ISO 23551-2:2006

Safety and control devices for gas burners and gas-burning appliances - Particular requirements - Part 2: Pressure regulators

ISO 23551-2:2006 specifies safety, constructional and performance requirements for pressure regulators 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. ISO 23551-2:2006 applies to pressure regulators for gas burners and gas burning appliances of nominal connection size up to and including DN 250 that can be used and tested independently of these appliances. These regulators are suitable for fuel gases, such as natural gas, manufactured gas or liquefied petroleum gas (LPG) at inlet pressures up to and including 50 kPa. ISO 23551-2:2006 covers type testing only. ISO 23551-2:2006 does not cover regulators connected directly to the mains pipe work or to a container that maintains a standard distribution pressure; regulators installed outdoors and exposed to the environment; regulators which use electrical auxiliary energy.

Dispositifs de commande et de sécurité pour brûleurs à gaz et appareils à gaz — Exigences particulières — Partie 2: Régulateurs de pression

General Information

• Status: Withdrawn
• Publication Date: 28-Jun-2006
• Withdrawal Date: 28-Jun-2006
• 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 - Controls and protective devices for gas and/or oil
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 20-Sep-2018
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 23551-2:2018 - Safety and control devices for gas burners and gas-burning appliances - Particular requirements - Part 2: Pressure regulators
• Effective Date: 10-May-2014

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23551-2
First edition
2006-07-01
Safety and control devices for gas
burners and gas-burning appliances —
Particular requirements —
Part 2:
Pressure regulators
Dispositifs de commande et de sécurité pour brûleurs à gaz et appareils
à gaz — Exigences particulières —
Partie 2: Régulateurs de pression

Reference number
©
ISO 2006
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©  ISO 2006
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ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols. 1
3.1 Regulators . 1
3.2 Pressures. 2
3.3 Flow rates . 3
3.4 Component parts . 3
3.5 Performance . 3
4 Classification. 4
4.1 Classes of control. 4
4.2 Groups of controls. 4
5 Test conditions . 4
6 Construction. 5
6.1 General. 5
6.2 Construction requirements. 5
6.3 Materials . 6
6.4 Gas connections. 6
7 Performance . 6
7.1 General. 6
7.2 Leak-tightness. 6
7.3 Torsion and bending . 7
7.4 Rated flow rate . 8
7.5 Durability . 8
7.6 Functional requirements. 8
7.7 Putting the regulator out of action. 8
7.8 Long-term performance . 8
7.9 Lock-up pressure. 9
8 EMC/Electrical requirements. 9
9 Marking, installation and operating instructions . 9
9.1 Marking . 9
9.2 Installation and operating instructions . 10
9.3 Warning notice . 10
Annex A (informative) Classification of fuel gases into gas families . 11
Annex B (normative) Functional requirements and regulator performance testing — Method A. 13
Annex C (normative) Functional requirements and regulator performance testing — Method B. 22
Annex D (normative) Specific performance testing in Japan. 36
Annex E (informative) Typical regulators and regulator parts . 37
Bibliography . 38

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 23551-2 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 regulators
⎯ Part 3: Gas/air ratio controls, pneumatic type
⎯ Part 4: Valve-proving systems for automatic shut-off valves
iv © ISO 2006 – All rights reserved

Introduction
This part of ISO 23551 is designed to be used in conjunction with ISO 23550:2004.
This part of ISO 23551 either references existing requirements of ISO 23550:2004 or indicates that there has
been an “addition”, “modification” or “replacement” in the cited requirement of ISO 23550:2004.
INTERNATIONAL STANDARD ISO 23551-2:2006(E)

