ISO 23551-10:2025

International
Standard
ISO 23551-10
Second edition
Safety and control devices for
2025-05
gas burners and gas-burning
appliances — Particular
requirements —
Part 10:
Vent valves
Dispositifs de commande et de sécurité pour brûleurs à gaz et
appareils à gaz — Exigences particulières —
Partie 10: Robinets d'évent
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification . 3
4.1 Classes of controls .3
4.2 Groups of controls .3
4.3 Types of DC supplied controls .3
4.4 Classes of control functions .3
5 Test conditions and tolerances . 3
6 Construction . 3
6.1 General .3
6.2 Construction requirements.3
6.2.1 Appearance .3
6.2.2 Holes .3
6.2.3 Breather holes .3
6.2.4 Vent limiter .3
6.2.5 Screwed fastenings .3
6.2.6 Moving parts .3
6.2.7 Sealing caps .4
6.2.8 Disassembling and assembling for servicing and/or adjustment for controls .4
6.2.9 Auxiliary channels and orifices .5
6.2.10 Pre-setting device .5
6.2.11 Open position indicator switch (OPS) .5
6.2.12 Controls assembled to a valve .6
6.3 Materials .6
6.3.1 Housing .6
6.3.2 General material requirements .6
6.3.3 Springs providing closing force and sealing force .6
6.3.4 Resistance to corrosion and surface protection .6
6.3.5 Impregnation .6
6.3.6 Seals for glands for moving parts.6
6.3.7 Jointing .6
6.3.8 Closure members .6
6.3.9 Springs providing opening force .7
6.4 Connections .7
6.4.1 General .7
6.4.2 Connection sizes .7
6.4.3 Connection types .7
6.4.4 Threads .7
6.4.5 Union joints .7
6.4.6 Flanges .7
6.4.7 Compression fittings .7
6.4.8 Flare connections .8
6.4.9 Nipples for pressure tests .8
6.4.10 Strainers . . .8
6.4.11 Pneumatic and hydraulic actuating mechanisms .8
6.5 Gas controls employing with electrical components in the gas way .8
7 Performance . 8
7.1 General .8
7.2 Leak-tightness .8

iii
7.2.1 General .8
7.2.2 Requirements .8
7.2.3 Test . . .9
7.3 Torsion and bending .9
7.4 Rated flow rate .9
7.5 Durability .9
7.6 Functional requirements . .9
7.6.1 Opening function . .9
7.6.2 Opening force .10
7.6.3 Delay time and closing time .10
7.6.4 Opening time .11
7.7 Endurance .11
7.7.1 Requirements .11
7.7.2 Test . . . 12
7.8 Open position indicator switch . 12
7.8.1 Requirement . 12
7.8.2 Test of open position indicator switch . 12
7.9 Hydrostatic withstand pressure test . 12
7.9.1 General . 12
7.9.2 Requirement . 13
7.9.3 Test . . . 13
8 Electrical equipment .13
8.1 General . 13
8.2 Requirements . 13
8.3 Test .14
8.4 Protection by enclosure .14
8.5 Electrical components .14
8.5.1 Switches .14
8.5.2 Plug connector .14
8.5.3 Power saving circuit . 15
9 EMC/Electrical requirements .15
9.1 Protection against environmental influences . 15
9.1.1 General . 15
9.1.2 Requirements . 15
9.2 Harmonics and interharmonics including mains signalling at a. c. power port, low
frequency immunity . 15
9.3 Voltage dips, voltage interruptions and voltage variations in the power supply network . 15
9.4 Test of influence of voltage unbalance .16
9.5 Surge immunity test .16
9.6 Electrical fast transient/burst .16
9.7 Ring wave immunity .16
9.8 Electrostatic discharge .16
9.9 Radio-frequency electromagnetic field immunity .16
9.10 Influence of supply frequency variations .16
9.11 Power frequency magnetic field immunity .16
9.12 Evaluation of compliance .16
10 Marking, installation and operating instructions .16
10.1 Marking .16
10.2 Installation and operating instructions .17
10.3 Warning notice .17
Annex A (informative) Leak-tightness test — Volumetric method .18
Annex B (informative) Leak-tightness test — Pressure-loss method . 19
Annex C (normative) Conversion of pressure loss into leakage rate .20
Annex D (normative) Gas quick connector (GQC).21
Annex E (normative) Elastomers/requirements resistance to lubricants and gas .22

