ISO 23551-1:2012

Safety and control devices for gas burners and gas-burning appliances - Particular requirements - Part 1: Automatic and semi-automatic valves

ISO 23551-1:2012 specifies safety, constructional and performance requirements and testing of automatic and semi-automatic shut-off valves for gas burners, gas appliances and appliances of similar use. It applies to normally closed valves, valves being mounted upstream to gas burners and gas appliances, valves with declared maximum working pressures up to and including 500 kPa, for use on burners or in appliances using fuel gases as natural gas, manufactured gas or liquefied petroleum gas (LPG), valves directly or indirectly actuated, electrically or by mechanical means, valves actuated by hydraulic or pneumatic means, 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. ISO 23551-1:2012 covers type testing only.

Dispositifs de commande et de sécurité pour brûleurs à gaz et appareils à gaz — Exigences particulières — Partie 1: Robinets automatiques et semi-automatiques

General Information

• Status: Published
• Publication Date: 07-Aug-2012
• ICS: 27.060.20 - Gas fuel burners
• Technical Committee: ISO/TC 161 - Controls and protective devices for gas and/or oil
• Drafting Committee: ISO/TC 161/WG 3 - Controls
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 22-Nov-2024
• Completion Date: 13-Dec-2025

Relations

• Revised: 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
• Effective Date: 06-Jun-2022
• Revises: ISO 23551-1:2006 - Safety and control devices for gas burners and gas-burning appliances - Particular requirements - Part 1: Automatic valves
• Effective Date: 20-Apr-2009

Overview

ISO 23551-1:2012 - "Safety and control devices for gas burners and gas‑burning appliances - Part 1: Automatic and semi‑automatic valves" - specifies safety, constructional and performance requirements and type testing for automatic and semi‑automatic shut‑off valves used with gas burners and gas‑burning appliances. It applies to normally closed valves mounted upstream of burners, with declared maximum working pressures up to and including 500 kPa, for fuel gases such as natural gas, manufactured gas and LPG. The scope covers valves actuated electrically, mechanically, hydraulically or pneumatically, valves with step or modulating control, and valves fitted with closed‑position indicator switches.

Key topics and requirements

ISO 23551‑1 sets out technical requirements and tests, including:

• Classification of valves by control type (automatic, semi‑automatic, step, modulating) and functional groups.
• Constructional requirements: materials, gas connections and design features (including balanced valve designs).
• Performance tests: leak‑tightness (volumetric and pressure‑loss methods), rated flow rate, torsion and bending resistance.
• Durability and endurance: life‑cycle operating tests and sealing/closing force verification.
• Functional requirements: correct operation under specified test conditions, valve‑proving considerations and closed position indication.
• EMC and electrical requirements: immunity and emission tests drawn from IEC/IEC 61000 series and IEC 60730 family (surge, ESD, radiated immunity, voltage variations).
• Marking and documentation: required markings, installation and operating instructions, and warning notices.
• Regional annexes: additional normative requirements for Europe, North America (Canada/USA) and Japan.

Note: this part covers type testing only and is intended to be used in combination with ISO 23550 (general requirements).

Applications and users

ISO 23551‑1 is practical for:

• Valve and appliance manufacturers designing automatic or semi‑automatic gas shut‑off valves.
• Product designers and OEMs developing gas burners, cookers and HVAC equipment that incorporate safety valves.
• Test laboratories and type‑test engineers performing compliance and EMC testing.
• Certification bodies and regulators assessing conformity to international safety standards.
• Safety and reliability engineers verifying performance criteria such as leak tightness, endurance and electrical immunity.

Using ISO 23551‑1 helps ensure gas safety, interoperability, and market acceptance for valves intended for domestic, commercial and industrial gas appliances.

