SIST EN 1839:2013
(Main)Determination of explosion limits of gases and vapours
Determination of explosion limits of gases and vapours
This European Standard specifies two test methods (method T and method B) to determine the explosion limits of gases, vapours and their mixtures, mixed with air. An air/inert gas mixture (volume fraction of the oxygen < 21 %) can be used as the oxidizer instead of air. In this European Standard, the term “air” includes such air/inert mixtures. This European Standard applies to gases, vapours and their mixtures at atmospheric pressure for temperatures up to 200 °C.
Bestimmung der Explosionsgrenzen von Gasen und Dämpfen
Dieses Dokument legt zwei Verfahren (Methode T) und (Methode B) zum Bestimmen der Explosionsgrenzen
von Gasen, Dämpfen und deren Gemischen in Mischung mit Luft fest. An Stelle von Luft kann als Oxidator
auch ein Luft/Inertgas-Gemisch (Volumenanteil des Sauerstoffs < 21 %) verwendet werden. In diesem
Dokument subsumiert der Ausdruck „Luft“ auch solche Luft/Inertgas-Gemische.
Dieses Dokument gilt für Gase, Dämpfe und deren Gemische bei Umgebungsdruck und Temperaturen von
Raumtemperatur bis 200 °C.
Détermination des limites d'exposivité des gaz et vapeurs
La présente Norme européenne spécifie deux méthodes d’essai (la méthode T et la méthode B) pour
déterminer les limites d’explosivité de gaz, de vapeurs et de mélanges de gaz et de vapeurs mélangés à l’air.
Un mélange d’air et de gaz inerte (fraction volumique de l’oxygène < 21 %) peut servir d’oxydant à la place de
l’air. Dans la présente norme, le terme « air » inclut ces mélanges d’air et gaz inerte.
La présente Norme européenne s’applique aux gaz, aux vapeurs et à leurs mélanges à la pression
atmosphérique et à des températures comprises entre la température ambiante et 200 °C.
Ugotavljanje mej eksplozivnosti plinov in hlapov
Ta evropski standard določa dve preskusni metodi (metodo T in metodo B) za ugotavljanje mej eksplozivnosti plinov, hlapov in njihovih mešanic, zmešanih z zrakom. Namesto zraka je kot oksidant mogoče uporabiti mešanico zraka in inertnega plina (delež prostornine kisika < 21 %). Izraz »zrak« v tem evropskem standardu vključuje take mešanice zraka/inertnega plina. Ta evropski standard se uporablja za pline, hlape in njihove mešanice pri atmosferskem tlaku pri temperaturah do 200 °C.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 1839:2013
01-januar-2013
1DGRPHãþD
SIST EN 1839:2003
Ugotavljanje mej eksplozivnosti plinov in hlapov
Determination of explosion limits of gases and vapours
Bestimmung der Explosionsgrenzen von Gasen und Dämpfen
Détermination des limites d'exposivité des gaz et vapeurs
Ta slovenski standard je istoveten z: EN 1839:2012
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
SIST EN 1839:2013 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 1839:2013
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SIST EN 1839:2013
EUROPEAN STANDARD
EN 1839
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2012
ICS 13.230 Supersedes EN 1839:2003
English Version
Determination of explosion limits of gases and vapours
Détermination des limites d'exposivité des gaz et vapeurs Bestimmung der Explosionsgrenzen von Gasen und
Dämpfen
This European Standard was approved by CEN on 27 July 2012.
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 CEN-CENELEC 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 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1839:2012: E
worldwide for CEN national Members.
