ISO 21266-1:2018

INTERNATIONAL ISO
STANDARD 21266-1
First edition
2018-10
Road vehicles — Compressed gaseous
hydrogen (CGH2) and hydrogen/
natural gas blends fuel systems —
Part 1:
Safety requirements
Véhicules routiers — Systèmes d'alimentation pour hydrogène gazeux
comprimé (CGH2) et mélanges d'hydrogène et de gaz naturel —
Partie 1: Exigences de sécurité
Reference number
©
ISO 2018
© ISO 2018
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Requirements . 4
4.1 Design . 4
4.1.1 General. 4
4.1.2 Components . 5
4.2 Refuelling connection . 6
4.2.1 General. 6
4.2.2 Receptacle location . 7
4.2.3 Receptacle mounting . 7
4.2.4 Minimum receptacle clearance . 7
4.3 Leakage control . 7
4.4 Mounting of the cylinder(s) . 8
4.5 Heat protection . 9
4.6 Minimizing risk of gas ignition . 9
4.7 Venting system . 9
4.7.1 General requirements . 9
4.7.2 Ventilation lines for PRDs and PRVs .10
5 Instruction for use .10
6 Marking .10
Annex A (informative) Technical solutions to functional requirements .11
Annex B (informative) Compressed gaseous hydrogen (CGH2) and hydrogen/natural gas
blends on-board fuel systems .12
Bibliography .14
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
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on the ISO list of patent declarations received (see www .iso .org/patents).
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.org/iso/foreword .html.
This document was prepared by Technical Committee TC 22, Road vehicles, Subcommittee SC 41, Specific
aspects for gaseous fuels.
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.
A list of all the parts in the ISO 21266 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved

Introduction
For the purposes of this document, all fuel system components in contact with natural gas have been
considered suitable for compressed gaseous hydrogen (CGH2), in accordance with ISO 14687-1 or
ISO 14687-2, and hydrogen/natural gas blends using natural gas, in accordance with ISO 15403-1 and
ISO/TR 15403-2.
When applying this document, it should be understood that a safety device to prevent overfilling the
vehicle's fuel system is part of the fuelling station. The pressure gauge has not been considered as a
safety component.
When necessary, technical solutions regarding functional requirements are given in this document, as
in Annex A.
This document refers to a service pressure of 20 MPa.
NOTE This document is based on a service pressure for compressed gaseous hydrogen (CGH2) and
hydrogen/natural gas blends as fuels of 20 MPa settled at 15 °C. Other service pressures can be accommodated
by adjusting the pressure by the appropriate factor (ratio). For example, pressures to be multiplied by 1,25 for a
25 MPa service pressure system.
INTERNATIONAL STANDARD ISO 21266-1:2018(E)
Road vehicles — Compressed gaseous hydrogen (CGH2)
and hydrogen/natural gas blends fuel systems —
Part 1:
Safety requirements
1 Scope
This document specifies the minimum safety requirements applicable for the functionality of
compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blends on-board fuel systems
intended for use on the types of motor vehicles defined in ISO 3833.
It is applicable to vehicles using compressed gaseous hydrogen (CGH2), in accordance with ISO 14687-1
or ISO 14687-2, and hydrogen/natural gas blends using natural gas, in accordance with ISO 15403-1
and ISO/TR 15403-2. It is not applicable to the following:
1) liquefied hydrogen (LH2) fuel system components;
2) fuel containers;
3) stationary gas engines;
4) container mounting hardware;
5) electronic fuel management;
6) refuelling receptacles; and
7) fuel cell vehicles.
NOTE 1 It is recognized that miscellaneous components not specifically covered herein can be examined to
meet the criteria of this document and tested according to the appropriate functional tests.
NOTE 2 All references to pressure in this document are considered gauge pressures unless otherwise
specified.
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 12619 (all parts), Road vehicles —Compressed gaseous hydrogen (CGH2) and hydrogen/natural gas
blends fuel system components
ISO 16380, Road vehicles — Blended fuels refuelling connector
ISO 17268, Gaseous hydrogen land vehicle refuelling connection devices
ISO 21266-2, Road vehicles — Compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blend fuel
system components — Part 2: test methods
ISO 20653, Road vehicles — Degrees of protection (IP code) — Protection of electrical equipment against
foreign objects, water and access
ISO 14687-1, Hydrogen fuel — Product specification — Part 1: All applications except proton exchange
membrane (PEM) fuel cell for road vehicles
ISO 14687-2, Hydrogen fuel — Product specification — Part 2: Proton exchange membrane (PEM) fuel cell
applications for road vehicles
1)
ISO 19881 , Gaseous hydrogen — Land vehicle fuel containers
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 12619-1 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 http: //www .electropedia .org/
3.1 General terms
3.1.1
service pressure
settled pressure of 20 MPa at a uniform gas temperature of 15 °C
3.1.2
compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blends on-board fuel system
compressed natural gas fuel system comprising cylinder, or cylinders according to ISO 19881 or
ISO/TS 15869 as applicable, mounting, one or more refuelling receptacles according to ISO 16380 or
ISO 17268 as applicable, and the components described in ISO 12619-3 and following parts
3.1.3
main shut-off valve
automatic valve designed to isolate a high-pressure source
3.1.4
bi-fuel HNGV
vehicle that has two independent fuel systems (one of them for compressed gaseous hydrogen and
hydrogen/natural gas blend ) and can run alternatively on either fuel, but only on one at a time
Note 1 to entry: The term Bi-fuel also applies to vehicles that run on both fuels simultaneously in limited amount
or duration.
3.2 Vehicle mass
3.2.1
kerb mass
complete shipping mass of a vehicle fitted with all equipment necessary for normal operation plus the
mass of the following elements for M1, N1 and M2 having a maximum authorized mass not exceeding
3 500 kg:
— lubricants, coolant (if needed), washer fluid;
— fuel (tank filled to at least 90 % of the capacity specified by the manufacturer);
1) Under preparation. Stage at the time of publication: ISO/FDIS 19881.
2 © ISO 2018 – All rights reserved

