EN 50495:2010

SLOVENSKI STANDARD
01-junij-2010
Varnostne naprave, potrebne za varno obratovanje opreme glede tveganja
eksplozije
Safety devices required for the safe functioning of equipment with respect to explosion
risks
Sicherheitseinrichtungen für den sicheren Betrieb von Geräten im Hinblick auf
Explosionsgefahren
Dispositifs de sécurité nécessaires pour le fonctionnement sûr d'un matériel vis-à-vis des
risques d'explosion
Ta slovenski standard je istoveten z: EN 50495:2010
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 50495
NORME EUROPÉENNE
February 2010
EUROPÄISCHE NORM
ICS 13.230; 29.260.30
English version
Safety devices required for the safe functioning of equipment
with respect to explosion risks

Dispositifs de sécurité nécessaires  Sicherheitseinrichtungen
pour le fonctionnement sûr d'un matériel für den sicheren Betrieb von Geräten
vis-à-vis des risques d'explosion im Hinblick auf Explosionsgefahren

This European Standard was approved by CENELEC on 2009-12-01. 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, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels

© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50495:2010 E
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 31, Electrical apparatus
for potentially explosive atmospheres. The text of the draft was submitted to the formal vote and was
approved by CENELEC as EN 50495 on 2009-12-01.
This European Standard is to be read in conjunction with the European Standards for the specific types of
protection listed in EN 60079 or EN 61241 series of standards.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent rights.
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) 2010-12-01
– latest date by which the national standards conflicting

with the EN have to be withdrawn
(dow) 2012-12-01
This European Standard has been prepared under a mandate given to CENELEC by the European
Commission and the European Free Trade Association and covers essential requirements of EC Directive
94/9/EC. See Annex ZZ.
_________
– 3 – EN 50495:2010
Contents
Introduction . 4
1 Scope . 5
2 Normative references . 6
3 Terms and definitions . 7
4 Ignition prevention by safety devices . 10
4.1 General concept of ignition risk reduction . 10
4.2 Selection of a safety device . 11
5 Functional requirements for a safety device . 11
5.1 General requirements . 11
5.2 Special requirements for safety components . 13
5.3 Requirements for achieving the Safety Integrity Level (SIL) . 13
6 Tests . 15
6.1 Type tests . 15
6.2 Routine tests . 16
6.3 Regular functional proof tests . 16
7 Marking . 16
8 Safety instructions . 17
Annex A (informative) Example of an assessment procedure for a simple safety device . 18
Annex B (informative) Example of an assessment procedure for the hardware safety integrity of a
safety device . 19
Annex C (informative) Example of determining the hardware safety integrity level . 24
Annex D (informative) Examples for safety devices . 33
Annex E (informative) Basic concept for safety devices . 34
Annex ZZ (informative) Coverage of Essential Requirements of EC Directives. 36
Bibliography . 37
Tables
Table 1 – Requirements for Safety Integrity Level and Fault Tolerance of a safety device . 11
Table B.1 – Failure rates assuming a series failure model . 20
Table B.2 – Safety Integrity Levels: Target failure measures for a safety function . 22
Table B.3 – Hardware safety integrity: Architectural constrains on Type A or B safety-related subsystems . 23
Table C.1 – Total hardware failure rates . 31
Table E.1 – Increase of the failure tolerance of equipment by the control of a safety device . 34
Table E.2 – Classified area, in which the ignition probability of controlled equipment would lead to a
tolerable risk . 35
Table E.3 – Required SIL and HFT of a safety device for the control of equipment . 35

