SIST EN 17624:2022
(Main)Determination of explosion limits of gases and vapours at elevated pressures, elevated temperatures or with oxidizers other than air
Determination of explosion limits of gases and vapours at elevated pressures, elevated temperatures or with oxidizers other than air
This document specifies a test method to determine the explosion limits of gases, vapours and their mixtures, mixed with a gaseous oxidizer or an oxidizer/inert gas mixture at pressures from 1 bar to 100 bar and for temperatures up to 400 °C.
Bestimmung der Explosionsgrenzen von Gasen und Dämpfen bei erhöhten Drücken, erhöhten Temperaturen oder mit Oxidationsmitteln, welche nicht aus Luft bestehen
Dieses Dokument legt ein Prüfverfahren zur Bestimmung der Explosionsgrenzen von Gasen, Dämpfen und deren Gemischen, gemischt mit einem gasförmigen Oxidator oder einem Oxidator-Inertgas-Gemisch, bei Drücken von 1 bar bis 100 bar und für Temperaturen bis 400 °C fest.
Détermination des limites d'explosivité des gaz et vapeurs à pressions et températures élevées avec des oxydants autres que l’air
Le présent document spécifie une méthode d’essai pour déterminer les limites d’explosivité de gaz, de vapeurs et de leurs mélanges, associés à un oxydant gazeux ou à un mélange oxydant/gaz inerte, à des pressions allant de 1 bar à 100 bar et à des températures pouvant atteindre 400 °C.
Določanje eksplozijskih mej plinov in hlapov pri povišanem tlaku, povišani temperaturi ali z oksidanti, ki niso sestavljeni iz zraka
Ta dokument določa preskusno metodo za določanje eksplozijskih mejnih vrednosti plinov, hlapov in njihovih mešanic, pomešanih s plinastim oksidantom ali mešanico oksidanta in inertnega plina, pri tlakih od 1 bara do 100 barov in temperaturah do 400 °C.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 17624:2022
01-september-2022
Določanje eksplozijskih mej plinov in hlapov pri povišanem tlaku, povišani
temperaturi ali z oksidanti, ki niso sestavljeni iz zraka
Determination of explosion limits of gases and vapours at elevated pressures, elevated
temperatures or with oxidizers other than air
Bestimmung der Explosionsgrenzen von Gasen und Dämpfen bei erhöhten Drücken,
erhöhten Temperaturen oder mit Oxidationsmitteln, welche nicht aus Luft bestehen
Détermination des limites d'explosivité des gaz et vapeurs à pressions et températures
élevées avec des oxydants autres que l’air
Ta slovenski standard je istoveten z: EN 17624:2022
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
SIST EN 17624:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 17624:2022
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SIST EN 17624:2022
EN 17624
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2022
EUROPÄISCHE NORM
ICS 13.230
English Version
Determination of explosion limits of gases and vapours at
elevated pressures, elevated temperatures or with
oxidizers other than air
Détermination des limites d'explosivité des gaz et Bestimmung der Explosionsgrenzen von Gasen und
vapeurs à pressions et températures élevées avec des Dämpfen bei erhöhten Drücken, erhöhten
oxydants autres que l'air Temperaturen oder mit Oxidationsmitteln, welche
nicht aus Luft bestehen
This European Standard was approved by CEN on 7 February 2022.
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, 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.
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. EN 17624:2022 E
worldwide for CEN national Members.
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SIST EN 17624:2022
EN 17624:2022 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Test methods . 7
4.1 General. 7
4.2 Reagents and materials . 7
4.2.1 Sample . 7
4.2.2 Oxidizer . 7
4.2.3 Inert gases . 7
4.2.4 Gaskets and mountings . 8
4.3 Apparatus . 8
4.3.1 Test vessel . 8
4.3.2 Measurement system to adjust the initial pressure and temperature . 8
4.3.3 Ignition source . 9
4.3.4 Equipment for preparing the test mixture . 11
4.3.5 Temperature regulating system . 12
4.3.6 Safety equipment . 12
4.4 Preparation of the test mixture . 12
4.4.1 General. 12
4.4.2 Preparation of the test mixture . 12
4.5 Procedure . 13
4.6 Recording of results . 14
5 Verification . 14
6 Test report . 14
Annex A (informative) Safety measures . 15
Annex B (normative) Verification . 16
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive2006/42/EC aimed to be covered . 18
Bibliography . 19
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SIST EN 17624:2022
EN 17624:2022 (E)
European foreword
This document (EN 17624:2022) 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 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 September 2022, and conflicting national standards shall
be withdrawn at the latest by September 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
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).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
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, 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 the United
Kingdom.