Related standards

• ISO 23550 (General requirements for safety and control devices)
• IEC 60730‑1 / IEC 60730‑2‑17 (automatic electrical controls)
• IEC 61000 series (EMC testing)
• IEC 60079‑11 (intrinsic safety)
• Various ISO pipe‑thread and material standards referenced for connections and components

Keywords: ISO 23551‑1, automatic and semi‑automatic valves, gas burners, gas‑burning appliances, safety requirements, type testing, leak‑tightness, EMC, durability, 500 kPa, LPG, natural gas.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23551-1
Second edition
2012-08-15
Safety and control devices for gas
burners and gas-burning appliances —
Particular requirements —
Part 1:
Automatic and semi-automatic valves
Dispositifs de commande et de sécurité pour brûleurs à gaz et appareils
à gaz — Exigences particulières —
Partie 1: Robinets automatiques et semi-automatiques

Reference number
©
ISO 2012
©  ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

Contents Page
Foreword . v
Introduction . vi
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Classification . 5
4.1  Classes of control . 5
4.2  Groups of controls . 5
5  Test conditions . 6
6  Construction . 6
6.1  General . 6
6.2  Construction requirements . 6
6.3  Materials . 9
6.4  Gas connections . 10
7  Performance . 11
7.1  General . 11
7.2  Leak-tightness . 12
7.3  Torsion and bending . 12
7.4  Rated flow rate . 13
7.5  Durability . 13
7.6  Functional requirements. 13
7.7  Endurance . 18
8  EMC/Electrical requirements . 22
8.1  Protection against environmental influences . 22
8.2  Variations in supply voltage . 22
8.3  Short-term voltage interruptions and drops . 22
8.4  Variations in supply frequency . 22
8.5  Surge immunity test . 22
8.6  Electrical fast transient/burst . 22
8.7  Immunity to conducted disturbances . 22
8.8  Immunity to radiated fields . 22
8.9  Electrostatic discharge immunity test . 22
8.10  Test for immunity to power-frequency magnetic field . 22
8.11  Electrical requirements . 22
8.101  Electrical components . 24
9  Marking, installation and operating instructions . 25
9.1  Marking . 25
9.2  Installation and operating instructions . 26
9.3  Warning notice . 26
Annex A (informative) Leak-tightness test - Volumetric method . 27
Annex B (informative) Leak-tightness test - pressure-loss method . 28
Annex C (normative) Conversion of pressure loss into leakage rate . 29
Annex D (normative) Test for immunity to power-frequency magnetic fields . 30
Annex E (normative) Specific regional requirements in European countries . 31
Annex F (normative) Specific regional requirements in Canada and the USA .32
F.1  General .32
F.2  Additional requirements and modifications .32
Annex G (normative) Specific regional requirements in Japan .34
G.1  General .34
G.2  Additional requirements and modifications .34
Bibliography .36

Figures
Figure 1 — Balanced valve with two ports. 8
Figure 2 — Balanced valve with one port . 9
Tables
Table 1 — Test pressure . 12
Table 2 — Sealing force requirements . 16
Table 3 — Operating cycles . 20
Table 4 — Operating cycles for automatic shut- off valves for cookers . 21
Table G.1 — Operating cycles . 35

iv © ISO 2012 – All rights reserved

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 23551-1 was prepared by Technical Committee ISO/TC 161, Control and protective devices for gas
and/or oil burners and appliances.
This second edition cancels and replaces the first edition (ISO 23551-1:2006), which has been technically
revised. In particular, the following has been changed:
a) integration of non electrical requirements from IEC 60730-2-17;
b) integration of electrical requirements from IEC 60730-2-17 which are unalterable for valves;
c) introduction of further classifications for valves;
d) introduction of requirements and tests for balanced valves;
e) introduction of requirements and tests for valves containing electrical components in the gas way.
ISO 23551 consists of the following parts, under the general title Safety and control devices for gas burners
and gas-burning appliances — Particular requirements:
 Part 1: Automatic and semi-automatic valves
 Part 2: Pressure regulators
 Part 3: Gas/air ratio controls, pneumatic type
 Part 4: Valve-proving systems for automatic shut-off valves
The following parts are under preparation:
 Part 5: Manual gas valves
 Part 6: Thermoelectric flame supervision devices
 Part 7: Pressure sensing devices
 Part 8: Multifunctional Controls
Introduction
This part of ISO 23551 is designed to be used in combination with ISO 23550. This part together with
ISO 23550 establishes the full requirements as they apply to the product covered by this International
Standard. This part adapts ISO 23550, where needed, by stating "with the following modification", "with the
following addition", "is replaced by the following" or "is not applicable," in the corresponding clause.
In order to identify specific requirements that are particular to this part, that are not already covered by
ISO 23550, this document may contain clauses or subclauses that are additional to the structure of
ISO 23550. These clauses are numbered starting from 101 or, in the case of an Annex, are designated AA,
BB, CC etc.
In an attempt to develop a full International Standard, it has been necessary to take into consideration the
differing requirements resulting from practical experience and installation practices in various regions of the
world and to recognize the variation in basic infrastructure associated with gas and/or oil controls and
appliances, some of which are addressed in Annexes E, F and G. This International Standard intends to
provide a basic framework of requirements that recognize these differences.