Safety and control devices for gas burners and gas-burning
appliances — Particular requirements —
Part 2:
Pressure regulators
1 Scope
This part of ISO 23551 specifies safety, constructional and performance requirements for pressure regulators
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 pressure regulators for gas burners and gas-burning appliances of nominal
connection size up to and including DN 250 that can be used and tested independently of these appliances.
These regulators are suitable for fuel gases, such as natural gas, manufactured gas or liquefied petroleum gas
(LPG) at inlet pressures up to and including 50 kPa.
This part of ISO 23551 covers type testing only.
This part of ISO 23551 does not cover
a) regulators connected directly to the mains pipe work or to a container that maintains a standard
distribution pressure;
b) regulators installed outdoors and exposed to the environment;
c) regulators which use electrical auxiliary energy.
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
3 Terms, definitions and symbols
For the purpose of this document, the terms and definitions given in ISO 23550:2004 and the following apply.
3.1 Regulators
3.1.1
pressure regulator
device that maintains the outlet pressure constant within given limits, independently of the variations in inlet
pressure and/or flow rate
3.1.2
adjustable pressure regulator
regulator provided with means for changing the outlet pressure setting
3.2 Pressures
3.2.1
test pressure
pressure to be applied during a test
3.2.2
pressure drop
differential pressure with valve open to its fullest extent
3.2.3
maximum inlet pressure
p
1max
highest inlet pressure at which tests have been conducted to determine that the regulator is able to control the
outlet pressure within acceptable limits as declared by the manufacturer
3.2.4
minimum inlet pressure
p
1min
lowest inlet pressure at which tests have been conducted to determine that the regulator is able to control the
outlet pressure within acceptable limits declared by the manufacturer
3.2.5
inlet pressure range
range of inlet pressure between the maximum and minimum values
3.2.6
maximum outlet pressure
p
2max
highest outlet pressure at which tests have been conducted to determine that the regulator is able to control
the outlet pressure within acceptable limits declared by the manufacturer
3.2.7
minimum outlet pressure
p
2min
lowest outlet pressure at which tests have been conducted to determine that the regulator is able to control
the outlet pressure within acceptable limits declared by the manufacturer
3.2.8
outlet pressure range
range of outlet pressure between the maximum and minimum values
3.2.9
setting point
inlet and outlet pressures declared by the manufacturer, at which the regulator is initially adjusted for test
purposes at a declared flow rate
NOTE The respective pressures and flow rate are termed “inlet setting pressure”, “outlet setting pressure” and
“setting flow rate”.
2 © ISO 2006 – All rights reserved

3.3 Flow rates
3.3.1
maximum flow rate
q
max
maximum rate, as a function of inlet and outlet pressures, declared by the manufacturer and expressed in
3 –1
m⋅h of air at standard conditions
NOTE For a non-adjustable regulator, there is only one maximum flow rate.
3.3.2
minimum flow rate
q
min
minimum rate, as a function of inlet and outlet pressures, declared by the manufacturer and expressed in
3 –1
m⋅h of air at standard conditions
NOTE For a non-adjustable regulator, there is only one minimum flow rate.
3.3.3
flow rate range
range of flow rate between the maximum and minimum values
3.4 Component parts
3.4.1
breather hole
orifice that allows atmospheric pressure to be maintained in a compartment of variable volume
3.4.2
diaphragm
flexible member which, under the influence of the forces arising from loading and pressure, operates the valve
3.4.3
diaphragm plate
stiffening plate fitted to the diaphragm
3.4.4
valve
device which varies the gas flow directly
3.5 Performance
3.5.1
lock-up pressure
outlet pressure at which a regulator closes when the outlet of the regulator is sealed
NOTE The increase in outlet pressure is expressed either in kilopascals or as a percentage.
3.5.2
put out of action
〈verb〉 inactivate a regulator, thereby ensuring that this setting does not undergo any changes
4 Classification
4.1 Classes of control
Pressure regulators are classified as class A, class B or class C, according to the appropriate inlet pressure
and flow rate limits, as given in Table 1.
NOTE 1 In the USA, regulators are classified either for main burner load application or for main burner and pilot load
application.
NOTE 2 In Japan, pressure regulators are not classified.
Table 1 — Deviation of outlet pressure from outlet setting pressure
a
Maximum outlet pressure deviation
%
Class of regulators
Manufactured Natural gas Liquefied
gas petroleum gas
Class A: q to q and p to p ± 15 ± 15 ± 15
max min 1max 1min
Class B: by variation of the inlet pressure for each of the flow
± 10
+ 15 + 10
rates
− 20 − 15
by variation of flow rates from q to q (constant
max min + 40 + 40 + 40
0 0 0
inlet pressure) for each of the inlet pressures
Class C: at constant q (within the flow rate range) ± 10
+ 15 + 10
− 20 − 15
NOTE 1 Classification of fuel gases see Annex A.
a
See Annex A.
4.2 Groups of controls
A regulator is classified as group 1 or group 2, according to the bending stresses that it is required to
withstand in accordance with ISO 23550:2004, Table 3.
⎯ Group 1 regulators: Regulator intended for use in an appliance and/or installation where it is not
subjected to bending stresses imposed by the pipe work (e.g. by the use of rigid
adjacent supports);
⎯ Group 2 regulators: Regulator for use in any situation, either internal or external to the appliance,
typically without support.
NOTE A regulator that complies with the requirements for group 2 can be deemed to comply also with the
requirements for group 1 regulators.
5 Test conditions
ISO 23550:2004, Clause 5, shall apply.
NOTE Specific requirements for testing are given in Annexes B and C.
4 © ISO 2006 – All rights reserved