iv
Annex F (normative) Specific regional requirements in European countries.23
Annex G (normative) Specific regional requirements in Canada and the USA .24
Annex H (normative) Specific regional requirements in Japan .25
Bibliography .26

v
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,
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 161, Control and protective devices for gaseous
and liquid fuels.
The second edition cancels and replaces the first edition (ISO 23551-10:2016), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the endurance test has been restructured and the test cycles changed;
— the hydrostatic withstand pressure test has been added;
— specific regional requirements that were previously contained in regional Annexes have been relocated
to the main body of the documents (and the annexes have been deleted);
— the document has been updated to align with IEC 60730-1:2022;
A list of all parts in the ISO 23551 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

vi
Introduction
This document is designed to be used in combination with ISO 23550. Together with ISO 23550, this
document establishes the full requirements as they apply to vent valves.
Where needed, this document adapts ISO 23550 by stating in the corresponding clause number and adding:
— “with the following modification”;
— “with the following addition”;
— “is replaced by the following”; or
— “is not applicable”.
In order to identify specific requirements that are particular to this document, that are not already covered
by ISO 23550, this document can contain clauses or subclauses that are additional to the structure of
ISO 23550. These subclauses are indicated by the introductory sentence: “Subclause (or Annex) specific to
this document.”
To ensure the global relevance of this document, the differing requirements resulting from practical
experience and installation practices in various regions of the world have been taken into account. The
variations in basic infrastructure associated with gas controls and appliances have also been recognized,
some of which are addressed in Annexes F, G and H. This document intends to provide a basic framework of
requirements that recognize these differences.

vii
International Standard ISO 23551-10:2025(en)
Safety and control devices for gas burners and gas-burning
appliances — Particular requirements —
Part 10:
Vent valves
1 Scope
This document specifies safety, constructional, performance and testing requirements of normally open
automatic vent valves, hereafter referred to as “valves”.
This document applies to valves with a declared maximum operating pressure up to and including 500 kPa
of nominal connection sizes up to and including DN 100 (4”), for use in gas control train of gas burners or
in appliances using gaseous fuels such as natural, manufactured or liquefied petroleum gas (LPG). It is not
applicable to corrosive and waste gases.
This document applies to:
— electrically operated valves and to valves actuated by fluids where the control valves for these fluids are
actuated electrically, but not to any external devices for switching the control signal or actuating energy;
— valves fitted with open position indicator switches.
This document covers type testing only.
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 23550:2018, Safety and control devices for gas and/or oil burners and appliances — General requirements
IEC 60730-1:2022, Automatic electrical controls — Part 1: General requirements
IEC 60529:2018, Degrees of protection provided by enclosures (IP Code)
IEC 61058-1, Switches for appliances — Part 1: General requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 23550 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp

3.1
automatic vent valve
device which closes when energized and opens automatically when de-energized
Note 1 to entry: These valves are typically used as bleed valves in a block and bleed application.
3.2
actuating mechanism
part of the valve which moves the closure member to the closed position
3.3
open position indicator switch
switch fitted to a valve which indicates when the closure member is in the open position
3.4
actuating energy
required energy for the actuating mechanism to move the closure member to the closed position
Note 1 to entry: The actuating energy may have an external source (electrical, hydraulic or pneumatic) and can be
transformed inside the valve.
3.5
opening force
force required to open the valve, independent of any force provided by fuel gas pressure
3.6
frictional force
largest force required to move the actuating mechanism and the closure member from the closed position to
the open position with the opener spring removed, independent of any force provided by fuel gas pressure
3.7
actuating pressure
hydraulic or pneumatic pressure supplied to the actuating mechanism of the valve
3.8
opening time
time interval between de-energizing the valve and the closure member attaining the open position
3.9
closing time
time interval between energizing the valve and the closure member attaining the closed position
3.10
delay time
time interval between energizing the valve and the start of the closure member moving to the closed position
3.11
control valve
valve which controls the hydraulic or pneumatic means supplied to the actuating mechanism
3.12
rated voltage
voltage as stated in the installation and operating instructions at which the valve may be operated
3.13
rated current
current as stated in the installation and operating instructions at which the valve may be operated
...