ISO 23551-11:2024

International
Standard
ISO 23551-11
First edition
Safety and control devices for
2024-11
gas burners and gas-burning
appliances — Particular
requirements —
Part 11:
Automatic and semi-automatic
shut-off valves for operating
pressure of above 500 kPa up to and
including 6 300 kPa
Dispositifs de commande et de sécurité pour brûleurs à gaz et
appareils à gaz — Exigences particulières —
Partie 11: Robinets automatiques et semi-automatiques de
sectionnement pour une pression de fonctionnement supérieure à
500 kPa et jusqu'à 6 300 kPa inclus
Reference number
© ISO 2024
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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 . 2
4 Classification . 3
4.1 Classes of controls .3
4.1.1 Classification based on sealing force .3
4.1.2 Classifications based on pressure surge .3
4.1.3 Classification with neither sealing force nor pressure surge .3
4.1.4 Classification of flow control valves for general purpose .3
4.2 Groups of controls .3
4.3 Types of DC supplied controls .3
4.4 Classes of control function .3
5 Test conditions and tolerances . 4
5.1 Test conditions .4
5.2 Tolerances .4
6 Construction . 4
6.1 General .4
6.2 Construction requirements.6
6.2.1 Appearance .6
6.2.2 Holes .6
6.2.3 Breather holes .6
6.2.4 Vent limiter .6
6.2.5 Screwed fastenings .6
6.2.6 Moving parts .7
6.2.7 Sealing caps .7
6.2.8 Disassembling and assembling for servicing and/or adjustment for controls .7
6.2.9 Auxiliary channels and orifices .8
6.2.10 Pre-setting device .8
6.2.11 Closed position indication .8
6.2.12 Specific construction .10
6.2.13 Flow rates of valves with modulating control .10
6.2.14 Bypass .10
6.2.15 Semi-automatic shut-off valve .10
6.2.16 Other controls assembled to a valve .11
6.2.17 Balanced valves .11
6.3 Materials .11
6.3.1 General material requirements .11
6.3.2 Housing . 12
6.3.3 Springs providing closing force and sealing force . 13
6.3.4 Resistance to corrosion and surface protection .14
6.3.5 Impregnation .14
6.3.6 Seals for glands for moving parts.14
6.3.7 Jointing .14
6.3.8 Closure members .14
6.3.9 Parts transmitting the closing force .14
6.3.10 Balanced valves .14
6.3.11 Bellows . 15
6.3.12 Hydrostatic withstand pressure test . 15
6.4 Connections .16
6.4.1 General .16
6.4.2 Connection sizes .16

iii
6.4.3 Connections types .16
6.4.4 Threads .16
6.4.5 Union joints .16
6.4.6 Flanges .17
6.4.7 Compression fittings .17
6.4.8 Flare connections .17
6.4.9 Nipples for pressure tests .17
6.4.10 Strainers . . .18
6.4.11 Gas connections by GQC .18
6.4.12 Welded connections . .18
6.5 Gas controls employing electrical components in the gas way .18
6.6 Pneumatic and hydraulic actuating mechanisms .18
7 Performance . 19
7.1 General .19
7.2 Leak-tightness . 20
7.2.1 General . 20
7.2.2 Requirements . 20
7.2.3 Test . . .21
7.2.4 Pressure surge test . 22
7.3 Torsion and bending . 22
7.3.1 General . 22
7.3.2 Torsion . 22
7.3.3 Bending moment . . 22
7.3.4 Torsion and bending tests . 22
7.4 Rated flow rate . 23
7.4.1 General . 23
7.4.2 Requirements . 23
7.4.3 Test . . . 23
7.5 Durability . 23
7.6 Functional requirements . . 23
7.6.1 Closing function .24
7.6.2 Closing force .24
7.6.3 Delay time and opening time . 25
7.6.4 Closing time . 25
7.6.5 Sealing force . 26
7.7 Endurance .27
7.7.1 Requirement .27
7.7.2 Test . . . 28
7.8 Vibration . 30
8 Electrical requirements .30
8.1 General . 30
8.2 Requirements . 30
8.3 Test . 30
8.4 Protection by enclosure . 30
8.5 Electrical components .31
8.5.1 Switches .31
8.5.2 Plug connector .31
8.5.3 Power saving circuit .31
9 Electromagnetic compatibility (EMC) . .32
9.1 Protection against environmental influences .32
9.2 Harmonics and interharmonics including mains signalling at a.c. power port, low
frequency immunity .32
9.3 Voltage dips, voltage interruptions and voltage variations in the power supply network .32
9.4 Test of influence of voltage unbalance .32
9.5 Surge immunity tests .32
9.6 Electrical fast transient/burst .32
9.7 Ring wave immunity .32

