SIST EN 61511-2:2007
(Main)Functional safety - Safety instrumented systems for the process industry sector -- Part 2: Guidelines for the application of IEC 61511-1
Functional safety - Safety instrumented systems for the process industry sector -- Part 2: Guidelines for the application of IEC 61511-1
This part provides guidance on the specification, design, installation, operation and maintenance of Safety Instrument Functions and related safety instrumented system as defined in IEC 61511-1. This standard has been organized to that each clause and subclause number herein adresses the same clause number in IEC 61511-1.
Funktionale Sicherheit - Sicherheitstechnische Systeme für die Prozessindustrie -- Teil 2: Anleitungen zur Anwendung des Teils 1
Sécurité fonctionnelle - Systèmes instrumentés de sécurité pour le secteur des industries de transformation -- Partie 2: Lignes directrices pour l'application de la CEI 61511-1
provides guidance on the specification, design, installation, operation and maintenance of Safety Instrumented Functions and related safety instrumented system as defined in EN 61511-1. This standard has been organized so that each clause and subclause number herein addresses the same clause number in EN 61511-1
Funkcijska varnost - Sistemi z varnostnimi instrumenti za sektor procesne industrije - 2. del: Smernice za uporabo IEC 61511-1 (IEC 61511-2:2003)
General Information
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EUROPEAN STANDARD EN 61511-2
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2004
ICS 25.040.01;13.110
English version
Functional safety –
Safety instrumented systems for the process industry sector
Part 2: Guidelines for the application of IEC 61511-1
(IEC 61511-2:2003)
Sécurité fonctionnelle – Funktionale Sicherheit -
Systèmes instrumentés de sécurité Sicherheitstechnische Systeme
pour le secteur des industries für die Prozessindustrie
de transformation Teil 2: Anleitungen zur Anwendung
Partie 2: Lignes directrices pour des Teils 1
l'application de la CEI 61511-1 (IEC 61511-2:2003)
(CEI 61511-2:2003)
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.
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 61511-2:2004 E
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EN 61511-2:2004 - 2 -
Foreword
The text of the International Standard IEC 61511-2:2003, 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 61511-2 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 61511-2:2003 was approved by CENELEC as a European
Standard without any modification.
__________
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NORME CEI
INTERNATIONALE IEC
61511-2
INTERNATIONAL
Première édition
STANDARD
First edition
2003-07
Sécurité fonctionnelle –
Systèmes instrumentés de sécurité
pour le secteur des industries
de transformation –
Partie 2:
Lignes directrices pour l'application
de la CEI 61511-1
Functional safety –
Safety instrumented systems
for the process industry sector –
Part 2:
Guidelines for the application
of IEC 61511-1
© IEC 2004 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
PRICE CODE XC
Commission Electrotechnique Internationale
International Electrotechnical Commission
ɆɟɠɞɭɧɚɪɨɞɧɚɹɗɥɟɤɬɪɨɬɟɯɧɢɱɟɫɤɚɹɄɨɦɢɫɫɢɹ
Pour prix, voir catalogue en vigueur
For price, see current catalogue
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61511-2 © IEC:2004 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11
1 Scope.17
2 Normative references.17
3 Terms, definitions and abbreviations .17
4 Conformance to this International Standard .17
5 Management of functional safety .19
5.1 Objective.19
5.2 Requirements.19
6 Safety lifecycle requirements.33
6.1 Objective.33
6.2 Requirements.33
7 Verification.35
7.1 Objective.35
8 Process hazard and risk assessment.35
8.1 Objectives.35
8.2 Requirements.35
9 Allocation of safety functions to protection layers .41
9.1 Objective.41
9.2 Requirements of the allocation process .41
9.3 Additional requirements for safety integrity level 4.47
9.4 Requirement on the basic process control system as a layer of protection.47
9.5 Requirements for preventing common cause, common mode and dependent
failures .49
10 SIS safety requirements specification .51
10.1 Objective.51
10.2 General requirements.51
10.3 SIS safety requirements .51
11 SIS design and engineering.55
11.1 Objective.55
11.2 General requirements.55
11.3 Requirements for system behaviour on detection of a fault .65
11.4 Requirements for hardware fault tolerance .65
11.5 Requirements for selection of components and subsystems .67
11.6 Field devices.73
11.7 Interfaces.73
11.8 Maintenance or testing design requirements.79
11.9 SIF probability of failure .81
12 Requirements for application software, including selection criteria for utility
software .85
12.1 Application software safety lifecycle requirements .85
12.2 Application software safety requirements specification .93
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61511-2 © IEC:2004 – 5 –
12.3 Application software safety validation planning.97
12.4 Application software design and development .97
12.5 Integration of the application software with the SIS subsystem .113
12.6 FPL and LVL software modification procedures .113
12.7 Application software verification.115
13 Factory acceptance testing (FAT) .117
13.1 Objectives.117
13.2 Recommendations.117
14 SIS installation and commissioning.119
14.1 Objectives.119