vi © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 23551-1:2012(E)

Safety and control devices for gas burners and gas-burning
appliances — Particular requirements —
Part 1:
Automatic and semi-automatic valves
1 Scope
This part of ISO 23551 specifies safety, constructional and performance requirements and testing of automatic
and semi-automatic shut-off valves for gas burners, gas appliances and appliances of similar use.
It applies to
 normally closed valves,
 valves being mounted upstream to gas burners and gas appliances,
 valves with declared maximum working pressures up to and including 500 kPa, for use on burners or in
appliances using fuel gases as natural gas, manufactured gas or liquefied petroleum gas (LPG),
 valves directly or indirectly actuated, electrically or by mechanical means,
 valves actuated by hydraulic or pneumatic means,
 valves where the flow rate is controlled by external electrical signals, either in discrete steps or propor-
tional to the applied signal and
 valves fitted with closed position indicator switches.
This part of ISO 23551 covers type testing only.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 7-1, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances
and designation
ISO 65, Carbon steel tubes suitable for screwing in accordance with ISO 7-1
ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions,
tolerances and designation
ISO 262, ISO general purpose metric screw threads — Selected sizes for screws, bolts and nuts
ISO 301, Zinc alloy ingots intended for castings
ISO 1817:1985 , Rubber, vulcanized — Determination of the effect of liquids
ISO 4400, Fluid power systems and components — Three-pin electrical plug connectors with earth contact —
Characteristics and requirements
ISO 6952, Fluid power systems and components — Two-pin electrical plug connectors with earth contact —
Characteristics and requirements
ISO 7005 (all parts), Metallic flanges
ISO 23550:2011, Safety and control devices for gas burners and gas burning appliances — General
requirements
IEC 60079-11, Explosive atmospheres — Part 11: Equipment protection by intrinsic safety "i"
IEC 60529, Degrees of protection provided by enclosures (IP-code)
IEC 60730-1:2010 (Edition 4.0), Automatic electrical controls for household and similar use — Part 1: General
requirements
IEC 61000-4-2, Electromagnetic compatibility (EMC) — Part 4-2: Testing and measurement techniques —
Electrostatic discharge immunity test
IEC 61000-4-3, Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement techniques —
Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-4, Electromagnetic compatibility (EMC) — Part 4-4: Testing and measurement techniques —
Electrical fast transient/burst immunity test
IEC 61000-4-5, Electromagnetic compatibility (EMC) — Part 4-5: Testing and measurement techniques —
Surge immunity test
IEC 61000-4-6, Electromagnetic compatibility (EMC) — Part 4-6: Testing and measurement techniques —
Immunity to conducted disturbances, induced by radio-frequency fields
IEC 61000-4-8, Electromagnetic compatibility (EMC) — Part 4-8: Testing and measurement techniques —
Power frequency magnetic field immunity test
IEC 61000-4-11, Electromagnetic compatibility (EMC) — Part 4-11: Testing and measurement techniques —
Voltage dips, short interruptions and voltage variations immunity tests
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.
3.101
valves
3.101.1
valve
device consisting essentially of a valve body, closure member, and actuator that controls the flow of gas
NOTE The actuation can be done by gas pressure, electrical, hydraulic, manual or pneumatic energy.

