oSIST prEN 13237:2022
(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 document 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 2014/34/EU 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 document. This document is not intended to provide means of complying with the essential health and safety requirements of Directive 2014/34/EU.
Explosionsgefährdete Bereiche - Begriffe für Geräte und Schutzsysteme zur Verwendung in explosionsgefährdeten Bereichen
Dieses Dokument 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 2014/34/EU über Geräte und Schutzsysteme zur bestimmungsgemäßen Verwendung in explosionsgefährdeten Bereichen kann auf in diesem Dokument behandelte Bauarten von Maschinen oder Einrichtungen anwendbar sein. Dieses Dokument ist nicht dafür vorgesehen, damit Übereinstimmung mit den grundlegenden Gesundheits- und Sicherheitsanforderungen der Richtlinie 2014/34/EU festzustellen.
Atmosphères explosibles - Termes et définitions pour les appareils et systèmes de protection destinés à être utilisés en atmosphères explosibles
Le présent document spécifie les termes et définitions (vocabulaire) à employer dans les normes spécifiques concernant les appareils et les systèmes de protection destinés à être utilisés en atmosphères explosibles.
NOTE La directive 2014/34/UE concernant les appareils et les systèmes de protection destinés à être utilisés en atmosphères explosibles peut être applicable au type de machine ou d’appareil couvert par le présent document. Ce dernier n'est pas destiné à fournir des mesures pour satisfaire aux exigences essentielles de santé et de sécurité de la directive 2014/34/UE.
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
oSIST prEN 13237:2022
01-september-2022
Potencialno eksplozivne atmosfere - Izrazi in definicije za opremo in zaščitne
sisteme, namenjene za uporabo v potencialno eksplozivnih atmosferah
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
Atmosphères explosibles - Termes et définitions pour les appareils et systèmes de
protection destinés à être utilisés en atmosphères explosibles
Ta slovenski standard je istoveten z: prEN 13237
ICS:
01.040.13 Okolje. Varovanje zdravja. Environment. Health
Varnost (Slovarji) protection. Safety
(Vocabularies)
01.040.29 Elektrotehnika (Slovarji) Electrical engineering
(Vocabularies)
13.230 Varstvo pred eksplozijo Explosion protection
29.260.20 Električni aparati za Electrical apparatus for
eksplozivna ozračja explosive atmospheres
oSIST prEN 13237:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 13237:2022
DRAFT
EUROPEAN STANDARD
prEN 13237
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2022
ICS 01.040.13; 01.040.29; 13.230; 29.260.20 Will supersede EN 13237:2012
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 Explosionsgefährdete Bereiche - Begriffe für Geräte
les appareils et systèmes de protection destinés à être und Schutzsysteme zur Verwendung in
utilisés en atmosphères explosibles explosionsgefährdeten Bereichen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 305.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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 CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 13237:2022 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
Annex A (informative) Definitions from the Directive 2014/34/EU and corrigenda . 27
Annex B (informative) Significant changes between this document and EN 13237:2012 . 30
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/34/EU aimed to be covered . 31
Bibliography . 32
2
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European foreword
This document (prEN 13237:2022) 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 document is currently submitted to the CEN Enquiry.
This document will supersede EN 13237:2012.
The significant changes between this document and EN 13237:2012 are given in Annex B.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of EU
Directive(s) / Regulation(s).
For relationship with EU Directive(s) / Regulation(s), see informative Annex ZA, which is an integral part
of this document.
3
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Introduction
This European Standard has been produced to assist designers, manufacturers and other interested
parties to use harmonized 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.
4
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1 Scope
This document 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 2014/34/EU 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 document. This
document is not intended to provide means of complying with the essential health and safety requirements of
Directive 2014/34/EU.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
air flow velocity
3 2
volume of air [m ] which flows through a defined surface [m ] per unit time [s]
[SOURCE: EN 17077:2018, 3.1]
3.2
ambient atmosphere
normal atmosphere surrounding the equipment and protective system
3.3
ambient temperature
temperature of the air or other medium where the equipment and protective system is to be used
3.4
atmospheric conditions
conditions with pressures ranging from 80 kPa to 110 kPa (0,8 bar to 1,1 bar); temperatures ranging
from −20°C to +60°C
[SOURCE: EN ISO 16852:2016, 3.25]
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3.5
combustible dust
finely divided solid particles, 500 µm or less in nominal size, which may form explosive mixtures with air
at standard atmospheric pressure and temperatures
Note 1 to entry: This includes dust and grit as defined in ISO 4225:2020.