3
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EN 17624:2022 (E)
Introduction
In accordance with EN ISO 12100:2010, this is a type-B standard.
The hazard of an explosion can be avoided by preventing the formation of explosive mixtures of gases
and/or vapours with oxidizers. To do so, the explosion limits (also known as “flammability limits”) of the
flammable substance need to be known. These limits are a strong function of the pressure and
temperature within the system.
Standard EN 1839:2017 has methods suitable for determining these limits at atmospheric conditions.
Technical conditions in plants, etc. can differ substantially from these assumed atmospheric conditions.
Furthermore, explosive mixtures of flammable substances and oxidizers other than air are likely to occur.
To obtain reliable and comparable results it is necessary to standardize the conditions for determining
the explosion limits at non-atmospheric conditions.
4
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SIST EN 17624:2022
EN 17624:2022 (E)
1 Scope
This document specifies a test method to determine the explosion limits of gases, vapours and their
mixtures, mixed with a gaseous oxidizer or an oxidizer/inert gas mixture at pressures from 0,10 MPa to
10 MPa and for temperatures up to 400 °C.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 10156:2017, Gas cylinders - Gases and gas mixtures - Determination of fire potential and oxidizing
ability for the selection of cylinder valve outlets (ISO 10156:2017)
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:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
flammable substance
substance in the form of gas, vapour or mixtures of these, able to undergo an explosive exothermic
reaction with an oxidizer or an oxidizer/inert gas mixture when ignited
[SOURCE: EN 13237:2012, 3.37, modified: removed reference to liquids and solids as they are not
relevant for this standard]
3.2
explosion range
range of the concentration of a flammable substance or mixture of substances with an oxidizer, within
which an explosion can occur, respectively range of the concentration of a flammable substance or
mixture of substances in mixture with oxidizer/inert gas, within which an explosion can occur,
determined under specified test conditions
Note 1 to entry: The explosion limits are not part of the explosion range.
[SOURCE: EN 13237:2012, 3.22, modified: changed air to oxidizer]
3.3
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.
[SOURCE: EN 13237:2012, 3.19.1, modified: removed “at which an explosion can occur”]
5
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EN 17624:2022 (E)
3.4
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.
[SOURCE: EN 13237:2012, 3.19.2, modified: removed “at which an explosion can occur”]
3.5
inert gas
gas that does not react with the test substance or oxidizer
3.6
explosion criterion
either an explosion pressure p relative to the initial pressure (p ) as follows (considering the
ex i
overpressure that is created by the ignition source alone (p )):
IS
p /p ≥ (1,05 + p /p − 1) (for initial pressures p ≤ 2)
ex i IS i i
p /p ≥ (1,02 + p /p − 1) (for initial pressures p > 2)
ex i IS i i
or a temperature rise (ΔT) of at least 100 K
3.7
oxidizer
any oxidising gas except highly reactive oxidisers with oxidizing potentials according to
EN ISO 10156:2017 higher than oxygen, e.g. ozone, fluorine, fluorinated compounds, etc.
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 oxidizer or oxidizer/inert gas
3.11
mole fraction
x(S)
mole fraction given in percent
6
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EN 17624:2022 (E)
4 Test methods
4.1 General
The determination consists of a series of ignition tests which are carried out with test mixtures varying
the test substance content.
The quiescent test mixture in the closed vessel is subjected to an ignition source. The overpressure and
the temperature rise as a result of the ignition is measured and characterizes 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 ascertained that there is no explosion range.
When it is established that a given test mixture will not ignite, it is recommended to analyse the
quantitative composition of the non-ignited test mixture flowing out of the test vessel in order to ensure
that no errors occurred either with the metering devices, or due to leakage.
NOTE 1 For organic substances consisting exclusively of carbon, hydrogen and oxygen (with the exception of
peroxides), the starting composition of the mixture to determine the LEL in air and oxygen can be roughly estimated.
For other oxidizers there is currently no estimation method available. At 20 °C, the LEL in air, in many cases, is
approximately half the test substance content of the stoichiometric composition in air. At 20 °C, the LEL in oxygen
is similar to that in air.
NOTE 2 The LEL is dependent on temperature. From ambient temperature the LEL in both air and oxygen
decreases more or less linearly with increasing temperature up to temperatures near the autoignition temperature,
where the relationship becomes non-linear. Where the relationship is still linear the LEL usually decreases by
between 5 % and 30 % per 100 K of temperature rise.
NOTE 3 Currently, neither for ambient conditions, nor for non-ambient conditions is there a method available
for readily estimating the UEL. However, the UEL rises remarkably with increasing temperature, increasing
pressure or oxidizing potential of the oxidizer.