Withdrawn.
2 © ISO 2012 – All rights reserved

3.101.2
semi-automatic shut-off valve
valve that is opened manually and returns to the closed position upon removal of the actuating energy
3.101.3
automatic shut-off valve
valve which opens when energized and closes automatically when de-energized
3.101.4
thermoelectric valve
automatic shut-off valve that receives its electrical actuating energy by means of a thermoelectric source
3.101.5
diaphragm type valve
automatic shut-off valve where a closing member is opened by application of gas pressure upon a flexible
diaphragm
3.102
valve with step control
multi stage valve
valve which controls the flow rate in steps
3.103
valve with modulating control
modulating valve
valve which controls the flow rate continuously between two limits in response to external signals
3.104
actuating mechanism
part of the valve which moves the closure member
3.105
closed position indicator switch
switch fitted to a valve which indicates when the closure member is in the closed position
3.106
actuating energy
required energy for the actuating mechanism to move the closure member to the open position; the actuating
energy can have an external source (electrical, hydraulic or pneumatic) and can be transformed inside the
valve
3.107
closing force
force available to close the valve, independent of any force provided by fuel gas pressure
3.108
sealing force
force acting on the valve seat when the closure member is in the closed position, independent of any force
provided by fuel gas pressure
3.109
frictional force
largest force required to move the actuating mechanism and the closure member from the open position to the
closed position with the closure spring removed, independent of any force provided by fuel gas pressure
3.110
actuating pressure
hydraulic or pneumatic pressure supplied to the actuating mechanism of the valve
3.111
pressure difference
difference between the inlet and outlet pressures
3.112
opening time
time interval between energizing the valve and the attainment of the maximum or other defined flow rate
3.113
closing time
time interval between de-energizing the valve and the closure member attaining the closed position
3.114
delay time
time interval between energizing the valve and the start of flow
3.115
control valve
valve which controls the hydraulic or pneumatic means supplied to the actuating mechanism
3.116
rated voltage
voltage declared by the manufacturer at which the valve may be operated
3.117
rated current
current declared by the manufacturer at which the valve may be operated
3.118
bypass
passage, provided in the body of the device or in a gas line around the body, which permits a gas flow from
the inlet to the outlet connections of the device entirely independent of the action of the valve
3.119
interlock
control or device to prove the physical state of a required condition, and to furnish proof to the automatic gas
ignition system or other safety control circuit
3.120
proof-of-closure switch
electrical switch which monitors the closed position of the valve closure member and which is used as an
interlock
3.121
switching device
electrical switch actuated by the valve actuator and used as an electrical output
3.122
valve actuator
electrically operated mechanism (for example an electric motor, or stepping solenoid), an electro-thermal
device (for example the heating element of an energy regulator) or a mechanical storage device (for example
a clockwork spring), used to effect the opening action of a valve
3.123
Commercial / industrial valve
C/I Valve
a normally closed automatic or semi-automatic shut-off valve having an operating pressure greater than
3,5 kPa
4 © ISO 2012 – All rights reserved

3.124
balanced valve with two ports
automatic shut-off valve with a balanced closure member, two valve discs and two valve seats where the inlet
pressure acts on the closure member in the closing direction
NOTE Examples are shown in Figure 1.
3.125
balanced valve with one port
automatic shut-off valve with a balanced closure member, one valve disc and balancing means where the inlet
pressure acts on the closure member in the closing direction
NOTE Example is shown in Figure 2.
4 Classification
4.1 Classes of control
Shall be according to ISO 23550:2011, 4.1 with the following addition:
4.1.101 Classification based on sealing force
If automatic shut-off valves are classified based on sealing force the following classes shall be used:
 Class A, B and C valves
Valves where the sealing force is not decreased by the gas inlet pressure. They are classified A, B or C
according to the sealing force requirements of 7.6.107.1. Balanced valves with two ports according to this
standard are Class A valves.
 Class D valves
Valves which are not subject to any sealing force requirements.
 Class J valves
Disc-on-seat valves where the sealing force is not decreased by the gas inlet pressure and which meet
the requirements of 7.6.107.1.
NOTE Specific regional requirements are given in Annex F and Annex G.
4.1.102 Classifications according to their purpose
 C/I valves;
 Automatic shut-off valves;
 Semi-automatic shut-off valves;
 valve with modulating control / modulating valve;
 valve with step control / multi-stage valve.
4.2 Groups of controls
Shall be according to ISO 23550:2011, 4.2.
5 Test conditions
Shall be according to ISO 23550:2011, Clause 5.
6 Construction
6.1 General
Shall be according to ISO 23550:2011, 6.1.
6.2 Construction requirements
6.2.1 Appearance
Shall be according to ISO 23550:2011, 6.2.1.
6.2.2 Holes
Shall be according to ISO 23550:2011, 6.2.2.
6.2.3 Breather holes
Shall be according to ISO 23550:2011, 6.2.3.
NOTE Specific regional requirements are given in Annex F.
6.2.4 Screwed fastenings
Shall be according to ISO 23550:2011, 6.2.4.
6.2.5 Jointing
Shall be according to ISO 23550:2011, 6.2.5.
6.2.6 Moving parts
Shall be according to ISO 23550:2011, 6.2.6 with the following addition:
 C/I valve screws and nuts:
Means that serve to attach operating parts to movable members shall be secured to prevent loosening
under the conditions of actual use.
6.2.7 Sealing caps
Shall be according to ISO 23550:2011, 6.2.7.
6.2.8 Dismantling and reassembling for servicing and/or adjustment
Shall be according to ISO 23550:2011, 6.2.8 with the following addition:
6.2.8.101 General
Factory adjustment, not intended for field adjustment, shall be secured by means providing protection against
access or shall be declared as requiring such protection in the application.
6 © ISO 2012 – All rights reserved

