EN ISO 16852:2016

SLOVENSKI STANDARD
01-februar-2017
1DGRPHãþD
SIST EN ISO 16852:2010
Plamenske zapore - Zahtevane lastnosti, preskusne metode in omejitve uporabe
(ISO 16852:2016)
Flame arresters - Performance requirements, test methods and limits for use (ISO
16852:2016)
Flammendurchschlagsicherungen - Leistungsanforderungen, Prüfverfahren und
Einsatzgrenzen (ISO 16852:2016)
Arrête-flammes - Exigences de performance, méthodes d'essai et limites d'utilisation
(ISO 16852:2016)
Ta slovenski standard je istoveten z: EN ISO 16852:2016
ICS:
13.220.10 Gašenje požara Fire-fighting
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16852
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2016
EUROPÄISCHE NORM
ICS 13.220.10 Supersedes EN ISO 16852:2010
English Version
Flame arresters - Performance requirements, test methods
and limits for use (ISO 16852:2016)
Arrête-flammes - Exigences de performance, méthodes Flammendurchschlagsicherungen -
d'essai et limites d'utilisation (ISO 16852:2016) Leistungsanforderungen, Prüfverfahren und
Einsatzgrenzen (ISO 16852:2016)
This European Standard was approved by CEN on 19 September 2016.

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

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16852:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/34/EU concerning equipment and protective
systems intended for use in potentially explosive atmospheres . 4

European foreword
This document (EN ISO 16852:2016) has been prepared by Technical Committee ISO/TC 21
“Equipment for fire protection and fire fighting” in collaboration with 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 May 2017, and conflicting national standards shall be
withdrawn at the latest by May 2017.
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 ISO 16852:2010.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
According to the CEN-CENELEC Internal Regulations, the national standards organizations 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.
Endorsement notice
The text of ISO 16852:2016 has been approved by CEN as EN ISO 16852:2016 without any modification.
Annex ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/34/EU concerning equipment and
protective systems intended for use in potentially explosive atmospheres
This European Standard has been prepared under a mandate given to CEN by the European
Commission and the European Free Trade Association to provide a means of conforming to Essential
Requirements of the New Approach Directive 2014/34/EU concerning equipment and protective
systems intended for use in potentially explosive atmospheres
Once this standard is cited in the Official Journal of the European Union under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the clauses of
this standard given in Table ZA.1 confers, within the limits of the scope of this standard, a presumption
of conformity with the corresponding Essential Requirements of that Directive and associated EFTA
regulations.
Table ZA.1 — Correspondence between this European Standard and Directive 2014/34/EU
concerning equipment and protective systems intended for use in potentially explosive
atmospheres
Essential Requirements (ERs) of Clause(s)/subclause(s) of this EN
Qualifying remarks/Notes
Directive 2014/34/EU
1.0.1 Principles of integrated Clause 5; 6.2
explosion safety
1.0.2 Design and manufacture 6.2; 7.1
considerations
1.0.3 Special checking and Annex C
maintenance conditions
1.0.4 Surrounding area conditions 6.2
1.0.5 Marking 12.2
1.0.6 Instructions 7.4; 8.4; 9.3; 10.3; 12.1
1.1.1 Operational stresses on 6.2; 7.1; Annex C
material
1.1.2 Reaction of material 6.2; Annex C
1.1.3 Wear of material 6.2; 7.1
1.2.1 Design and construction for 5.1; 6.2; 6.3; 6.4; 6.5; 7.1;
safe operation
1.2.3 Enclosed structures and 6.6
prevention of leaks
1.2.5 Additional mans of protection 12.1
1.2.8 Overloading of equipment 7.3.4; 10.1; 11.1
1.2.9 Flameproof enclosure systems 6.3; 6.4; 7.3.2.3
1.3.1 Hazards arising from different 6.2
ignition sources
1.3.2 Hazards arising from static Annex B; Annex C
electricity
1.4.1 External effects 6.2
1.4.2 Mechanical, thermal and 6.2
chemical stresses
1.6.4 Hazards arising from 6.4
connections
3.0.1 Dimensioning 6; 7; 8; 9; 10; 11
3.0.2 Design and position 6; 7; 8; 9; 10; 11
3.1.2 Shock waves 6.5; 7.3.3
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling
within the scope of this standard.
INTERNATIONAL ISO
STANDARD 16852
Second edition
2016-10-15
Flame arresters — Performance
requirements, test methods and
limits for use
Arrête-flammes — Exigences de performance, méthodes d’essai et
limites d’utilisation
Reference number
ISO 16852:2016(E)
©
ISO 2016
ISO 16852:2016(E)
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
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www.iso.org
ii © ISO 2016 – All rights reserved

