ISO 23551-4:2005

INTERNATIONAL ISO
STANDARD 23551-4
First edition
2005-08-15

Safety and control devices for gas
burners and gas-burning appliances —
Particular requirements —
Part 4:
Valve-proving systems for automatic
shut-off valves
Dispositifs de contrôle et de sécurité pour les brûleurs à gaz et pour les
appareils utilisant le gaz — Exigences particulières —
Partie 4: Systèmes de contrôle d'étanchéité pour robinets automatiques
de sectionnement




Reference number
ISO 23551-4:2005(E)
©
ISO 2005

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ISO 23551-4:2005(E)
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©  ISO 2005
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ISO 23551-4:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Classification. 3
5 Test conditions . 3
6 Construction. 3
6.1 General. 3
6.2 Construction requirements. 4
6.3 Materials . 4
6.4 Gas connections. 4
6.5 Electrical material . 4
6.6 Additional constructional requirements for VPS systems. 4
7 Performance . 4
7.1 General. 4
7.2 Leak-tightness. 5
7.3 Torsion and bending . 6
7.4 Rated flow rate . 6
7.5 Durability . 6
7.6 Functional requirements. 6
7.7 Endurance . 8
8 EMC/Electrical requirements. 11
8.1 Protection against environmental influences. 11
8.2 Variations in supply voltage . 11
8.3 Short-term voltage interruptions and drops . 11
8.4 Variations in supply frequency . 11
8.5 Surge immunity test . 12
8.6 Electrical fast transient/burst . 12
8.7 Immunity to conducted disturbances. 12
8.8 Immunity to radiated fields . 12
8.9 Electrostatic discharge immunity test. 12
8.10 Power frequency magnetic field immunity test . 13
8.11 Electrical requirements . 13
8.12 Protection against internal faults. 13
9 Marking, installation and operating instructions . 14
9.1 Marking . 14
9.2 Installation and operating instructions . 14
9.3 Warning notice . 15

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ISO 23551-4:2005(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 23551-4 was prepared by Technical Committee ISO/TC 161, Control and protective devices for gas and
oil burners and gas and oil burning appliances.
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 valves
 Part 2: Pressure governors
 Part 3: Gas/air ratio controls, pneumatic type
 Part 4: Valve-proving systems for automatic shut-off valves
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ISO 23551-4:2005(E)
Introduction
This part of ISO 23551 is to be used in conjunction with ISO 23550:2004. This part of ISO 23551 both refers
to and modifies clauses of ISO 23550:2004; the latter are indicated by stating that the clause of this part of
ISO 23551 includes additions to, modifications of or replacements of the corresponding clause in
ISO 23550:2004.
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INTERNATIONAL STANDARD ISO 23551-4:2005(E)

Safety and control devices for gas burners and gas-burning
appliances — Particular requirements —
Part 4:
Valve-proving systems for automatic shut-off valves
1 Scope
This part of ISO 23551 specifies safety, constructional and performance requirements of valve-proving
systems, hereafter referred to as VPS, intended for use with gas burners and gas-burning appliances. It also
describes the test procedures for checking compliance with these requirements and provides information
necessary for the purchaser and user. This part of ISO 23551 applies to all types of VPS which are used for
the automatic detection of leakage in a gas burner section having at least two valves designed in accordance
with ISO 23551-1 and which give a signal if the leakage of one of the valves exceeds the detection limit.
This part of ISO 23551 applies to VPSs with a declared maximum working pressure up to and including
500 kPa for use in systems using fuel gases.
This part of ISO 23551 does not apply to VPSs for use in explosive atmospheres.
2 Normative references
The following referenced documents are indispensable for the application 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 23550:2004, Safety and control devices for gas burners and gas-burning appliances — General
requirements
1)
ISO 23551-1:— , Safety and control devices for gas burners and gas-burning appliances — Particular
requirements — Part 1: Automatic valves
IEC 60529:2001, Degrees of protection provided by enclosures (IP Code)
IEC 60730-1:2003, Automatic electrical controls for household and similar use — Part 1: General
requirements
IEC 60730-2-5:2004, Automatic electrical controls for household and similar use — Part 2-5: Particular
requirements for automatic electrical burner control systems
IEC 60730-2-6:1991, Automatic electrical controls for household and similar use — Part 2: Particular
requirements for automatic electrical pressure sensing controls including mechanical requirements
IEC 61000-4-5:2001, Electromagnetic compatibility (EMC) — Part 4-5: Testing and measurement
techniques — Surge immunity test

1) To be published.
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ISO 23551-4:2005(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
valve proving system
VPS
system to check the effective closure of automatic shut-off valves by detecting leakage, that often consists of
a programming unit, a measuring device, valves and other functional assemblies
3.2
VPS programming unit
unit which follows a predetermined sequence of valve proving actions
3.3
detecting device
device for direct or inferential detection of leakage, e. g. by measuring flow or pressure
3.4
VPS operational time
time taken by the VPS to perform its entire cycle of operation
3.5
detection limit
maximum amount of leakage that can occur before the VPS is required to give a signal
NOTE See Figure 1.
3.6
detection setting
actual leakage rate setting specified by the manufacturer at which the VPS gives a signal
NOTE See Figure 1.

