BS EN ISO 5175-2017

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BS EN ISO 5175‑1:2017
BSI Standards Publication
Gas welding equipment - Safety devices
Part 1: Devices incorporating a flame (flashback) arrestor
BS EN ISO 5175‑1:2017
BRITISH STANDARD
National foreword
This British Standard is the UK implementation of EN ISO 5175‑1:2017.
It is identical to ISO 5175‑1:2017. It supersedes BS EN 730‑1:2002, which
is withdrawn.
The UK participation in its preparation was entrusted to Technical
Committee WEE/18, Gas welding and cutting appliances.
A list of organizations represented on this committee can be obtained on
request to its secretary.
This publication does not purport to include all the necessary provisions
of a contract. Users are responsible for its correct application.
© The British Standards Institution 2017
Published by BSI Standards Limited 2017
ISBN 978 0 580 92470 5
ICS 25.160.30
Compliance with a British Standard cannot confer immunity from
legal obligations.
This British Standard was published under the authority of the
Standards Policy and Strategy Committee on 31 December 2017.
Amendments/corrigenda issued since publication
Date
Text affected
EUROPEAN STANDARD
EN ISO 5175‑1
EUROPÄISCHE NORM
November 2017
NORME EUROPÉENNE
ICS 25.160.30
Supersedes EN 730‑1:2002
English Version
Gas welding equipment - Safety devices - Part 1:
Devices incorporating a flame (flashback) arrestor (ISO
5175-1:2017)
Matériel de soudage au gaz - Dispositifs
de sécurité - Partie 1: Dispositifs avec
arrêt de flamme (ISO 5175-1:2017)
Gasschweißgeräte - Sicherheitseinrichtungen - Teil 1:
Mit integrierter Flammensperre (ISO 5175-1:2017)
This European Standard was approved by CEN on 20 November 2017.
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, 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: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN
All rights of exploitation in any form and by any means reserved
worldwide for CEN national Members
Ref. No. EN ISO 5175‑1:2017: E
BS EN ISO 5175‑1:2017
EN ISO 5175‑1:2017 (E)
European foreword
This document (EN ISO 5175‑1:2017) has been prepared by Technical Committee ISO/TC 44 “Welding
and allied processes” in collaboration with Technical Committee CEN/TC 121 “Welding and allied
processes” 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 2018, and conflicting national standards shall be
withdrawn at the latest by May 2018.
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 supersedes EN 730‑1:2002.
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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
the United Kingdom.
Endorsement notice
The text of ISO 5175‑1:2017 has been approved by CEN as EN ISO 5175‑1:2017 without any modification.
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BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Contents
Page
Foreword......................................................................................................................................................................................................................................... iv
1Scope.................................................................................................................................................................................................................................. 1
2
3
4
Normative references....................................................................................................................................................................................... 1
Terms and definitions...................................................................................................................................................................................... 1
Design and materials........................................................................................................................................................................................ 4
4.1
Connection. ................................................................................................................................................................................................. 4
4.2
Materials. ...................................................................................................................................................................................................... 4
5Requirements........................................................................................................................................................................................................... 4
5.1
General. .......................................................................................................................................................................................................... 4
5.2
Gas tightness. ............................................................................................................................................................................................ 5
5.2.1 External gas tightness.................................................................................................................................................. 5
5.2.2 Internal gas tightness................................................................................................................................................... 5
5.3
Pressure resistance.............................................................................................................................................................................. 5
5.4
Flame arrestor. ........................................................................................................................................................................................ 6
5.5
Flame arrestor with non-return valve................................................................................................................................. 6
5.6
Flame arrestor with temperature-sensitive cut-off valve................................................................................... 6
5.7
Flame arrestor with pressure-sensitive cut-off valve............................................................................................ 6
5.8
Other multifunctional safety devices. .................................................................................................................................. 6
6
7
8
Methods for type testing............................................................................................................................................................................... 6
6.1
General. .......................................................................................................................................................................................................... 6
6.2
Accuracy of pressure and flow measurements............................................................................................................ 6
6.3
Test gases. .................................................................................................................................................................................................... 7
6.4
Gas tightness test................................................................................................................................................................................... 7
6.5
Pressure resistance test................................................................................................................................................................... 7
6.6
Non-return valve test......................................................................................................................................................................... 7
6.6.1 General...................................................................................................................................................................................... 7
6.6.2 Tests with reverse flow of gas............................................................................................................................... 7
6.7
Flame arrestor test............................................................................................................................................................................... 7
6.8
Temperature-sensitive cut-off valve test........................................................................................................................... 8
6.9
Pressure-sensitive cut-off valve test. .................................................................................................................................... 9
6.10 Internal leakage test for cut-off valves............................................................................................................................. 10
Further tests...........................................................................................................................................................................................................10
Manufacturer’s instructions..................................................................................................................................................................10
9Marking........................................................................................................................................................................................................................ 10
Annex A (informative) Gas flow measurement........................................................................................................................................12
Annex B (informative) Third party testing information................................................................................................................14
Annex C (informative) Production tests. ........................................................................................................................................................15
© ISO 2017 – All rights reserved

