ISO/FDIS 20766-19

Road vehicles — Liquefied petroleum gas (LPG) fuel system components — Part 19: Gas-tube pressure relief valves

Specify tests and requirements for Gas-tube relief valve (Part 19) of LPG fuel system components, intended for use on the types of motor vehicles defined in ISO 3833.

Véhicules routiers — Équipements pour véhicules utilisant le gaz de pétrole liquéfié (GPL) comme combustible — Partie 19: Soupape de sécurité à tube de gaz

General Information

• Status: Not Published
• ICS: 43.060.40 - Fuel systems
• Technical Committee: ISO/TC 22 - Road vehicles
• Drafting Committee: ISO/TC 22 - Road vehicles
• Current Stage: 4060 - Close of voting
• Start Date: 20-May-2024
• Due Date: 21-May-2024
• Completion Date: 21-May-2024

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 22/SC 41
Road vehicles — Liquefied
Secretariat: UNI
petroleum gas (LPG) fuel system
Voting begins on:
components —
2024-12-11
Part 19:
Voting terminates on:
2025-02-05
Gas-tube pressure relief valves
Véhicules routiers — Équipements pour véhicules utilisant le gaz
de pétrole liquéfié (GPL) comme combustible —
Partie 19: Soupape de sécurité à tube de gaz
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
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
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.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 22/SC 41
Road vehicles — Liquefied
Secretariat: UNI
petroleum gas (LPG) fuel system
Voting begins on:
components —
Part 19:
Voting terminates on:
Gas-tube pressure relief valves
Véhicules routiers — Équipements pour véhicules utilisant le gaz
de pétrole liquéfié (GPL) comme combustible —
Partie 19: Soupape de sécurité à tube de gaz
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.
© ISO 2024
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Markings . 2
5 Construction and assembly . 2
6 Tests . 3
6.1 Applicability .3
6.2 Hydrostatic strength .3
6.3 Leakage .3
6.4 Continued operation (endurance) .4
6.5 Operational test .4
6.5.1 General .4
6.5.2 Test procedure.4
6.5.3 Test No. 1: Start-to-discharge and resealing pressures of pressure relief valves .4
6.5.4 Test No. 2: Flow capacity .5
6.5.5 Test No. 3: Recheck start-to-discharge and resealing pressures .6
6.6 Creep test.6
7 Production batch inspection and acceptance testing . 6
Bibliography . 7

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 22, Road vehicles, Subcommittee SC 41, Specific
aspects for gaseous fuels.
A list of all parts in the ISO 20766 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.

iv
FINAL DRAFT International Standard ISO/FDIS 20766-19:2024(en)
Road vehicles — Liquefied petroleum gas (LPG) fuel system
components —
Part 19:
Gas-tube pressure relief valves
1 Scope
This document specifies general requirements and definitions of liquefied petroleum gas fuel (LPG)
components, intended for use on the types of motor vehicles as defined in ISO 3833. It also provides general
design principles and specifies requirements for instructions and marking.
This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) that use gaseous fuels in
accordance with ISO 9162. It is not applicable to:
— fuel containers;
— stationary gas engines;
— container mounting hardware;
— electronic fuel management;
— refuelling receptacles.
Miscellaneous components not specifically addressed in this document can be examined for conformity with
the criteria of any applicable part of the ISO 20766 series, including testing to the appropriate functional tests.
All references to pressure in this document are considered gauge pressures unless otherwise specified.
This document applies to devices that have a service pressure in the range of 110 kPa (butane rich at 20 °C)
and 840 kPa (propane at 20 °C). Other service pressures can be accommodated by adjusting the pressure by
the appropriate factor (ratio).
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 20766-1, Road vehicles — Liquefied petroleum gas (LPG) fuel systems components — Part 1: General
requirements and definitions
ISO 20766-2:2018, Road vehicles — Liquefied petroleum gas (LPG) fuel systems components — Part 2:
Performance and general test methods
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20766-1 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
discharge pressure
pressure at which the pressure relief valve opens to release the pressure
3.2
flow capacity
relieving capacity of a gas-tube pressure relief valve measured at the flow-rating pressure
Note 1 to entry: Flow capacity is expressed in m /min of air at a temperature of 15 °C and at a pressure of 100 kPa.
4 Markings
Marking of the component shall provide sufficient information to trace:
a) the manufacturer or agent’s name, trademark or symbol;
b) the model designation (part number);
c) the discharge pressure or discharge pressure and temperature range;
d) the flow capacity;
e) the direction of flow (when necessary for correct installation).
The following additional markings are recommended:
— the type of fuel;
— electrical ratings (if applicable);
— the symbol of the certification agency;
— the type approval number;
— the serial number or date code;
— a reference to this document.
NOTE This information can be provided by a suitable identification code on at least one part of the component
when it consists of more than one part.
5 Construction and assembly
The gas-tube pressure relief valve is a device used to prevent the build-up of pressure in the tubes above a
pre-set value. The gas-tube pressure relief valve shall comply with the applicable provisions of ISO 20766-1
and ISO 20766-2, and with the tests specified in Clause 6 of this document.
General provisions for the gas-tube pressure relief valve are:
— mounting location shall ensure the unrestricted discharge flow and
shall not impinge on enclosed areas, other vehicles, exterior-mounted systems with air intake (i.e. air-
conditioning systems), engine intakes, or engine exhaust;
— gas-tube pressure relief valves shall have the following discharge pressures:
— 3,200 ± 100 kPa if the working pressure (WP) is <3 MPa;