Note 2 to entry: The term “solid particles” is intended to address particles in the solid phase but does not preclude
a hollow particle.
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 , modified — reference date in Note 1 to entry has been
updated]
3.5.1
conductive dust
combustible metal dusts and other combustible dusts with electrical resistivity equal to or less than
1 × 103 Ω m
Note 1 to entry: Metal dust is treated as conductive dust because it is assumed that surface oxidation cannot be
depended upon to always ensure electrical resistivity greater than 1 × 103 Ω m
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 ]
3.5.2
non-conductive dust
combustible dust with electrical resistivity greater than 1 × 103 Ω m
1
]
[SOURCE: EN ISO/IEC 80079-20-2:2016
3.6
combustible flyings
solid particles, including fibres, where one dimension is greater than 500 μm in nominal size, which may
form an explosive mixture with air at standard atmospheric pressure and temperature
Note 1 to entry: The ratio of length to width is 3 or more.
Note 2 to entry: Examples of flyings include carbon fibre, rayon, cotton (including cotton linters and cotton
waste), sisal, jute, hemp, cocoa fibre, oakum and baled waste kapok.
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 ]
3.7
constructional safety “c”
ignition protection where constructional measures are applied so as to protect against the possibility of
ignition from hot surfaces, sparks and adiabatic compression generated by moving parts
[SOURCE: EN ISO 80079-37:2016, 3.1]
1
As impacted by EN ISO/IEC 80079-20-2:2016/AC:2017.
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3.8
control of ignition source “b”
ignition protection where mechanical or electrical devices are used in conjunction with nonelectrical
equipment to manually or automatically reduce the likelihood of a potential ignition source from
becoming an effective ignition source
Note 1 to entry: This might for example be a level sensor used to indicate loss of oil, a temperature sensor to
indicate a hot bearing or a speed sensor to indicate over-speed.
[SOURCE: EN ISO 80079-37:2016, 3.3]
3.9
control measure
3.9.1
automatic control measure
action taken without manual intervention, to reduce the likelihood of a potential ignition source from
becoming an effective ignition source
[SOURCE: EN ISO 80079-37:2016, 3.3.1]
3.9.2
manual control measure
action taken by a person as a result of a warning, indication, or alarm, to reduce the likelihood of a
potential ignition source from becoming an effective ignition source
[SOURCE: EN ISO 80079-37:2016, 3.3.2]
3.10
ignition prevention devices/systems
arrangement that converts signals from one or more sensors into an action, or indication, to reduce the
likelihood of a potential ignition source from becoming an effective ignition source
[SOURCE: EN ISO 80079-37:2016, 3.3.3]
3.11
safety devices
devices intended for use inside or outside explosive atmospheres but required for or contributing to the
safe functioning of equipment and protective systems with respect to the risks of explosion
[SOURCE: EN ISO 80079-37:2016, 3.3.4]
3.12
continuous grade of release
release which is continuous or is expected to occur frequently or for long periods
[SOURCE: EN IEC 60079-10-1:2021, 3.4.2]
3.13
deflagration
explosion propagating at subsonic velocity
[SOURCE: ISO 8421-1:1987]
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3.14
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
Note 1 to entry: The enclosure which provides the degree of protection IP is not necessarily identical with the
types of protection as defined in EN IEC 60079-0.
2
[SOURCE: EN 60529:1991 , 3.3]
3.15
detonation
explosion propagating at supersonic velocity and characterised by a shock wave
[SOURCE: ISO 8421-1:1987]
3.16
dust
small solid particles in the atmosphere which settle out under their own weight, but which may remain
suspended in air for some time
Note 1 to entry: Generally combustible dusts with a median value below 500 µm may form explosible dust/air-
mixtures.
[SOURCE: EN 14034-1:2004+A1:2011, 3.1, modified — definition has been changed]
3.17
electrical equipment
items applied as a whole or in part for the utilisation of electrical energy
Note 1 to entry: These include, among others, items for the generation, transmission, distribution, storage,
measurement, regulation, conversion and consumption of electrical energy and items for telecommunications.
3
[SOURCE: EN IEC 60079-0:2018 , 3.14]
3.18
electrostatic leakage resistance
electrical resistance measured between an object and earth
[SOURCE: EN 14983:2007, 3.1]
3.19
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)
2
As impacted by EN 60529:1991/A1:2000, EN 60529:1991/A2:2013, EN 60529:1991/AC:2016-12 and
EN 60529:1991/corrigendum May 1993.
