ISO 19723-2

Road vehicles — Liquefied natural gas (LNG) fuel systems — Part 2: Test methods

This document specifies performance and general test methods for liquefied natural gas fuel system components intended for use on the types of motor vehicles defined in ISO 3833. This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) using liquefied gas in accordance with the ISO 15403 series. It is not applicable to the following: original-production and converted vehicles. This document is only applicable on the components in the "LNG system" meaning an assembly of components (tanks, valves, flexible fuel lines, etc.) and connecting parts (fuel lines, fittings, etc.) fitted on motor vehicles using LNG in their propulsion system and related components up to and including the vaporizer. Other parts downstream from the vaporizer are considered as CNG components covered by ISO 15501. NOTE All references to pressures, given in megapascals and bar (1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2) are considered gauge pressures, unless otherwise specified.

Véhicules routiers — Systèmes à carburant gaz naturel liquéfié (GNL) — Partie 2: Méthodes de test

General Information

• Status: Not Published
• ICS: 43.060.40 - Fuel systems
• Technical Committee: ISO/TC 22/SC 41 - Specific aspects for gaseous fuels
• Drafting Committee: ISO/TC 22/SC 41 - Specific aspects for gaseous fuels
• Current Stage: 6000 - International Standard under publication
• Start Date: 30-Oct-2025
• Completion Date: 01-Nov-2025

Relations

• Revises: ISO 19723-2:2018 - Road vehicles — Liquefied natural gas (LNG) fuel systems — Part 2: Test methods
• Effective Date: 08-Mar-2023

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 19723-2
ISO/TC 22/SC 41
Road vehicles — Liquefied natural
Secretariat: UNI
gas (LNG) fuel systems —
Voting begins on:
2025-09-03
Part 2:
Test methods
Voting terminates on:
2025-10-29
Véhicules routiers — Systèmes à carburant gaz naturel liquéfié
(GNL) —
Partie 2: Méthodes de test
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
ISO/FDIS 19723-2:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 19723-2:2025(en)
International
Standard
ISO/FDIS 19723-2
ISO/TC 22/SC 41
Road vehicles — Liquefied natural
Secretariat: UNI
gas (LNG) fuel systems —
Voting begins on:
Part 2:
Test methods
Voting terminates on:
Véhicules routiers — Systèmes à carburant gaz naturel
liquéfié (GNL) —
Partie 2: Méthodes de test
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 2025
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
ISO/FDIS 19723-2:2025(en) © ISO 2025

ii
ISO/FDIS 19723-2:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test methods . 2
4.1 Tank mounting strength tests .2
4.1.1 General .2
4.1.2 Inertia test . .2
4.1.3 Static test .2
4.1.4 Acceptance criteria .3
4.1.5 Best practice examples (for reference only) by engineering experience .3
4.2 Leak test .3
4.3 Functional liquefied natural gas/compressed natural gas automatic valve test .4
4.4 Receptacle .4
4.4.1 General .4
4.4.2 Receptacle clearance test .4
4.4.3 Receptacle mounting tests .4
4.5 Hold time test.4
4.5.1 General .4
4.5.2 Procedure .4
4.5.3 Acceptable test results .5
4.6 Venting system check .5
4.7 LNG accumulation system check .5
4.8 Bonfire test .5
5 Marking . . 5
Annex A (informative) Engineering experience for the mounting of LNG tanks . 7
Bibliography .11

iii
ISO/FDIS 19723-2:2025(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 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).
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.
This second edition cancels and replaces the first edition (ISO 19723-2:2018), which has been technically
revised.
The main changes are as follows:
— generally updated wording and update of some requirements.
A list of all parts in the ISO 19723 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/FDIS 19723-2:2025(en)
Introduction
All fuel system components in contact with liquid natural gas are suitable for natural gas as defined in the
ISO 15403 series.
When applying this document, it is understood that a safety device to prevent overfilling the vehicle's fuel
system is part of the refueling station. The pressure gauge has not been considered as a safety component.
When necessary, technical solutions regarding functional requirements are given in Annex A.