iii
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(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 voluntary nature of standards, 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.
This document was prepared by Technical Committee ISO/TC 44, Welding and allied processes,
Subcommittee SC 8, Equipment for gas welding, cutting and allied processes.
This first edition of ISO 5175‑1, together with ISO 5175‑2, cancels and replaces ISO 5175:1987, which has
been technically revised. It also incorporates the Amendment ISO 5175:1987/Amd 1:2015.
A list of all parts in the ISO 5175 series can be found on the ISO website.
Requests for official interpretations of any aspect of this document should be directed to the Secretariat
of ISO/TC 44/SC 8 via your national standards body. A complete listing of these bodies can be found at
www.iso.org.
iv

© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
INTERNATIONAL STANDARD
ISO 5175-1:2017(E)
Gas welding equipment — Safety devices —
Part 1:
Devicesincorporatingaflame(flashback)arrestor
1Scope
This document specifies the general requirements and tests for safety devices for fuel gases and oxygen
or compressed air incorporating a flame (flashback) arrestor used downstream of manifold, cylinder
and/or pipeline outlet regulators, and upstream of blowpipes for welding, cutting and allied processes.
This document does not specify the location of these devices in the gas system.
This document is not applicable to safety devices not incorporating a flame arrestor, covered
by ISO 5175‑2.
This document does not apply to the use of safety devices incorporating flame arrestors for applications
with premixed oxy/fuel or air/fuel gas supply systems, e.g. downstream of gas mixers or a generator to
produce hydrogen/oxygen mixture by electrolytic decomposition of water.
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 554, Standard atmospheres for conditioning and/or testing — Specifications
ISO 5175‑2, Gas welding equipment — Safety devices — Part 2: Not incorporating a flame
(flashback) arrestor
ISO 7289, Gas welding equipment — Quick-action couplings with shut-off valves for welding, cutting and
allied processes
ISO 9090, Gas tightness of equipment for gas welding and allied processes
ISO 9539, Gas welding equipment — Materials for equipment used in gas welding, cutting and allied processes
ISO 10225, Gas welding equipment — Marking for equipment used for gas welding, cutting and
allied processes
ISO 15296, Gas welding equipment —Vocabulary
EN 560, Gas welding equipment — Hose connections for equipment for welding, cutting and allied processes
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15296 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
© ISO 2017 – All rights reserved

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BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

3.1
flame arrestor
device which arrests a flame front
EXAMPLE
The good thermal conductivity, high porosity and small pore size (larger surface) of sintered
metal elements lead to flame quenching. An example is given in Figure 1.
Key
1 normal direction of gas flow
2 e.g. sintered metal element
3 flame
Figure 1 — Flame arrestor (example)
3.2
maximum operating pressure
maximum pressure to which the equipment may be subjected in service
3.3
multifunctional safety device
device that incorporates two or more of the safety functions
EXAMPLE
Flame arrestor (3.1) with non-return valve (3.4) and cut-off valve.
Note 1 to entry: The temperature-sensitive cut-off valve (3.6) is normally used in combination with a flame
arrestor as its purpose is to cut-off the gas flow before the temperature at the flame arrestor reaches a point
where flame transmission across the flame arrestor takes place. It is normal for pressure and or temperature cutoff valves only to be used in combination with flame arrestors. Due to the burning characteristics of hydrogen, it
is recommended that all flame arrestors for hydrogen incorporate a temperature-sensitive cut-off valve.
3.4
non-return valve
device that prevents passage of gas in the direction opposite to the intended flow
EXAMPLE
Valve is held open by energy in gas stream and closes when downstream pressure is approximately
equal to or greater than that in normal direction of flow. An example is given in Figure 2.
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© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Key
1 normal direction of gas flow
Figure 2 — Non-return valve (example)
3.5
pressure-sensitive cut-off valve
device that stops the gas flow when the downstream pressure is higher than the upstream pressure by
more than a predetermined value
EXAMPLE
Valve is held open, e.g. by a spring; it is actuated by a pressure wave from downstream and is then
automatically held closed by a special device. An example is given in Figure 3.
Key
1 normal direction of gas flow
2 back-pressure wave
Figure 3 — Pressure-sensitive cut-off valve (example)
3.6
temperature-sensitive cut-off valve
device which stops the gas flow when a predetermined temperature is exceeded
EXAMPLE
Valve is held open, e.g. by a fusible metal, and actuated by sustained temperature rise. An example
is given in Figure 4.
© ISO 2017 – All rights reserved