3
As impacted by EN IEC 60079-0:2018/AC:2020-02.
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3.20
equipment grouping
classification system of equipment related to the explosive atmosphere for which they are intended to be
used
Note 1 to entry: EN IEC 60079-0 identifies three equipment groups:
Group I − equipment for mines susceptible to fire damp;
Group II, which is sub-divided into groups IIA, IIB and IIC − equipment for all places with an explosive gas
atmosphere other than mines susceptible to fire damp;
Group III, which is sub-divided into groups IIIA, IIIB and IIIC − equipment for all places with an explosive dust
atmosphere other than mines susceptible to fire damp.
4
[SOURCE: EN ISO 80079-36:2016 ]
3.21
Ex Component
part of Ex Equipment or a module, marked with the symbol “U”, which is not intended to be used alone
and requires additional consideration when incorporated into Ex Equipment or systems for use in
explosive atmospheres
4
[SOURCE: EN ISO 80079-36:2016 ]
3.22
Ex Equipment
equipment where measures have been applied to ensure that effective ignition sources are mitigated as
required by the Equipment Protection Level (EPL)
Note 1 to entry: This includes the ignition hazard assessment and/or protective measures in accordance with this
standard.
4
[SOURCE: EN ISO 80079-36:2016 , 3.11]
3.23
explosion
sudden increase of pressure and temperature, due to oxidation or other exothermic reaction
3.24
explosion region
area inside the boundary curve formed by the explosion limits of a flammable substance in various
mixtures with air and inert gas
Note 1 to entry: In many cases the apex of the boundary curve corresponds to the limiting air concentration, LAC.
Note 2 to entry: In many cases this is also called explosion range.
4
As impacted by EN ISO 80079-36:2016/AC:2019.
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Key
1 explosion region
2 apex
3 stoichiometric line
x molar fraction in %
IN inert gas
TS test substance
a air
Figure 1 — Explosion region for a ternary system of test substance, air and inert gas
3.25
explosion diverter
passive device typically installed in a duct preventing flame jet ignition, pressure piling and reducing the
probability of flame transmission into connected equipment
3.26
explosion isolation flap valve
valve containing a flap which is fixed to the housing on an axis perpendicular to the flow direction, kept
open by the process flow and able to stop explosions from propagating through pipelines in the direction
opposite to the normal process flow through the valve
[SOURCE: EN 16447:2014, 3.1, modified — Note 1 to entry has been deleted]
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3.27
explosion isolation system
3.27.1
active explosion isolation system
protective system which is designed to stop explosions from travelling through pipelines or limit the
associated destructive effects of the explosion and is activated by detectors and control and indicating
equipment (CIE) which are inherent parts of the system
[SOURCE: EN 14983:2007, 3.2, modified — definition has been changed, EN 15089:2009, 3.7.1, modified
— definition has been changed]
3.27.2
passive explosion isolation system
protective system which is designed to stop explosions from travelling through pipelines or limit the
associated destructive effects of the explosion and does not require detectors and a control and indicating
equipment (CIE)
[SOURCE: EN 15089:2009, 3.7.2, modified — definition has been changed]
3.28
explosion limits
3.28.1
lower explosion limit
LEL
lowest concentration of the explosion range
Note 1 to entry: Those concentrations are given at which an explosion just fails during the tests (see
EN 1839:2017, EN 14034-3:2006+A1:2011).
[SOURCE: EN 1839:2017]
3.28.2
upper explosion limit
UEL
highest concentration of the explosion range
Note 1 to entry: Those concentrations are given at which an explosion just fails during the tests (see
EN 1839:2017, EN 14034-3:2006+A1:2011).
[SOURCE: EN 1839:2017]
3.29
explosion points
3.29.1
lower explosion point
temperature of a flammable liquid at which the concentration of the saturated vapour in air is equal to
the lower explosion limit
3.29.2
upper explosion point
temperature of a flammable liquid at which the concentration of the saturated vapour in air is equal to
the upper explosion limit
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3.30
explosion pressure
p
ex
highest pressure occurring in a closed vessel during the explosion of a specific mixture of flammable
substances with air or air and inert gases determined under specified test conditions
Note 1 to entry: pex is expressed as absolute pressure with gases and vapour and as overpressure with dusts.
