Road vehicles — Compressed natural gas (CNG) fuel system components — Part 21: Discharge line closures

This document specifies tests and requirements for discharge lines closures, a compressed natural gas (CNG) fuel system component 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 natural gas in accordance with the ISO 15403-1. It is not applicable to the following: a) liquefied natural gas (LNG) fuel system components located upstream of, and including, the vaporizer; b) fuel containers; c) stationary gas engines; d) container-mounting hardware; e) electronic fuel management; f) refuelling receptacles.

Véhicules routiers — Composants des systèmes de combustible gaz naturel comprimé (GNC) — Partie 21: Fermeture des lignes de décharge

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ISO 15500-21:2023 - Road vehicles — Compressed natural gas (CNG) fuel system components — Part 21: Discharge line closures Released:2/3/2023
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Standards Content (Sample)

STANDARD 15500-21
First edition
Road vehicles — Compressed natural
gas (CNG) fuel system components —
Part 21:
Discharge line closures
Véhicules routiers — Composants des systèmes de combustible gaz
naturel comprimé (GNC) —
Partie 21: Fermeture des lignes de décharge
Reference number
ISO 15500-21:2023(E)
© ISO 2023

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ISO 15500-21:2023(E)
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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  © ISO 2023 – All rights reserved

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ISO 15500-21:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Marking . . 2
5 Construction and assembly .2
6 Tests . 2
6.1 Applicability . 2
6.2 Continued operation . 3
6.3 Internal leakage vent test . 3
6.4 Water jet protection . 3
Bibliography . 4
© ISO 2023 – All rights reserved

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ISO 15500-21:2023(E)
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This document was prepared by Technical ISO/TC 22, Road vehicles, Subcommittee SC 41, Specific
aspects for gaseous fuels.
A list of all parts in the ISO 15500 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
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  © ISO 2023 – All rights reserved

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ISO 15500-21:2023(E)
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. However, 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.
All references to pressure in this document are considered to be gauge pressures unless otherwise
This document 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

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