ISO 23555-2:2022
(Main)Gas pressure safety and control devices for use in gas transmission, distribution and installations for inlet pressures up to and including 10 MPa — Part 2: Gas pressure regulator
Gas pressure safety and control devices for use in gas transmission, distribution and installations for inlet pressures up to and including 10 MPa — Part 2: Gas pressure regulator
This document specifies safety, constructional, performance, testing and documentation requirements for gas pressure regulators for use in gas transmission and distribution installations (hereafter referred to as regulators). This document is applicable to regulators with operating pressures greater than 500 kPa and up to and including 10 MPa (100 bar) and nominal diameters up to DN 400 for use with fuel gases as natural gas, manufactured gas, biomethane or liquefied petroleum gas (LPG). This document is applicable to: — test methods which are intended for product type test, routine tests and product surveillance tests; — regulators which use the pipeline gas as a source of control energy unassisted by any external power source; — regulators integrating on the same body a second regulator, used as monitor, complying with the requirements in this document; — regulators integrating a safety shut off device (SSD) according to ISO 23555-3; — regulators incorporating a creep (venting) relief device and/or a vent limiter complying with the requirements in this document. This document does not apply to: — regulators upstream from/on/in domestic gas‑consuming appliances which are installed downstream of domestic gas meters; — regulators designed to be incorporated into pressure control systems used in service lines (pipework from the main pipework in a gas infrastructure to the point of delivery of the gas) with declared volumetric flow rate ≤ 200 m3/h at normal conditions and declared inlet pressure ≤ 500 kPa (5 bar); — industrial process control valves, such as IEC 60534 (all parts); — regulators used in aggressive/sour gas environments (gas environments containing water and H2S are considered sour) or severely corrosive conditions; — regulators in service conditions with renewables (e.g. H2NG with hydrogen more than 10 %) and/or waste gases (e.g. biogas etc.), if additional information is not provided (e. g. contaminant, liquid, etc.).
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INTERNATIONAL ISO
STANDARD 23555-2
First edition
2022-01
Gas pressure safety and control
devices for use in gas transmission,
distribution and installations for
inlet pressures up to and including 10
MPa —
Part 2:
Gas pressure regulator
Reference number
ISO 23555-2:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 23555-2:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23555-2:2022(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions and symbols .2
3.1 Terms and definitions . 2
3.1.1 General terms . 2
3.1.2 Terms related to flow . 5
3.1.3 Terms related to variables in the controlling process . 6
3.1.4 Terms related to the controlled process . 6
3.1.5 Terms related to functional performance . 6
3.1.6 Feature related to accuracy . 8
3.1.7 Terms related to lock-up behaviour . 8
3.1.8 Terms related to design and tests . 10
3.1.9 Summary of symbols for creep relief valves . 10
3.2 Symbols . 10
4 Classification .11
4.1 General . 11
4.2 Temperature classes . 11
4.3 Strength types . 11
4.4 Fail conditions . 11
5 Materials .11
6 Design .11
6.1 General . 11
6.2 Strength of metallic body and its inner metallic partition walls .12
6.3 Other pressure metallic containing parts of integral and differential strength
controls.12
6.4 Strength of parts transmitting actuating forces .12
6.5 Strength of diaphragms (elastomeric parts) .12
6.6 Welding . .12
6.7 Main function of a regulator . 12
6.7.1 General .12
6.7.2 Gas pressure regulators with associated safety devices .13
7 Performance and testing requirements .14
7.1 General . 14
7.1.1 Approach to stable product phase . 14
7.1.2 Test conditions . 15
7.1.3 Test tolerances . . .15
7.1.4 Overview table . 15
7.2 Requirements . 16
7.2.1 Test rig . 16
7.2.2 Classification of stable production tests . 16
7.2.3 Dimensional check and visual inspection . 16
7.2.4 Shell strength . 16
7.2.5 External/Internal tightness . 16
7.2.6 Antistatic characteristics . 16
7.2.7 Sound emission . 16
7.2.8 Control classifications . 17
7.2.9 Fail close conditions . 18
7.2.10 Fail open conditions. 18
7.2.11 Closing force for monitor at full open position . 18
7.2.12 Gas pressure regulator sizing . 19
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ISO 23555-2:2022(E)
7.3 Tests .22
7.3.1 General .22
7.3.2 Materials check at stable production phase. 22
7.3.3 Dimensional check and visual inspection . 22
7.3.4 Mounting position . 22
7.3.5 Shell strength . 22
7.3.6 External tightness . 22
7.3.7 Internal tightness .23
7.3.8 Antistatic characteristics . 23
