SIST EN 13237:2003
(Main)Potentially explosive atmospheres - Terms and definitions for equipment and protective systems intended for use in potentially explosive atmospheres
Potentially explosive atmospheres - Terms and definitions for equipment and protective systems intended for use in potentially explosive atmospheres
This European Standard specifies terms and definitions (vocabulary) to be used in suitable standards dealing with equipment and protective systems intended for use in potentially explosive atmospheres.
Explosionsgefährdete Bereiche - Begriffe für Geräte und Schutzsysteme zur Verwendung in explosionsgefährdeten Bereichen
Diese Europäische Norm legt Begriffe für die Anwendung in Normen fest, die sich mit Geräten und Schutzsystemen befassen, die für den Einsatz in explosionsgefährdeten Bereichen bestimmt sind.
ANMERKUNG Die Richtlinie 94/9/EG über Geräte und Schutzsysteme zur bestimmungsgemäßen Verwendung in explosionsgefährdeten Bereichen kann auf in dieser Norm behandelte Bauarten von Maschinen oder Einrichtungen anwendbar sein. Die vorliegende Norm ist nicht dafür vorgesehen, damit Übereinstimmung mit den grundlegenden Gesundheits- und Sicherheitsanforderungen der Richtlinie 94/9/EG festzustellen.
Atmospheres explosibles - Termes et définitions pour les appareils et systemes de protection destinés a etre utilisés en atmospheres explosibles
La présente norme européenne spécifie les termes et définitions (vocabulaire) a employer dans les normes spécifiques concernant les appareils et systemes de protection destinés a etre utilisés en atmospheres explosibles.
NOTE La Directive 94/9/CE concernant les appareils et systemes de protection destinés a etre utilisés en atmospheres explosibles peut etre applicable au type de machine ou équipement couvert par cette norme européenne. La présente norme n'est pas destinée a fournir des mesures pour satisfaire les exigences essentielles de santé et de sécurité de la Directive 94/9/CE.
Potencialno eksplozivne atmosfere - Izrazi in definicije za opremo in zaščitne sisteme namenjene za uporabo v potencialno eksplozivnih atmosferah
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 13237:2003
01-december-2003
3RWHQFLDOQRHNVSOR]LYQHDWPRVIHUH,]UD]LLQGHILQLFLMH]DRSUHPRLQ]DãþLWQH
VLVWHPHQDPHQMHQH]DXSRUDERYSRWHQFLDOQRHNVSOR]LYQLKDWPRVIHUDK
Potentially explosive atmospheres - Terms and definitions for equipment and protective
systems intended for use in potentially explosive atmospheres
Explosionsgefährdete Bereiche - Begriffe für Geräte und Schutzsysteme zur
Verwendung in explosionsgefährdeten Bereichen
Atmospheres explosibles - Termes et définitions pour les appareils et systemes de
protection destinés a etre utilisés en atmospheres explosibles
Ta slovenski standard je istoveten z: EN 13237:2003
ICS:
01.040.13 Varstvo okolja in zdravja. Environment and health
Varnost (Slovarji) protection. Safety
(Vocabularies)
13.230 Varstvo pred eksplozijo Explosion protection
SIST EN 13237:2003 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 13237:2003
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SIST EN 13237:2003
EUROPEAN STANDARD
EN 13237
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2003
ICS 01.040.13; 01.040.29; 13.230; 29.260.20
English version
Potentially explosive atmospheres - Terms and definitions for
equipment and protective systems intended for use in potentially
explosive atmospheres
Atmosphères explosibles - Termes et définitions pour les Explosionsgefährdete Bereiche - Bennenungen und
appareils et systèmes de protection destinés à être utilisés Definitionen für Geräte und Schutzsysteme zur
en atmosphères explosibles Verwendung in explosionsgefährdeten Bereichen
This European Standard was approved by CEN on 9 June 2003.
CEN 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 Management Centre or to any CEN 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 CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2003 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13237:2003 E
worldwide for CEN national Members.