4.2 Reagents and materials
4.2.1 Sample
The sample is either a single substance or a specified mixture of substances, or a process sample (of
known, or unknown composition).
When a single substance, or a specified mixture of substances, is used, the purity of each substance shall
be x(S) = 99,8 %, or better. In the case of a mixture of substances or a process sample of known
composition, its composition (including the scatter) shall be stated in the test report. In the case of a
process sample of unknown composition, the sample shall be defined as precisely as is possible e.g. by
process conditions.
Sample containers shall be kept closed before and after sampling to avoid changes in the sample
composition (e.g. loss of volatile components from mixtures).
4.2.2 Oxidizer
3
The oxidizer shall be free of water (x(S) ≤ 0,1 mol%, as water vapour) and oil (≤0,1 g/m oil).
If synthetic air is used, it shall be stated in the report.
4.2.3 Inert gases
The purity of the inert gas or the mixture of inert gases, shall be x(S) = 99,8 %, or better.
If a mixture of inert gases is used, the composition of the mixture shall be stated in the test report.
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4.2.4 Gaskets and mountings
In oxygen enriched mixtures it is absolutely necessary to take care that the materials of the gaskets and
mountings are not of organic origin and that they are oil and grease free to avoid accidents.
Special care shall be taken in the case of corrosive oxidizers or corrosive flammable substances.
4.3 Apparatus
4.3.1 Test vessel
The test vessel shall be cylindrical or spherical. If a cylindrical vessel is used, the length to diameter ratio
shall be between 1,0 and 1,5. The minimum internal volume of the test vessel depends on the initial
pressure in the tests and shall be according to the following Table 1.
Table 1 — Fundamental requirements of the apparatus
Minimum internal volume of
Initial pressure Ignition source
the test vessel
p
i
3
10 dm exploding wire
0,1 MPa ≤ p < 0,5 MPa
i
3
5 dm induction spark, surface-gap spark
surface-gap spark up to 2,5 MPa,
3
0,5 MPa ≤ p < 5 MPa
3 dm
i
exploding wire
3
p ≥ 5 MPa
1 dm exploding wire
i
The test vessel and any equipment (valves, ignition source, pressure and temperature sensors, etc.) fitted
to the vessel shall be designed to withstand a maximum overpressure of at least 15 times the initial
pressure if air is the oxidizer. For mixtures with an oxidizer having an oxidizing potential according to
EN ISO 10156:2017 higher than air, the test vessel and the equipment shall be designed to withstand a
maximum overpressure of at least 30 times the initial pressure.
The vessel shall be made of stainless steel or any material free of any catalytic effects and resistant to
corrosion from the initial gas mixture and the products of combustion. It has to be grounded.
The test vessel shall be equipped with sufficient ports to allow filling, evacuating and purging.
It has to be equipped with an ignition source, a temperature and pressure measuring system to set the
initial pressure and temperature and a temperature and pressure measuring system to measure the
generated temperature rise and overpressure after ignition.
4.3.2 Measurement system to adjust the initial pressure and temperature
4.3.2.1 Initial pressure
The pressure measuring system may contain a piezoresistive pressure transducer. If the test mixture is
prepared inside the test vessel by partial pressures using this pressure transducer then it shall be
calibrated. It is recommended that this pressure measuring system is disconnected, via a valve to protect
it, during the ignition trials.
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4.3.2.2 Initial temperature
The temperature measuring system consists of a sheath thermocouple and recording equipment. The
thermocouple shall have a limit deviation of not more than 1,5 K. The diameter of the thermocouple shall
not exceed 1,5 mm. It is recommended that the diameter of this thermocouple is larger than that of the
thermocouple used to detect the temperature rise because comparison of the starting temperature with
both temperature measuring systems may indicate any fault of the temperature measuring system to
measure the generated temperature rise.
4.3.2.3 Explosion overpressure measurement system
The pressure measuring system for detecting the overpressure after ignition shall contain a piezoelectric
or piezoresistive pressure transducer. If the head of the pressure transducers is not flush to the internal
wall the maximum distance between the head of the pressure transducer and inner surface shall be
100 mm.
The pressure transducers shall have a resonance frequency greater than 30 kHz.
The pressure measurement system shall have an accuracy that allows the explosion overpressure to be
−4
measured in accordance with the explosion criterion (see 3.6). It shall have a resolution of at least 10
of full scale.
4.3.2.4 Measurement system to measure the temperature rise
The temperature measuring system consists of a sheath thermocouple and recording equipment. The
thermocouple shall be mounted inside the vessel above the ignition source with a distance of (10 ± 1) mm
from the top of the vessel. Its diameter shall be 0,5 mm.
