SIST-TP CLC/R0BT-004:2004

SLOVENSKI SIST-TP CLC/R0BT-004:2004

STANDARD
september 2004
Direktive ES, funkcionalna varnost in vloga standardizacije CENELEC
EC Directives, functional safety and the role of CENELEC standardization
ICS 01.120; 13.110 Referenčna številka
SIST-TP CLC/R0BT-004:2004(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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CENELEC R0BT-004
REPORT October 2001
English version
EC Directives, functional safety
and the role of CENELEC standardization
This CENELEC Report has been prepared by the CENELEC BTWG 99-2, "Functional safety". It was
approved for publication by the CENELEC Technical Board on 2000-04-01.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, 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
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. R0BT-004:2001 E

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R0BT-004:2001 - 2 -
Foreword
This CENELEC Report on functional safety has been prepared by CENELEC BTWG 99-2,
Functional safety.
This report provides a definition of functional safety and considers the relationship between
functional safety and CENELEC standards including those that have been harmonized under
relevant EC directives e.g. the LVD, ATEX, MDD, MD, EMC.
The text of the draft was approved by the CENELEC Technical Board for final editing and
publication on 2000-04-01.
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1 Task
Arising from the background given in annex A, CENELEC BTWG 99-2 was asked to prepare
a report on functional safety which addressed:-
� the definition of functional safety;
� the way in which functional safety is being handled, from a CENELEC standardization
viewpoint, under various EC Directives but specifically those relevant for the
electrotechnical field such as the LVD, ATEX, MDD, MD, EMC.;
� the implications of functional safety related to safety-related EMC-immunity within the
scope of the Low Voltage Directive and other EC Directives from a CENELEC
standardization viewpoint.
2 Functional safety
2.1 Definition of functional safety
Functional safety is, for the purpose of this Report, defined as:-
“Part of the overall safety relating to the equipment and its associated control system which
depends on the correct functioning of electrical, electronic, programmable electronic
(E/E/PE) safety-related systems, other technology safety related systems”, external risk
reduction facilities.
This definition is based on IEC 61508-4 (see Annex B for an overview of IEC 61508).
2.2 What is functional safety?
The key to understanding functional safety is the concept of a safety-related system. The
term ‘safety related’ is used to describe those systems (i.e. a safety-related system) which
are required to perform a specific function or functions (i.e. safety functions) to reduce risks
to a level which is considered tolerable.
The key to the understanding of safety-related systems is the concept that a safety-related
system carries out safety functions and that a safety function should be specified both in
terms of its functionality (what the function does) and its safety integrity (the probability of a
safety function being performed satisfactorily).
Safety-related systems may be implemented in any technology, but in the context of
CENELEC standardisation the primary concern are those which are implemented in E/E/PE
technologies.
The following are examples of E/E/PE safety-related systems:
� an emergency shut-down system in a hazardous chemical process plant;
� a crane safe load indicator;
� a railway signalling system;

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R0BT-004:2001 - 4 -
� guard interlocking systems and emergency stopping systems for machinery and
household appliances;
� a variable speed motor drive used to control a restricted speed as a means of protection;
� the system for interlocking and controlling the exposure dose of a medical radiotherapy
machine.
� the indicator lights, anti-lock braking, and engine-management systems on a motor car.
It should be noted that an E/E/PE safety-related system covers all parts of the system that
implements the safety function (i.e. from sensor, control logic, communication systems
through to the final actuator).
2.3 Safety integrity
The specification for safety integrity is derived by undertaking a risk analysis and determining
the necessary risk reduction t
...