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Contents
Foreword.3
Introduction .4
1 Scope .4
2 Normative references .4
3 Terms and definitions.5
Annex A (informative) Definitions from the Directive 94/9/EC and corrigenda.18
A.1 Explosive atmosphere.18
A.2 Potentially explosive atmosphere.18
A.3 Equipment.18
A.4 Intended use.18
A.5 Protective systems .18
A.6 Equipment group .18
A.6.1 Equipment group I .19
A.6.2 Equipment group II .19
A.7 Component .20
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other
provisions of EU Directives .21
Bibliography .23
2
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Foreword
This document (EN 13237:2003) has been prepared by Technical Committee CEN/TC 305 "Potentially explosive
atmospheres - Explosion prevention and protection", the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by December 2003, and conflicting national standards shall be withdrawn at the latest
by December 2003.
This document has been prepared under a mandate given to CEN by the European Commission and the European
Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this document.
Annex A is informative.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,
Slovakia, Spain, Sweden, Switzerland and the United Kingdom.
3
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Introduction
This European Standard has been produced to assist designers, manufacturers and other interested parties to use
harmonised terms and definitions (vocabulary) for equipment and protective systems intended for use in potentially
explosive atmospheres. It describes the vocabulary to be used to give all standards in this area an overall
uniformity of terminology. Throughout this European Standard, the only hazard considered is the explosion of an
explosive atmosphere.
1 Scope
This European Standard specifies terms and definitions (vocabulary) to be used in suitable standards dealing with
equipment and protective systems intended for use in potentially explosive atmospheres.
NOTE Directive 94/9/EC concerning equipment and protective systems intended for use in potentially explosive
atmospheres can be applicable to the type of machine or equipment covered by this European Standard. The
present standard is not intended to provide means of complying with the essential health and safety requirements
of Directive 94/9/EC.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN 746-2:1997, Industrial thermoprocessing equipment - Part 2: Safety requirements for combustion and fuel
handling systems.
EN 1127-1:1997, Explosive atmospheres - Explosion prevention and protection – Part 1: Basic concepts and
methodology.
EN 1127-2 2002, Explosive atmospheres - Explosion prevention and protection – Part 2: Basic concepts and
methodology for mining.
EN 12874:2001, Flame arresters – Performance requirements, test methods and limits for use.
EN 13980:2002, Potentially explosive atmospheres – Application of quality systems.
prEN 14373:2002, Explosion suppression systems.
EN 50014:1997, Electrical apparatus for potentially explosive atmospheres - General requirements.
EN 50015:1998, Electrical apparatus for potentially explosive atmospheres - Oil-immersion "o".
EN 50016:1995, Electrical apparatus for potentially explosive atmospheres - Pressurized apparatus "p".
EN 50017:1998, Electrical apparatus for potentially explosive atmospheres – Powder filling "q".
EN 50018:1994, Electrical apparatus for potentially explosive atmospheres - Flameproof enclosure "d".
EN 50019:1994, Electrical apparatus for potentially explosive atmospheres - Increased safety "e".
EN 50020:1994, Electrical apparatus for potentially explosive atmospheres – Intrinsic safety “i”.
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EN 50021:1999, Electrical apparatus for potentially explosive atmospheres – Type of protection “n”.
EN 50028:1987, Electrical apparatus for potentially explosive atmospheres – Encapsulation “m”.
EN 50281-1-1:1998, Electrical apparatus for use in the presence of combustible dust - Part 1-1: Electrical
apparatus protected by enclosures; Construction and testing.
EN 50281-1-2:1997, Electrical apparatus for use in the presence of combustible dust - Part 1-2: Electrical
apparatus protected by enclosures; Selection, installation and maintenance.
EN 50281-2-1:1998, Electrical apparatus for use in the presence of combustible dust – Part 2-1: test methods –
Methods of determining the minimum ignition temperature of dust.
EN 60079-10:1996, Electrical apparatus for explosive gas atmospheres - Part 10: Classification of hazardous areas
(IEC 60079-10:1995).
EN 60529:1991, Degree of protection provided by enclosures (IP code) (IEC 60529:1989 + A1 1999).