NOTE For example, these means can:
a) be sealed with a material suitable for the temperature range of the valve such that tampering is apparent, or
b) be accessible only with the use of special purpose tools, or
c) be accompanied by instructions requiring the equipment manufacturer to mount the valve such that the adjustment
means is inaccessible.
Compliance is checked by inspection. Where sealing is used, inspection is done before and after the
endurance tests.
6.2.8.102 Maintaining of adjustments
Suitable means for maintaining all adjustments shall be provided.
NOTE Lock nuts or adjusting nuts held by springs or compression are acceptable unless their adjustment can be
accidentally disturbed.
6.2.8.103 Field adjustments
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.
6.2.9 Auxiliary channels
Shall be according to ISO 23550:2011, 6.2.9.
6.2.101 Closed position indicator switch
Closed position indicator switches, where fitted, shall not impair the correct operation of valves. Adjusters shall
be sealed to indicate interference. Any drift of the switch and actuating mechanism from its setting shall not
impair correct valve operation.
If a closed position indicator switch is used as proof-of-closure switch, the switch contacts shall close only
after the valve port is closed and shall open before the valve port opens. Additional movement to operate the
switch after the valve port is closed shall be provided either directly by the port closure member or by
additional valve actuating mechanism movement, which relies on the port closure member being in the closed
position. The switch shall be factory set and sealed to prevent field adjustment.
6.2.102 C/I valve construction
A C/I valve shall not utilize fuel gas pressure or flow trough the valve or an external power source for closure.
6.2.103 Visual position indicator
If a C/I valve incorporates an integral visual position indicator which indicates when the valve is closed it shall
be connected to the valve closure member.
6.2.104 Flow rates
Flow rates of valves with modulating control shall be adjustable over the full range declared by the
manufacturer. If the adjustment of one flow rate affects the setting of any other flow rate, this shall be clearly
indicated in the manufacturer's instructions for setting up. The setting of any flow rate shall require the use of
tools and shall be sealed to discourage unauthorized adjustment.
6.2.105 Protection of the valve mechanism
The mechanisms of valves shall be protected by substantial enclosures so as to prevent interference with the
safe operation of the devices.
6.2.106 By-pass
Valves classified as classes A, B, C, D, J and C/I shall not incorporate a by-pass.
NOTE Specific regional requirements are given in Annex G.
6.2.107 Semi-automatic C/I valve
A semi-automatic C/I valve that is manually open shall only allow a fully open position.
6.2.108 Diaphragm type valve
Parts of the valve coming in contact with the diaphragm shall not have sharp edges which might chafe or
abrade it.
6.2.109 Balanced valves with one or two ports
The closure member of a balanced valve with one or two ports shall have a resulting force in the closing
direction where the sealing force is not decreased by the gas inlet pressure.
For a balanced valve with one port a resulting force in the closing direction shall remain if the balancing force
is removed and the closure member shall have the same closing direction as the flow direction through the
valve.
NOTE Examples are shown in Figure 1 and Figure 2.

a) Example 1 b) Example 2
Key
1 spring 4 valve disc big
2 valve seat big 5 valve disc small
3 valve seat small
Figure 1 — Balanced valve with two ports
8 © ISO 2012 – All rights reserved