— other equipment if included as basic parts for the vehicle, such as spare wheel(s), wheel chocks, fire
extinguisher(s), spare parts and tool kit
Note 1 to entry: The definition of kerb mass may vary from country to country, but in this document it refers to
the definition contained in ISO 1176.
3.2.2
maximum authorized mass
kerb mass plus the maximum allowable payload
3.3 Vehicle categories
3.3.1
category M
power-driven vehicles having at least four wheels and used for the carriage of passengers
3.3.1.1
category M1
vehicles used for the carriage of passengers and comprising no more than eight seats in addition to the
driver's seat
3.3.1.2
category M2
vehicles used for the carriage of passengers and comprising more than eight seats in addition to the
driver's seat and having a maximum authorized mass not exceeding 5 000 kg
3.3.1.3
category M3
vehicles used for the carriage of passengers and comprising more than eight seats in addition to the
driver's seat and having a maximum authorized mass exceeding 5 000 kg
3.4.2
category N
power-driven vehicles having at least four wheels and used for the carriage of goods
3.4.2.1
category N1
vehicles used for the carriage of goods and having a maximum authorized mass not exceeding 3 500 kg
3.4.2.2
category N2
vehicles used for the carriage of goods and having a maximum authorized mass exceeding 3 500 kg but
not exceeding 12 000 kg
3.4.2.3
category N3
vehicles used for the carriage of goods and having a maximum authorized mass exceeding 12 000 kg
3.5
electronic control unit
device which controls the compressed gaseous hydrogen (CGH2) or hydrogen/natural gas blends
demand of the engine and establishes the cut-off of the automatic valve in case of a broken fuel supply
pipe or in case of stalling of the engine, or during a crash
4 Requirements
4.1 Design
4.1.1 General
The compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blends on-board fuel system
2)
components shall comply with ISO 19881 ISO/TS 15869, ISO 16380, ISO 17268 and ISO 12619, as
applicable.
For bi-fuel HNGV, provision shall be made to avoid accelerated deterioration of the non-compressed
gaseous hydrogen (CGH2) and hydrogen/natural gas blends fuel system as a result of sustained
operation on compressed gaseous hydrogen and hydrogen/natural gas blends. Such measures shall be
as recommended by the original vehicle manufacturer (e.g. fuel hoses).
All fuel system components shall fulfil the following conditions.
a) They shall withstand the environmental temperatures and other environmental conditions safely
during their operational life.
b) They shall be located with full regard for anticipated damage while the vehicle is being used safely.
Such damage can be caused by the vehicle itself, by extraneous factors such as heat, road debris,
automotive fluids (brake liquid, oil, petrol, cooling liquid, etc.), or by rust, etc.
c) They shall be fitted so that they are not the outermost, highest or lowest parts of the vehicles;
otherwise they shall be protected.
d) They shall be fitted so as not to affect ground clearance, approach angle, ramp (break-over) angle
or departure angles as defined by the vehicle manufacturer.
e) They shall be located so that they do not suffer corrosion damage by accumulation of water or cargo
chemicals.
f) They shall assure the proper electrical conductivity throughout the fuel system in order to avoid
the electrostatic charges. This provision does not apply to gas-tight housing and ventilation hoses.
g) All connections shall be made in locations where access is possible for inspection.
The compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blends system shall be installed
in such a way that it has suitable protection against damage, such as damage due to moving vehicle
components, collision, grit or due to the loading or unloading of the vehicle or the shifting of those loads.
The compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blends system shall include
automatic valves designed to close when the engine is not running on compressed gaseous hydrogen
(CGH2) and hydrogen/natural gas blends, and shall be able to be manually opened or closed in case of
failure of the automatism (see Annex B).
The compressed gaseous hydrogen (CGH2) and hydrogen/natural gas blends on-board fuel system shall
include:
— an automatic valve installed directly on every compressed gaseous hydrogen (CGH2) and hydrogen/
natural gas blends cylinder, with a manual valve rigidly fixed to the compressed gaseous hydrogen
(CGH2) and hydrogen/natural gas blends cylinder, which may be integrated into the automatic
valve. The manual valve shall be able to isolate the cylinder content from the automatic valve;
— a PRD installed on each cylinder, functionally independent from any other component;
2) Under preparation. Stage at the time of publication: ISO/FDIS 19881.
4 © ISO 2018 – All rights reserved

3)
— one or more additional PRD as applicable to the approval of the cylinder according to ISO 19881 or
according to any other recommendations of ISO/TS 15869;
— an excess flow valve inside, and optionally outside, every cylind
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