EN 61779-1:2000, Electrical apparatus for the detection and measurement of flammable gases – Part 1: General
requirements and test methods (IEC 61779-1:1998, modified).
EN ISO 9000:2000, Quality management systems – Fundamentals and vocabulary (ISO 9000:2000).
EN ISO 13702:1999, Petroleum and natural gas industries – Control and migration of fires and explosions on
offshore production installations – Requirements and guidelines (ISO 13702:1999).
EN ISO 13736:1997, Petroleum products and other liquids – Determination of flash point – Abel closed cup method
(ISO 13736:1997).
ISO 4225:1994, Air quality - General aspects – Vocabulary.
IEC 60050-191:1990, International Electrotechnical Vocabulary - Chapter 191: Dependability and quality of service.
IEC 60079-4:1975, Electrical apparatus for explosive gas atmospheres - Part 4: Method of test for ignition
temperature.
IEC 60204-32:1998, Safety of machinery – Electrical equipment of machines – Part 32: Requirements for hoisting
machines.
3 Terms and definitions
3.1
ambient atmosphere
normal atmosphere surrounding the equipment and protection system
3.2
ambient temperature
temperature of the air or other medium where the equipment is to be used (IEV 426-01-04) (IEC 60204-32:1998)
NOTE For the application of the Directive 94/9/EC only air is considered.
3.3
cable entry
device permitting the introduction of one or more electric and/or fibre optics cables into an electrical apparatus so
as to maintain the relevant type of protection (EN 50014:1997)
3.4
clamping device
element of a cable entry for preventing tension or torsion in the cable from being transmitted to the connections
(EN 50014:1997)
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3.5
clearance
shortest distance measured in air between two conductive parts (EN 50019:1994)
3.6
combustible dust
dust, fibres or flyings that can burn or glow in air and could form explosive mixtures with air at atmospheric
pressure and normal temperatures (EN 50281-1-1:1998)
3.7
compound
thermosetting, thermoplastic, and elastomeric materials with or without fillers and/or additives, are considered after
their solidification to be compounds (EN 50028:1987)
3.8
compression element
element of a cable entry acting on the sealing ring to enable the latter to fulfil its function (EN 50014:1997)
3.9
conductive dust
3
dust, fibres or flyings with electrical resistivity equal to or less than 10 50281-1-1:1998)
3.10
conduit entry
means of introducing a conduit into an electrical apparatus so as to maintain the relevant type of protection
(EN 50014:1997)
3.11
connection facilities
terminals, screws or other parts, used for the electrical connection of conductors of external circuits (EN 50014:
1997)
3.12
containment system
part of the apparatus containing the flammable gas, vapour or liquid that may constitute an internal source of
release (EN 50016:1995)
NOTE This is related to electrical apparatus where a type of protection "pressurisation" is used.
3.13
continuous grade of release
release which is continuous or is expected to occur for long periods (EN 60079-10:1996)
3.14
creepage distance
shortest distance along the surface of an insulating material between two conductive parts (EN 50019:1994)
3.15
deflagration
explosion propagating at subsonic velocity (EN 1127-1:1997)
3.16
degree of protection
extent of protection provided by an enclosure against access to hazardous parts, against ingress of solid foreign
objects and/or ingress of water and verified by standardised test methods (EN 60529:1991)
3.17
degree of protection of enclosure (IP)
numerical classification according to EN 60529:1991 preceded by the symbol IP applied to the enclosure of
electrical apparatus to provide for
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protection of persons against contact with or approach to live parts and against contact with moving parts
(other than smooth rotating shafts and the like) inside the enclosure;
protection of the electrical apparatus against ingress of solid foreign objects and,
where indicated by the classification, protection of the electrical apparatus against harmful ingress of water
NOTE The enclosure which provides the degree of protection IP is not necessarily identical with the types of protection as
defined in EN 50014:1997 under 1.2).
3.18
detonation
explosion propagating at supersonic velocity and characterised by a shock wave (EN 1127-1:1997)
3.19
dust
small solid particles in the atmosphere which settle out under their own weight, but which may remain suspended in
air for some time (includes dust and grit, as defined in ISO 4225:1994 (EN 50281-1-2:1998)
NOTE Generally maximum particle size will not exceed 500 μm.