ISO 16852:2016(E)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms and symbols . 5
5 Hazards and flame arrester classifications . 6
5.1 Flame transmission: deflagration, stable and unstable detonation . 6
5.2 Flame transmission: stabilized burning . 7
6 General requirements . 7
6.1 Measuring instruments . 7
6.2 Construction . 7
6.3 Housings . 7
6.4 Joints . 8
6.5 Pressure test . 8
6.6 Leak test . 8
6.7 Flow measurement (air) . 8
6.8 Flame transmission test . 8
6.8.1 General. 8
6.8.2 Test mixtures . 9
6.9 Summary of tests to be conducted .10
7 Specific requirements for static flame arresters .11
7.1 Construction .11
7.2 Design series .11
7.3 Flame transmission test .12
7.3.1 General.12
7.3.2 Deflagration test .12
7.3.3 Detonation test .16
7.3.4 Short time burning test .21
7.3.5 Endurance burning test .23
7.4 Limits for use .25
7.4.1 General.25
7.4.2 In-line flame arrester .26
7.4.3 Pre-volume flame arrester .26
7.4.4 Detonation flame arrester .26
7.4.5 Short time burn flame arresters .26
8 Specific requirements for liquid product detonation flame arresters .27
8.1 Liquid seals .27
8.2 Foot valves .27
8.3 Flame transmission test .28
8.4 Limits for use .29
9 Specific requirements for dynamic flame arresters (high velocity vent valves).29
9.1 General .29
9.2 Flame transmission tests .30
9.2.1 Low flow flame transmission test .30
9.2.2 Flame transmission test by opening and closing .31
9.2.3 Deflagration test .32
9.2.4 Endurance burning test .32
9.3 Limits for use .33
10 Specific requirements for hydraulic flame arresters .33
ISO 16852:2016(E)
10.1 Equipment .33
10.2 Flame transmission test .33
10.2.1 General.33
10.2.2 Short time burning test .33
10.2.3 Deflagration test .34
10.2.4 Detonation test .34
10.3 Limits for use .34
11 Test of flame arresters installed on or within gas conveying equipment .37
11.1 General .37
11.2 Flame transmission test .37
11.2.1 General.37
11.2.2 Test procedure for gas conveying equipment with inlet pressure >600 hPa .39
11.2.3 Test procedure for gas conveying equipment with inlet pressure ≤600 hPa .39
12 Information for use .40
12.1 Instructions for use .40
12.2 Marking .41
12.2.1 Flame arrester .41
12.2.2 Flame arrester element .43
Annex A (normative) Flow measurement .44
Annex B (informative) Information for selecting flame arresters .48
Annex C (informative) Best practice .49
Bibliography .50
iv © ISO 2016 – All rights reserved