v
FINAL DRAFT International Standard ISO/FDIS 19723-2:2025(en)
Road vehicles — Liquefied natural gas (LNG) fuel systems —
Part 2:
Test methods
1 Scope
This document specifies performance and general test methods for liquefied natural gas fuel system
components intended for use on the types of motor vehicles defined in ISO 3833.
This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) using liquefied gas
according to the ISO 15403 series. It is applicable to original-production and converted vehicles.
This document is only applicable on the components in the "liquefied natural gas (LNG) system" meaning an
assembly of components (tanks, valves, flexible fuel lines, etc.) and connecting parts (fuel lines, fittings, etc.)
fitted on motor vehicles using LNG in their propulsion system and related components up to and including
the vaporizer. Other parts downstream from the vaporizer are considered as compressed natural gas (CNG)
components covered by ISO 15501.
5 2
NOTE All references to pressures, given in megapascals and bar (1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm ) are
considered gauge pressures, unless otherwise specified.
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 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and
studs with specified property classes — Coarse thread and fine pitch thread
ISO 6487, Road vehicles — Measurement techniques in impact tests — Instrumentation
ISO 12617, Road vehicles — Liquefied natural gas (LNG) refuelling connector — 3,1 MPa connector
ISO 12991:2012, Liquefied natural gas (LNG) — Tanks for on-board storage as a fuel for automotive vehicles
ISO 19723-1:2018, Road vehicles — Liquefied natural gas (LNG) fuel systems — Part 1: Safety requirements
3 Terms and definitions
No terms and definitions are listed in this document.
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/

ISO/FDIS 19723-2:2025(en)
4 Test methods
4.1 Tank mounting strength tests
4.1.1 General
When a vehicle is equipped with several tanks, they should be tested as a unit.
When a tank or groups of tanks are installed on a vehicle such that they are separately anchored to the
original structure of the vehicle, then each tank or separate group of tanks can be tested individually.
When performing these tests, accessories and piping shall not contribute to reinforcing the tank mounting.
The general design requirements of ISO 19723-1 shall be verified by the tests specified in 4.1.2 or 4.1.3.
4.1.2 Inertia test
The
...

2024-10-31
ISO/DISFDIS 19723-2:2024(en)
ISO/TC 22/SC 41/WG
Secretariat: UNI
Date: 2025-08
Road vehicles — Liquefied natural gas (LNG) fuel systems —
Part 2:
Test methods
Véhicules routiers — Systèmes à carburant gaz naturel liquéfié (GNL) —
—
Partie 2: Méthodes de test
FDIS stage
ISO/FDIS 19723-2:2018(E2025(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 2018 – All rights reserved
ii
ISO/DISFDIS 19723-2:20242025(en)
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test methods . 2
4.1 Tank mounting strength tests . 2
4.2 Leak test . 3
4.3 Functional liquefied natural gas/compressed natural gas automatic valve test . 4
4.4 Receptacle. 4
4.5 Hold time test . 5
4.6 Venting system check . 5
4.7 LNG accumulation system check . 6
4.8 Bonfire test . 6
5 Marking . 6
Annex A (informative) Engineering experience for the mounting of LNG tanks . 7
Bibliography . 14

iii
ISO/FDIS 19723-2:2018(E2025(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 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).
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/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.
This second edition cancels and replaces the first edition (ISO 19723-2:2018), which has been technically
revised.
The main changes are as follows:
— — generalgenerally updated for wording and forupdate of some requirementrequirements.
A list of all parts in the ISO 19723 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 2018 – All rights reserved
iv
ISO/DISFDIS 19723-2:20242025(en)
Introduction
All fuel system components in contact with liquid natural gas are suitable for natural gas as defined in the
ISO 15403 series.
When applying this document, it is understood that a safety device to prevent overfilling the vehicle's fuel
system is part of the refueling station. The pressure gauge has not been considered as a safety component.
When necessary, technical solutions regarding functional requirements are given in Annex AAnnex A.
v
DRAFT INTERNATIONAL STANDARD ISO/DIS 19723-2:2024(en)