14.2 Requirements.119
15 SIS safety validation.119
15.1 Objective.119
15.2 Requirements.119
16 SIS operation and maintenance.121
16.1 Objectives.121
16.2 Requirements.121
16.3 Proof testing and inspection .121
17 SIS modification.125
17.1 Objective.125
17.2 Requirements.125
18 SIS decommissioning.125
18.1 Objectives.125
18.2 Requirements.125
19 Information and documentation requirements .127
19.1 Objectives.127
19.2 Requirements.127
Annex A (informative) Example of techniques for calculating the probability of failure
on demand for a safety instrumented function.129
Annex B (informative) Typical SIS architecture development.131
Annex C (informative) Application features of a safety PLC .141
Annex D (informative) Example of SIS logic solver application software development
methodology .145
Annex E (informative) Example of development of externally configured diagnostics
for a safety-configured PE logic solver.155
Figure 1 – Overall framework of this standard.15
Figure 2 – BPCS function and initiating cause independence illustration.49
Figure 3 – Software development lifecycle (the V-model) .87
Figure C.1 – Logic solver .143
Figure E.1 – EWDT timing diagram .159
Table 1 – Typical Safety Manual organisation and contents .109
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61511-2 © IEC:2004 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FUNCTIONAL SAFETY –
SAFETY INSTRUMENTED SYSTEMS
FOR THE PROCESS INDUSTRY SECTOR –
Part 2: Guidelines for the application of IEC 61511-1
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61511-2 has been prepared by subcommittee 65A: System
aspects, of IEC technical committee 65: Industrial-process measurement and control.
This bilingual version (2004-07) replaces the English version.
The text of this standard is based on the following documents:
FDIS Report on voting
65A/387A/FDIS 65A/390/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
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61511-2 © IEC:2004 – 9 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 61511 series has been developed as a process sector implementation of IEC 61508
series.
IEC 61511 consists of the following parts, under the general title Functional safety – Safety
Instrumented Systems for the process industry sector (see Figure 1):
Part 1: Framework, definitions, system, hardware and software requirements
Part 2: Guidelines for the application of IEC 61511-1
Part 3: Guidance for the determination of the required safety integrity levels
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
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61511-2 © IEC:2004 – 11 –
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.
This International Standard addresses the application of safety instrumented systems for the
Process Industries. It also deals with the interface between safety instrumented systems and
other safety systems in requiring that a process hazard and risk assessment be carried out.
The safety instrumented system includes sensors, logic solvers and final elements.
This International Standard has two concepts, which are fundamental to its application; safety
lifecycle and safety integrity levels. The safety lifecycle forms the central framework which
links together most of the concepts in this International Standard.
The safety instrumented system logic solvers addressed include Electrical (E)/Electronic (E)/
and Programmable Electronic (PE) technology. Where other technologies are used for logic
solvers, the basic principles of this standard may also 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 the IEC 61508 series.
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 is used. The objective of this standard is to provide guidance on
how to comply with IEC 61511-1.
To facilitate use of this standard, the clause and subclause numbers provided are identical to
the corresponding normative text in 61511-1 (excluding the annexes).
In most situations, safety is best achieved by an inherently safe process design whenever
practicable, combined, if necessary, with a number of protective systems which rely on
different technologies (for example, chemical, mechanical, hydraulic, pneumatic, electrical,
electronic, thermodynamic (for example, flame arrestors), programmable electronic) which
manage any residual identified risk. Any safety strategy considers each individual safety
instrumented system in the context of the other protective systems. To facilitate this
approach, this standard
í requires that a hazard and risk assessment is carried out to identify the overall safety
requirements;
í requires that an allocation of the safety requirements to the safety functions and related
safety systems, such as the safety instrumented system(s), is carried out;
í works within a framework which is applicable to all instrumented methods of achieving
functional safety;
í details the use of certain activities, such as safety management, which may be applicable
to all methods of achieving functional safety.
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61511-2 © IEC:2004 – 13 –
This International Standard on safety instrumented systems for the process industry:
í addresses relevant safety lifecycle stages from initial concept, through design,
implementation, operation and maintenance and decommissioning;
í 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.