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BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Key
1 normal direction of gas flow
2 e.g. fusible metal
Figure 4 — Temperature-sensitive cut-off valve (example)
3.7
safety device
device which prevents the damage resulting from misuse or malfunction of gas equipment and gas
installations
4 Design and materials
4.1Connection
Threaded connections up to G1 shall be in accordance with EN 560. Quick release connections shall be
in accordance with ISO 7289.
4.2Materials
Materials used for safety devices shall conform to the requirements laid down in ISO 9539.
5Requirements
5.1General
Requirements for each safety device vary depending upon the device and combination of functions in
the device. A summary of the requirements and test sequence is given in Table 1.
Table 1 — Summary of requirements and test sequence for the most commonly available
safety devices
Safety device
function(s)
Flame arrestor
Flame arrestor + nonreturn valve
a
4
Requirements
(Subclause no.)
5.2.1
5.3
5.4
5.2.1
5.2.2
5.3
5.5
Tests (in test order)
(Subclause no.)
6.4 External gas tightness
6.5 Pressure resistance
6.7 Flashback resistance
6.4 External gas tightness
6.5 Pressure resistance
6.6 Reverse flow
6.7 Flashback resistance
6.6 Reverse flow
Use a new device for this test. Do not use for any other test.

Number of
devices required
for each test
Total number
of devices
required
5
1a
5
6
5
1a
5
5
5
6
© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Safety device
function(s)
Requirements
(Subclause no.)
Flame arrestor +
temperature-sensitive
cut-off valve
5.2.1
5.2.2
5.3
5.6
5.2.1
5.2.2
5.3
5.5
5.7
Flame arrestor + nonreturn valve +
temperature-sensitive
cut-off valve
Flame arrestor +
non-return valve +
pressure-sensitive cutoff valve
Flame arrestor +
non-return valve +
temperature-sensitive
cut-off valve +
pressure-sensitive
cut-off valve
a
5.2.1
5.2.2
5.3
5.5
5.6
5.2.1
5.2.2
5.3
5.5
5.6
5.7
Tests (in test order)
(Subclause no.)
Number of
devices required
for each test
Total number
of devices
required
6.4 External gas tightness
6.5 Pressure resistance
6.7 Flashback resistance
6.8 Temperature cut-off
6.10 Internal leakage
5
1a
5
1a
5
7
6.4 External gas tightness
6.5 Pressure resistance
6.6 Reverse flow
6.7 Flashback resistance
6.9 Pressure cut-off
6.10 Internal leakage
5
1a
5
5
5
5
6
6.4 External gas tightness
6.5 Pressure resistance
6.6 Reverse flow
6.7 Flashback resistance
6.6 Reverse flow
6.8 Temperature cut-off
6.10 Internal leakage
6.4 External gas tightness
6.5 Pressure resistance
6.6 Reverse flow
6.7 Flashback resistance
6.8 Temperature cut-off
6.9 Pressure cut-off
6.10 Internal leakage
Use a new device for this test. Do not use for any other test.
5
1a
5
5
5
1a
5
7
5
1a
5
5
1a
5
5
7
NOTE
In the following subclauses, the terms “upstream” and “downstream” refer to the normal direction of
gas flow in the device.
5.2 Gas tightness
5.2.1
External gas tightness
The general requirements on external gas tightness and the test procedures shall be in accordance
with ISO 9090.
5.2.2
Internal gas tightness
Where internal gas tightness is required in this document, the leakage rate shall not exceed 50 cm3/h
for devices with a connection internal bore (diameter) less than 11 mm or 0,41 d 2 for larger diameters
(see 6.6 and/or 6.10 for tests).
NOTE
The value 0,41 d 2 is the flow in cm3/h where d is the internal bore (diameter) in mm of the largest
connection of the device.
5.3 Pressure resistance
The housings of the safety devices shall resist a pressure equal to ten times the maximum operating
pressure, with the test pressure in all cases not less than 6 MPa (60 bar).
NOTE
1 bar = 0,1 MPa = 105 Pa. 1 Pa = 1 N/m2. All pressures are gauge pressure.
When the device is tested in accordance with 6.5, no permanent deformation of the pressure retaining
components shall occur after a test duration of at least 5 min.
© ISO 2017 – All rights reserved