Key
1 spring 4 valve disc big
2 valve seat big 5 compensating diaphragm (smaller than 2)
3 breather hole
Breather hole as bypass to valve port is not allowed.
Figure 2 — Balanced valve with one port
6.3 Materials
6.3.1 General material requirements
Shall be according to ISO 23550:2011, 6.3.1.
6.3.2 Housing
6.3.2.1 Housing design
Shall be according to ISO 23550:2011, 6.3.2.1 with the following addition:
When a diaphragm separates parts of the housing from the gas-carrying compartment from atmosphere then
this is considered to be indirectly separated. Those parts shall be made from metallic material.
For C/I valves the body and its internal parts, except the soft part of valve disk, gasket, O-rings and the like,
shall be of material having melting points not less than 427 °C.
NOTE Specific regional requirements are given in Annex F.
6.3.2.2 Test for leakage of housing after removal of non-metallic parts
Shall be according to ISO 23550:2011, 6.3.2.2.
6.3.3 Springs
6.3.3.1 Closure springs
Shall be according to ISO 23550:2011, 6.3.3.1.
6.3.3.2 Springs providing closing force and sealing force
Shall be according to ISO 23550:2011, 6.3.3.2 with the following addition:
Springs shall be protected against abrasion and guided or arranged to minimize binding, buckling, or other
interference with their free movement.
6.3.4 Resistance to corrosion and surface protection
Shall be according to ISO 23550:2011, 6.3.4.
6.3.5 Impregnation
Shall be according to ISO 23550:2011, 6.3.5.
6.3.6 Seals for glands for moving parts
Shall be according to ISO 23550:2011, 6.3.6.
6.3.101 Closure members
Closure members of valves above DN 25 shall either have a mechanical support (e. g. metallic) to withstand
the sealing force or shall be made of metal.
This requirement also applies to:
 all valves with a maximum working pressure above 15 kPa;
 parts transmitting the closing force.
The strength of the connection between the
 two valve discs of a balanced valve with two ports or
 one valve disc and balancing means of a balanced valve with one port
shall be at least five multiplied by the maximum inlet pressure multiplied by the
 total opening area of the valve ports for a balanced valve with two ports or
 opening area of the valve port and the area of the balancing means of a balanced valve with one port.
6.4 Gas connections
6.4.1 Making connections
Shall be according to ISO 23550:2011, 6.4.1.
6.4.2 Connection sizes
Shall be according to ISO 23550:2011, 6.4.2.
6.4.3 Threads
Shall be according to ISO 23550:2011, 6.4.3 with the following addition:
C/I valves up to a size of DN 80 may have thread or flange connection. If threads are used they shall have
female pipe threads.
NOTE Specific regional requirements are given in Annex F.
10 © ISO 2012 – All rights reserved

6.4.4 Union joints
Shall be according to ISO 23550:2011, 6.4.4.
6.4.5 Flanges
Shall be according to ISO 23550:2011, 6.4.5 with the following addition:
C/I valves larger than DN 80 shall incorporate flange connections.
NOTE Specific regional requirements are given in Annex F.
6.4.6 Compression fittings
Shall be according to ISO 23550:2011, 6.4.6.
6.4.7 Nipples for pressure tests
Shall be according to ISO 23550:2011, 6.4.7.
6.4.8 Strainers
Shall be according to ISO 23550:2011, 6.4.8 with the following addition:
Class J valves shall incorporate an inlet strainer. The maximum strainer hole dimension shall not exceed
0,28 mm and it shall prevent the passage of a 0,2 mm diameter pin gauge.
Strainers fitted to valves of DN 25 and above shall be accessible for cleaning or replacement without removing
the valve body pipe connections from the pipe work.
6.4.101 Hydraulic and pneumatic actuating mechanisms
Hydraulically or pneumatically actuated valves shall be provided with protection to ensure that the blockage of
an orifice in the control system does not adversely affect the ability of the valve to close.
7 Performance
7.1 General
Shall be according to ISO 23550:2011, 7.1 with the following addition:
The electrical control valve of hydraulic or pneumatic actuating mechanisms shall also meet these
requirements.
The closing of hydraulically or pneumatically actuated valves shall be ensured over the range from 85 % to
110 % of the actuating pressure or pressure range declared by the manufacturer.
For semi-automatic shut-off valves, permanent blocking of the manual actuating means shall be discouraged
by suitable means.
For the following DC supplies a tolerance of 20 % to the minimum and the maximum rated voltage applies:
 stand-alone battery systems;
 battery systems for mobile vehicle applications;
 systems which are intended to be connected to DC supply networks;
For DC supplies of other types the tolerance shall be declared by the manufacturer.
7.2 Leak-tightness
7.2.1 Requirement
Shall be according to ISO 23550:2011, 7.2.1 with the following addition:
Addition:
Balanced valves with two ports shall be leak-tight when tested with rates given in Table 1.
Table 1 — Test pressure
Test pressure p in flow direction Maximum leakage rate
Inlet pressure
kPa
2  p
0 Pa  p  50 kPa
max For internal leak-tightness
p = p x [ 2 – ( p – 50)/900 ] see values in ISO 23550:2011, Table 2.
50 kPa < p  500 kPa
max max
7.2.2 Test for leak-tightness
Shall be according to ISO 23550:2011, 7.2.2 with the following addition:
7.2.2.101 C/I valve gas pressure surge test
A closed C/I valve shall remain closed on a sudden change of upstream pressure over a range of 0 to 150 %
of the maximum rated inlet pressure.
1) The maximum leakage test pressure is applied within 0,5 s.
2) The pressure is maintained and leakage is accumulated over a 2 min test period.
3) Accumulated total leakage from above, resulting in an equivalent leakage rate per hour.
4) The test shall be repeated 5 times and the highest internal leakage for any one test shall not exceed the
leakage allowed in ISO 23550:2011, 7.2.1 when tested according to ISO 23550:2011, 7.2.2.
7.2.2.102 Test of leak-tightness for balanced valves with two ports
For balanced valves with two ports pressurize the inlet to test pressures given in 7.2.1 and measure the
leakage rate.
7.3 Torsion and bending
Shall be according to ISO 23550:2011, 7.3.
12 © ISO 2012 – All rights reserved