iv
9.8 Electrostatic discharge . 33
9.9 Radio-frequency electromagnetic field immunity . 33
9.10 Influence of supply frequency variations . 33
9.11 Power frequency magnetic field immunity . 33
9.12 Evaluation of compliance . 33
10 Marking, installation and operating instructions .33
10.1 Marking . 33
10.2 Installation and operating instructions . 33
10.3 Warning notice . 34
10.4 Annexes . 34
Annex A (normative) Specific regional requirements in European countries .35
Annex B (normative) Specific regional requirements in Canada and USA .36
Annex C (normative) Specific regional requirements in Japan .37
Annex D (normative) Specific regional requirements in China .38
Bibliography .39

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,
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 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)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
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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, Controls and protective devices for gaseous
and liquid fuels.
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, they establish the full
requirements as they apply to the product covered by this document.
Where needed, this document adapts ISO 23550 by stating in the corresponding clause:
— “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 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 A, B, C and D. This document intends to provide a basic framework of requirements
that recognize these differences.

vii
International Standard ISO 23551-11:2024(en)
Safety and control devices for gas burners and gas-burning
appliances — Particular requirements —
Part 11:
Automatic and semi-automatic shut-off valves for operating
pressure of above 500 kPa up to and including 6 300 kPa
1 Scope
This document specifies safety, constructional and performance requirements and testing of automatic,
semi-automatic shut-off valves, and general purpose valves for gas burners, gas appliances and appliances of
similar use excluding use in fuel gas infrastructures (transportation and distribution systems).
This document applies to controls for use at maximum operating pressures above 500 kPa up to and
including 6 300 kPa with sizes up to DN 250 for use on burners or in appliances using fuel gases, such as
natural gas, manufactured gas or liquefied petroleum gas (LPG).
This document applies to:
— valves being mounted in gas installations;
— valves directly or indirectly actuated, electrically or by mechanical means;
— valves actuated by hydraulic or pneumatic means, including the pilot valves for these fluids if actuated
electrically and including release valves, but not to any external electrical devices for switching the
actuating energy;
— valves where the flow rate is controlled by external electrical signals, either in discrete steps or
proportional to the applied signal and valves fitted with closed position indicator switches;
— valves to be used in appliances, but not in gas transfer systems outside appliances.
This document covers type testing only.
This document does not apply to valves covered under the scope of ISO 23551-1 or the ISO 23555 series.
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 7005-1, Pipe flanges — Part 1: Steel flanges for industrial and general service piping systems
ISO 7005-2, Metallic flanges — Part 2: Cast iron flanges
ISO 7005-3, Pipe flanges — Part 3: Copper alloy and composite flanges
ISO 9692-1, Welding and allied processes — Types of joint preparation — Part 1: Manual metal arc welding, gas-
shielded metal arc welding, gas welding, TIG welding and beam welding of steels
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

ISO 23550:2018, Safety and control devices for gas and/or oil burners and appliances — General requirements
ISO 23551-1:2024, Safety and control devices for gas burners and gas-burning appliances — Particular
requirements — Part 1: Automatic and semi-automatic shut-off valves
IEC 60730-1:2022, Automatic electrical controls— Part 1: General requirements
IEC 61058-1, Switch for appliances — Part 1: General requirements
IEC 60529, Degrees of Protection Provided by Enclosures (IP Code)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 23550, ISO 23551-1 and the
following apply.
ISO and IEC maintain terminology 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
pilot valve
valve which controls the fluid (e.g. compressed air) supplied to the actuating mechanism
Note 1 to entry: A typical pilot and release valve (3.2) application is shown in Figure 1.
3.2
release valve
valve in the line from the pilot valve (3.1) to the actuating mechanism which closes the vent automatically
when the actuating fluid is released by the pilot valve and opens it automatically when the pilot valve is closed
Note 1 to entry: A typical pilot and release valve application is shown in Figure 1.
Key
1 control under test
2 pilot valve (normally closed)
3 release valve (normally open)
Figure 1 — Typical pilot and release valve application
3.3
design pressure
DP
pressure on which design calculations are based
Note 1 to entry: In particular, DP is the maximum pressure for which the body, its inner metallic partition walls and
some other pressure-containing parts are designed.
Note 2 to entry: According to local regulations, DP can be defined as maximum allowable pressure.

