ISO 23551-1:2012

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 23551-1:2012(E)
©
ISO 2012

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ISO 23551-1:2012(E)

©  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,
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Published in Switzerland

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ISO 23551-1:2012(E)
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
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ISO 23551-1:2012(E)
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

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ISO 23551-1:2012(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.
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
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ISO 23551-1:2012(E)
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.

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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
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ISO 23551-1:2012(E)
1
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.

1
Withdrawn.
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ISO 23551-1:2012(E)
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
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ISO 23551-1:2012(E)
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
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ISO 23551-1:2012(E)
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.
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ISO 23551-1:2012(E)
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.
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ISO 23551-1:2012(E)
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.
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ISO 23551-1:2012(E)
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
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ISO 23551-1:2012(E)

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 requ
...