By comparison of the starting temperature with both temperature measuring systems any fault of the
temperature measuring system to measure the generated temperature rise can be detected.
4.3.3 Ignition source
4.3.3.1 General
The ignition source shall be positioned above the bottom of the test vessel. Suitable types of an ignition
source are either a series of induction sparks, a surface gap spark or an exploding wire. In the test report,
the type of ignition source used shall be stated.
4.3.3.2 Induction spark
This ignition source may be used for initial pressures up to 0,5 MPa.
A series of induction sparks between two electrodes is used as the ignition source.
The electrodes shall end (50 ± 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 3,0 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 voltage 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.
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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 an arrangement gives a power of
approximately 10 W.
Fluorinated substances, e.g. SF , CF , etc., can suppress induction sparks. In such cases an ignition source
6 4
according to 4.3.3.3 or 4.3.3.4 shall apply.
4.3.3.3 Surface-gap spark
This ignition source may be used for initial pressures up to 2,5 MPa.
An electric arc which is generated by passing an electric charge along the straight length of a graphite rod
connected between two metal rods is used as the ignition source.
The metal rods shall end (50 ± 1) mm above the bottom of the test vessel.
The electrical power necessary to generate the arc is supplied by a capacitive discharge or an isolating
transformer. If the arc is generated by using capacitive discharge the ignition energy delivered by the arc
depends on the capacity and charging voltage.
The energy delivered shall be in the range of 10 J to 20 J as within this range there is no significant
influence onto the results. 10 J to 20 J are achieved by adjusting the capacity to about 220 μF and the
charging voltage to about 440 V.
Stainless steel is a suitable material for the rods. The rods having a diameter between 3,0 mm and 4,0 mm
shall be parallel to each other with a separation distance of (6 ± 1) mm. The graphite rod having a
diameter of (2 ± 0,2) mm shall be fixed between the metal rods at their end. The electrodes shall be
mounted in the vessel such that they are gas tight at the highest pressures generated during the test. The
mounting shall be resistant to heat, resistant to corrosion from the test mixture and combustion products
and shall provide adequate electrical resistance from the test vessel body.
2
The cross-section of the wires connecting the power supply to the rods shall be between 2,5 mm and
2
7,0 mm . The length of the wires shall be less than 10 m.
4.3.3.4 Exploding wire
This ignition source may be used for initial pressures up to 10 MPa (see Table 1).
A strong electric current flows through a short thin wire between two metal rods, causing it to vaporize.
An electric arc ignites for a short time in the metal vapor and forms the ignition source.
The metal rods shall end (50 ± 1) mm above the bottom of the test vessel.
The electrical power required to melt the wire and generate the arc is supplied by an isolating
transformer or a capacitor with an inductor. The ignition energy delivered by the arc depends on its
duration and on the power rating of the isolating transformer or on capacity and voltage of the capacitor
respectively. The energy delivered shall be in the range of 10 J to 20 J as within this range there is no
significant variation in the explosion limits. This is achieved by limiting the power rating of the isolating
transformer to between 0,7 kW and 3,5 kW and by the use of a phase control technique. This is a chopping
technique that allows only part of the AC waveform from the transformer secondary windings to energize
the wire. If a capacitor is used, a capacity of 470 μF and a charging voltage up to 450 V is sufficient. The
inductor should have an inductance of about 5 mH and copper wire of a diameter equal or greater than
2,0 mm. The ignition energy can be determined by measuring current and voltage of the electric arc. The
voltage should be measured directly at the igniter and the current via a shunt with a sampling rate of at
least 10 kHz. If necessary, the energy can be reduced by reducing the charging voltage.
Brass and stainless steel are suitable materials for the rods. The rods shall be parallel to each other with
a separation distance of (5,0 ± 1,0) mm. For the fusing wire, a straight length of a NiCr wire (diameter
0,05 mm to 0,2 mm) shall be soldered to the tips of the metal rods. The electrodes shall be mounted in
the vessel such that they are gas tight at the highest pressures generated during the test. The mounting
10
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EN 17624:2022 (E)
shall be resistant to heat, resistant to corrosion from the test mixture and combustion products and shall
provide adequate electrical resistance from the test vessel body.
To reduce the time required for replacing the fusing wire after each test, the rods can be mounted in a
plug that can be screwed into the test vessel wall.
2
The cross-section of the wires connecting the transformer to the rods shall be between 2,5 mm and
2
7,0 mm . The length of the wires shall be less than 5 m. The diameter of the rods shall be between 3,0 mm
and 4,0 mm.