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EN 1839:2012 (E)
Contents Page
Foreword . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Test Methods . 7
4.1 Method T (“tube” method) . 7
4.1.1 Principle . 7
4.1.2 Reagents and Materials . 7
4.1.3 Apparatus . 8
4.1.4 Preparation of the test mixture . 10
4.1.5 Procedure . 10
4.2 Method B ("bomb" method) . 11
4.2.1 Principle . 11
4.2.2 Reagents and materials . 11
4.2.3 Apparatus . 11
4.2.4 Preparation of the test mixture . 13
4.2.5 Procedure . 13
4.3 Recording of results . 15
4.4 Test report . 15
Annex A (normative) Method for determination of the explosion limits of substances that are difficult
to ignite . 17
A.1 Background . 17
A.2 Explanation . 17
A.3 Apparatus . 17
A.4 Safety equipment . 18
A.5 Preparation of the test mixture . 18
A.6 Procedure . 18
Annex B (informative) Examples to describe flame detachment . 20
Annex C (informative) Example of recommended evaporator equipment . 21
Annex D (normative) Safety measures . 23
D.1 General . 23
D.2 General safety measures . 23
D.3 Additional safety measures concerning the tube method . 23
)
Annex E (informative) Example of a form expressing the results Test report . 24
Annex F (normative) Verification . 25
Annex G (informative) Conversion of the values for the explosion limits . 27
G.1 Abbreviations and symbols . 27
G.2 Substance characteristics of air . 27
G.3 Definitions . 28
G.4 Mixture preparation . 28
G.5 Conversion . 29
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Annex H (informative) Significant Changes between this European Standard and EN 1839:2003 . 31
Annex ZA (informative) Relationship between this European Standard and the Essential Requirements
of EU Directive 94/9/EC . 32
Bibliography . 33
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Foreword
This document (EN 1839:2012) 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 March 2013, and conflicting national standards shall be withdrawn at the latest by
March 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.
CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 1839:2003.
The significant changes between this European Standard and EN 1839:2003 are given in Table H.1.
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 94/9/EC.
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
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Introduction
The hazard of an explosion can be avoided by preventing the formation of explosive mixtures of gases and/or
vapours. To do so, the explosion limits (also known as “flammability limits") of the flammable substance need to be
known. These limits depend mainly on:
the properties of the flammable substance;
temperature and pressure;
size and shape of the test vessel;
ignition source (type, energy);
the criterion for self-propagating combustion.
To obtain reliable and comparable results it is necessary to standardise the conditions for determining the
explosion limits (i.e. apparatus and procedure). However, it is not possible to provide one single method that is
suitable for all types of substances. For practical reasons, it is preferable to use apparatus that can also be used for
the determination of other explosion characteristics. This European Standard, therefore, details two methods,
namely, the tube method (method T) and the bomb method (method B). In general, the tube method gives a wider
explosion range. Differences in the explosion limits determined by the two methods can vary by up to 10 % relative.
For substances which are difficult to ignite with large quenching distances, only a modified tube method is suitable.
This is described in Annex A.
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1 Scope
This European Standard specifies two test methods (method T and method B) to determine the explosion limits of
gases, vapours and their mixtures, mixed with air. An air/inert gas mixture (volume fraction of the oxygen < 21 %)
can be used as the oxidizer instead of air. In this European Standard, the term “air” includes such air/inert mixtures.
This European Standard applies to gases, vapours and their mixtures at atmospheric pressure for temperatures up
to 200 °C.
2 Normative references
Not applicable.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
explosion range
range of the concentration of a flammable substance or mixture of substances in air, within which an explosion can
occur, respectively range of the concentration of a flammable substance or mixture of substances in mixture with
air/inert gas, within which an explosion can occur, determined under specified test conditions
[SOURCE: EN 13237:2012, 3.22]
3.2
lower explosion limit
LEL
lowest concentration of the explosion range at which an explosion can occur
Note 1 to entry: Those concentrations are given at which an explosion just fails during the tests.
[SOURCE: EN 13237:2012, 3.19.1]
3.3
upper explosion limit
UEL
highest concentration of the explosion range at which an explosion can occur
Note 1 to entry: Those concentrations are given at which an explosion just fails during the tests.