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61511-2 © IEC:2004 – 15 –
Support
Technical
Parts
requirements
PART 1
References
Clause 2
Development of the overall safety
PART 1
requirements (concept, scope definition,
hazard and risk assessment)
Definitions and
abbreviations
Clause 8
Clause 3
PART 1
PART 1
Conformance
Allocation of the safety requirements to
Clause 4
the safety instrumented functions and
development of safety requirements
PART 1
Specification
Management of
Clauses 9 and 10
functional safety
Clause 5
PART 1
PART 1
Safety lifecycle
Design phase for Design phase for
requirements
safety
safety
Clause 6
Instrumented instrumented
PART 1
system software
systems
Clause 11 Clause 12
Verification
Clause 7
PART 1
PART 1
Information
Factory acceptance testing,
requirements
installation and commissioning and
Clause 19
safety validation of safety
PART 1
instrumented systems
Clauses 13, 14, and 15
Differences
Annex A
PART 1
PART 1
Operation and maintenance,
modification and retrofit, Guidelines for the
decommissioning or disposal of application of part 1
safety instrumented systems
PART 2
Clauses 16, 17, and 18
Guidance for the
determination of the
required safety
integrity levels
PART 3
IEC 1827/03
Figure 1 – Overall framework of this standard
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61511-2 © IEC:2004 – 17 –
FUNCTIONAL SAFETY –
SAFETY INSTRUMENTED SYSTEMS
FOR THE PROCESS INDUSTRY SECTOR –
Part 2: Guidelines for the application of IEC 61511-1
1 Scope
IEC 61511-2 provides guidance on the specification, design, installation, operation and
maintenance of Safety Instrumented Functions and related safety instrumented system as
defined in IEC 61511-1. This standard has been organized so that each clause and subclause
number herein addresses the same clause number in IEC 61511-1 (with the exception of the
annexes).
2 Normative references
No further guidance provided.
3 Terms, definitions and abbreviations
No further guidance provided except for 3.2.68 and 3.2.71 of IEC 61511-1.
3.2.68 A safety function should prevent a specified hazardous event. For example, “prevent
the pressure in vessel #ABC456 exceeding 100 bar.” A safety function may be achieved by
a) a single safety instrumented system (SIS), or
b) one or more safety instrumented systems and/or other layers of protection.
In case b), each safety instrumented system or other layer of protection has to be capable of
achieving the safety function and the overall combination has to achieve the required risk
reduction (process safety target).
3.2.71 Safety instrumented functions are derived from the safety function, have an
associated safety integrity level (SIL) and are carried out by a specific safety instrumented
system (SIS). For example, “close valve #XY123 within 5 s when pressure in vessel #ABC456
reaches 100 bar”. Note that components of a safety instrumented system may be used by
more than one safety instrumented function.
4 Conformance to this International Standard
No further guidance provided.
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61511-2 © IEC:2004 – 19 –
5 Management of functional safety
5.1 Objective
The objective of Clause 5 of IEC 61511-1 is to provide requirements for implementing the
management activities that are necessary to ensure that the functional safety objectives
are met.
5.2 Requirements
5.2.1 General
5.2.1.1 No further guidance provided.
5.2.1.2 When an organization has responsibility for one or more activities necessary for
functional safety and that organization works according to quality assurance procedures, then
many of these activities described in this clause will already be carried out for the purposes of
quality. Where this is the case, it may be unnecessary to repeat these activities for the
purposes of functional safety. In such cases, the quality assurance procedures should be
reviewed to establish that they are suitable so that the objectives of functional safety will
be achieved.
5.2.2 Organization and resources
5.2.2.1 The organizational structure associated with safety instrumented systems within a
Company/Site/Plant/Project should be defined and the roles and responsibilities of each
element clearly understood and communicated. Within the structure, individual roles, including
their description and purpose should be identified. For each role, unambiguous
accountabilities should be identified; and specific responsibilities should be recognised. In
addition, whom the individual reports to and who makes the appointment should be identified.
The intent is to ensure that everyone in an organization understands their role and
responsibilities for safety instrumented systems.
5.2.2.2 The skills and knowledge required to implement any of the activities of the safety life
cycle relating to the safety instrumented systems should be identified; and for each skill, the
required competency levels should be defined. Resources should be assessed against each
skill for competency and also the number of people per skill required. When differences are
identified, development plans should be established to enable the required competency levels
to be achieved in a timely manner. When shortages of skills arise, suitably qualified and
experienced personnel may be recruited or contracted.
5.2.3 Risk evaluation and risk management
The requirement stated in 5.2.3 of IEC 61511 is that hazards are identified, risks evaluated
and the necessary risk reduction is determined. It is recognized that there are numerous
different methodologies available for conducting these evaluations. IEC 61511-1 does not
endorse any particular methodology. Instead, the reader is encouraged to review a number of
methodologies on this issue in IEC 61511-3. See 8.2.1 for further guidance.
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61511-2 © IEC:2004 – 21 –
5.2.4 Planning
The intent of this subclause is to ensure that, within the overall project, adequate safety
planning is conducted so that all of the required activities during each phase of the lifecycle
(for example, engineering design, plant operation) are addressed. The standard does not
require any particular structure for these planning activities, but it does require periodic
update or revie
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