[SOURCE: EN 15967:2022, 3.1]
3.30.1
maximum explosion pressure
p
max
maximum value of explosion pressure measured in the tests for explosion pressure when the content of
the flammable substances in the mixture is varied
Note 1 to entry: pmax is expressed as absolute pressure with gases and vapour and as overpressure with dusts.
[SOURCE: EN 15967:2022, 3.2]
3.30.2
rate of explosion pressure rise
(dp/dt)
ex
highest value of the slope (first derivative) of the pressure-time curve (smoothed if necessary), measured
in a closed vessel during the explosion of a specific mixture of flammable substances with air or air and
inert substances determined under specified test conditions
[SOURCE: EN 15967:2022, 3.3]
3.30.3
maximum rate of explosion pressure rise
(dp/dt)
max
maximum value of the explosion pressure rise per unit time measured in the tests when the content of
the flammable substances in the mixture is varied
[SOURCE: EN 15967:2022, 3.4, modified — Note 1 to entry has been deleted]
3.31
explosion resistant
property of vessels and equipment designed to be either explosion-pressure-resistant or explosion-
pressure-shock resistant
3.31.1
explosion-pressure-resistant
property of vessels and equipment designed to withstand the expected explosion pressure without
becoming permanently deformed
3.31.2
explosion-pressure-shock resistant
property of vessels and equipment designed to withstand the expected explosion pressure without
rupturing, but allowing permanent deformation
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3.32
explosion suppression
technique by which burning in an explosive atmosphere is detected and arrested during incipient stages,
restricting development of pressure
[SOURCE: EN 14373:2021, 3.8]
3.33
explosion suppression system
protective system to detect automatically the onset of an explosion and initiate the deployment of
suppressant to limit destructive effects of an explosion and has to be activated by a detector and control
and indicating equipment (CIE) which are inherent parts of the system
[SOURCE: EN 14373:2021, 3.9, modified — definition has been changed]
3.34
explosion venting
protective measure which will prevent the explosion pressure in a vessel or other closed volume from
exceeding the vessel design strength by exhausting the explosion through an explosion venting device in
the vessel walls
[SOURCE: EN 14797:2006, 3.3]
3.35
explosion venting device
device which protects a vessel or other closed volume by explosion venting
[SOURCE: EN 14797:2006, 3.4]
3.36
explosive atmosphere
see A.1
3.36.1
hazardous explosive atmosphere
explosive atmosphere which causes harm, if it explodes
3.36.2
potentially explosive atmosphere
atmosphere which could become explosive due to local and operational conditions
3.37
explosive dust atmosphere
mixture with air, under atmospheric conditions, of combustible substances in the form of dust, fibres, or
flyings which, after ignition, permits self-sustaining propagation
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 ]
3.38
minimum ignition temperature of a dust cloud
lowest temperature of a hot surface on which the most ignitable mixture of the dust with air is ignited
under specified test conditions
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 ]
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3.39
minimum ignition temperature of a dust layer
lowest temperature of a hot surface at which ignition occurs in a dust layer under specified test conditions
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 ]
3.40
minimum ignition energy (of a combustible dust/air mixture)
lowest electrical energy stored in a capacitor which upon discharge is sufficient to effect ignition of the
most sensitive dust/air mixture under specified test conditions
1
[SOURCE: EN ISO/IEC 80079-20-2:2016 ]
3.41
extinguishing barrier
active explosion isolation system that is used to discharge suppressant agent into ductwork to isolate a
flame and keep it from propagating to other process areas
[SOURCE: EN 15089:2009, 3.11, modified — definition has been changed]
3.42
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
Note 1 to entry: This device should not be confused with a fire barrier, which is ineffective in case of explosion.
[SOURCE: EN ISO 16852:2016, 3.1]
3.43
flame arrester element
portion of a flame arrester whose principal function is to prevent flame transmission
[SOURCE: EN ISO 16852:2016, 3.3]
3.44
flameless explosion venting
explosion venting protective measure which will in addition prevent the transmission of flames and
reduce the external explosion effects
Note 1 to entry: Examples of external explosion effects are: temperature, pressure and dust/combustion
products.