[SOURCE: EN 13237:2012, 3.19.2]
3.4
explosion criterion — flame detachment
in method T, the criterion for an explosion (self-propagating combustion) is the upward movement of the flame from
the spark gap for at least 100 mm or the formation of a halo which either reaches the top of the tube or reaches a
minimum height of 240 mm
Note 1 to entry: Throughout the duration of the ignition, spark test mixtures, whose test substance content lies just outside
the explosion range, may exhibit a luminous phenomenon (referred to as a “halo”) above the spark gap which does not detach
from the latter (see Annex B). For some test substances (e.g. halogenated hydrocarbons), this luminous phenomenon can
occupy a large portion of the test vessel. The formation of a halo alone is not considered to count as an ignition of the test
mixture unless it reaches the top of the tube or a minimum height of 240 mm.
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3.5
explosion criterion — pressure rise
in method B, the criterion for an explosion (self-propagating combustion) is the generation of explosion
overpressure which is equal to or greater than the overpressure created by the ignition source alone in air plus
(5 ± 0,1) % of the initial pressure
3.6
vapour
gaseous phase emanating or being emanated from a liquid
Note 1 to entry: If not otherwise mentioned, the term “gas” in this standard also includes such vapours but not mists.
3.7
oxidizer
air or an air/inert gas mixture (volume fraction of the oxygen < 21 %)
3.8
sample
substance or mixture of substances for which explosion limits are to be determined
3.9
test substance
sample in the gaseous state; in the case of liquid samples, after complete evaporation
3.10
test mixture
mixture of test substance and air
4 Test Methods
4.1 Method T (“tube” method)
4.1.1 Principle
The test mixture flows through the cylindrical test vessel from the bottom upwards to the top until the contents
previously in the test vessel have been completely replaced. Then, under quiescent conditions, an ignition is
initiated using a series of induction sparks. It is observed whether or not flame detachment occurs. The test
substance content of the test mixture is varied stepwise until the LEL or the UEL (explosion criterion — flame
detachment) have been determined or until it is established that there is no explosion range.
4.1.2 Reagents and Materials
3
4.1.2.1 Air, which shall be free of water (≤0,1 mol% water vapour absolute) and oil (≤0,1 g/m oil).
If synthetic air is used, it has to be stated in the report.
4.1.2.2 Inert gases, the purity of the inert, or the mixture of inerts, shall be 99,8 % mol. or better.
If a mixture of inerts is used, the composition of the mixture shall be stated in the test report.
4.1.2.3 Flammable substances, which may be either a single substance or a defined mixture of substances or a
process sample (of known or unknown composition).
When a single substance or a defined mixture of substances is used, the purity of each substance shall be
99,8 % mol. or better. In the case of a mixture of substances or a process sample of known composition, the
precision of the composition shall be stated in the test report. In the case of a process sample of unknown
composition, the sample shall be defined as well as possible process conditions.
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If the flammable gas is derived from a liquid containing more than one component, the gas phase composition can
differ from the composition of the liquid phase. When large volumes of the gas are removed, the composition of
both the liquid and gas phases can change with time. For these reasons, the test sample shall be taken from the
liquid phase.
4.1.2.4 Heat-resistant, chemically inert material for gaskets and adhesive mountings.
Sample containers shall be kept closed before and after sampling to avoid changes in the sample composition
within the container (e.g. loss of volatile components from mixtures). If a sample container contains a mixture with
both gaseous and liquid phases present, the mixture composition of the two phases will be different. Under such
conditions, it is recommended that the test substance sample be removed from the liquid phase. If the sample is
taken from the gaseous phase, account must be taken of the difference in composition.
4.1.3 Apparatus
4.1.3.1 Test vessel.
The test vessel is an upright cylindrical vessel made of glass or other transparent material (e.g. polycarbonate) with
an inner diameter of (80 ± 2) mm and a minimum length of 300 mm.
The vessel is equipped with an inlet pipe with a three-way valve for the test mixture, located at the bottom, and an
outlet pipe and pressure vent in the upper part.
The bottom and top may be made of other material. However, the material must be free of any catalytic effect and
resistant to corrosion from the test mixture or the reaction products.
4.1.3.2 Ignition source.
A series of induction sparks between two electrodes is used as the ignition source.
The electrodes shall end (60 ± 1) mm above the bottom of the test vessel.