6 Construction
6.1 General
ISO 23550:2004, 6.1, shall apply.
6.2 Construction requirements
ISO 23550:2004, 6.2, shall apply, except as in 6.2.1 to 6.2.3:
6.2.1 Breather holes
ISO 23550:2004; 6.2.3, shall apply with the addition of 6.2.1.1 and 6.2.1.2:
6.2.1.1 Vent limiters
Vent limiters used with regulators shall limit the flow through the vent of the regulator as shown in Table 2
when tested at room temperature.
Table 2 — Maximum allowable vent limiter venting rate
Type of vent limiter Specific gravity Maximum allowable flow rate
3 3
cm /s (ft /h)
Vent limiter for use only with natural, manufactured, 0,64 19,7 (2,5)
mixed gases and LP gas-air mixtures
Vent limiter for use with liquefied petroleum gas 1,53 7,87 (1,0)
6.2.1.2 Separate vent limiters test
Separate vent limiters shall be installed in an upright position in a gas-tight piping system so that the test
medium passes through the vent limiter. It shall then be determined that there is no leakage at the points other
than through the vent limiter. The rate of flow through the test meter shall be determined at pressures from
498 Pa (2 in water column) up to and including the maximum working pressure of the regulator and corrected
for a specific gravity of 1,53 for vent limiters for use with liquefied petroleum gases, and a specific gravity of
0,64 for vent limiters for use only with natural, manufactured, mixed gases and LP gas-air mixtures. The
corrected flow rate shall not exceed the maximum allowable specified values. If the vent limiter is not a limiting
orifice type and is designed for use in positions other than upright, additional test to determine the rate of flow
shall be conducted when the vent limiter is installed in other positions.
When the vent limiter is an integral part of the regulator, the regulator diaphragm shall be substantially
removed to permit the test medium to flow feely through the vent limiter. With the regulator installed in a gas-
tight piping system in the manufacturer’s specified upright position, the flow rate through the integral vent
limiter shall be determined as described for separate vent limiters. The corrected flow rate shall not exceed
the maximum allowable specified values. Additional tests to determine the rate of flow shall be conducted with
the regulator in any other position for which compliance with this standard is desired.
6.2.2 Sealing caps
ISO 23550:2004, 6.2.7, shall be replaced with the following:
Sealing caps on field adjustable regulators shall be capable of being removed and replaced using standard
tools and shall be capable of being sealed (e.g. by lacquer). A sealing cap shall not hinder adjustment with the
outlet pressure range declared by the manufacturer.
ISO 23550:2004, 6.2, shall apply with the addition of 6.2.3.
6.2.3 Adjustment means
Adjustable type regulators and the adjustable stages of multi-stage regulators shall be provided with means
for making any necessary adjustment of outlet pressure. The adjustment means of spring-type regulators shall
be concealed. Suitable means for maintaining the positions of all adjustments shall be provided. Locknuts or
adjusting nuts held by springs or compression are considered satisfactory, except when their adjustment can
be accidentally disturbed. Factory adjustment means not intended for field adjustment shall be sealed by
means suitable for both continuous and intermittent exposure at the manufacturer’s specified minimum and
maximum ambient temperatures.
Suitability of the sealing means shall be judged before and after completion of all tests specified in this
standard. Mechanical sealing means shall require the use of special tools.
6.3 Materials
6.3.1 General material requirements
ISO 23550:2004, 6.3.1, shall apply.
6.3.2 Housing
6.3.2.1 Housing design
ISO 23550:2004, 6.3.2.1, shall apply with the following addition:
When a diaphragm inside a housing separates the gas-carrying compartment from atmosphere, then the gas-
carrying compartment is considered to be indirectly separated.
6.3.2.2 Test for leakage of housing after removal of non-metallic parts
Carry out the test given in ISO 23550:2004, 6.3.2.2.
6.4 Gas connections
ISO 23550:2004, 6.4, shall apply.
7 Performance
7.1 General
ISO 23550:2004, 7.1, shall apply.
7.2 Leak-tightness
7.2.1 Criteria
ISO 23550:2004, 7.2.1, shall apply with the following modification of Table 2:
Internal leakage rates shall not apply.
Replace “controls” with “assembled regulators”.
6 © ISO 2006 – All rights reserved