3.20
dust ignition protection
all relevant measures specified in the EN 50281 series of standards (e.g. dust ingress protection and surface
temperature limitation) applied to electrical apparatus to avoid ignition of a dust layer or cloud (EN 50281-1-1:1998)
3.21
dust protected enclosure
enclosure in which the ingress of dust is not totally prevented but dust does not enter in sufficient quantity to
interfere with the safe operation of the equipment; dust shall not accumulate in a position within the enclosure
where it is liable to cause an ignition hazard (EN 50281-1-1:1998)
3.22
dust tight enclosure
enclosure capable of preventing the ingress of all observable dust particles (EN 50281-1-1:1998)
3.23
electrical apparatus
items applied as a whole or in part for the utilisation of electrical energy. These include, among others, items for the
generation, transmission, distribution, storage, measurement, regulation, conversion and consumption of electrical
energy and items for telecommunications. (EN 50014:1997)
3.24
encapsulation
process of applying the compound to enclose any electrical device(s) by suitable means such as embedding and
potting (EN 50028:1987)
3.25
enclosure
(of equipment or protective system) all the walls including doors, covers, cable entries, rods, spindles and shafts
which contribute to the type of protection and/or their degree of protection (IP) of the electrical apparatus
(EN 50014:1997)
3.26
equipment category
within an equipment group, a category is the classification according to the required level of protection. (See A.6).
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3.27
Ex component
part of electrical apparatus or module (other than an Ex cable entry), marked with the symbol "U", which is not
intended to be used alone in such atmospheres and requires additional certification when incorporated into
electrical apparatus or systems for use in potentially explosive atmospheres (EN 50014:1997)
3.28
explosion
abrupt oxidation or decomposition reaction producing an increase in temperature, pressure or in both
simultaneously (EN 1127-1:1997)
3.29
explosions limits
limits of explosion range (EN 1127-1:1997)
3.30
explosion points
lower and upper explosion points (EN 1127-1:1997)
3.31
explosion-pressure-resistant
property of vessels and equipment designed to withstand the expected explosion pressure without becoming
permanently deformed (EN 1127-1:1997)
3.32
explosion-pressure-shock resistant
property of vessels and equipment designed to withstand the expected explosion pressure without rupturing, but
allowing permanent deformation (EN 1127-1:1997)
3.33
explosion range
range of the concentration of a flammable substance in air, within which an explosion can occur (EN 1127-1:1997)
3.34
explosion resistant
property of vessels and equipment designed to be either explosion-pressure-resistant or explosion-pressure-shock
resistant (EN 1127-1:1997)
3.35
explosion suppression system
composite arrangement of devices to detect automatically the onset of an explosion and initiate the deployment of
suppressant to limit destructive effects of an explosion (prEN 14373:2002)
3.36
explosion venting system
system designed to prevent an excessive pressure rise in a confined explosive atmosphere by using of vents to
allow the escape of substances resulting from explosion
3.37
explosive dust atmosphere
mixture with air under atmospheric conditions, of flammable substances in the form of dust or fibres in which, after
ignition, combustion spreads throughout the unconsumed mixture (see IEV 426-02-04)
3.38
explosive gas atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gas or vapour , in which,
after ignition, combustion spreads throughout the unconsumed mixture (EN 60079-10:1996)
NOTE Although a mixture which has a concentration above the upper explosive limit (UEL) is not an explosive gas
atmosphere, it can readily become so and, in certain cases for area classification purposes it is advisable to consider it as an
explosive gas atmosphere.
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3.39
explosive test mixture
specified explosive mixture used for the testing of electrical apparatus for potentially explosive atmospheres
(EN 50014:1997)
3.40
firedamp
any potentially explosive mixture of gases or any flammable gas naturally occurring in a mine (EN 1127-2:2002)
NOTE Because firedamp normally consists mainly of methane, the term ‘firedamp’ and ‘methane’ are used frequently in
mining practice as synonyms.