7.3.9 Methods for calculating and measuring the sound pressure level .23
7.3.10 Control classifications .23
7.3.11 Final visual inspections . 32
7.3.12 Verification of closing force for monitor in fully open position under
normal operating conditions . 33
8 Documentation .33
8.1 General . 33
8.2 Documentation related to type test. 33
8.3 Documentation related to batch surveillance . 33
8.4 Documentation related to the routine tests . 33
8.4.1 Documentation provided at the request of the customer . 33
8.4.2 Documentation provided with the regulator . 33
9 Marking . .33
9.1 General . 33
9.2 Basic requirements .34
9.3 Markings for the various connections .34
9.4 Marking of integrated safety devices .34
9.5 Other additional requirements .34
10 Packaging and transportation of finished product .34
Annex A (normative) List of materials .35
Annex B (normative) Elastomeric material .36
Annex C (normative) High pressure vent limiter .37
Annex D (normative) Compliance evaluation .38
Annex E (informative) Alternative methods for the determination of the accuracy class,
the lock-up pressure class, the maximum accuracy flow rate, the flow coefficients
and the verification of the hysteresis band .39
Annex F (informative) Inspection certificate .47
Annex G (informative) Acceptance test .50
Annex H (normative) Token (creep) relief device .51
Annex I (informative) Order specification .53
Annex J (informative) Dynamic force calculation method .55
Bibliography .58
iv
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ISO 23555-2:2022(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 161, Controls and protective devices for
gas and/or oil.
A list of all parts in the ISO 23555 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
© ISO 2022 – All rights reserved
---------------------- Page: 5 ----------------------
ISO 23555-2:2022(E)
Introduction
This document is designed to be used in combination with ISO 23555-1. This document together with
ISO 23555-1 establishes the complete standard as it applies to the specific control covered by the
ISO 23555 series.
Where needed, this document adapts ISO 23555-1 by stating in the corresponding clause:
— “with the following modification”;
— “with the following addition”;
— “is replaced by the following”; or
— “is not applicable”.
In order to identify specific requirements that are particular to this document but not already covered
by ISO 23555-1, this document can contain clauses or subclauses that are additional to the structure
of ISO 23555-1. These subclauses are indicated by the introductory sentence: “Subclause (or Annex)
specific to this document.”.
vi
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INTERNATIONAL STANDARD ISO 23555-2:2022(E)
Gas pressure safety and control devices for use in gas
transmission, distribution and installations for inlet
pressures up to and including 10 MPa —
Part 2:
Gas pressure regulator
1 Scope
This document specifies safety, constructional, performance, testing and documentation requirements
for gas pressure regulators for use in gas transmission and distribution installations (hereafter
referred to as regulators).
This document is applicable to regulators with operating pressures greater than 500 kPa and up to and
including 10 MPa (100 bar) and nominal diameters up to DN 400 for use with fuel gases as natural gas,
manufactured gas, biomethane or liquefied petroleum gas (LPG).
This document is applicable to:
— test methods which are intended for product type test, routine tests and product surveillance tests;
— regulators which use the pipeline gas as a source of control energy unassisted by any external
power source;
— regulators integrating on the same body a second regulator, used as monitor, complying with the
requirements in this document;
— regulators integrating a safety shut off device (SSD) according to ISO 23555-3;
— regulators incorporating a creep (venting) relief device and/or a vent limiter complying with the
requirements in this document.
This document does not apply to:
— regulators upstream from/on/in domestic gas-consuming appliances which are installed
downstream of domestic gas meters;
— regulators designed to be incorporated into pressure control systems used in service lines (pipework
from the main pipework in a gas infrastructure to the point of delivery of the gas) with declared
3
volumetric flow rate ≤ 200 m /h at normal conditions and declared inlet pressure ≤ 500 kPa (5 bar);
— industrial process control valves, such as IEC 60534 (all parts);
— regulators used in aggressive/sour gas environments (gas environments containing water and H2S
are considered sour) or severely corrosive conditions;
— regulators in service conditions with renewables (e.g. H2NG with hydrogen more than 10 %) and/
or waste gases (e.g. biogas etc.), if additional information is not provided (e. g. contaminant, liquid,
etc.).