ISO 16852:2016(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 21, Equipment for fire protection and firefighting.
This second edition cancels and replaces the first edition (ISO 16852:2008), which has been technically
revised with the following changes:
— Clause 1: information concerning existing standard from IMO (International Maritime Organization)
for maritime application added;
— 3.18: definition of dynamic flame arrester revised;
— Clause 4: abbreviation for the time t added;
Ppeak
— 6.5: production test procedure for flame arresters of welded construction and of cast components
revised;
— 6.7: flow measurement (air) revised;
— 7.3.3.2 and 7.3.3.4: in the flame transmission test for stable and unstable detonation without
restriction the deflagration tests with L /D = 5 deleted;
u
— 7.3.3.2: formula for the calculation of the average value p added;
md
— Figure 1 and Figure 3: figures for the test apparatus for deflagration tests of end-of-line flame
arrester and of pre-volume flame arresters revised;
— Figure 6 and Figure 7: figures for the test apparatus for short time burning test and for endurance
burning test revised;
— 7.3.4: short time burning test for inline flame arresters revised;
— 7.3.5: test pressure for the endurance burning test of inline flame arresters added;
— 7.4.5: limits for use of short time burn flame arresters added;
— 8.3: flame transmission test for liquid product detonation flame arresters revised;
ISO 16852:2016(E)
— Clause 9: “Specific requirements for dynamic flame arresters (high velocity vent valves)” revised;
— Clause 11: “Test of flame arresters installed on or within gas conveying equipment” added;
— 12.1: “Instructions for use” revised;
— 12.2: “Marking” revised;
— Figure A.1: pipe lengths revised;
— Annex C: “Best practice” revised;
— Annex D: “Use of in-line stable detonation flame arresters” deleted;
— Bibliography: updated.
It also incorporates the Technical Corrigenda ISO 16852:2008/Cor 1:2008 and ISO 16852:2008/Cor 2:2009.
vi © ISO 2016 – All rights reserved