Stainless steel is a suitable material for the electrodes. The electrodes shall be pointed rods with a diameter of
maximum 4 mm. The angle of the tips shall be (60 ± 3)°. The distance between the tips shall be (5 ± 0,1) mm. The
electrodes shall be mounted in the vessel so that they are gas tight at the highest pressures generated during the
test. The mounting shall be resistant to heat and the test mixture, and provide adequate electrical resistance from
the test vessel body.
A high voltage transformer, with a root mean square of 13 kV to 16 kV and a short circuit current of 20 mA to
30 mA, shall be used for producing the ignition spark. The primary winding of the high voltage transformer shall be
connected to the mains via a timer set to the required discharge time.
The spark discharge time shall be adjusted to 0,2 s. If a spark discharge time of 0,2 s does not result in the ignition
of the test mixture, the test may be repeated with a spark discharge time of up to 0,5 s.
The power of the induction sparks is dependent on the gas mixture and its pressure. In air at atmospheric
conditions, according to calorimetric and electric measurements, such a source gives a spark with a power of
approximately 10 W.
4.1.3.3 Equipment for preparing the test mixture.
The test mixture is prepared by mixing flows of gaseous components. This requires the following equipment:
metering device for air, gaseous samples or additional inert gases (e.g. mass flow controller, volume flow
controller, metering pump for gases);
metering device for liquid samples (e.g. volumetric metering pumps);
evaporator equipment in the case of a liquid sample (for example see Annex C);
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mixing vessel for homogenizing the test mixture.
The metering devices and the equipment for preparing the test mixture have to be designed in such a way that the
uncertainty of measurement of the test substance content in the test mixture is not higher than the data given in
Table 1.
Table 1 — Maximum permissible uncertainty of measurement for the amount of test substance in the test
mixture
molar amount of test substance maximum uncertainty of measurement
% %
relative absolute
± 10
≤ 2
> 2 ± 0,2
4.1.3.4 Temperature regulating system.
For measurements at temperatures above ambient temperature, the apparatus requires a temperature regulating
system. When this is used, it has to be ensured that the temperature difference inside the test vessel is not more
than 10 K. This has to be checked when initially setting up the apparatus, whenever parts are renewed and at
every verification.
Key
1 test vessel 7 timer
2 electrodes 8 facility for keeping the temperature
3 three-way valve 9 flammable substance
4 mixing vessel 10 air
5 metering devices 11 power supply
6 high-voltage transformer
Figure 1 — Scheme of the ‘tube’ apparatus for determining the explosion limits
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4.1.3.5 Safety equipment.
The safety measures specified in Annex D shall be followed.
4.1.4 Preparation of the test mixture
When evaporating liquid samples, it is important to remember that the mixture composition of the gaseous phase in
equilibrium with a liquid phase (”vapour”) generally differs from the mixture composition of the liquid phase itself.
Furthermore, the mixture compositions of the liquid and the vapour phases may change when removing material
from the vapour phase. Allowance for this is necessary when determining explosion limits for flammable liquids,
when handling liquid samples and when preparing test mixtures by evaporating liquid samples. To avoid error, the
method of dynamic total evaporation is used. An example of a suitable evaporator set up is described in Annex C.
When liquids are metered, it has to be ensured that bubbles are not formed in any component carrying the liquid
(e.g. pipes). To achieve complete homogenization, the test mixture flows through a mixing vessel, preferably made
of glass. For a mixing vessel with no built-in elements, a volume of at least 600 ml is recommended. It is expedient
to introduce the test mixture tangentially. The mixing vessel is not necessary if homogenization is effectively
achieved by the metering device. The temperature of the mixing vessel and of all parts carrying the test mixture is
kept constant to prevent the test substance from condensing. It is recommended that the components carrying the
test mixture are heated along with the test vessel.
4.1.5 Procedure
If the explosion limits are to be determined at elevated temperature, preheat the test vessel and all parts carrying
the test mixture to the required temperature. For liquid samples, the temperature of the test mixture shall be at least
25 K higher than the condensation temperature. Prior to each ignition attempt, it has to be ensured that the
temperature in the test vessel differs by no more than 5 K from the required value.