1
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ISO 23555-2:2022(E)
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 23555-1:2022, Gas pressure safety and control devices for use in gas transmission, distribution and
installations for inlet pressures up to and including 10 MPa — Part 1: General requirements
IEC 60534-1:2005, Industrial-process control valves — Part 1: Control valve terminology and general
considerations
IEC 60534-2-3, Industrial-process control valves — Part 2-3: Flow capacity — Test procedures
IEC 60534-4, Industrial-process control valves — Part 4: Inspection and routine testing
3 Terms and definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 23555-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1 General terms
3.1.1.1
gas pressure regulator
device whose function is to maintain the value of the controlled variable (3.1.3.1) within its tolerance
field irrespective of disturbance variables
3.1.1.2
direct acting gas pressure regulator
regulator in which the net force required to move the control member is supplied directly by the
controlled variable
Note 1 to entry: See example in Figure 1.
2
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ISO 23555-2:2022(E)
a) Direct acting regulator - type integral b) Direct acting regulator - type differential
strength strength
Key
1 + 2 = Controller
1 setting element 6 sensing line
2 pressure detecting element 7 regulator body
3 breather/exhaust line 8 valve seats
4 actuator 9 seat ring
5 casing of actuator 10 control member
Figure 1 — Examples of a direct acting regulator
3.1.1.3
pilot-controlled gas pressure regulator
regulator in which the net force required to move the control member is supplied by a pilot
Note 1 to entry: See example in Figures 2 and 3.
3
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ISO 23555-2:2022(E)
Key
1 auxiliary device 6 regulator body
2 pilot 7 valve seats
3 actuator 8 seat ring
4 casing of actuator 9 control member
5 sensing/process line 10 motorization chamber
Figure 2 — Example of a pilot-controlled regulator
Key
1 auxiliary device 6 sensing/process lines
2 pilot 7 regulator body
3 throttle 8 valve seat
4 control member 9 motorization chamber
5 casing of control member
Figure 3 — Example of a pilot-controlled regulator with a diaphragm as control member
3.1.1.4
monitor
second regulator installed in series with an active regulator, normally upstream, which has the task
of maintaining the controlled variable within allowable limits in the event of its value exceeds pre-
established values (e.g. in the event of opening of the active regulator due to a failure, etc.)
4
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ISO 23555-2:2022(E)
3.1.1.5
fail close regulator
regulator whose control member automatically tends to close or close when failures occur
Note 1 to entry: This definition is based on typical control failure modes.
3.1.1.6
fail open regulator
regulator whose control member automatically tends to open or open when failures occur
Note 1 to entry: This definition is based on typical control failure modes.
3.1.1.7
regulator size
nominal size DN of the inlet connection
Note 1 to entry: The preferred DN values are specified in ISO 6708.
3.1.1.8
series of regulators
regulators with the same design concept but differing only in size
3.1.2 Terms related to flow
3.1.2.1
flow coefficient in critical conditions
Cg
characteristic value for the flow capacity of regulator in critical conditions
Note 1 to entry: Flow coefficient Cg is a non-SI regulator coefficient.
Note 2 to entry: Numerically, Cg is represented as the number of normal cubic feet per hour of air flowing through
a regulator in critical conditions with inlet absolute pressure 1 psia and with a reference inlet temperature t
ur
1) 3
= 15 °C . The numerical value in SI units is equal to the number of m /h of air flowing through a regulator in
critical conditions with inlet absolute pressure 243 kPa (2,43 bar) and inlet temperature of 15 °C.
Note 3 to entry: IEC 60534-2-1:2011, Clause 7 and Appendix B deals with this flow coefficient.
3.1.2.2
flow coefficient in normal conditions
KG
characteristic value for the flow capacity of a regulator in normal conditions
Note 1 to entry: The flow coefficient is equal to the volumetric flow rate at normal conditions through the
regulator under the following reference conditions:
3
— reference natural gas at normal conditions with the relative density d = 0,64 (density ρ = 0,827 5 kg/m );
r r
— fully opened control member (mechanical stop);
— reference inlet temperature of t = 15 °C;
ur
— reference absolute gas inlet pressure p = 200 kPa (2 bar);
ur
— reference absolute gas outlet pressure p = 100 kPa (1 bar).
dr
3
Note 2 to entry: The KG value is specified in (m /h)/bar.