4.3.4 Equipment for preparing the test mixture
It is recommended to prepare the test mixture by partial pressures.
In case all components of the mixtures to test are gaseous this can be done inside or outside the test
vessel.
In this case the vessel used for the preparation of the mixture shall be fitted with:
— a vacuum pump and a vacuum gauge;
— a pressure measuring system to measure the partial pressures;
— a means of homogenizing the test mixture (e.g. a stirrer).
The pressure measuring system used to measure the partial pressures shall have a limit deviation which
corresponds to half of the incremental change of test substance content mentioned in 4.5 or better.
Especially when initial pressures higher than 2,5 MPa are used it is recommended to prepare the mixture
outside the explosion vessel at a pressure lower than the necessary initial pressure and to fill the test
vessel using a compressor.
In case the flammable components of the mixtures to test are liquid at ambient conditions it is
recommended to prepare the respective mixture inside the test vessel.
In this case the test vessel shall be fitted with:
— a vacuum pump and a vacuum gauge;
— a pressure measuring system to measure the partial pressures;
— a metering system capable of metering the necessary amount of the liquid with respect to the initial
pressure (e.g. HPLC pump);
— a means of homogenizing the test mixture (e.g. a stirrer).
The pressure measuring system used to measure the partial pressures shall have a limit deviation which
corresponds to half of the incremental change of test substance content mentioned i
...
SLOVENSKI STANDARD
oSIST prEN 17624:2021
01-januar-2021
Določanje eksplozijskih mej plinov in hlapov pri povišanem tlaku, povišani
temperaturi ali z oksidanti, ki niso sestavljeni iz zraka
Determination of explosion limits of gases and vapours at elevated pressures, elevated
temperatures or with oxidizers other than air
Bestimmung der Explosionsgrenzen von Gasen und Dämpfen bei erhöhten Drücken,
erhöhten Temperaturen oder mit Oxidationsmitteln, welche nicht aus Luft bestehen
Détermination des limites d'explosivité des gaz et vapeurs à pressions et températures
élevées avec des oxydants autres que l’air
Ta slovenski standard je istoveten z: prEN 17624
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
oSIST prEN 17624:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 17624:2021
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oSIST prEN 17624:2021
DRAFT
EUROPEAN STANDARD
prEN 17624
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2020
ICS 13.230
English Version
Determination of explosion limits of gases and vapours at
elevated pressures, elevated temperatures or with
oxidizers other than air
Détermination des limites d'explosivité des gaz et Bestimmung der Explosionsgrenzen von Gasen und
vapeurs à pressions et températures élevées avec des Dämpfen bei erhöhten Drücken, erhöhten
oxydants autres que l'air Temperaturen oder mit Oxidationsmitteln, welche
nicht aus Luft bestehen
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
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17624:2020 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
4 Test methods . 6
4.1 General . 6
4.2 Reagents and materials . 7
4.2.1 Sample . 7
4.2.2 Oxidizer. 7
4.2.3 Inert gases . 7
4.2.4 Gaskets and mountings . 7
4.3 Apparatus . 7
4.3.1 Test vessel . 7
4.3.2 Measurement system to adjust the initial pressure and temperature . 8
4.3.2.1 Initial pressure . 8
4.3.2.2 Initial temperature. 8
4.3.2.3 Explosion overpressure measurement system . 8
4.3.2.4 Measurement system to measure the temperature rise . 9
4.3.3 Ignition source . 9
4.3.3.1 Induction spark . 9
4.3.3.2 Surface-gap spark . 9
4.3.3.3 Exploding wire . 10
4.3.4 Equipment for preparing the test mixture . 10
4.3.5 Temperature regulating system . 11
4.3.6 Safety equipment. 12
4.4 Preparation of the test mixture . 12
4.4.1 General . 12
4.4.2 Preparation of the test mixture . 12
4.5 Procedure. 12
4.6 Recording of results . 13
5 Verification . 14
6 Test report . 14
Annex A (normative) Safety measures . 15
Annex B (normative) Verification . 16
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive2006/42/EC aimed to be covered . 18
Bibliography . 19
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European foreword
This document (prEN 17624:2020) 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 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) 2006/42/EC.
For relationship with EU Directive 2006/42/EC, see informative Annex ZA, which is an integral part of
this document.
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Introduction
In accordance with EN ISO 12100:2010, this is a type B standard.