ISO 16852:2016(E)
Introduction
Flame arresters are safety devices fitted to openings of enclosures or to pipe work and are intended to
allow flow but prevent flame transmission. They have widely been used for decades in the chemical and
oil industry, and a variety of national standards is available. This International Standard was prepared
by an international group of experts, whose aim was to establish an international basis by harmonizing
and incorporating recent national developments and standards as far as reasonable.
This International Standard addresses manufacturers (performance requirements) and test institutes
(test methods), as well as customers (limits for use).
Only relatively general performance requirements are specified and these are kept to a strict minimum.
Experience has shown that excessively specific requirements in this field often create unjustified
restrictions and prevent innovative solutions.
The hazard identification of common applications found in industry leads to the specification of the test
methods. These test methods reflect standard practical situations and, as such, form the heart of this
International Standard because they also allow classification of the various types of flame arresters
and then determination of the limits of use.
A considerable number of test methods and test conditions had to be taken into account for two main
reasons.
a) Different types of flame arresters are covered with respect to the operating principle (static,
hydraulic, liquid, dynamic) and each type clearly needs its specific test set-up and test procedure.
b) It is necessary to adapt flame arresters to the special conditions of application (gas, installation)
because of the conflicting demands of high flame quenching capability and low pressure loss; this
situation is completely different from the otherwise similar principle of protection by flameproof
enclosure (of electrical equipment), where the importance of process gas flow through gaps is
negligible; importance being placed on the flame quenching effect of the gap.
Consequently, in this International Standard, the testing and classification related to the gas groups
and the installation conditions have been subdivided more than is usually the case. In particular,
— explosion group IIA is subdivided into sub-groups IIA1 and IIA,
— explosion group IIB is subdivided into sub-groups IIB1, IIB2, IIB3 and IIB, and
— the type “detonation arrester” is divided into four sub-types, which take into account specific
installation situations.
The test conditions lead to the limits for use which are most important for the customer. This
International Standard specifies this safety relevant information and its dissemination through the
manufacturer’s written instructions for use and the marking of the flame arresters.
The limits for use are also a link to more general (operational) safety considerations and regulations,
which remain the responsibility of national or corporate authorities. Annex B and Annex C offer some
guidance in this field.
INTERNATIONAL STANDARD ISO 16852:2016(E)
Flame arresters — Performance requirements, test
methods and limits for use
1 Scope
This International Standard specifies the requirements for flame arresters that prevent flame
transmission when explosive gas-air or vapour-air mixtures are present. It establishes uniform principles
for the classification, basic construction and information for use, including the marking of flame arresters,
and specifies test methods to verify the safety requirements and determine safe limits of use.
This International Standard is valid for pressures ranging from 80 kPa to 160 kPa and temperatures
ranging from −20 °C to + 150 °C.
NOTE 1 For flame arresters with operational conditions inside the scope, but outside atmospheric conditions,
see 7.4.
NOTE 2 In designing and testing flame arresters for operation under conditions other than those specified
above, this International Standard can be used as a guide. However, additional testing related specifically to the
intended conditions of use is advisable. This is particularly important when high temperatures and pressures are
applied. The test mixtures might need to be modified in these cases.
NOTE 3 An additional standard IMO MSC/Circ. 677 for maritime application from IMO (International Maritime
Organization) exists.
This International Standard is not applicable to the following:
— external safety-related measurement and control equipment that might be required to keep the
operational conditions within the established safe limits;
NOTE 4 Integrated measurement and control equipment, such as integrated temperature and flame sensors
as well as parts which, for example, intentionally melt (retaining pin), burn away (weather hoods) or bend
(bimetallic strips), is within the scope of this International Standard.
— flame arresters used for explosive mixtures of vapours and gases, which tend to self-decompose
(e.g. acetylene) or which are chemically unstable;
— flame arresters used for carbon disulphide, due to its special properties;
— flame arresters whose intended use is for mixtures other than gas-air or vapour-air mixtures (e.g.
higher oxygen-nitrogen ratio, chlorine as oxidant, etc.);
— flame arrester test procedures for internal-combustion compression ignition engines;
— fast acting valves, extinguishing systems and other explosion isolating systems.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For undated references, the latest edition of the referenced document
(including any amendments) applies.
IEC 60079-1, Explosive atmospheres — Part 1: Equipment protection by flameproof enclosures “d”
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO 16852:2016(E)
3.1
flame arrester
device fitted to the opening of an enclosure, or to the connecting pipe work of a system of enclosures,
and whose intended function is to allow flow but prevent the transmission of flame
3.2
housing
portion of a flame arrester (3.1) whose principal function is to provide a suitable enclosure for the flame
arrester element (3.3) and allow mechanical connections to other systems
3.3
flame arrester element
portion of a flame arrester (3.1) whose principal function is to prevent flame transmission
3.4
stabilized burning
steady burning of a flame stabilized at, or close to, the flame arrester element (3.3)
3.5
short time burning
stabilized burning (3.4) for a specified time
3.6
endurance burning
stabilized burning (3.4) for an unlimited time
3.7
explosion
abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or both
simultaneously
[SOURCE: ISO 8421-1:1987, 1.13]
3.8
deflagration
explosion (3.7) propagating at subsonic velocity
[SOURCE: ISO 8421-1:1987, 1.11]
3.9
detonation
explosion (3.7) propagating at supersonic velocity and characterized by a shock wave
[SOURCE: ISO 8421-1:1987, 1.12]
3.10
stable detonation
detonation (3.9) progressing through a confined system without significant variation of velocity and
pressure characteristics
Note 1 to entry: For the atmospheric conditions, test mixtures and test procedures of this International Standard,
typical velocities range between 1 600 m/s and 2 200 m/s.
3.11
unstable detonation
detonation (3.9) during the transition of a combustion process from a deflagration (3.8) into a stable
detonation
Note 1 to entry: The transition occurs in a limited spatial zone, where the velocity of the combustion wave is not
constant and where the explosion pressure is significantly higher than in a stable detonation. The position of this
transition zone depends, amongst other factors, on pipe diameter, pipe configuration, test gas and explosion group.
2 © ISO 2016 – All rights reserved