1) The definition of this flow coefficient is based on IEC 60534-1.
5
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ISO 23555-2:2022(E)
3.1.3 Terms related to variables in the controlling process
3.1.3.1
controlled variable
variable which is monitored by the controlling process
Note 1 to entry: In this document, only the outlet pressure, p , is considered as the controlled variable.
d
3.1.3.2
disturbance variable
variable acting from outside on the controlling process
Note 1 to entry: In the case of regulators with outlet pressure as the controlled variable, the disturbance variables
are essentially:
— changes in the inlet pressure;
— changes in the volumetric flow rate.
3.1.3.3
reference inlet temperature
t
ur
temperature at the inlet of control in the assessment of its functional performance
Note 1 to entry: This document considers as reference temperature 15 °C.
Note 2 to entry: The use of reference inlet temperature is necessary to obtain homogeneous set of test results
when comparing the functional performances of different ty
...
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23555-2
ISO/TC 161
Gas pressure safety and control
Secretariat: DIN
devices for use in gas transmission,
Voting begins on:
2021-10-01 distribution and installations for
inlet pressures up to and including 10
Voting terminates on:
2021-11-26
MPa —
Part 2:
Gas pressure regulator
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 23555-2:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 23555-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 23555-2:2021(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions and symbols .2
3.1 Terms and definitions . 2
3.1.1 General terms . 2
3.1.2 Terms related to flow . 5
3.1.3 Terms related to variables in the controlling process . 6
3.1.4 Terms related to the controlled process . 6
3.1.5 Terms related to functional performance . 6
3.1.6 Feature related to accuracy . 8
3.1.7 Terms related to lock-up behaviour . 8
3.1.8 Terms related to design and tests . 10
3.1.9 Summary of symbols for creep relief valves . 10
3.2 Symbols . 10
4 Classification .11
4.1 General . 11
4.2 Temperature classes . 11
4.3 Strength types . 11
4.4 Fail conditions . 11
5 Materials .11
6 Design .11
6.1 General . 11
6.2 Strength of metallic body and its inner metallic partition walls .12
6.3 Other pressure metallic containing parts of integral and differential strength
controls.12
6.4 Strength of parts transmitting actuating forces .12
6.5 Strength of diaphragms (elastomeric parts) .12
6.6 Welding . .12
6.7 Main function of a regulator . 12
6.7.1 General .12
6.7.2 Gas pressure regulators with associated safety devices .13
7 Performance and testing requirements .14
7.1 General . 14
7.1.1 Approach to stable product phase . 14
7.1.2 Test conditions . 15
7.1.3 Test tolerances . . .15
7.1.4 Overview table . 15
7.2 Requirements . 16
7.2.1 Test rig . 16
7.2.2 Classification of stable production tests . 16
7.2.3 Dimensional check and visual inspection . 16
7.2.4 Shell strength . 16
7.2.5 External/Internal tightness . 16
7.2.6 Antistatic characteristics . 16
7.2.7 Sound emission . 16
7.2.8 Control classifications . 17
7.2.9 Fail close conditions . 18
7.2.10 Fail open conditions. 18
7.2.11 Closing force for monitor at full open position . 18
7.2.12 Gas pressure regulator sizing . 19
iii
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---------------------- Page: 3 ----------------------
ISO/FDIS 23555-2:2021(E)
7.3 Tests .22
7.3.1 General .22
7.3.2 Materials check at stable production phase. 22
7.3.3 Dimensional check and visual inspection . 22
7.3.4 Mounting position . 22
7.3.5 Shell strength . 22
7.3.6 External tightness . 22
7.3.7 Internal tightness .23
7.3.8 Antistatic characteristics . 23
7.3.9 Methods for calculating and measuring the sound pressure level .23
7.3.10 Control classifications .23
7.3.11 Final visual inspections .33
7.3.12 Verification of closing force for monitor in fully open position under
normal operating conditions . 33
8 Documentation .33
8.1 General . 33
8.2 Documentation related to type test. 33
8.3 Documentation related to batch surveillance . 33
8.4 Documentation related to the routine tests . 33
8.4.1 Documentation provided at the request of the customer . 33
8.4.2 Documentation provided with the regulator . 33
9 Marking . .34
9.1 General .34
9.2 Basic requirements .34
9.3 Markings for the various connections .34
9.4 Marking of integrated safety devices .34
9.5 Other additional requirements .34
10 Packaging and transportation of finished product .34
Annex A (normative) List of materials .35
Annex B (normative) Elastomeric material .36
Annex C (normative) High pressure vent limiter .37
Annex D (normative) Compliance evaluation .38
Annex E (informative) Alternative methods for the determination of the accuracy class,
the lock-up pressure class, the maximum accuracy flow rate, the flow coefficients
and the verification of the hysteresis band .39
Annex F (informative) Inspection certificate .47
Annex G (informative) Acceptance test .50
Annex H (normative) Token (creep) relief device .51
Annex I (informative) Order specification .53
Annex J (informative) Dynamic force calculation method .55
Bibliography .58
iv
© ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 23555-2:2021(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 161, Controls and protective devices for
gas and/or oil.