[SOURCE: ISO 23555-1:2022, 3.1.4.3 modified — Note 2 to entry has been added.]
4 Classification
4.1 Classes of controls
Shall be according to ISO 23550:2018, 4.1, with the following addition:
4.1.1 Classification based on sealing force
Subclause specific to this document.
Automatic shut-off valves where the sealing force is not decreased by the gas inlet pressure are classified
according to sealing force requirements and shall be designated according to Class A (see Tables 1, 4, 6, 7 and 8).
These valves may also have:
— modulating control function, or
— step control function/multi-stage.
4.1.2 Classifications based on pressure surge
Subclause specific to this document.
Automatic and semi-automatic valves with pressure surge requirements shall be designated according to
class C/I (see ISO 23551-1:2024 3.1.4 and Tables 1, 4, 6, 7 and 8).
4.1.3 Classification with neither sealing force nor pressure surge
Subclause specific to this document.
Automatic and semi-automatic shut-off valves without sealing force and without pressure surge
requirements shall be designated according to Class E (see Tables 1, 4, 6, 7 and 8).
4.1.4 Classification of flow control valves for general purpose
Subclause specific to this document.
General purpose valves with modulating control that do not provide a shut-off function shall be designated
according to Class D (see Tables 1, 4, 6, 7 and 8).
These valves include:
— valves with modulating control function,
— valves with step control function/multi-stage.
4.2 Groups of controls
Shall be according to ISO 23550:2018, 4.2.
4.3 Types of DC supplied controls
Shall be according to ISO 23550:2018, 4.3.
4.4 Classes of control function
Shall be according to ISO 23550:2018, 4.4.

5 Test conditions and tolerances
5.1 Test conditions
Shall be according to ISO 23550:2018, 5.1.
5.2 Tolerances
Shall be according to ISO 23550:2018, 5.2 with the following addition:
The full range of the measuring apparatus is chosen to be suitable for maximum anticipated value.
The measurement uncertainties concern individual measurements. For measurements requiring a
combination of individual measurements (e.g. efficiency measurements), lower uncertainties for the
individual measurements can be necessary to limit the total uncertainty.
Testing labs performing equipment calibration and testing measurement uncertainty are in conformity with
ISO/IEC 17025.
Therefore, where specified, the tolerances in this document apply. Otherwise, ISO/IEC 17025 applies.
6 Construction
6.1 General
Shall be according to ISO 23550:2018, 6.1, with the following addition:
If an automatic shut-off valve requires a release and/or a pilot valve to fulfil the requirements of this
document, these are considered to be part of the automatic shut-off valve and shall be specified in the
installation and operating instructions.
The combination of automatic shut-off valve and release and/or pilot valve shall conform to all requirements
of this document.
The interaction of all valves participating in the closing mechanism shall be evaluated. An appropriate risk
assessment shall be carried out.
For each pressurized compartment, the local maximum pressure shall be considered for the strength
design and for the selection of the material. It shall be ensured by mechanical means that parts for different
pressures are separated. A diaphragm shall not be used for this purpose.
Table 1 describes applicable constructions requirements and tests for the classified valves. Combination of
valve types are not excluded (e.g. automatic Class A and C/I valve). If the respective construction requirement
is used, the design shall be according to the assigned clause in Table 1, if applicable.
The marking "x” identifies the minimum requirements to be verified by the given subclauses in this
document.
Requirements without existing construction or performance properties cannot be verified and those
associated clauses are therefore not applicable.
EXAMPLE Strainers are an optional element in the design of the valve. Therefore, 6.4.10 is not always applicable
even though the assignment is given in Table 1.