— 1,07 WP of the pipe ±100 kPa if the working pressure is >3 MPa;
— gas-tube pressure relief valves shall not have leakage up to:
— 3,000 kPa if the working pressure is <3 MPa;
— working pressure of the pipe if the working pressure is >3 MPa.
6 Tests
6.1 Applicability
Table 1 indicates the tests that shall be carried out.
Table 1 — Applicable tests
Test procedure as
Specific test requirements
required by
Test Applicable
of this document
ISO 20766-2
Hydrostatic strength X X X (see 6.2)
Leakage X X X (see 6.3)
Excess torque resistance X X
Bending moment X X
Continued operation (en-
X X (see 6.4)
durance)
Corrosion resistance X X
Operational test X X (see 6.5)
Vibration resistance X X
Brass material
X X
compatibility
Oxygen ageing X X
Non-metallic
X X
material immersion
Ozone ageing X X
Resistance to dry-heat X X
Temperature cycle test X X
Flow capacity test X X (see 6.5.4)
Creep test X X (see 6.6)
6.2 Hydrostatic strength
Te
...

ISO/DISFDIS 20766-19:2023(E)
ISO/TC 22/SC 41
Secretariat: UNI
Date: 2024-05-0711-26
Road vehicles — Liquefied petroleum gas (LPG) fuel system
components —
Part 19:
Gas-tube pressure relief valves
Véhicules routiers — Équipements pour véhicules utilisant le gaz de pétrole liquéfié (GPL) comme
combustible —
Partie 19: Soupape de sécurité à tube de gaz
FDIS stage
ISO/DISFDIS 20766-19:2023(E2024(en)
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
Fax: [phone]
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2023 – All rights reserved
ii
ISO/DISFDIS 20766-19:2023(E2024(en)
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Markings . 2
5 Construction and assembly . 3
6 Tests . 3
6.1 Applicability . 3
6.2 Hydrostatic strength . 4
6.3 Leakage . 4
6.4 Continued operation (endurance) . 4
6.5 Operational test . 5
6.6 Creep test . 7
7 Production batch inspection and acceptance testing . 7
Bibliography . 8