ISO 16852:2016(E)
Note 2 to entry: An unstable detonation presents a higher level of hazard than a stable detonation due to higher
flame speeds and pressures.
3.12 Characteristic safety data of explosive mixtures
3.12.1
maximum experimental safe gap
MESG
maximum gap between the two parts of the interior chamber which, under the test conditions specified
below, prevents ignition of the external gas mixture through a 25 mm long flame path when the internal
mixture is ignited, for all concentrations of the tested gas or vapour in air
Note 1 to entry: Safe gap measured in accordance with IEC 60079-20-1:2010.
3.12.2
explosion group
Ex.G
ranking of flammable gas-air mixtures with respect to the MESG
Note 1 to entry: See Table 2, columns 1 and 2.
3.13
bi-directional flame arrester
flame arrester (3.1) that prevents flame transmission from both sides
3.14
deflagration flame arrester
DEF
flame arrester (3.1) designed to prevent the transmission of a deflagration (3.8)
Note 1 to entry: It can be an end-of-line flame arrester (3.21) or an in-line flame arrester (3.22).
3.15
detonation flame arrester
DET
flame arrester (3.1) designed to prevent the transmission of a detonation
Note 1 to entry: It can be an end-of-line flame arrester (3.21) or an in-line flame arrester (3.22), and can be used for
both stable detonations (3.10) and unstable detonations (3.11).
3.16
endurance flame arrester
flame arrester (3.1) that prevents flame transmission during and after endurance burning (3.6)
3.17
static flame arrester
flame arrester (3.1) designed to prevent flame transmission by quenching gaps
3.17.1
measurable type
flame arrester (3.1) where the quenching gaps of the flame arrester element (3.3) can be technically
drawn, measured and controlled
3.17.2
non-measurable type
flame arrester (3.1) where the quenching gaps of the flame arrester element (3.3) cannot be technically
drawn, measured or controlled
EXAMPLE Random structures such as knitted mesh, sintered materials and gravel beds.
ISO 16852:2016(E)
3.18
dynamic flame arrester
high velocity vent valve
pressure relief valve designed always to have efflux velocities that prevent the flame propagation
against the flow direction
Note 1 to entry: It can be deflagration proof (see 3.14) or endurance burn proof (see 3.16).
3.19
liquid product detonation flame arrester
flame arrester (3.1) in which the liquid product is used to form a liquid seal as a flame arrester medium,
in order to prevent flame transmission of a detonation
Note 1 to entry: There are two types of liquid product detonation flame arrester for use in liquid product lines:
liquid seals and foot valves.
3.19.1
liquid seal flame arrester
flame arrester (3.1) designed to use the liquid product to form a barrier to flame transmission
3.19.2
foot valve flame arrester
flame arrester (3.1) designed to use the liquid product combined with a non-return valve to form a
barrier to flame transmission
3.20
hydraulic flame arrester
flame arrester (3.1) designed to break the flow of an explosive mixture into discrete bubbles in a water
column, thus preventing flame transmission
3.21
end-of-line flame arrester
flame arrester (3.1) that is fitted with one pipe connection only
3.22
in-line flame arrester
flame arrester (3.1) that is fitted with two pipe connections, one on each side of the flame arrester
3.23
pre-volume flame arrester
VDEF
flame arrester (3.1) that, after ignition by an internal ignition source, prevents flame transmission from
inside an explosion-pressure-resistant containment (e.g. a vessel or closed pipe work) to the outside, or
into the connecting pipe work
Note 1 to entry: Explosion-pressure resistance is a property of vessels and equipment designed to withstand the
expected explosion pressure without becoming permanently deformed.
3.24
integrated temperature sensor
temperature sensor integrated into the flame arrester, as specified by the manufacturer of the flame
arrester, in order to provide a signal suitable to activate counter measures
3.25
atmospheric conditions
conditions with pressures ranging from 80 kPa to 110 kPa and temperatures ranging from −20 °C
to +60 °C
4 © ISO 2016 – All rights reserved