The scope of EC Directive 2014/34 (ATEX) deals with explosive atmospheres of mixtures of flammable
substances and air in the pressures range between 0,8 kPa and 1,1 kPa and the temperature range
between −20 °C and 60 °C (atmospheric conditions). Therefore, the scope of the standards dealing with
the determination of safety characteristic data, for which CEN gave a mandate with respect to EU
Directive 2014/34 (ATEX), covers in general only such pressure and temperature conditions, and air as
the only oxidizer.
Technical conditions in plants etc. may differ remarkably from the pressure and temperature range of
the ATEX. Furthermore, explosive mixtures of flammable substances and oxidizers other than air are
likely to occur.
Safety characteristic data may, however, depend remarkably on both pressure and temperature, and
also the oxidizer.
The hazard of an explosion can be avoided by preventing the formation of explosive mixtures of gases
and/or vapours with oxidizers. To do so, the explosion limits (also known as “flammability limits) of the
flammable substance at the respective non-atmospheric conditions need to be known.
To obtain reliable and comparable results it is necessary to standardize the conditions for determining
the explosion limits at non-atmospheric conditions.
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1 Scope
This document specifies a test method to determine the explosion limits of gases, vapours and their
mixtures, mixed with a gaseous oxidizer or an oxidizer/inert gas mixture at pressures from 1 bar to
100 bar and for temperatures up to 400 °C.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 10156:2017, Gas cylinders — Gases and gas mixtures — Determination of fire potential and oxidizing
ability for the selection of cylinder valve outlets
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:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
flammable substance
substance in the form of gas, vapour or mixtures of these, able to undergo an explosive exothermic
reaction with an oxidizer or an oxidizer/inert gas mixture when ignited
[SOURCE: EN 13237:2012, 3.37, modified]
3.2
explosion range
range of the concentration of a flammable substance or mixture of substances with an oxidizer, within
which an explosion can occur determined under specified test conditions
Note 1 to entry: The explosion limits are not part of the explosion range.
[SOURCE: EN 13237:2012, 3.22, modified]
3.3
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.
[SOURCE: EN 13237:2012, 3.19.1, modified]
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3.4
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.
[SOURCE: EN 13237:2012, 3.19.2, modified]
3.5
inert gas
gas that does not react with the test substance or oxidizer
3.6
explosion criterion
either an explosion pressure p relative to the initial pressure (p ) as follows (considering the
ex i
overpressure that is created by the ignition source alone (p )):
IS
p /p ≥ (1,05 + p /p − 1) for initial pressures p ≤ 2)
ex i IS i i
p /p ≥ (1,02 + p /p − 1) (for initial pressures p > 2)
ex i IS i i
or a temperature rise (ΔT) of at least 100 K
3.7
oxidizer
any oxidising gas except highly reactive oxidisers with oxidizing potentials according to
EN ISO 10156:2017 higher than oxygen, e.g. ozone, fluorine, fluorinated compounds etc.
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 or air/inert gas
4 Test methods
4.1 General
The determination consists of a series of ignition tests which are carried out with test mixtures varying
the test substance content.
The quiescent test mixture in the closed vessel is subjected to an ignition source. The overpressure and
the temperature rise as a result of the ignition is measured and characterizes 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 ascertained that there is no explosion range.
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When it is established that a given test mixture will not ignite, it is recommended to analyse the
quantitative composition of the non-ignited test mixture flowing out of the test vessel in order to ensure
that no errors occurred either with the metering devices, or due to leakage.
NOTE 1 For organic substances consisting exclusively of carbon, hydrogen and oxygen (with the exception of
peroxides), the starting composition of the mixture to determine the LEL in air and oxygen can be roughly
estimated. For other oxidizers there is currently no estimation method available.
NOTE 2 At 20 °C, the LEL in air, in many cases, is approximately half the test substance content of the
stoichiometric composition in air. At 20 °C, the LEL in oxygen is similar to that in air. The temperature
dependence of the LEL has to be taken into account. Up to 200 °C resp. up to temperatures near to the auto-
ignition temperature, the LEL in air and oxygen decreases more or less linearly up to 50 % of the value estimated
for 20 °C.
NOTE 3 Currently, neither for ambient conditions, nor for non-ambient conditions is there a method available
for readily estimating the UEL. However, the UEL rises remarkably with increasing temperature, increasing
pressure or oxidizing potential of the oxidizer.
4.2 Reagents and materials
4.2.1 Sample
The sample is 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, its composition (including the scatter) shall be stated in the test report. In the case of a
process sample of unknown composition, the sample shall be defined as precisely as is possible e.g. by
process conditions.
Sample containers shall be kept closed before and after sampling to avoid changes in the sample
composition (e.g. loss of volatile components from mixtures).
4.2.2 Oxidizer
3
The oxidizer shall be free of water (≤0,1 mol% water vapour absolute) and oil (≤0,1 g/m oil).