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BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

5.4 Flame arrestor
Flame arrestors shall quench flashbacks when tested in accordance with 6.7.
5.5 Flame arrestor with non-return valve
Flame arrestor with non-return valve shall quench flashbacks when tested in accordance with 6.7 and
shall not allow the reverse flow of gases when tested in accordance with 6.6 both before and after the
flashback test in 6.7.
5.6 Flame arrestor with temperature-sensitive cut-off valve
Flame arrestor with temperature-sensitive cut-off valve shall quench flashbacks when tested in
accordance with 6.7 and shall stop the gas flow before the upstream gas is ignited when tested in
accordance with 6.8.
It shall not be possible to reset the temperature-sensitive cut-off valve.
If the temperature-sensitive cut-off valve operates before the fifth flashback in the test in 6.7 and the
flame is not transmitted upstream, the unit shall be considered to meet the flashback test requirement,
but the test in 6.8 shall still be carried out on a new unit.
5.7 Flame arrestor with pressure-sensitive cut-off valve
Flame arrestor with pressure-sensitive cut-off valve shall quench flashbacks when tested in accordance
with 6.7 and the pressure-sensitive cut-off function shall activate at each flashback. The pressuresensitive cut-off valve shall remain closed until it is manually reset.
The pressure-sensitive cut-off valve shall be reset after each flashback during the test in 6.7.
Flame arrestor with pressure-sensitive cut-off valve shall also stop the gas flow when tested in
accordance with 6.9, both before and after completing the flashback test in 6.7.
5.8 Other multifunctional safety devices
Multifunctional safety devices not included in Table 1, but incorporating functions described in this
document or in ISO 5175‑2, shall be tested according to the relevant requirements. Functions in this
document shall be tested before the functions in ISO 5175‑2.
6 Methods for type testing
6.1General
The test methods in this clause are not intended as production inspection tests, but are to be applied
to sample devices to be tested for compliance with this document. Tests shall be carried out on new
devices with all safety functions operational as designed.
Third party conformity testing is not a requirement of this document. See Annex B for information
relating to third party conformity testing if required.
6.2 Accuracy of pressure and flow measurements
The allowable total error of the measured values are as follows:
— flow:
±10 %;
— pressure: ±3 %.
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© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

All flows and pressures shall be expressed in standard atmospheric conditions in accordance with
ISO 554. All pressure values are given as gauge pressure, expressed in bars.
6.3 Test gases
Unless otherwise stated, tests shall be carried out at ambient pressure conditions and at (20 ± 5) °C
with air or nitrogen free from oil and grease.
Air is considered as oil-free if it comprises
— a mass fraction of oil vapour of less than 5 × 10−6, and
— less than 1 mg/m3 of suspended droplets.
In all cases, tests shall be carried out with dry gas with a maximum moisture content corresponding to
a dew point of 0 °C.
Safety devices for hydrogen shall be tested with hydrogen or helium for the gas tightness test only.
6.4 Gas tightness test
Conformity with the requirements of 5.2.1 shall be checked on five samples in accordance with ISO 9090.
6.5 Pressure resistance test
Conformity with the requirements of 5.3 shall be checked by means of a hydraulic pressure test on one
sample. No other tests shall be carried out on the sample either before or after this test nor shall the
sample tested be used for any other purposes.
6.6 Non-return valve test
6.6.1General
Conformity with the requirements of 5.5 shall be checked on five samples as follows. Before proceeding
with this test, pass the test gas through the device in the normal direction of flow for 5 s to operate the
valve. Connect the downstream side of the device under test to a gas source, with the upstream side at
atmospheric pressure and connected to a leak detection device. Proceed to pressurize in the reverse
direction according to 6.6.2. For the tests, the samples shall be installed in the most disadvantageous
position (gravity acting to open the valve).
6.6.2
Tests with reverse flow of gas
Pressurize the device in the reverse direction as follows:
a)
increase the back-pressure at a rate of 600 Pa/min (6 mbar/min) up to 3 000 Pa (30 mbar);
b) increase the back-pressure within 1 s from 0 to maximum operating pressure.
The maximum reverse flow during the period of reverse pressure application and for 1 min afterwards
shall meet the requirements of 5.2.2.
When the device incorporates a pressure-sensitive cut-off valve, it is acceptable for the valve to operate
during the non-return valve test.
6.7 Flame arrestor test
A diagram of the test equipment is shown in Figure 5.
© ISO 2017 – All rights reserved