7.4 Rated flow rate
7.4.1 Requirement
Shall be according to ISO 23550:2011, 7.4.1 with the following addition:
Where the manufacturer declares opening and closing characteristics for valves with modulating control, these
shall be within  10 % of the manufacturer’s declared value.
For valves with step control, where applicable, the manufacturer shall declare the maximum flow rate for each
step as a percentage of the fully open flow rate. It shall not be possible to adjust the maximum flow rate for
each step in excess of 1,1 times the declared value when tested to 7.4.2.
When the flow rate changes in response to external electrical signals, it shall not, when tested to 7.4.2,
overshoot in either direction while attaining the new flow rate by more than 20 % of the flow rate at that
particular set point, or as declared by the manufacturer.
7.4.2 Test for rated flow rate
Shall be according to ISO 23550:2011, 7.4.2 with the following addition:
7.4.2.101 Characteristics for valves with modulating or step control
Verify the declared opening and closing characteristics at rated voltage or current before and after the
endurance test for conformity with 7.4.1.
7.5 Durability
Shall be according to ISO 23550:2011, 7.5.
7.6 Functional requirements
Shall be according to ISO 23550:2011, 7.6 with the following addition:
7.6.101 Closing function
7.6.101.1 Requirement
Automatic shut-off valves shall close automatically on reducing the voltage or current to 15 % of the minimum
rated value. Automatic shut-off valves with hydraulic or pneumatic actuating mechanisms shall close
automatically on reducing the voltage or current to 15 % of the minimum rated voltage of the control valve.
Automatic shut-off valves shall close automatically on removal of the voltage or current of between 15 % of
the minimum rated value and 110 % of the maximum rated value.
In all cases, the closing time shall be in accordance with 7.6.106
NOTE Specific regional requirements are given in Annex F and Annex G.
7.6.101.2 Test of closing function
Energize the valve at the maximum rated voltage or current and at the maximum actuating pressure, if
applicable. Slowly reduce the voltage or current to 15 % of the minimum rated value. Verify that the valve has
closed.
Energize the valve at the maximum rated voltage or current and at the maximum actuating pressure, if
applicable. Increase the voltage or current to 110 % of the maximum rated value, keeping the actuating
pressure, if any, unchanged. De-energize the valve and verify that it has closed. For a.c. valves, remove the
voltage at the peak of the current waveform.
Energize the valve at the maximum rated voltage or current and at the maximum actuating pressure, if
applicable. Reduce the voltage or current to a value between 15 % of the minimum rated value and 85 % of
the maximum rated value, keeping the actuating pressure, if any, unchanged. De-energize the valve and
verify that it has closed. Carry out this test at 3 different voltages or currents between 15 % of the minimum
rated value and 85 % of the maximum rated value.
7.6.102 Open and closing function of thermoelectric valves
7.6.102.1 Requirement
For a thermoelectric valve the pull-in current, if applicable, and the drop-out current shall be within the
manufacturer's specified range.
7.6.102.2 Test of thermoelectric valves
A direct current power source of appropriate voltage in series with an ammeter shall be used. Each device
shall be tested 3 times under each of the following test conditions, as applicable. For automatic pull-in
devices, the current shall be set below the manufacturer's specified pull-in current. The current shall be slowly
increased. The current at which the device pulls in, shall not be less than the minimum or greater than the
maximum value specified by the manufacturer. The current shall be set at the manufacturer's specified
maximum operating current. The resetting mechanism, if provided, shall be operated in accordance with the
manufacturer's instructions. The current at which the valve drops out shall not be less than the minimum or
greater than the maximum value specified by the manufacturer.
7.6.103 Diaphragm assisting the shut-off function
7.6.103.1 General
Shut-off functions using a diaphragm in combination with a closure member to assist in the shut-off function
shall be designed in such a way that, when the diaphragm is damaged, the internal leakage of the valve shall
not be more than 1 dm³/h at the maximum inlet pressure. Conformity shall be verified by the method given in
7.6.103.2.
7.6.103.2 Leakage test for valves
Remove or rupture the part(s) originating the balancing force. Ensure the coil of the shut-off function is de-
energized. Measure the internal leakage rate of the valve according to 7.2.2.
7.6.104 Closing force
7.6.104.1 Requirement
Valves with sealing force independent of the closing force (e. g. ball valve, gate valves etc.) shall have a
closing force of:
 at least 5 times the value of the frictional force where the frictional force is up to and including 5 N;
 at least 2,5 times the value of the frictional force but at least 25 N where the frictional force is above 5 N.
The frictional force is measured in the ungreased condition.
This requirement also applies to disc-on-seat valves with a working pressure above 50 kPa.
14 © ISO 2012 – All rights reserved