7.2.2 Test for leak-tightness
7.2.2.1 Performance of the test
Carry out the test given in ISO 23550:2004, 7.2.2.1, with the following modification:
The test shall be carried out using a pressure equal to 1,5 times the maximum inlet pressure, but at least
15 kPa.
NOTE Specific regional test conditions in Japan are given in D.1.
7.2.2.2 External leak-tightness
Replace ISO 23550:2004, 7.2.2.2, as follows:
The assembled regulator is to be mounted on the test equipment. It shall then be subjected to the test
pressure given in 7.2.2.1; the inlet valve of the test equipment and the valve downstream of the sample shall
be in the closed position.
If there are any signs of leakage of the sample, the leakage rate is to be measured.
Closure parts that are intended to be dismantled for servicing or adjustment shall be dismantled and
reassembled five times, using standard tools according to the manufacturer's instructions, after which the leak
tightness is to be checked.
NOTE Specific regional test conditions in Canada and USA are given in Annex C.
7.3 Torsion and bending
7.3.1 General
ISO 23550:2004, 7.3.1, shall apply, except that only the external leakage shall be applicable.
After testing, there shall be no permanent deformation, and the leakage shall not exceed that measured
before the test.
7.3.2 Torsion
7.3.2.1 Torsion — Group 1 and group 2 regulators with threaded connections
The regulator shall be subjected to the torque specified in ISO 23550:2004, Table 4, and tested according to
ISO 23550:2004, 7.3.4.2.
7.3.2.2 Torsion — Group 1 and group 2 regulators with compression fittings
The regulator shall be subjected to the torque specified in ISO 23550:2004, Table 4, and tested according to
ISO 23550:2004, 7.3.4.3.
7.3.3 Bending — Group 1 and group 2 regulators
The regulator shall be subjected to the bending moment specified in ISO 23550:2004, Table 4, and tested
according to ISO 23550:2004, 7.3.4.4. For group 1 devices, the test as described in ISO 23550:2004, 7.3.4.5,
shall additionally be carried out.
7.3.4 Torsion and bending tests
Carry out the tests given in ISO 23550:2004, 7.3.4.
7.4 Rated flow rate
No requirements.
7.5 Durability
ISO 23550:2004, 7.5, shall apply.
7.6 Functional requirements
Alternative methods for functional requirements and testing are given in Annexes B and C.
NOTE 1 Specific requirements in EU countries are given in Annex B.
NOTE 2 Specific requirements in Canada and USA are given in Annex C.
7.7 Putting the regulator out of action
7.7.1 Criteria
If it is claimed that a regulator can be put out of action, the method shall be given in the manufacturer's
instructions and shall result in the valve being fixed in the fully open position.
When the regulator is put back into operation, it shall comply with the requirements of this part of ISO 23551.
7.7.2 Test putting the regulator out of action
The regulator shall be deactivated in accordance with the procedure described in the manufacturer's
instructions. After it has been visually checked that the valve is in its fully open position, the leak tightness is to
be determined in accordance with the method given in 7.2.2.2.
After it has been made operative again, the regulator is to be tested by the methods given in this part of
ISO 23551.
It is recommended that this test is made before the performance tests.
7.8 Long-term performance
7.8.1 Criteria
The leak tightness and performance shall remain within the limits specified in 7.2 and 7.3, respectively, after
testing in accordance with 7.8.2.
7.8.2 Test of long-term performance
Position the regulator in a temperature-controlled chamber with an air supply at ambient temperature and at
the maximum inlet pressure as declared by the manufacturer. With a quick-acting shut-off valve both
upstream and downstream, for example as shown in Figure B.1, connect the valves to a suitable time switch
so that as one opens the other one closes, with a complete cycle of 10 s.
The test consists of 50 000 cycles, in each of which the diaphragm is to be fully flexed and held in this position
for at least 5 s. Of the 50 000 cycles:
⎯ 25 000 cycles shall be with the regulator environment at the maximum ambient temperature declared by
the manufacturer, but at least 60 °C;
8 © ISO 2006 – All rights reserved

