ISO/FDIS 15501-1

ISO/TC 22/SC 41
Date: 2024-11-11
ISO/DIS 15501-1:2024(en)
Secretariat: UNI
Date: 2025-08
Road vehicles — Compressed natural gas (CNG) fuel systems —
Part 1:
Safety requirements
Véhicules routiers — Systèmes d'alimentation en gaz naturel comprimé (GNC) —
Partie 1: Exigences de sécurité
FDIS stage
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ISO/DISFDIS 15501-1:20242025(en)
Contents
Foreword . iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Requirements . 5
4.1 Design . 5
4.2 Refuelling connection . 8
4.3 Leakage control . 10
4.4 Mounting of the cylinders . 10
4.5 Heat protection . 12
4.6 Minimizing risk of gas ignition . 12
4.7 Venting system . 12
4.8 Gas temperature sensor . 13
5 Marking . 13
Annex A (informative) Technical solutions to functional requirements . 14
Annex B (informative) Compressed natural gas (CNG) on-board fuel systems . 15
Bibliography . 18

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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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 41, Specific
aspects for gaseous fuels.
This fourth edition cancels and replaces the third edition (ISO 15501-1:2016), which has been technically
revised. It also incorporates the Amendment ISO 15501-1:2016/Amd. 1:2021.
The main changes are as follows:
— — normative references have been updated;
— Definitionterminological entries have been updated;
— Deletedthe reference to the series PRD has been removed;
— Addedan electronic control unit requirement for Electronic control unithas been added;
— Added requirement foran electrical connections requirement has been added;
— Updatedthe minimum receptacle clearance has been updated;
— Added vent line closures requirements have been added;
— Added gas temperature sensor requirements have been added.
A list of all parts in the ISO 15501 series can be found on the ISO website.
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ISO/DISFDIS 15501-1:20242025(en)
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
Introduction
For the purposes of this document, all fuel system components in contact with natural gas have been
considered suitable for natural gas as defined in ISO 15403-1.
When applying this document, it is to be understood that a safety device to prevent overfilling the vehicle's
fuel system is part of the refuelling 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.
This document refers to a service pressure of 20 MPa (200 bar).
5 2
NOTE 1 1 bar = = 0,1 MPa = = 10 Pa. 1 MPa = 1 N/mm .
NOTE 2 This document is based upon a service pressure for natural gas as fuel of 20 MPa (200 bar) settled at 15 °C.
Other service pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio). For example,
a 25 MPa (250 bar) service pressure system will require pressures to be multiplied by 1,25.
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DRAFT International Standard ISO/DIS 15501-1:2024(en)

Road vehicles — Compressed natural gas (CNG) fuel systems —
Part 1:
Safety requirements
1 Scope
This document specifies the minimum safety requirements applicable for the functionality of compressed
natural gas (CNG) on-board fuel systems intended for use on the types of motor vehicles defined in ISO 3833.
This document is applicable to vehicles using compressed natural gas in accordance with ISO 15403-1,
including mono-fuel, bi-fuel or dual-fuel applications, original-production and converted vehicles.
All matters relating to the skills of installers and converters have been excluded from this document.
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 1176, Road vehicles — Masses — Vocabulary and codes
ISO 7637-1, Road vehicles — Electrical disturbances from conduction and coupling — Part 1: Vocabulary and
general considerations
ISO 7637-2, Road vehicles — Electrical disturbances from conduction and coupling — Part 2: Electrical transient
conduction along supply lines only
ISO 11439, Gas cylinders — High pressure cylinders for the on-board storage of natural gas as a fuel for
automotive vehicles
ISO 11451-1, Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 1: General principles and terminology
ISO 11451-2, Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 2: Off-vehicle radiation sources
ISO 11451-4, Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 4: Harness excitation methods
ISO 11452-1, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 1: General principles and terminology
ISO 11452-2, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 2: Absorber-lined shielded enclosure
ISO 11452-3, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 3: Transverse electromagnetic (TEM) cell
ISO 11452-4, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 4: Harness excitation methods
ISO 11452-5, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 5: Stripline
ISO 14469, Road vehicles — Compressed natural gas (CNG) refuelling connector
ISO 15500 (all parts), Road vehicles — Compressed natural gas (CNG) fuel system components
ISO 15501--2, Road vehicles — Compressed natural gas (CNG) fuel systems — Part 2: Test methods
ISO 20653, Road vehicles — Degrees of protection (IP code) — Protection of electrical equipment against foreign
objects, water and access
ISO 11451-1, Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 1: General principles and terminology
ISO 11451-2, Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 2: Off-vehicle radiation sources
ISO 11451-4, Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 4: Harness excitation methods
ISO 11452-1, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 1: General principles and terminology
ISO 11452-2, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 2: Absorber-lined shielded enclosure
ISO 11452-3, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 3: Transverse electromagnetic (TEM) cell
ISO 11452-4, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 4: Harness excitation methods
ISO 11452-5, Road vehicles — Component test methods for electrical disturbances from narrowband radiated
electromagnetic energy — Part 5: Stripline
ISO 7637-1, Road vehicles — Electrical disturbances from conduction and coupling — Part 1: Vocabulary and
general considerations
ISO 7637-2, Road vehicles — Electrical disturbances from conduction and coupling — Part 2: Electrical transient
conduction along supply lines only
IEC 60079-10-1, Explosive atmospheres — Part 10-1: Classification of areas — Explosive gas atmospheres
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1176, ISO 15500-1, -6, ISO 15500-7,
ISO 15500-9, ISO 15500-12, ISO 15500-13, ISO 15500-14 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
ISO/DISFDIS 15501-1:20242025(en)
— — IEC Electropedia: available at https://www.electropedia.org/

3.1 3.1
service pressure
settled pressure at a uniform gas temperature of 15 °C
Note 1 to entry: The ISO 15501 series is based on a service pressure for natural gas used as fuel of 20 MPa (200 bar),
settled at 15 °C. Other service pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio).
For example, a 25 MPa (250 bar) service pressure system will require pressures to be multiplied by 1,25.
3.2 3.2
CNG on-board fuel system
compressed natural gas fuel system compr
...