ISO 16852:2016(E)
4 Abbreviated terms and symbols
A free area of a static flame arrester element
A nominal cross sectional area of the flame arrester connection
p
A cross sectional area on the unprotected side of the flame arrester element
t
A effective open area of the flame arrester element on the protected side
u
D pipe diameter
D minimum diameter of the pipe on the protected side of a dynamic flame arrester
M
L maximum length without undamped oscillations
M
L pipe length upstream of the dynamic flame arrester used in flame transmission test
m
L pipe length on the protected side
p
L pipe length between flame arrester and restriction
r
L pipe length on the unprotected side, maximum allowable run-up length for installation
u
L , L , pipe lengths in the flow test
1 2
L , L
3 4
p time average value of the detonation pressure in the time interval of 200 μs after arrival of the deto-
md
nation shock wave
p maximum time average value of the transient pressure of an unstable detonation over a time inter-
mu
val of 200 μs
p pressure in the pressure test
t
p pressure in the flow test of an end-of-line flame arrester
T
p pressure before ignition
TB
p maximum operational pressure
Δ pressure drop in the flow test of an in-line flame arrester
p
p maximum pressure for the endurance burning test of dynamic flame arresters
E
p pressure which cause the maximum temperature at endurance burning test
m
R ratio of the effective open area of the flame arrester element to pipe cross sectional area
A
R ratio of the free volume of the flame arrester element to the whole volume
U
t burning time
BT
t time at which the peak pressure correlating to the leading shock front is achieved in the test
Ppeak
T temperature of the flame arrester before ignition
TB
T maximum operational temperature of the flame arrester
v maximum flow velocity during the volume flow-pressure drop measurement (flow test)
max
v minimum flow velocity during the volume flow-pressure drop measurement (flow test)
min

volume flow rate
V

critical volume flow rate
V
c

flow rate at closing point of dynamic flame arresters
V
CL

minimum volume flow rate for endurance burning on dynamic flame arresters
V

maximum volume flow rate for endurance burning on dynamic flame arresters
V
E

maximum volume flow rate for dynamic flame arresters at the set pressure
V
K

volume flow rate leading to maximum temperature
V
m
ISO 16852:2016(E)
minimum volume in the protected tank
V
M

safe volume flow rate
V
max

safe volume flow rate including a safety margin
V
s

maximum volume flow rate leading to flame transmission
V
t
Z minimum water seal immersion depth at rest above the outlet openings of the immersion tubes
Rmin
Z immersion depth at rest, corresponding to Z plus the manufacturer’s recommended safety margin
R Rmin
Z minimum operational water seal immersion depth when the mixture flow displaces the water from
0min
the immersion tubes, where Z > Z
0min Rmin
Z operational immersion depth, corresponding to Z plus the manufacturer’s recommended safe-
0 0min
ty margin
All pressure values are absolute pressures.
NOTE Symbols in the figures for the flame arrester are in line with ISO 14617-7.
5 Hazards and flame arrester classifications
5.1 Flame transmission: deflagration, stable and unstable detonation
The ignition of an explosive mixture will initiate a deflagration. A flame arrester covering only this
hazard is classified as a deflagration flame arrester.
A deflagration when confined in a pipe may accelerate and undergo transition through an unstable to
a stable detonation, provided sufficient pipe length is available. This pipe length may vary depending
upon the initial conditions of the mixture and the pipe work configuration.
A flame arrester tested in accordance with 7.3.3.2 or 7.3.3.3 is classified as a stable detonation flame
arrester and is suitable for deflagrations and stable detonations.
Unstable detonations are a specific hazard requiring higher performance flame arresters than for
stable detonations.
A flame arrester tested in accordance with 7.3.3.4 or 7.3.3.5 is classified as an unstable detonation
flame arrester and is suitable for deflagrations, stable detonations and unstable detonations.
These hazards relate to specific installations and in each case the flame arrester successfully tested
at p is suitable for operational pressures p ≤ p , and the application is limited to mixtures with an
TB 0 TB
MESG equal to or greater than that tested.
The specific hazards covered by this International Standard, the classification and the testing required
for the appropriate flame arrester are listed in Table 1.
Table 1 — Flame arrester classification for deflagration, stable and unstable detonation
Application Flame arrester classification
a) unconfined deflagration into an enclosure or vessel end-of-line deflagration
b) confined deflagration propagating along a pipe into
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