⎯ 25 000 cycles shall be with the regulator environment at the minimum ambient temperature declared by
the manufacturer, but at most 0 °C.
After cycling, the regulator is to be subjected to testing as described in 7.2 and 7.6, without further adjustment
of the setting point of the regulator.
NOTE 1 Alternatively, see C.2.6.
NOTE 2 Specific requirements in Japan are given in D.2.
7.9 Lock-up pressure
7.9.1 Criteria
When a regulator is claimed by the manufacturer to have the ability to lock up, the outlet pressure shall not
rise by more than 15 % or 0,75 kPa, whichever is greater, above an outlet pressure equal to 5 % of q .
max
Such a regulator shall be tested in accordance with the test method described in 7.9.2.
7.9.2 Lock-up pressure test
Proceed as follows.
a) Install the regulator in the apparatus shown for example in Figure B.1.
b) Adjust the inlet pressure to p and adjust the control valve 6 to q /20.
1max max
c) Measure the outlet pressure.
d) Slowly close control valve No. 6 in not less than 5 s.
e) 30 s after the control valve No. 6 has been completely closed, measure the outlet pressure.
8 EMC/Electrical requirements
If regulators are of mechanical types there are no requirements.
9 Marking, installation and operating instructions
9.1 Marking
The following information, at least, shall be durably marked on the regulator in a clearly visible position:
a) manufacturer and/or trade mark;
b) model designation;
c) in EU, class and group references; in USA and Canada, delta P or circle P, as applicable;
d) date of manufacture (at least the year); this may be in coded form;
e) direction of gas flow; in EU by an arrow (e.g. cast or embossed);
f) maximum working pressure;
g) outlet pressure setting.
9.2 Installation and operating instructions
One set of instructions shall be supplied with each consignment, written in the language(s) of the country into
which the controls are delivered.
They shall include all relevant information on use, installation, operation and servicing, in particular, the
following:
a) regulator class and group;
b) gas families for which the regulator is suitable;
c) performance curves including inlet pressure range, outlet pressure range and flow rate range (see, for
example, Figures B.1 and B.2) according to the declared classification;
d) setting point (inlet pressure, outlet pressure and flow rate);
e) ambient temperature range, in °C;
f) mounting position(s);
g) instructions for changing from one gas family to another (e.g. changing the spring or putting the regulator
out of action);
h) lock-up pressure, if applicable.
9.3 Warning notice
ISO 23550:2004, 9.3, shall apply.
10 © ISO 2006 – All rights reserved

Annex A
(informative)
Classification of fuel gases into gas families
A.1 Gas families used in European countries
Gases are classified into three families, each family may be divided into groups, (themselves being divided
into ranges), as a function of the Wobbe index, according to the values given in Table A.1.
Table A.1 — Classification of gases
a
Gross Wobbe index
Gas families and groups MJ/m
Minimum Maximum
Manufactured gas
Group A 22,4 24,8
natural gas 39,1 54,7
Group H 45,7 54,7
Group L 39,1 44,8
Group E 40,9 54,7
Liquefied petroleum gas 72,9 87,3
Group B/P 72,9 87,3
Group P 72,9 76,8
Group B 81,8 87,3
a
At 15 °C and 101,325 kPa.
A gas family is a group of fuel gases with similar burning behaviour linked together by a range of Wobbe-
indices.
A gas group is a specified range of Wobbe index within that of the first, second or third families of gas. This
range is selected on the general principle that appliances utilizing this gas group operate safely when burning
all gases within this range without adjustment.
NOTE 1 Adjustment of the appliance can be permitted in accordance with the special national or local conditions that
apply in some countries.
NOTE 2 As ISO/TC 28 Petroleum products and lubricants and ISO/TC 193 Natural gas are working on gas
specifications, this table will be replaced when an appropriate ISO International Standard is available.
A.2 Gas families used in Japan and South Korea
Table A.2 — Classification of gases
a
Gross Wobbe index
Gas families and groups MJ/m
Minimum Maximum
Manufactured gas 16,2 28,9
Natural gas 49,2 57,8
Liquefied petroleum gas 81,3 92,8
a
At 0 °C and 101,325 kPa.
12 © ISO 2006 – All rights reserved