7.6.104.2 Test of closing force
This measurement is performed in the ungreased condition.
Measure the minimum closing force over the travel of the closure member from the open position to the closed
position.
Remove the spring(s) providing the closing force from the valve and measure the maximum force required to
move the closure member from the open position to the closed position.
7.6.105 Delay time and opening time
7.6.105.1 Requirement
The delay time and the opening time shall be:
 within  20 % of the manufacturer's declared value for times above 1 s;
 less than 1 s for declared times up to and including 1 s.
7.6.105.2 Test of delay time and opening time
Opening time: Measure the time interval between energizing the valve and the attainment of a flow rate equal
to 80 % of the rated flow rate.
This test is also used to measure the time interval between energizing the valve and the start of the release of
the closure member (delay time).
Carry out the tests under the following conditions, allowing the de-energized valve to reach thermal
equilibrium before carrying out the tests:
 at 60 °C (or at the maximum ambient temperature, if higher), at the maximum working pressure, at 110 %
of the maximum rated voltage or current and at the maximum actuating pressure, if applicable;
 at 0 °C (or at the minimum ambient temperature, if lower), at a working pressure of 0,6 kPa, at 85 % of
the minimum rated voltage or current and at the minimum actuating pressure, if applicable.
NOTE Specific regional requirements are given in Annex G.
7.6.106 Closing time
7.6.106.1 Requirement
The closing time for valves of classes A, B, and C shall not exceed 1 s when tested to 7.6.106.3.
The closing time for Class D valves shall not exceed the manufacturer's declared value.
The closing time for Class J valves shall not exceed 5 s or any lower value declared by the manufacturer.
The closing time for C/I valves shall not exceed 2 s. The test to 7.6.106.3 shall be repeated during the period
of opening of the valve.
7.6.106.2 Closing time for controlling function
The closing time for any controlling function shall be within  10 % of the manufacturer’s declared value.
7.6.106.3 Test of closing time
Measure the time interval between de-energizing the valve and the closure member attaining the closed
position, under the following conditions:
 at the maximum working pressure, at a pressure difference declared by the manufacturer, at 110 % of the
maximum rated voltage or current and at the maximum actuating pressure, if applicable;
 at a working pressure of 0,6 kPa, at the minimum pressure difference declared by the manufacturer, at
110 % of the maximum rated voltage or current and at the maximu
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