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BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

The gas mixture and pressure for testing flame arrestors depend on the gas application and the
maximum operating pressure specified by the manufacturer (see Table 2).
Five flame arrestors shall each be subjected to five flashbacks with a static mixture of fuel gas and
oxygen given in Table 2. Between two flashbacks, a sufficient delay is required to return the initial
conditions. Each flame arrestor shall prevent the upstream gas igniting for all five flashbacks.
WARNING — All precaution shall be taken to protect personnel from the effect of fire
and explosion.
Dimensions in metres
Key
1 flame detector
2 inlet pressure, p1
3 sample
4 outlet pressure, p2
5 steel tube
6 ignition
a
Pressure gauges: class 1,0 at least.
For connections up to G 3/8 LH (left-hand thread): internal diameter, di = 10 mm. For connections larger than
G 3/8 LH (left-hand thread): di shall be equal to the nominal outlet bore, the steel tube shall be straight.
Figure 5 — Test equipment for testing efficiency of flame arrestors
Table 2 — Gas applications concerning test pressures and test mixtures
Gas application
Acetylene
Oxygen
Air
LPG
Hydrogen
Other fuel gases
Test pressure
Test mixture volume fraction in
percentage % of fuel gas in oxygen
0,15 MPa (1,5 bar)
32 % to 35 % Acetylene
maximum operating pressure
40 % to 50 % Hydrogen
maximum operating pressure
maximum operating pressure
6.8 Temperature-sensitive cut-off valve test
13 % to 15 % Propane
80 % to 90 % of stochiometric mixture
A diagram of the test equipment is shown in Figure 6.
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© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Dimensions in metres
Key
1 fuel gas
2 flame detector
3 sample
4 steel tube
5 needle vale
6 oxygen
a
Internal diameter of tube shall be equal to internal diameter of the outlet of the device.
Figure 6 — Test equipment for testing temperature-sensitive cut-off valves
This test is to be carried out on one new unit. The fuel gas used for the test shall be as given in Table 3.
Adjust the fuel gas valve so that the flame at the outlet side of the steel tube is stable. Slowly open the
oxygen valve until the flame retreats into the tube and device. The cut-off valve shall automatically cut
off the gas flow before the upstream gas is ignited. After the cut-off valve has closed, the device shall be
tested in accordance with 6.10 to test for internal leakage.
When the device incorporates a pressure-sensitive cut-off valve which operates during the test, the
pressure-sensitive cut-off valve shall be disabled and the test repeated.
Table 3 — Test gas for the temperature-sensitive cut-off valve test
Gas application
Fuel test gas in oxygen
Acetylene
Hydrogen
Acetylene
LPG
Hydrogen
Hydrogen
LPG
Acetylene
Acetylene
Hydrogen
Hydrogen
LPG
Propane
For other fuel gases, the test shall be conducted with the fuel gas.
6.9 Pressure-sensitive cut-off valve test
The requirements specified in 5.7 shall be checked on five samples as follows. Connect the downstream
side of the device under test to a gas source, with the upstream side open to the atmosphere.
Progressively increase the downstream pressure to check that the device is actuated by a pressure
less than or equal to 0,12 MPa (1,2 bar). After the cut-off valve has closed, the device shall be tested in
accordance with 6.10 to test for internal leakage.
© ISO 2017 – All rights reserved

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BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