Annex B
(normative)
Functional requirements and regulator performance testing — Method A
B.1 Requirements
B.1.1 General
Regulators shall be tested as described in B.2 for outlet pressure variations over the range of inlet pressure
from p to p and/or over the range of flow rate from q to q .
1max 1min min max
If the inlet pressure range includes two corresponding values for the minimum and maximum pressure as
given in Table B.1, then the inlet setting pressure shall be the respective nominal pressure according to that
table. Otherwise, the inlet setting pressure and the inlet pressure range shall be declared by the manufacturer.
The deviation of the outlet pressure from the outlet setting pressure shall not exceed ± 0,1 kPa.
B.1.2 Pressure drop
The pressure drop measured by the method specified in B.2.5 shall not exceed that declared by the
manufacturer by more than + 10 %.
B.1.3 Class A
Over the full range of inlet pressure, p , to p , and over the full gas flow rate range, q to q , the
1min 1max max min
deviation of the outlet pressure from the outlet setting pressure shall not exceed the values given in Table 1 or
± 0,1 kPa, whichever is greater. The declared minimum flow rate, q , shall not exceed 10 % of q .
min max
B.1.4 Class B
For any change of inlet pressure within the range of inlet pressure p to p at any flow rate within the
1min 1max
declared flow range q to q , the deviation of the outlet pressure from the outlet setting pressure shall not
min max
exceed the values given in Table 1 or ± 0,1 kPa, whichever is greater.
Table B.1 — Gas pressure at regulator inlet
Gas pressure at inlet to regulator
kPa
Type of gas
Nominal pressure Minimum pressure Maximum pressure
Manufactured gas 0,8 0,6 1,5
Natural gas Group 2H 2,0 1,7 2,5
Natural gas Group 2L 2,5 2,0 3,0
Natural gas Group 2E 2,0 1,7 2,5
Liquefied petroleum gas 2,9 2,0 3,5
2,9 2,5 3,5
3,7 2,5 4,5
5,0 4,25 5,75
6,7 5,0 8,0
11,2 6,0 14,0
14,8 10,0 18,0
For any change of flow rate within the declared range of flow rate q to q at any inlet pressure within the
min max
permissible inlet pressure range p to p , the deviation of the outlet pressure from the outlet setting
1min 1max
pressure shall not exceed the values given in Table 1 or ± 0,1 kPa, whichever is greater.
B.1.5 Class C
For any change of inlet pressure within the range of inlet pressure p to p at any flow rate within the
1min 1max
manufacturer's declared flow range q to q , the deviation of the outlet pressure from the outlet setting
min max
pressure shall not exceed the values given in Table 1 or ± 0,1 kPa, whichever is the greater.
B.2 Test procedure
The regulator shall be tested in the sequence shown in Table B.2.
Table B.2 — Sequence of testing
Clause no. Test
7.7.2 Putting the regulator out of action
7.2.2 External leak tightness of assembled regulator
7 Regulator performance
7.8 Long-term performance
7.9 Lock-up pressure
7.3 Torsion and bending
ISO 23550:2004, 7.5.4.2 Test for marking resistance
ISO 23550:2004, 7.5.5.29 Scratch test
ISO 23550:2004, 7.5.6.2 Humidity test
6.3.2.2 External leak tightness of regulator with non-metallic
part(s) removed
ISO 23550:2004, 7.5.1 Elastomers in contact with gas
6.2 Construction requirements
14 © ISO 2006 – All rights reserved