If synthetic air is used, it shall be stated in the report.
4.2.3 Inert gases
The purity of the inert gas or the mixture of inert gases, shall be 99,8 mol%, or better.
If a mixture of inert gases is used, the composition of the mixture shall be stated in the test report.
4.2.4 Gaskets and mountings
In oxygen enriched mixtures it is absolutely necessary to take care that the materials of the gaskets and
mountings are not of organic origin and that they are oil and grease free to avoid accidents.
Special care shall be taken in the case of corrosive oxidizers or corrosive flammable substances.
4.3 Apparatus
4.3.1 Test vessel
The test vessel shall be cylindrical or spherical. If a cylindrical vessel is used, the length to diameter
ratio shall be between 1,0 and 1,5. The minimum internal volume of the test vessel depends on the
initial pressure in the tests and shall be according to the following Table 1.
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Table 1 — Fundamental requirements of the apparatus
Minimum internal volume of
Initial Pressure (p )
Ignition source
i
the test vessel
3
exploding wire
10 dm
1 bar ≤ p < 5 bar
i
3
induction spark, surface-gap spark
5 dm
surface-gap spark up to 25 bar,
5 bar ≤ p < 50 bar 3
i 3 dm
exploding wire
p ≥ 50 bar 3
exploding wire
i 1 dm
The test vessel and any equipment (valves, ignition source, pressure and temperature sensors etc.)
fitted to the vessel shall be designed to withstand a maximum overpressure of at least 15 times the
initial pressure if air is the oxidizer. For mixtures with an oxidizer having an oxidizing potential
according to EN ISO 10156:2017 higher than air, the test vessel and the equipment shall be designed to
withstand a maximum overpressure of at least 30 times the initial pressure.
The vessel shall be made of stainless steel or any material free of any catalytic effects and resistant to
corrosion from the initial gas mixture and the products of combustion. It has to be grounded.
The test vessel shall be equipped with sufficient ports to allow filling, evacuating and purging.
It has to be equipped with an ignition source, a temperature and pressure measuring system to set the
initial pressure and temperature and a temperature and pressure measuring system to measure the
generated temperature rise and overpressure after ignition.
4.3.2 Measurement system to adjust the initial pressure and temperature
4.3.2.1 Initial pressure
The pressure measuring system may contain a piezoresistive pressure transducer. If the test mixture is
prepared inside the test vessel by partial pressures using this pressure transducer then it shall be
calibrated. It is recommended that this pressure measuring system is disconnected, via a valve to
protect it, during the ignition trials.
4.3.2.2 Initial temperature
The temperature measuring system consists of a sheath thermocouple and recording equipment. The
thermocouple shall have a limit deviation of not more than 1,5 K. The diameter of the thermocouple
shall not exceed 1,5 mm. It is recommended that the diameter of this thermocouple is larger than that of
the thermocouple used to detect the temperature rise because comparison of the starting temperature
with both temperature measuring systems may indicate any fault of the temperature measuring system
to measure the generated temperature rise.
4.3.2.3 Explosion overpressure measurement system
The pressure measuring system for detecting the overpressure after ignition shall contain a
piezoelectric or piezoresistive pressure transducer. If the head of the pressure transducers is not flush
to the internal wall the maximum distance between the head of the pressure transducer and inner
surface shall be 100 mm.
The pressure transducers shall have a resonance frequency greater than 30 kHz.
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The pressure measurement system shall have an accuracy that allows the explosion overpressure to be
−4
measured in accordance with the explosion criterion (see 3.6). It shall have a resolution of at least 10
of full scale.
4.3.2.4 Measurement system to measure the temperature rise
The temperature measuring system consists of a sheath thermocouple and recording equipment. The
thermocouple shall be mounted inside the vessel above the ignition source with a distance of
10 mm ± 1 mm from the top of the vessel. Its diameter shall be 0,5 mm.
By comparison of the starting temperature with both temperature measuring systems any fault of the
temperature measuring system to measure the generated temperature rise can be detected.
4.3.3 Ignition source
The ignition source shall be positioned above the bottom of the test vessel. Suitable types of an ignition
source are either a series of induction sparks, a surface gap spark or an exploding wire. In the test
report, the type of ignition source used shall be stated.
4.3.3.1 Induction spark
This ignition source may be used for initial pressures up to 5 bar.
A series of induction sparks between two electrodes is used as the ignition source.
The electrodes shall end (50 ± 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 3,0 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 an arrangement
gives a power of approximately 10 W.