A list of all parts in the ISO 23555 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
© ISO 2021 – All rights reserved
---------------------- Page: 5 ----------------------
ISO/FDIS 23555-2:2021(E)
Introduction
This document is designed to be used in combination with ISO 23555-1. This document together with
ISO 23555-1 establishes the complete standard as it applies to the specific control covered by the
ISO 23555 series.
Where needed, this document adapts ISO 23550 by stating in the corresponding clause:
— “with the following modification”;
— “with the following addition”;
— “is replaced by the following”; or
— “is not applicable”.
In order to identify specific requirements that are particular to this document but not already covered
by ISO 23550, this document can contain clauses or subclauses that are additional to the structure of
ISO 23550. These subclauses are indicated by the introductory sentence: “Subclause (or Annex) specific
to this document.”.
vi
© ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23555-2:2021(E)
Gas pressure safety and control devices for use in gas
transmission, distribution and installations for inlet
pressures up to and including 10 MPa —
Part 2:
Gas pressure regulator
1 Scope
This document specifies safety, constructional, performance, testing and documentation requirements
for gas pressure regulators for use in gas transmission and distribution installations (hereafter
referred to as regulators).
This document is applicable to regulators with operating pressures greater than 500 kPa and up to and
including 10 MPa (100 bar) and nominal diameters up to DN 400 for use with fuel gases as natural gas,
manufactured gas, biomethane or liquefied petroleum gas (LPG).
This document is applicable to:
— test methods which are intended for product type test, routine tests and product surveillance tests;
— regulators which use the pipeline gas as a source of control energy unassisted by any external
power source;
— regulators integrating on the same body a second regulator, used as monitor, complying with the
requirements in this document;
— regulators integrating a safety shut off device (SSD) according to ISO 23555-3.
— regulators incorporating a creep (venting) relief device and/or a vent limiter complying with the
requirements in this document.
This document does not apply to:
— regulators upstream from/on/in domestic gas-consuming appliances which are installed
downstream of domestic gas meters;
— regulators designed to be incorporated into pressure control systems used in service lines (pipework
from the main pipework in a gas infrastructure to the point of delivery of the gas) with declared
3
volumetric flow rate ≤ 200 m /h at normal conditions and declared inlet pressure ≤ 500 kPa (5 bar);
— industrial process control valves, such as IEC 60534 (all parts);
— regulators used in aggressive/sour gas environments (gas environments containing water and H2S
are considered sour) or severely corrosive conditions;
— regulators in service conditions with renewables (e.g. H2NG with hydrogen more than 10 %) and/
or waste gases (e.g. biogas etc.), if additional information is not provided (e. g. contaminant, liquid,
etc.).
1
© ISO 2021 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/FDIS 23555-2:2021(E)
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 23555-1:2021, Gas pressure safety and control devices for use in gas transmission, distribution and
installations for inlet pressures up to and including 10 MPa — Part 1: General requirements
IEC 60534-1:2005, Industrial-process control valves — Part 1: Control valve terminology and general
considerations
IEC 60534-2-3, Industrial-process control valves — Part 2-3: Flow capacity — Test procedures
IEC 60534-4, Industrial-process control valves — Part 4: Inspection and routine testing
3 Terms and definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 23555-1 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1 General terms
3.1.1.1
gas pressure regulator
device whose function is to maintain the value of the controlled variable (3.1.3.1) within its tolerance
field irrespective of disturbance variables
3.1.1.2
direct acting gas pressure regulator
regulator in which the net force required to move the control member is supplied directly by the
controlled variable
Note 1 to entry: See example in Figure 1.
