ISO 15501-2:2025

International
Standard
ISO 15501-2
Third edition
Road vehicles — Compressed
2025-12
natural gas (CNG) fuel systems —
Part 2:
Test methods
Véhicules routiers — Systèmes d'alimentation en gaz naturel
comprimé (GNC) —
Partie 2: Méthodes d'essai
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test methods . 1
4.1 Cylinder mounting strength tests .1
4.1.1 General .1
4.1.2 Inertia test . .2
4.1.3 Static test .2
4.1.4 Alternative method .3
4.1.5 Acceptance criteria .3
4.2 Leak test .3
4.3 Functional test .3
4.3.1 Main shut-off valve test .3
4.3.2 Receptacle clearance test .4
4.4 Receptacle mounting tests .4
Annex A (informative) Engineering experience for the mounting of steel cylinders . 5
Bibliography . 8

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
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has been established has the right to be represented on that committee. International organizations,
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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)
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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 third edition cancels and replaces the second edition (ISO 15501-1:2016), which has been technically
revised.
The main changes are as follows:
— reference to 20 MPa has been deleted and a reference to service pressure has been added;
— technical changes were done in 4.1.2;
— technical changes were done in 4.1.5.2;
— technical changes were done in 4.4.
A list of all parts in the ISO 15501 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
International Standard ISO 15501-2:2025(en)
Road vehicles — Compressed natural gas (CNG) fuel
systems —
Part 2:
Test methods
1 Scope
This document specifies the test methods for checking the minimum safety requirements specified in
ISO 15501-1. It is applicable to the functionality of the fuel systems designed to operate on compressed
natural gas of motor vehicles as defined in ISO 3833.
NOTE For tests of individual components, refer to the ISO 15500 series, ISO 14469 and ISO 11439.
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 indicated applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 6487, Road vehicles — Measurement techniques in impact tests — Instrumentation
ISO 15500-1, Road vehicles — Compressed natural gas (CNG) fuel system components — Part 1: General
requirements and definitions
ISO 15501-1:2025, Road vehicles — Compressed natural gas (CNG) fuel systems — Part 1: Safety requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15500-1and ISO 15501-1 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/
4 Test methods
4.1 Cylinder mounting strength tests
4.1.1 General
When a vehicle is equipped with several cylinders, they should preferably be tested as a unit.
When groups of cylinders are installed on a vehicle such that they are separately anchored to the original
structure of the vehicle, then each separate group of cylinders may be tested individually.
When performing these tests, accessories and piping shall not contribute to reinforcing the cylinder
mounting.
The requirements of ISO 15501-1:2025, 4.4.3 shall be verified by the test specified in 4.1.2, 4.1.3, 4.1.4 or 4.1.5.
4.1.2 Inertia test
The cylinder or cylinders 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 v
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