3.41
flame arrester
device fitted to the opening of an enclosure or to the connecting pipework of a system of enclosures and whose
intended function is to allow flow, but prevent the transmission of flame (EN 12874:2001)
NOTE This device should not be confused with a fire barrier, which is ineffective in case of explosion.
3.42
flameproof enclosure
type of protection in which the parts which can ignite an explosive atmosphere are placed in an enclosure which
can withstand the pressure developed during an internal explosion of an explosive mixture and which prevents the
transmission or the explosion to the explosive atmosphere surrounding the enclosure (EN 50018:1994)
3.43
flameproof joint
place where corresponding surfaces of two parts of an enclosure come together, or the conjunction of enclosures,
and prevent the transmission of an internal explosion to the explosive atmosphere surrounding the enclosure
(EN 50018:1994)
3.44
flammable gas or vapour
gas or vapour which, when mixed with air in certain proportions, will form an explosive gas atmosphere
(EN 60079-10:1996)
3.45
flammable liquid
liquid capable of producing a flammable vapour under any foreseeable operating condition (EN 60079-10:1996)
3.46
flammable material
material which is flammable of itself, or is capable of producing a flammable gas, vapour or mist
(EN 60079-10:1996)
3.47
flammable mist
droplets of flammable liquid, dispersed in air so as to form an explosive atmosphere (EN 60079-10:1996)
3.48
flammable substance
substance in the form of gas, vapour, liquid, solid, or mixtures of these, able to undergo an exothermic reaction with
air when ignited (EN 1127-1:1997)
3.49
flash point
minimum temperature at which, under specific test conditions, a liquid gives off sufficient combustible gas or vapour
to ignite momentarily on application of an effective ignition source (EN 1127-1:1997)
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3.50
gap of flameproof joint
distance between the corresponding surfaces of a flameproof joint when the electrical apparatus enclosure has
been assembled. For cylindrical surfaces, forming cylindrical joints, the gap is the difference between the diameters
of the bore and the cylindrical component (EN 50018:1994)
3.51
grades of release
there are three basic grades of release, as listed below in order of decreasing frequency and likelihood of the
explosive gas atmosphere being present: a) continuous grade, see 3.13; b) primary grade, see 3.93; c) secondary
grade, see 3.104. A source of release may give rise to any one of these grades of release, or to a combination of
more than one (EN 60079-10:1996)
3.52
group (of an electrical apparatus for explosive atmospheres)
classification of electrical apparatus related to the explosive atmosphere for which it is to be used (EN 50014:1997)
3.53
group I apparatus
electrical apparatus for mines susceptible to firedamp (EN 61779-1:2000)
NOTE See also the definition of "Group" in annex A.
3.54
group II apparatus
electrical apparatus for places with a potentially explosive atmosphere, other than mines susceptible to firedamp
(EN 61779-1:2000)
NOTE See also the definition of "Group" in annex A.
3.55
hazardous area
area in which an explosive atmosphere is present, or may be expected to be present in quantities such as to
require special precautions for the construction, installation and use of equipment
NOTE 1 Layers, deposits and heaps of combustible dust should be considered as a source which can form an explosive
atmosphere.
NOTE 2 Normal operation means a situation where installations perform within their design parameters.
NOTE 3 The terms “flammable” and “combustible” are used as synonymous.
3.56
hazardous condition 1
underground parts of mines and those parts of surface installations of such mines endangered by firedamp and/or
flammable dusts
NOTE This includes underworkings where the concentration of firedamp is within the explosion range e.g. by malfunction
(e.g. breakdown of fans), by sudden release of large amounts of firedamp (gas blow, gas eruption) or by increase of gassing
(due to decrease of air pressure or increased coaling) (EN 1127-2:2002).
3.57
hazardous condition 2
underground parts of mines and those parts of surface installations of such mines likely to be endangered by
firedamp and/or flammable dusts
NOTE This includes underworkings where the concentration of firedamp in ventilation air flow or firedamp drainage
systems is outside the explosion range (EN 1127-2: 2002).