If adhesive labels are used, it is necessary to provide two additional parts carrying the label.
If special equipment is necessary for the test, it should be supplied with the samples.
B.2.1 General
Classes A, B and C regulators shall be tested in accordance with the test sequences given in B.2.2, B.2.3,
B.2.4, respectively (see also B.3).
Equilibrium conditions shall always be reached before readings are taken.
Examples of performance curves with p as ordinate and p as abscissa, with variable inlet pressure, are
2 1
shown in Figure B.3 and those with variable flow rate, in Figure B.2.
Dimensions in millimetres
Figure B.1 — Regulator performance test rig
Dimensions in millimetres
Key
Relation of nominal size to internal diameter
1 inlet control tap
2 regulator for inlet pressure
Nominal size Internal diameter
DN d
3 inlet pressure gauge
mm
4 test sample
5 outlet pressure gauge 6 6
6 flow meter
8 9
7 differential pressure gauge
10 13
8 temperature measuring point
15 16
9 holes, four, 1,5 mm diameter
10 outlet control tap
20 22
25 28
32 35
40 41
50 52
65 67
80 82
100 106
125 131
150 159
Figure B.1 (continued)
16 © ISO 2006 – All rights reserved

Key
1 upper tolerance limit
2 setting point
3 lower tolerance limit
4 control characteristic at q
min
5 control characteristic at q
max
Figure B.2 — Graph of performance using inlet pressure variation
Key
1 upper tolerance limit
2 setting point
3 lower tolerance limit
4 control characteristic at p
1max
5 control characteristic at p
1min
Figure B.3 — Graph of performance using flow rate variation
B.2.2 Class A pressure regulators
Proceed as follows for the variation of the inlet pressure, p , and of the flow rate, q:
a) Adjustment of regulator outlet setting pressure: set the outlet control tap to obtain a flow rate of 0,5 q
max
(or any other value declared by the manufacturer). For adjustable regulators, adjust the outlet setting
pressure to the maximum value (p ), the inlet pressure, p , being the nominal pressure (or any other
2max 1
value declared by the manufacturer).
b) The outlet setting pressure being set, there shall be no further adjustment of the regulator.
c) Vary the inlet pressure, p , from the nominal value over the minimum (p ) to the maximum value (p )
1 min 1max
and back to the minimum value, and record the outlet pressure, p , for at least five values of p , in each
2 1
direction, without resetting the flow rate.
d) With inlet pressure, p , kept constant, vary the flow rate from q to q and back to q by using
1min max min max
the outlet control tap, the outlet pressure, p , being recorded for at least five values of q in each case.
Make sure that there is no change of the inlet pressure throughout this procedure.
e) Readjust the inlet pressure from p to p and then vary the flow rate from q to q [as in step c)].
1min 1max max min
18 © ISO 2006 – All rights reserved