iii
ISO/DISFDIS 20766-19:2023(E2024(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 22, Road vehicles, Subcommittee SC 41, Specific
aspects for gaseous fuels.
A list of all parts in the ISO 20766 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.
iv © ISO 2023 – All rights reserved
iv
ISO/DIS 20766-19:2023(E)
DRAFT INTERNATIONAL STANDARD
Road vehicles — Liquefied petroleum gas (LPG) fuel system
components — —
Part 19:
Gas-tube pressure relief valves
1 Scope
This document specifies general requirements and definitions of liquefied petroleum gas fuel (LPG)
components, intended for use on the types of motor vehicles as defined in ISO 3833. It also provides general
design principles and specifies requirements for instructions and marking.
This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) that use gaseous fuels in
accordance with ISO 9162. It is not applicable to:
— — fuel containers;
— — stationary gas engines;
— — container mounting hardware;
— — electronic fuel management;
— — refuelling receptacles.
Miscellaneous components not specifically addressed in this document can be examined for conformity with
the criteria of any applicable part of the ISO 20766 series, including testing to the appropriate functional tests.
All references to pressure in this document are considered gauge pressures unless otherwise specified.
This document applies to devices that have a service pressure in the range of 110 kPa (butane rich at 20 °C)
and 840 kPa (propane at 20 °C). Other service pressures can be accommodated by adjusting the pressure by
the appropriate factor (ratio).
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 20766--1, Road vehicles — Liquefied petroleum gas (LPG) fuel systems components — Part 1: General
requirements and definitions
ISO 20766--2:2018, Road vehicles — Liquefied petroleum gas (LPG) fuel systems components — Part 2:
Performance and general test methods
ISO/DISFDIS 20766-19:2023(E2024(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20766--1 and the following apply.
ISO and IEC maintain terminologicalterminology databases for use in standardization at the following
addresses:
— — IEC Electropedia: available at
— — ISO Online browsing platform: available at https://www.iso.org/obp
3.1
— IEC Electropedia: available at https://www.electropedia.org/
3.1
discharge pressure
pressure at which the pressure relief valve opens to release the pressure
3.2 3.2
flow capacity
relieving capacity of a gas-tube pressure relief valve measured at the flow-rating pressure
Note 1 to entry: Flow capacity is expressed in m /min of air at a temperature of 15 °C and at a pressure of 100 kPa.
4 Markings
Marking of the component shall provide sufficient information to trace:
a) a) the manufacturer or agent’s name, trademark or symbol;
b) b) the model designation (part number);
c) c) the discharge pressure or discharge pressure and temperature range;
d) d) the flow capacity;
e) e) the direction of flow (when necessary for correct installation).
The following additional markings are recommended:
— — the type of fuel;
— — electrical ratings (if applicable);
— — the symbol of the certification agency;
— — the type approval number;
— — the serial number or date code;
— — a reference to this document.
2 © ISO 2023 – All rights reserved
ISO/DISFDIS 20766-19:2023(E2024(en)
NOTE This information can be provided by a suitable identification code on at least one part of the component when
it consists of more than one part.
5 Construction and assembly
The gas-tube pressure relief valve is a device used to prevent the build-up of pressure in the tubes above a
pre-set value. The gas-tube pressure relief valve shall comply with the applicable provisions of ISO 20766--1
and ISO 20766--2, and with the tests specified in Clause 6Clause 6 of this document.
General provisions for the gas-tube pressure relief valve are:
— — mounting location shall ensure the unrestricted discharge flow and
shall not impinge on enclosed areas, other vehicles, exterior-mounted systems with air intake (i.e. air-
conditioning systems), engine intakes, or engine exhaust.; ;
— — Gasgas-tube pressure relief valves shall have the following discharge pressures:
— — 3,200 ± 100 kPa if the working pressure (WP) is <3 MPa;
— — 1,07 WP of the pipe ±100 kPa if the working pressure is >3 MPa.;
— — Gasgas-tube pressure relief valves shall not have leakage up to:
— — 3,000 kPa if the working pressure is <3 MPa;
— — working pressure of the pipe if the working pressure is >3 MPa.
6 Tests
6.1 Applicability
Table 1Table 1 indicates the tests that shall be carried out.
Table 1 — Applicable tests
Test procedure as
Specific test
required by
Test Applicable requirements of this
document
ISO 20766-2
Hydrostatic strength X X X (see 6.26.2))
Leakage X X X (see 6.36.3))
Excess torque resistance X X
Bending moment X X
Continued operation
X  X (see 6.46.4))
(endurance)
Corrosion resistance X X
Operational test X  X (see 6.56.5))
Vibration resistance X X
ISO/DISFDIS 20766-19:2023(E2024(en)
Test procedure as
Specific test
required by
Test Applicable requirements of this
document
ISO 20766-2
Brass material
X X
compatibility
Oxygen ageing X X
Non-metallic
X X
material immersion
Ozone ageing X X
Resistance to dry-heat X X
Temperature cycle test X X
Flow capacity test X  X (see 6.5.46.5.4))
Creep test X  X (see 6.66.6))
6.2 Hydrostatic strength
Test the gas-tube pressure relief valve in accordance with the procedure for testing hydrostatic strength
specified in ISO 20766--2:2018, clause Clause 5. The test pressure shall be 2,25 times the working pressure.
The purpose of this test shallis to check the strength of the body of the gas-tube pressure relief valve. If
necessary, the moving part should be blocked to achieve the 2,25 times working pressure.
6.3 Leakage
Test the gas-tube pressure relief valve at the temperatures and pressures given in Table 2Table 2.
Table 2 — Test temperatures and pressures
Pressure
Temperature
Factor × working pressure
°C
(WP)
(±5 °C)
First test Second test
−40 or −20 1 × WP 0,025 × WP
20 0,025 × WP
1 × WP
85 or 120 0,05 × WP
6.4 Continued operation (endurance)
The gas-tube pressure relief valve shall be capable of withstanding 200 cycles when tested in accordance with
the provisions of the continued operation test procedure given in ISO 20766--2:2018, clause Clause 9 and the
following.
a) a) A test cycle consists of pressurizing the gas-tube pressure relief valve to the discharge pressure. This
shall cause the gas-tube pressure relief valve to open and vent. Once the valve is venting, reduce the inlet
pressure. The cycle is finished when the gas-tube pressure relief valve re-seats. Cycle time shall be within
a period of 10 s ± 2 s.
4 © ISO 2023 – All rights reserved
ISO/DISFDIS 20766-19:2023(E2024(en)
b) b) After 200 cycles, test the gas-tube pressure relief valve for leakage at 20 °C ± 5 °C at its 1 × working
pressure.
6.5 Operational test
6.5.1 General
Verify the opening and re-seating pressures of the gas-tube pressure relief valve.
6.5.2 Test procedure
Three samples of each size, design and setting shall be used for start-to-discharge and resealing pressure tests.
This same set of three valves shall be used for flow capacity tests for other observations indicated in the
following paragraphs.
Not less than two successive start-to-discharge and resealing pressure observations shall be made on each of
the three test valves under the tests outlined in 6.5.36.5.3 and 6.5.56.5.5.
6.5.3 Test No. 1: Start-to-discharge and resealing pressures of pressure relief valves —
6.5.3.1 6.5.3.1 Before being subjected to a flow capacity test, the start-to-discharge pressure of each
of three samples of a pressure relief v
...