Road vehicles — Liquefied natural gas (LNG) fuel systems —
Part 2:
Test requirementsmethods
1 Scope
This document specifies performance and general test methods for liquefied natural gas fuel system
components intended for use on the types of motor vehicles defined in ISO 3833.
This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) using liquefied gas
according to the ISO 15403 series. It is applicable to the following: original-production and converted vehicles.
This document is only applicable on the components in the " Liquefiedliquefied natural gas (LNG) system"
meaning an assembly of components (tanks, valves, flexible fuel lines, etc.) and connecting parts (fuel lines,
fittings, etc.) fitted on motor vehicles using LNG in their propulsion system and related components up to and
including the vaporizer. Other parts downstream from the vaporizer are considered as Compressed Natural
Gascompressed natural gas (CNG) components covered by ISO 15501.
5 2
NOTE All references to pressures, given in megapascals and bar (1 bar = = 0,1 MPa = = 10 Pa; 1 MPa = = 1 N/mm )
are considered gauge pressures, unless otherwise specified.
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 898--1, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and
studs with specified property classes — Coarse thread and fine pitch thread
ISO 6487, Road vehicles — Measurement techniques in impact tests — Instrumentation
ISO 12617, Road vehicles — Liquefied natural gas (LNG) refuelling connector — 3,1 MPa connector
ISO 12991:2012, Liquefied natural gas (LNG) — Tanks for on-board storage as a fuel for automotive vehicles
ISO 19723--1:2018, Road vehicles — Liquefied natural gas (LNG) fuel systems — Part 1: Safety requirements
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminologicalterminology 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/
ISO/FDIS 19723-2:2018(E2025(en)
4 Test methods
4.1 Tank mounting strength tests
4.1.1 General
When a vehicle is equipped with several tanks, they should be tested as a unit.
When a tank or groups of tanks are installed on a vehicle such that they are separately anchored to the original
structure of the vehicle, then each tank or separate group of tanktanks can be tested individually.
When performing these tests, accessories and piping shall not contribute to reinforcing the tank mounting.
The general design requirements of ISO 19723--1 shall be verified by the tests specified in 4.1.2 4.1.2 or
4.1.34.1.3.
4.1.2 Inertia test
The tank or group of tanks to be tested shall be mounted on the vehicle body or a part of the vehicle body,
according to the specifications of the original equipment manufacturer (OEM) or after-market converter.
The vehicle body or part of the vehicle body shall be firmly anchored to the test trolley. The method used for
anchoring the vehicle body to the test trolley shall not result in reinforcement of the tank anchorages or the
part of the vehicle structure participating in anchoring the tank or tanks. Testing performed with a trolley
shall geometrically match original vehicle conditions.
The test shall be carried out using the following procedure.
a) a) Fill the tank or tanks with an equivalent full weight of liquid nitrogen saturated to one-half the
working pressure.
b) b) Measure the trolley deceleration with data channels of channel frequency class (CFC) 60
corresponding to the characteristics given in ISO 6487.
c) c) Maintain the value of the deceleration as defined in ISO 19723--1:2018, 4.4.3, for at least 30 ms.
4.1.3 Static test
This test may be carried out on a vehicle body or on a part of a vehicle body.
The tank or group of tanks to be tested shall be mounted on the vehicle body or on part of the vehicle body,
according to OEM or after-market converter specifications.
The method used for anchoring the vehicle body or the part of the vehicle body in this test shall not:
— — submit the anchorages and anchorage area (300 mm diameter circle) to abnormal stresses and
deformation;
— — result in reinforcement of the tank or group of tanks anchorages, or the part of the vehicle structure
participating in anchoring the tank or group of tanks.
The traction force is defined by Formula (1)::
2 © ISO 2018 – All rights reserved
ISO/DISFDIS 19723-2:20242025(en)
F = (M + 0,9 ρV)a (1)
c
where
F is the traction force, in newtons;
M is the mass of empty tank(s), in kilograms;
c
a is the acceleration as defined in ISO 19723-1:2018, 4.4.3;
V is the volume of the tank(s) in litres;
ρ is the density of LNG at 0 MPa and -161°C (0.48 kg/L).
F is the traction force, in newtons;
Mc is the mass of empty tank(s), in kilograms;
a is the acceleration as defined in ISO 19723-1:2018, 4.4.3;
V is the volume of the tank(s), in litres;
ρ is the density of LNG at 0 MPa and −161 °C (0,48 kg/L).
The test shall be carried out using the following procedure.
a) a) Apply the traction force to the tank or tanks’ centre of gravity in the specified directions within
0,2 s.
b) b) Hold the specified traction force for at least 0,2 s.
c) c) Release the traction force.
4.1.4 Acceptance criteria
4.1.4.1 By testing
At the conclusion of either of these tests, the tank or group of tanks shall:
— — remain attached to the vehicle body or part of the vehicle body;
— — not interfere with the seat structure.
4.1.4.2 By calculation
Appropriate calculations shall be carried out, depending on the individual technical parameters.
4.1.5 4.1.5 Best practice examples (FOR REFERENCE ONLYfor reference only) by engineering
experience
See Annex AFor for details of a practical means of conformance for tanks (in accordance withaccording to
ISO 12991), determined as a result of calculations and substantiated by experience over time. Annex ASee
Annex A for also includes tank mounting design examples that have been demonstrated to meet above
acceptance criteria.
4.2 Leak test
This test may be conducted at ambient temperature. It shall be performed on each vehicle after the fuel system
installation has been completed.
a) a) Fill the vehicle fuelling system with an appropriate medium at 90 % of working pressure.
ISO/FDIS 19723-2:2018(E2025(en)
b) b) During this test, make provisions to have the main shut-off valve open as well as the other
automatic valves on the system that should be open during the normal operation of the vehicle.
c) c) Check all components (valves, fittings, excludin
...