Table 1 — Assignment of valve construction requirements and tests
Clause Title Shut-off valve (Classes) General
purpose
automatic automatic semi- automatic semi-
valve
automatic automatic
(Class)
A C/I C/I E E D
6.2 Construction requirements
6.2.1 Appearance x x x x x x
6.2.2 Holes x x x x x x
6.2.3 Breather holes x x x x x x
6.2.4 Vent limiter x x x x x x
6.2.5 Screwed fastenings x x x x x x
6.2.6 Moving parts x x x x x x
6.2.7 Sealing caps x x x x x x
6.2.8 Disassembling and assem- x x x x x x
bling for servicing and/or
adjustment for controls
6.2.9 Auxiliary channels and x x x x x x
orifices
6.2.10 Pre-setting device x x x x x x
6.2.11 Closed position indication x x x x x —
6.2.12 Specific construction x x x — — —
6.2.13 Flow rates of valves with x x x x x x
modulating control
6.2.14 Bypass x x x x x —
6.2.15 Semi-automatic shut-off — — x — x —
valve
6.2.16 Other controls assembled to x x x x x x
a valve
6.2.17 Balanced valves x x x x x x
6.3 Materials x x x x x X
6.4 Connections
6.4.1 General x x x x x x
6.4.2 Connection sizes x x x x x x
6.4.3 Connection types x x x x x x
6.4.4 Threads x x x x x x
6.4.5 Union joints x x x x x x
6.4.6 Flanges x x x x x x
6.4.7 Compression fittings x x x x x x
6.4.8 Flare connections x x x x x x
6.4.9 Nipples for pressure tests x x x x x x
6.4.10 Strainers x x x x x x
6.4.11 Gas connections by GQC x x x x x x
Key
x  required only if the construction is present in the design of the valve
—  no requirement even if the function is present
GQC  gas quick connector
TTabablele 1 1 ((ccoonnttiinnueuedd))
Clause Title Shut-off valve (Classes) General
purpose
automatic automatic semi- automatic semi-
valve
automatic automatic
(Class)
A C/I C/I E E D
6.4.12 Welded connections x x x x x x
6.5 Gas controls employing x x x x x x
electrical components in the
gas way
6.6 Pneumatic and hydraulic x x x x x x
actuating mechanisms
Key
x  required only if the construction is present in the design of the valve
—  no requirement even if the function is present
GQC  gas quick connector
6.2 Construction requirements
6.2.1 Appearance
Shall be according to ISO 23550:2018, 6.2.1.
6.2.2 Holes
6.2.2.1 General
Shall be according to ISO 23550:2018, 6.2.2.1.
6.2.2.2 Requirements
ISO 23550:2018, 6.2.2.2 is replaced by the following:
The wall thickness between the holes and gas ways shall take into account the design, material selected and
method of manufacturing. Holes necessary during manufacture, which connect gas ways passageways to
the atmosphere but which do not affect the operation of the control, shall be permanently sealed by metallic
means. Suitable jointing compounds may additionally be used.
6.2.2.3 Test
Shall be according to ISO 23550:2018, 6.2.2.3.
6.2.3 Breather holes
ISO 23550:2018, 6.2.3, is not applicable.
6.2.4 Vent limiter
ISO 23550:2018, 6.2.4, is not applicable.
6.2.5 Screwed fastenings
Shall be according to ISO 23550:2018, 6.2.5.

6.2.6 Moving parts
Shall be according to ISO 23550:2018, 6.2.6, with the following modification to 6.2.6.1:
6.2.6.1 General
Shall be according to ISO 23550:2018, 6.2.6.1 with the following addition:
Fastening parts (e.g. screws and nuts) shall be secured to prevent loosening under the conditions of actual use.
6.2.7 Sealing caps
Shall be according to ISO 23550:2018, 6.2.7.
6.2.8 Disassembling and assembling for servicing and/or adjustment for controls
Shall be according to ISO 23550:2018 6.2.8, with the following modification:
6.2.8.1 General
Shall be according to ISO 23550:2018, 6.2.8.1.
6.2.8.2 Requirements
Shall be according to ISO 23550:2018, 6.2.8.2.
6.2.8.3 Test
Shall be according to ISO 23550:2018, 6.2.8.3.
6.2.8.4 Factory adjustment
Subclause specific to this document.
6.2.8.4.1 General
Factory adjustment, not intended for field adjustment, shall be securely protected.
6.2.8.4.2 Requirements
Factory adjustment not intended for field adjustment shall be secured by suitable means that provides
protection against access or shall be declared as requiring such protection in the application.
Examples of "suitable means" include the following:
a) being sealed with a material suitable for the temperature range of the valve such that tampering is
apparent;
b) being accessible only with the use of special purpose tools; or
c) being accompanied by instructions requiring the equipment manufacturer to mount the valve such that
the adjustment means is inaccessible.
6.2.8.4.3 Test
Conformance is checked by inspection. Where sealing is used, inspection is carried out before and after the
endurance tests.
6.2.8.5 Maintaining of adjustments
Subclause specific to this document.
6.2.8.5.1 General
All factory adjustments shall be designed so that they are maintained in the field.
6.2.8.5.2 Requirements
Suitable means for maintaining all adjustments shall be provided.
Lock nuts or adjusting nuts held by springs or compression are acceptable unless their adjustment can be
accidentally disturbed.
6.2.8.5.3 Test
Conformance is checked by inspection.
6.2.8.6 Field adjustments
Subclause specific to this document.
6.2.8.6.1 General
Field adjustments shall be protected.
6.2.8.6.2 Requirements
Necessary field adjustments shall be capped according to 6.2.7 or otherwise protected in such a manner as
to resist tampering and prevent accidental change.
...