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ISO/FDIS 23555-2:2021(E)
a) Direct acting regulator - type integral b) Direct acting regulator - type differential
strength strength
Key
1 + 2 = Controller
1 setting element 6 sensing line
2 pressure detecting element 7 regulator body
3 breather/exhaust line 8 valve seats
4 actuator 9 seat ring
5 casing of actuator 10 control member
Figure 1 — Examples of a direct acting regulator
3.1.1.3
pilot-controlled gas pressure regulator
regulator in which the net force required to move the control member is supplied by a pilot
Note 1 to entry: See example in Figures 2 and 3.
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ISO/FDIS 23555-2:2021(E)
Key
1 auxiliary device 6 regulator body
2 pilot 7 valve seats
3 actuator 8 seat ring
4 casing of actuator 9 control member
5 sensing/process line 10 motorization chamber
Figure 2 — Example of a pilot-controlled regulator
Key
1 auxiliary device 6 sensing / process lines
2 pilot 7 regulator body
3 throttle 8 valve seat
4 control member 9 motorization chamber
5 casing of control member
Figure 3 — Example of a pilot-controlled regulator with a diaphragm as control member
3.1.1.4
monitor
second regulator installed in series with an active regulator, normally upstream, which has the task
of maintaining the controlled variable within allowable limits in the event of its value exceeds pre-
established values (e.g. in the event of opening of the active regulator due to a failure, etc.)
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ISO/FDIS 23555-2:2021(E)
3.1.1.5
fail close regulator
regulator whose control member automatically tends to close or close when failures occur
Note 1 to entry: This definition is based on typical control failure modes.
3.1.1.6
fail open regulator
regulator whose control member automatically tends to open or open when failures occur
Note 1 to entry: This definition is based on typical control failure modes.
3.1.1.7
regulator size
nominal size DN of the inlet connection
Note 1 to entry: The preferred DN values are specified in ISO 6708.
3.1.1.8
series of regulators
regulators with the same design concept but differing only in size
3.1.2 Terms related to flow
3.1.2.1
flow coefficient in critical conditions
Cg
characteristic value for the flow capacity of regulator in critical conditions
Note 1 to entry: Flow coefficient Cg is a non-SI regulator coefficient.
Note 2 to entry: Numerically, Cg is represented as the number of normal cubic feet per hour of air flowing through
a regulator in critical conditions with inlet absolute pressure 1 psia and with a reference inlet temperature t
ur
1) 3
= 15 °C . The numerical value in SI units is equal to the number of m /h of air flowing through a regulator in
critical conditions with inlet absolute pressure 243 kPa (2,43 bar) and inlet temperature of 15 °C.
Note 3 to entry: IEC 60534-2-1:2011, Clause 7 and Appendix B deals with this flow coefficient.
3.1.2.2
flow coefficient in normal conditions
KG
characteristic value for the flow capacity of a regulator in normal conditions
Note 1 to entry: The flow coefficient is equal to the volumetric flow rate at normal conditions through the
regulator under the following reference conditions:
3
— reference natural gas at normal conditions with the relative density d = 0,64 (density ρ = 0,827 5 kg/m )
r r
— fully opened control member (mechanical stop);
— reference inlet temperature of t = 15 °C;
ur
— reference absolute gas inlet pressure p = 200 kPa (2 bar);
ur
— reference absolute gas outlet pressure p = 100 kPa (1 bar).
dr
3
Note 2 to entry: The KG value is specified in (m /h)/bar.
1) The definition of this flow coefficient is based on IEC 60534-1.
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ISO/FDIS 23555-2:2021(E)
3.1.3 Terms related to variables in the controlling process
3.1.3.1
controlled variable
variable which is monitored by the controlling process
Note 1 to entry: In this document, only the outlet pressure, p , is considered as the controlled variable.
d
3.1.3.2
disturbance varia
...
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