The determination of the explosion limits consists of a series of ignition tests which are carried out with test
mixtures whose test substance content is varied.
For safety reasons, the initial ignition tests are carried out using a test mixture with test substance content which, if
possible, lies outside the expected explosion range.
For organic substances which consist exclusively of carbon, hydrogen and oxygen (with the exception of
peroxides), the LEL can be roughly estimated. At 20 °C, the LEL, in many cases, is approximately half the test
substance content of the stoichiometric composition. The temperature dependence of the LEL has to be taken into
account. Up to 200 °C, the LEL decreases more or less linearly between 30 % and 50 % of the value estimated for
20 °C.
There is currently no method which readily estimates the UEL.
Prior to each ignition attempt, the test vessel is purged with the test mixture. The purging volume has to be at least
ten times the volume of the test vessel. When purging is complete, the inlet to the test vessel is sealed. The test
mixture then by-passes the test vessel and flows directly into the exhaust system. An ignition is attempted using
the induction spark under quiescent conditions (i.e. after a 6 s to 10 s delay). It is observed whether a flame
detaches from the ignition source (see Annex B).
It is recommended that the ignition testing is carried out without interruption of the production of the test mixture. If
restarting, it will take a finite time to produce a test mixture of constant composition even if the adjustment has not
been changed.
If an ignition is observed, the test substance content in the test mixture is iteratively varied until no further flame
detachment follows. Close to the explosion limits, the incremental change of test substance content is selected so
that it is almost equal to the relative deviation given in Table 1. The test mixture with which a further flame
detachment just fails has to be repeated four times. The determination is terminated when all five tests have taken
place with no observed flame detachment. If flame detachment does occur, the test substance content has to be
further changed, i.e. for determination of the LEL, the test substance content has to be reduced by one increment;
for the UEL, it has to be increased by one increment. Five tests are carried out at the new test substance content.
When it is established that a given test mixture will not ignite, it is recommended that the composition of the non-
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ignited test mixture flowing out of the test vessel is measured in order to determine whether any errors have arisen
either with the metering devices or due to leakage.
4.2 Method B ("bomb" method)
4.2.1 Principle
The quiescent test mixture in a closed vessel (the bomb) is subjected to an ignition source. The overpressure given
by the ignition is measured and characterises the explosivity of the test mixture. The amount of test substance in
the test mixture is varied incrementally until the LEL or the UEL is determined, or until it is certain that no explosion
range exists.
4.2.2 Reagents and materials
See 4.1.2.
4.2.3 Apparatus
4.2.3.1 Test vessel.
The test vessel shall be cylindrical or spherical. The internal volume of the test vessel shall be equal to or greater
3
than 0,005 m . If a cylindrical vessel is used, the length to diameter ratio shall be between 1 and 1,5.
The test vessel and any equipment (valves, ignition source, transducer etc.) fitted to the vessel shall be designed to
withstand a maximum overpressure of at least 15 bar.
The vessel shall be made of stainless steel or any material free of any catalytic effect and resistant to corrosion
from the initial gas mixture and the products of combustion.
The test vessel shall be fitted with sufficient ports to allow filling, evacuating and purging.
If the test mixture is prepared inside the test vessel by partial pressures, it is recommended to disconnect the
pressure measuring system used to prepare the test mixture, via a valve, to protect it during the ignition trials.
The components of the temperature measuring system located inside the test vessel (e.g. thermocouple) have to
be mounted so that propagation of the flame is not hindered.
4.2.3.2 Ignition source.
The ignition source shall be positioned in the centre of the test vessel. Suitable types of ignition source are either a
series of induction sparks or a fuse wire. In the test report, the type of ignition source used shall be stated.
4.2.3.2.1 Induction spark.
See 4.1.3.2.
4.2.3.2.2 Fuse wire.
An electric arc is generated by passing an electric charge along a straight length of fuse wire connected between
two metal rods.
The electrical power required to melt the wire and generate the arc is supplied by an isolating transformer. The
ignition energy delivered by the arc depends on its duration and on the power rating of the isolating transfor
...
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