6.10 Internal leakage test for cut-off valves
With the device under test in the tripped condition, connect the upstream side to a gas source at the
maximum operating pressure, with the downstream side open to atmosphere. Check that internal leaks
at the device outlet meet the requirement of 5.2.2.
7 Further tests
A further test concerning the flame arrestor function is given in Annex C and should be performed.
8 Manufacturer’s instructions
When distributed, the safety device shall be accompanied by the manufacturer’s instructions which
shall contain, as a minimum, the following information:
a) the function of the safety device;
b) operational and performance data (maximum working pressure, gas flow characteristics;
see Annex A);
c) permissible types of gas;
d) an explanation of the abbreviations marked on the device;
e) instruction for installation of equipment [The method of installing these devices (e.g. types
selected, order of installation, etc) varies with operating conditions. It is essential to follow the
manufacturer’s instructions regarding installation and operation to ensure that the overall
pressure drop due to the combination is as low as possible.];
f) procedures to be carried out prior to operation;
g) procedures for safe operation;
h) instructions in case of malfunction;
i) recommendations for inspection, testing and maintenance;
j) explanation of the marking.
9Marking
All marking shall be legible and durable. The following information shall be included:
a) reference to this document (i.e. ISO 5175‑1);
b) the name or trade mark of the manufacturer and/or distributor;
c) the model designation or code number relating to the manufacturer’s installation instructions;
d) the direction of normal gas flow (arrow);
e) the name of the gas or its abbreviation;
f) the maximum operating pressure, p max, expressed in bar;
g) the indication of the safety functions incorporated in the device as shown below.
Abbreviations for the safety functions shall be marked as follows:
— flame arrestor FA
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© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

— non-return valve NV
— pressure-sensitive cut-off valve PV
— temperature-sensitive cut-off valve TV
The appropriate letters shall be enclosed in a square as in the following examples:
flame arrestor only
flame arrestor +
non-return valve
flame arrestor +
non-return valve +
pressure-sensitive cut-off valve
flame arrestor +
non-return valve +
pressure-sensitive cut-off valve +
temperature-sensitive cut-off valve
FA
FA
NV
FA
NV
PV
TV
FA NV PV If the full name of the gas cannot be marked, the letter codes according to ISO 10225 shall be used for
marking of equipment. If in addition, a colour coding is used, red shall be used for fuel gases, blue for
oxygen, black for compressed air.
© ISO 2017 – All rights reserved

11
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Annex A
(informative)
Gas flow measurement
A.1General
The gas flow characteristics for each safety device (single or multifunction) can be measured by means
of a performance test using the circuit shown in Figure A.1. The results can be reported graphically; a
typical example is shown in Figure A.2.
A.2Procedure
With the device discharging directly to the atmosphere, the upstream pressure should progressively
be increased to the maximum operating pressure, p max, and the gas flow rate should be measured at
different intermediate pressures.
The same test should be repeated with upstream pressures equal to 0,25 p max, 0,5 p max and 0,75 p max,
and the gas flow rate for different pressure drops, Δp, should be measured.
The average of the results obtained from 5 samples shall be considered to be the nominal value. The
flow rates of the 5 samples should not diverge by more than ±10 %.
Key
1 inlet pressure, p1
2 outlet pressure, p2
3 sample
4 flow meter
Pressure gauges: class 1,0 at least.
Pressure drop, Δp = p1 – p2.
Figure A.1 — Typical example of circuit for gas flow measurement
12

© ISO 2017 – All rights reserved
5p
0,2
0p
0,5
x.
ma
ma
5p
x.
.
x
ma
0,7
pressure drop, p, bar
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

flow rate, q v, m³/h
Figure A.2 — Typical example of gas flow characteristics
© ISO 2017 – All rights reserved

13
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Annex B
(informative)
Third party testing information
B.1General
Third party testing is not a requirement of this document.
Third party testing is used when either the manufacturer or user desire independent verification of
the product.
The following is given for guidance only but can vary according to the third party involved.
B.2
Samples and documentation
Recommended for third party conformity testing:
a) sufficient samples to enable the device to be tested (see Table 1);
b) two copies of all detail drawings;
c) three copies of the general drawing with a list of spare parts;
d) a statement by the manufacturer indicating the nature of the materials and their compatibility
with the gases.
14

© ISO 2017 – All rights reserved
BS EN ISO 5175‑1:2017
ISO 5175-1:2017(E)

Annex C
(informative)
Production tests
C.1General
The following test should be carried out after manufacture on all safety devices conforming to
this document.
C.2
Production flashback test
A single flashback test should be carried out on each device. Conditions for the gas mixture for all devices
should be as given for acetylene in Table 2 and the equipment used, conforming to the requirements of
Figure 5. Devices which do not quench the flashback during this test should be rejected.
© ISO 2017 – All rights reserved

15
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