Introduction
Safety devices, controlling devices and regulating devices which are used for the protection concept of
equipment for explosive atmospheres, shall function reliably for the intended purpose. This shall be
expressed in terms of some measure of confidence that the devices will be able to maintain a required level
of safety at all times. This measure of confidence needs to be in conformity with [1], CENELEC standards of
the series EN 60079 and EN 61241 for apparatus for use in explosive atmospheres and relevant control
standards.
CENELEC identified the need for research to determine whether existing and proposed standards in the field
of safety-related control systems were suitable for this purpose. Research proposals on this topic were
invited under the Standardisation, Measurement and Testing (SMT) Programme of the EU-commission and
the SAFEC project was selected for funding (contract SMT4-CT98-2255). The project was a 12 month
project which began in January 1999. The SAFEC partners were the Health and Safety Laboratory (HSL) of
the Health and Safety Executive in the UK (the project coordinator), the Deutsche Montan Technologie
(DMT) in Germany, the National Institute for Industrial Environment and Risks (INERIS) in France and the
Laboratorio Oficial J.M. Madariaga (LOM) in Spain. The result of this project is summarised in [2] and
recommends the application of Safety Integrity Levels as specified in EN 61508-1 for safety devices. A short
description of the basic concept is provided in Annex E of this standard.

– 5 – EN 50495:2010
1 Scope
This European Standard specifies the requirements of electrical safety devices, which are used to avoid
potential ignition sources of equipment in explosive atmospheres.
This also includes safety devices, which are operated outside areas with explosive atmospheres, to
guarantee the safe function of equipment with respect to explosion hazards.
NOTE 1 This European Standard can also be used to design and assess safety devices for protective systems.
Electrical equipment, which is intended for use in explosive atmospheres, may rely on the correct operation
of safety devices which for example maintain certain characteristics of the equipment within acceptable
limits. Examples of such safety devices are motor protection devices (to limit temperature rise during stall
conditions) and controlling devices for pressurisation protection.
By means of control or monitoring devices, sources of ignition can be avoided. Therefore these devices shall
execute the appropriate measures in the appropriate reaction time, for example the initiation of an alarm or
an automatic shut down.
NOTE 2 Some potential ignition sources might not be controllable by safety devices, e.g. electrostatic discharges, ignition sparks
caused by mechanical impact. Also some protection measures might not be controllable by safety devices, e.g.
flameproof enclosures.
Safety devices, whose safety function can not adequately be specified under the existing EN 60079 or
EN 61241 series of standards, shall additionally be designed according to the requirements of this standard.
Generally for complex safety devices appropriate design requirements are not provided in the existing types
of protection (see 3.13 for the definition of a complex device).
NOTE 3 In general the levels of safety required by this standard are considered to be equivalent to those provided by conformity
to EN 60079-0 or EN 61241-0. No increase or decrease of safety is intended or required. Similarly neither increase nor
decrease of safety with respect to EN 61508 series is intended.
Safety devices can be classified in 2 types:
a) devices, which are included as component in the equipment under control (see 3.8). The combined
apparatus is considered as equipment.
EXAMPLES
- thermal switch or thermistor to avoid overheating,
- temperature monitoring devices to control the surface temperature.
b) devices, which are installed separately from the equipment under control and considered as
associated apparatus exclusively for a specific type of protection or specific equipment under control.
The combined apparatus is considered as a system.
EXAMPLES
- external control devices or safety related parts of a control system for type of protection pressurisation,
- overload protective device for electric motors of type of protection Ex e ‘Increased Safety’,
- control devices for battery charging equipment (protection against overcharging or deep discharging),
- level detectors for the control of submersible pumps.
Exclusions from this standard:
Safety devices, where the safety function is adequately covered in the existing standards of EN 60079 and
EN 61241 series do not need any additional assessment according to this standard.
EXAMPLES Intrinsically safe associated apparatus, fuses, electromechanical overload protection, simple thermal protection devices
(e.g. thermal fuses, thermal switches).
The standard does not include devices or systems to prevent the occurrence of explosive atmospheres, e.g.
inerting systems, ventilation in workplaces and containers/vessels.

Gas detectors, which are covered under EN 61779 series, EN 50271 or EN 50402 are also excluded from
the scope of this standard.
This standard does not deal with protection by control of ignition source ‘b’ for non-electrical equipment as
defined in EN 13463-6.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
docume
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