3.58
hybrid mixture
mixture of flammable substances with air in different physical states
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NOTE Examples for hybrid mixtures are mixtures of methane, coal dust and air or mixtures of gasoline vapour and
gasoline droplets with air (EN 1127-1:1997).
3.59
ignition capable apparatus
apparatus which in normal operation constitutes a source of ignition for a specified explosive atmosphere. This
includes electrical apparatus not protected by a type of protection listed in 1.8.1 of EN 50016:1995
3.60
ignition of a dust cloud
initiation of an explosion by the transfer of energy to a dust cloud in air (EN 50281-2-1:1998)
3.61
ignition of a dust layer
ignition shall be considered to have occurred if glowing or flaming is initiated in the material, or a temperature of
450 °C or more, or a temperature rise of 250 K or more above the temperature of the prescribed hot surface, is
measured in the test (EN 50281-2-1:1998)
3.62
ignition source
any source with sufficient energy to initiate combustion (EN ISO 13702:1999)
3.63
ignition temperature of a dust cloud
lowest temperature of the hot inner wall of a furnace at which ignition occurs in a dust cloud in air contained therein
(EN 50281-2-1:1998)
NOTE When carrying out this test, it is essential that all necessary precautions be taken to safeguard the health of
personnel, for example, against the risk of fire, explosion, inhalation of smoke or any toxic products of combustion.
3.64
limiting oxygen concentration (LOC)
maximum oxygen concentration in a mixture of a flammable substance and air and an inert gas, in which an
explosion will not occur, determined under specified test conditions (EN 1127-1:1997)
3.65
minimum ignition temperature of a dust layer
lowest temperature of a hot surface at which ignition occurs in a dust layer of specified thickness on this hot
surface (EN 50281-2-1:1998)
NOTE 1 Because of the wide range of processes in industry, the ignition of dust layers may be dependent upon local
conditions. This method of test is not necessarily representative of all industrial conditions, where account may need to be taken
of such factors as the presence of thick layers of dust and of the distribution of temperature in environment.
NOTE 2 When carrying out this test, it is essential that all necessary precautions be taken to safeguard the health of
personnel, for example, against the risk of fire, explosion, inhalation of smoke or any toxic products of combustion.
3.66
ignition temperature of an explosive atmosphere
lowest temperature of a heated surface at which, under specified conditions the ignition of an explosive
atmosphere will occur
NOTE IEC 60079-4:1975 is only applicable to gas and vapour. For dust, see 3.63.
3.67
increased safety "e"
type of protection applied to electrical apparatus in which additional measures are applied so as to give increased
security against the possibility of excessive temperatures and of the occurrence of arcs and sparks in normal
service or under specified abnormal conditions (IEV 426-08-01) (EN 50019:1994)
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3.68
inert gas
non-flammable gas which will not support combustion and does not react to produce a flammable gas
3.69
inerting
addition of inert substances to prevent explosive atmospheres (EN 1127-1:1997)
3.70
intended operating conditions
duty assigned to equipment or protective system by the manufacturer and based on rated values given by the
manufacturer
NOTE For electrical equipment, “intended operating conditions” is equivalent to “rating”
3.71
intrinsically safe apparatus
electrical apparatus in which all the circuits are intrinsically safe (EN 50020:1994)
3.72
intrinsically-safe circuit
circuit in which any spark or any thermal effect produced in the conditions specified in this standard, which include
normal operation and specified fault conditions, is not capable of causing ignition of a given explosive gas
atmosphere (EN 50020:1994)
3.73
length (width) of flameproof joint (length of flame path)
shortest path through a flameproof joint from the inside to the outside of a flameproof enclosure (EN 50018:1994)
3.74
lower explosion limit
lower limit of the explosion range (EN 1127-1:1997)
3.75
lower explosion point
temperature of the combustible liquid at which the concentration of the saturated vapour in air is equal to the lower
explosion limit (EN 1127-1:1997)
3.76
lower flammable limit
lowest concentration of fuel in air at which the air/fuel mixture is flammable (EN 746-2:1997)
NOTE See also the definition of “flammable substance”.
3.77
maintainability
ability of equipment, protective system or component under given conditions of intended use to be reta
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