[SOURCE: EN 16009:2011, 3.1]
3.45
flameless explosion venting device
device which protects a vessel or other closed volume by flameless explosion venting
[SOURCE: EN 16009:2011, 3.2]
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3.46
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 of the explosion to the explosive atmosphere surrounding the enclosure
3.47
flameproof joint
place where the corresponding surfaces of two parts of an enclosure, or the conjunction of enclosures,
come together and which prevents the transmission of an internal explosion to the explosive gas
atmosphere surrounding the enclosure
5
[SOURCE: EN 60079-1:2014 , 3.3]
3.47.1
gap of flameproof joint
distance between the corresponding surfaces of a flameproof joint when the electrical apparatus
enclosure has been assembled
Note 1 to entry: For cylindrical surfaces, forming cylindrical joints, the gap is the difference between the
diameters of the bore and the cylindrical component.
5
[SOURCE: EN 60079-1:2014 , 3.6]
3.47.2
length of flameproof joint
length of flame path
shortest path through a flameproof joint from the inside to the outside of a flameproof enclosure
3.47.3
width of a flameproof joint
see length of a flameproof joint, definition 3.47.2
3.48
flame velocity
S
f
velocity of a flame front relative to a fixed reference point
[SOURCE: EN 15089:2009, 3.14]
3.49
flammable gas or vapour
gas or vapour which, when mixed with air in certain proportions, will form an explosive gas atmosphere
[SOURCE: EN IEC 60079-10-1:2021, 3.6.4]
3.50
flammable liquid
liquid capable of producing a flammable vapour under any foreseeable operating conditions
[SOURCE: EN IEC 60079-10-1:2021, 3.6.2, modified — original Notes to entry deleted]
5
As impacted by EN 60079-1:2014/AC:2018-09.
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3.51
flammable mist
droplets of liquid, dispersed in air so as to form an explosive atmosphere
[SOURCE: EN IEC 60079-10-1:2021, 3.6.5]
3.52
flammable/combustible substance
substance in the form of gas, vapour, or mixtures of these, able to undergo an exothermic reaction with
air or air/inert gas mixture when ignited
3.53
flash point
FP
lowest liquid temperature at which, under specified test conditions, a liquid gives off vapours in quantity
such as to be capable of forming an ignitable vapour-air mixture
[SOURCE: EN ISO/IEC 80079-20-1:2019]
3.54
flammable limits
lower flammable limit (LFL) and upper flammable limit (UFL) of gas in a gas-air mixture, between which
a flammable mixture is formed
Note 1 to entry: The term “explosive limits” is used especially in European standardization and regulations
interchangeably to describe these limits.
Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.
[SOURCE: EN ISO/IEC 80079-20-1:2019]
3.54.1
lower flammable limit
LFL
concentration of flammable gas or vapour in air, below which an explosive gas atmosphere does not form
Note 1 to entry: For the purposes of Ex Equipment, this was previously referred to as the lower explosive limit
(LEL).
Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.
[SOURCE: EN ISO/IEC 80079-20-1:2019]
3.54.2
upper flammable limit
UFL
concentration of flammable gas or vapour in air, above which an explosive gas atmosphere does not form
Note 1 to entry: For the purposes of Ex Equipment, this was previously referred to as the upper explosive limit
(UEL).
Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.
[SOURCE: EN ISO/IEC 80079-20-1:2019]
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3.55
functional safety
part of the overall safety relating to the intended use in terms of the function and integrity of the
protective system including any safety related devices that are part of the protective system performance
Note 1 to entry: Functional safety covers all aspects where safety depends on the correct functioning of the
protective system and other technology safety-related systems.
Note 2 to entry: This definition deviates from the definition in EN 61508-4:2010 to reflect differences in
explosion safety terminology.
[SOURCE: EN 15233:2007, 3.2]
3.55.1
functional safety estimation
determination of the probability of occurrence of the failures violating the functional safety of the
protective system
[SOURCE: EN 15233:2007, 3.4]
3.55.2
functional safety evaluation
procedure to determine whether the functional safety of the protective system meets the predefined
acceptance criteria
[SOURCE: EN 15233:2007, 3.5]
3.56
gas
gaseous phase of a substance that cannot reach equilibrium with its liquid or solid state in the
temperature and pressure range of interest
Note 1 to entry: This is a simplification of the scientific definition, and merely requires that the substance is
above its boiling point or sublimation point at the ambient temperature and pressure.
[SOURCE: EN ISO/IEC 80079-20-1:2019]
3.57
gas explosion constant
K
G
maximum value of the pressure rise per unit time (d /d )max during the explosion of a specific explosive
p t
atmosphere involving gas or vapour in a closed vessel under specified test conditions normalised to a
3 1/3
vessel volume of 1 m multiplied by V
[SOURCE: EN 14491:2012, 3.5]
17
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