Fluorinated substances, e.g. SF6, CF4 etc., can suppress induction sparks. In such cases an ignition
source according to 4.3.3.2 or 4.3.3.3 shall apply.
4.3.3.2 Surface-gap spark
This ignition source may be used for initial pressures up to 25 bar.
An electric arc which is generated by passing an electric charge along the straight length of a graphite
rod connected between two metal rods is used as the ignition source.
The metal rods shall end (50 ± 1) mm above the bottom of the test vessel.
The electrical power necessary to generate the arc is supplied by a capacitive discharge or an isolating
transformer. If the arc is generated by using capacitive discharge the ignition energy delivered by the
arc depends on the capacity and charging voltage.
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The energy delivered shall be in the range of 10 J to 20 J as within this range there is no significant
influence onto the results. Ten J to 20 J are achieved by adjusting the capacity to about 220 μF and the
charging voltage to about 440 V.
Stainless steel is a suitable material for the rods. The rods having a diameter between 3,0 mm and
4,0 mm shall be parallel to each other with a separation distance of (6 ± 1) mm. The graphite rod having
a diameter of (2 ± 0,2) mm shall be fixed between the metal rods at their end. The electrodes shall be
mounted in the vessel such that they are gas tight at the highest pressures generated during the test.
The mounting shall be resistant to heat, resistant to corrosion from the test mixture and combustion
products and shall provide adequate electrical resistance from the test vessel body.
2
The cross-section of the wires connecting the power supply to the rods shall be between 2,5 mm and
2
7,0 mm . The length of the wires shall be less than 10 m.
4.3.3.3 Exploding wire
This ignition source may be used for initial pressures up to 100 bar (see Table 1).
An electric arc is generated by passing an electric charge along a straight length of exploding wire
connected between two metal rods.
The metal rods shall end (50 ± 1) mm above the bottom of the test vessel.
The electrical power required to melt the wire and generate the arc is supplied by an isolating
transformer or a capacitor with an inductor. The ignition energy delivered by the arc depends on its
duration and on the power rating of the isolating transformer or on capacity and voltage of the
capacitor respectively. The energy delivered shall be in the range of 10 J to 20 J as within this range
there is no significant variation in the explosion limits. This is achieved by limiting the power rating of
the isolating transformer to between 0,7 kW and 3,5 kW and by the use of a phase control technique.
This is a chopping technique that allows only part of the AC waveform from the transformer secondary
windings to energize the wire. If a capacitor is used, a capacity of 470 μF and a charging voltage up to
450 V is sufficient. The inductor should have an inductance of about 5 mH and copper wire of a
diameter equal or greater than 2,0 mm. The ignition energy can be determined by measuring current
and voltage of the electric arc. The voltage should be measured directly at the igniter and the current via
a shunt with a sampling rate of at least 10 kHz. If necessary, the energy can be reduced by reducing the
charging voltage.
Brass and stainless steel are suitable materials for the rods. The rods shall be parallel to each other with
a separation distance of (5,0 ± 1,0) mm. For the fusing wire, a straight length of a NiCr wire (diameter
0,05 mm to 0,2 mm) shall be soldered to the tips of the of the metal rods. The electrodes shall be
mounted in the vessel such that they are gas tight at the highest pressures generated during the test.
The mounting shall be resistant to heat, resistant to corrosion from the test mixture and combustion
products and shall provide adequate electrical resistance from the test vessel body.
To reduce the time required for replacing the fusing wire after each test, the rods can be mounted in a
plug that can be screwed into the test vessel wall.
2
The cross-section of the wires connecting the transformer to the rods shall be between 2,5 mm and
2
7,0 mm . The length of the wires shall be less than 5 m. The diameter of the rods shall be between
3,0 mm and 4,0 mm.
4.3.4 Equipment for preparing the test mixture
It is recommended to prepare the test mixture by partial pressures.
In case all components of the mixtures to test are gaseous this can be done inside or outside the test
vessel.
In this case the vessel used for the preparation of the mixture shall be fitted with:
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— a vacuum pump and a vacuum gauge;
— a pressure measuring system to measure the partial pressures;
— a means of homogenizing the test mixture (e.g. a stirrer).
The pressure measuring system used to measure the partial pressures shall have a limit deviation
which corresponds to half of the incremental change of test substance content mentioned in 4.5 or
better. Especially when initial pressures higher than 25 bar are used it is recommended to prepare the
mixture outside the explosion vessel at a pressure lower than the necessary initial pressure and to fill
the explosion vessel using a compressor.
In case the flammable components of the mixtures to test are liquid at ambient conditions it is
recommended to prepare the respective mixture inside the test vessel.
In this case the test vessel s
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