f) For adjustable regulators, repeat steps b) to d) after the outlet setting pressure has been readjusted
according to step a) to the value p .
2min
B.2.3 Class B regulators
Proceed as follows for the variation of the inlet pressure, p , and of the flow rate, q:
a) Adjustment of regulator outlet setting pressure: set the flow rate to q by adjusting the outlet control tap.
max
For adjustable regulators, adjust the outlet setting pressure to the maximum value (p ), the inlet
2max
pressure, p , being the nominal pressure (or another value declared by the manufacturer).
b) The outlet setting pressure being set, there shall be no further adjustment of the regulator.
c) Vary the inlet pressure, p , from the nominal value over the minimum (p ) to the maximum value
1 1min
(p ) and back to the minimum value, and record the outlet pressure, p , for at least five values of p in
1max 2 1
each direction, without resetting the flow rate.
d) With inlet pressure, p , kept constant, readjust the flow rate, q , by using the outlet control tap without
1 max
any other adjustment of the already set value of the outlet pressure to q .
min
e) Repeat step b).
f) For adjustable regulators repeat steps b) to d), the outlet setting pressure as per step a) having been
readjusted to the value p .
2min
B.2.4 Class C regulators
Proceed as follows for the variation of the inlet pressure p :
a) Adjustment of regulator outlet setting pressure: set the flow rate to q by means of the outlet control tap.
max
For adjustable regulators, adjust the outlet setting pressure to the maximum value (p ), the inlet
2max
pressure, p , being the nominal pressure (or any other value declared by the manufacturer).
b) The outlet pressure being set, there shall be no further adjustment of the regulator.
c) Vary the inlet pressure, p , from the minimum value (p ) to the maximum value (p ) and back to the
1 1min 1max
minimum value, and record the outlet pressure, p , for at least five values of p in each direction, without
2 1
resetting the flow rate.
d) By means of the outlet control tap, adjust the flow rate to q , the outlet setting pressure having been
min
readjusted as in step a).
e) Repeat step b).
f) For adjustable regulators repeat steps b) to d), the outlet setting pressure having been readjusted as in
step a) to the value p .
2min
B.2.5 Pressure drop
Adjust the inlet pressure, p , to 0,1 kPa less than the value of the outlet pressure obtained at minimum inlet
pressure and at maximum flow. The regulator valve shall then be fully open.
Measure the differential pressure between the inlet and outlet pressures under these conditions.
For regulator that may be set over a range, measure the differential pressure for the lowest setting pressure.
B.3 Summary of requirements and test procedures
B.3.1 Requirements
Table B.3 — Requirements
Outlet pressure, p
Class A regulator Class B regulator Class C regulator
Parameter
First Second Third First Second Third First Second Third
family family family family family family family family family
Tolerance on the outlet
+ 15 + 10 + 15 + 10
pressure, p , (as a percentage
± 15 ± 15 ± 15 ± 10 ± 10
− 20 − 20
− 15 − 15
of the outlet setting pressure)
⎯ with change of inlet
pressure from p to or ± 0,1 kPa or ± 0,1 kPa
1min
p
1max
or ± 0,1 kPa
⎯ with change of flow rate
+ 40 + 40 + 40
from q to q
max min
Setting pressure Nominal pressure according to Table B.1 or as declared by the manufacturer
Inlet pressure range According to Table B.1 or as declared by the manufacturer
Maximum inlet pressure As declared by the manufacturer
20 © ISO 2006 – All rights reserved

B.3.2 Test procedure
Table B.4
Setting or testing Class A regulator Class B regulator Class C regulator
1 Setting
Set the outlet pressure, p , to p p p
2 2max 2max 2max
1.1 at an inlet pressure, p , equal to Nominal pressure according to Table B.1 or as declared by the manufacturer
1.2 and at a flow rate, q, equal to 0,5 q q q
max max max
Once the outlet pressure has been set, there shall be no further adjustment of
the regulator.
2 Testing After each change of p or q, record the outlet pressure, p
1 2
2.1 Change p to p p p
1 1min 1min 1min
2.2 Change q from → to 0,5 q → q → q No change No change
max min max
2.3 Change p to p p p
1 1max 1max 1max
2.4 Change q from → to q → q → q No change No change
max min max
2.5 Change p to — p —
1 min
2.6 Change q from → to — q → q —
max min
3 Setting
Set the outlet pressure, p , to  p
2 2max
3.1 at an inlet pressure, p , — — as indicated in 1.1
3.2 and at a flow rate, q, of — — q
min
Once the outlet pressure has been set, there shall be no further adjustment of
the regulator.
4 Testing After each change of p or q, record the outlet pressure, p
1 2
4.1 Change p to — p p
1 1min 1min
4.2 Change q from → to — No change No change
4.3 Change p to — p p
1 1max 1max
4.4 Change q from → to — No change No change
4.5 Change p to — p p
1 1min 1min
For all regulators, irrespective of their class, repeat the complete test procedure, including steps 1 to 4, but
with the outlet pressure reset to p .
2min
Annex C
(normative)
Functional requirements and regulator performance testing — Method B
C.1 Requirements
C.1.1 Mounting regulator for test
The regulator shall be installed in the appropriate test rig shown in Figure C.1. The regulator shall be placed in
the mounting position specified for the particular test to be conducted.
C.1.2 Outlet pressure range
Nonadjustable regulators shall be tested as described in C.2.2.1 for outlet pressure performance as specified
in Table C.2. Adjustable regulators shall be tested for outlet pressure performance as specified.
C.1.3 Range of regulation capacity
The range of regulation capacity as determined by test described in C.2.3 shall include the upper and lower
limits specified by the manufacturer.
C.1.4 Regulators designated to operate at pilot flow rate
The specified maximum regulation
...