Key
X burner heat, gas flow, expressed in cubic metres per hour
Y detected leakage rate, expressed in cubic decimetres per hour

1 detection limit
2 detection setting
Figure 1 —Illustration of detection limit and detection setting
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ISO 23551-4:2005(E)
3.7
leakage testing time
time in which the VPS monitors a gas valve for leakage
3.8
volatile lock-out
safety shut-down condition of the system, such that a restart can be accomplished only by either the manual
reset of the system or an interruption of the main power and its subsequent restoration
3.9
non volatile lock-out
safety shut-down condition of the system, such that a restart can be accomplished only by a manual reset of
the system and by no other means
4 Classification
There is no classification.
5 Test conditions
ISO 23550:2004, Clause 5, applies, with the following addition.
The error of measurement shall not exceed
 for time measurements: ± 0,1 s,
 for temperature measurements: ± 1 K,
 for supply frequency measurements: ± 0,1 Hz,
 for electrical supply measurements: ± 0,5 %.
All measurements shall be made after stable temperature conditions have been achieved.
6 Construction
6.1 General
ISO 23550:2004, 6.1, applies, with the following addition.
The VPS shall be designed such that changes in critical circuit component values (such as those affecting
timing or sequence) within the component manufacturer's declared worst case tolerances, including the long-
term stability, shall result in the system continuing to function in accordance with this part of ISO 23551.
Compliance shall be checked by worst-case analysis.
The construction of any additional functions included in the VPS for which no provisions exist in this part of
ISO 23551 shall be such that they do not degrade the safe and correct operation.
Where components are used to complete the VPS, these components shall comply with the relevant
component International Standard. Valves (e. g. for pressurizing and relieving the test section) integrated into
the VPS functional sequence shall comply with ISO 23551-1:—, class A, and pressure-sensing devices, with
IEC 60730-2-6:1991.
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ISO 23551-4:2005(E)
6.2 Construction requirements
ISO 23550:2004, 6.2, applies.
6.3 Materials
ISO 23550:2004, 6.3, applies.
6.4 Gas connections
ISO 23550:2004, 6.4, applies.
6.5 Electrical material
6.5.1 Degree of protection
The class of protection for a system with its own enclosure shall be a minimum of IP 40 as specified in
IEC 60529:2001 when installed in accordance with the manufacturer's instructions. For systems used in the
open air, the protection shall conform to at least IP 54 when installed in accordance with the manufacturer's
instructions. For systems without enclosure, equivalent protection shall be provided by the appliance in which
it is installed.
6.5.2 Switches
ISO 23551-1:—, 6.5.2, applies.
6.5.3 Power-saving circuit
ISO 23551-1:—, 6.5.4, applies.
6.6 Additional constructional requirements for VPS systems
6.6.1 Signal for indication
A signal for indication, e.g. optical indication, shall be given when the leakage exceeds the detection limit.
6.6.2 VPS setting
The setting of a detecting device shall require the use of tools. If the VPS is adjustable, the manufacturer shall
supply information for its setting, e. g. detection setting.
7 Performance
7.1 General
ISO 23550:2004, 7.1, applies, with the following addition.
Where components are used to complete the VPS, these components shall comply with the relevant
component International Standard.
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ISO 23551-4:2005(E)
7.2 Leak-tightness
7.2.1 Criteria
A VPS shall be leaktight. A VPS is considered to be leaktight if no single component of a VPS has an external
3 –1
leakage rate no higher than 60 cm · h , unless a lower value is specified in the relevant component
International Standard.
An integrated VPS is considered to be a single component. Integrated VPS shall have a leakage rate no
3 –1
higher than 120 cm · h .

a)  External valves supervised by a VPS

b)  VPS with integrated valves

c)  VPS with partly integrated valves
Figure 2 — Examples of VPS configurations
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ISO 23551-4:2005(E)
7.2.2 Test for leak-tightness
7.2.2.1 General
ISO 23550:2004, 7.2.2.1, applies, except the 3rd paragraph.
7.2.2.2 External leak-tightness
ISO 23550:2004, 7.2.2.2, applies.
7.3 Torsion and bending
ISO 23550:2004, 7.3, applies.
7.4 Rated flow rate
ISO 23551-1:—, 7.4, applies.
7.5 Durability
ISO 23550:2004, 7.5, applies.
7.6 Functional requirements
7.6.1 General
The VPS shall allow the opening of the valves to the burner and subsequent ignition below the detection limit.
The VPS shall prevent the opening of the valve and operation of the ignition system when the detection limit is
exceeded.
Interruption of the mains supply and its restoration shall not affect the safety of the programme sequence. If
mains interruption and its restoration result in automatic recycling and overriding of any interlock, the VPS
shall restart from the beginning of the programme sequence.
7.6.2 Programme sequence
The programme sequence for the VPS shall enable ignition and opening of the valves to operate the burner
below the detection limit, and shall prevent ignition and opening of the valves when the detection limit is
exceeded, in accordance with 7.6.5, followed by a lock-out. The lock-out may be executed on the system
application direct or by the VPS itself. An automatic start-up attempt by a control function shall not override the
lock-out conditions.
Any gas necessary for the operation of the VPS may be discharged into the combustion chamber during the
programme sequence if the maximum release volume, expressed in litres per switching sequence, does not
exceed 0,05 % of the burner heat input referred to the nominal volume flow, expressed in cubic metres per
hour.
However, when the VPS is used as an alternative for pre-purge or post-purge, discharge of
...