (for example, protection layer model) 2 Terms, definitions and abbreviations For the purposes of this document, the definitions and abbreviations given in Clause 3 of IEC 61511-1 apply. 3 Risk and safety integrity general guidance 3.1 General This clause provides information on the underlying concepts of risk and the relationship of risk to safety integrity. This information is common to each of the diverse hazard and risk a