ISO 12614-7:2021

Road vehicles - Liquefied natural gas (LNG) fuel system components - Part 7: Pressure relief valve (PRV)

This document specifies tests and requirements for the pressure relief valve (PRV), a liquefied natural gas fuel system component intended for use on the types of motor vehicles defined in ISO 3833. This document is not applicable to the following: a) fuel containers; b) stationary gas engines; c) container mounting hardware; d) electronic fuel management; e) refuelling receptacles. 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 to be considered gauge pressures unless otherwise specified. This document is based upon a working pressure for natural gas as a fuel of 1,6 MPa [16 bar1]. Other working pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio). For example, 2 MPa (20 bar) working pressure system will require pressures to be multiplied by 1,25. 1 1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2.

Véhicules routiers — Équipements pour véhicules utilisant le gaz naturel liquéfié (GNL) comme combustible — Partie 7: Soupape de sécurité à la pression

General Information

• Status: Published
• Publication Date: 03-Jun-2021
• 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/WG 4 - Fuel system components and refuelling connector for vehicles propelled by Liquefied Natural Gas (LNG)
• Current Stage: 6060 - International Standard published
• Start Date: 04-Jun-2021
• Due Date: 08-Jan-2022
• Completion Date: 04-Jun-2021

Relations

• Revises: ISO 12614-7:2014 - Road vehicles - Liquefied natural gas (LNG) fuel system components - Part 7: Pressure relief valve
• Effective Date: 23-Apr-2020

Overview

ISO 12614-7:2021 is an international standard that specifies the tests and requirements for pressure relief valves (PRVs) used as components in liquefied natural gas (LNG) fuel systems for road vehicles. It focuses on PRVs designed for motor vehicles as defined by ISO 3833, ensuring safety, performance, and reliability within LNG fuel systems operating at typical working pressures around 1.6 MPa (16 bar). This standard excludes fuel containers, stationary engines, mounting hardware, electronic fuel management, and refuelling receptacles.

Developed by ISO Technical Committee ISO/TC 22 (Road vehicles), Subcommittee SC 41 (Specific aspects of gaseous fuels), ISO 12614-7:2021 enhances safety protocols by detailing specific construction, marking, and rigorous testing procedures to ensure the optimal function of PRVs under various operational conditions and temperatures.

Key Topics

• Scope and Application: Specifies the PRV’s role and excludes unrelated components, focusing on motor vehicle LNG systems.
• Marking Requirements: PRVs must be marked for traceability with manufacturer details, model, working pressures, flow direction, fuel type, certification markings, and reference to ISO 12614-7.
• Construction and Assembly: Compliance with general LNG fuel system component requirements per ISO 12614-1 and ISO 12614-2 is mandatory.
• Testing Protocols:
  • Hydrostatic Strength Test: PRVs are tested at 2.5 times their working pressure to verify structural integrity.
  • Leakage Test: Ensures no leakage at temperatures ranging from cryogenic (below -162 °C) to elevated temperatures (up to 85 °C or 120 °C).
  • Continued Operation Test: Validates valve durability through 600 operational cycles, including pressure cycling and reseating.
  • Operational Tests: Confirm opening and reseating pressures within tight tolerances at multiple temperatures (-162 °C, 20 °C, 85 °C/120 °C).
• Pressure References: All pressure values are gauge pressures; adjustments allow for working pressures different from the base 1.6 MPa.

Applications

ISO 12614-7:2021 supports the development and certification of safe and efficient LNG fuel systems in road vehicles, particularly for:

• LNG-powered trucks and buses: Ensuring critical safety components like PRVs meet stringent operational standards to handle LNG fuel pressures.
• LNG fuel system manufacturers: Assisting in the design, testing, and quality assurance of PRVs compliant with international safety standards.
• Regulatory bodies and certification agencies: Providing benchmarks for approving LNG fuel system components.
• Vehicle manufacturers integrating LNG systems: Helping ensure components fulfill rigorous safety and performance criteria before integration.
• Maintenance and inspection services: Offering testing references for evaluating PRV condition and functionality during vehicle servicing.

Related Standards

ISO 12614-7 forms part of a broader standard series focused on LNG fuel system components for road vehicles:

• ISO 12614-1: General requirements and definitions for LNG fuel system components.
• ISO 12614-2: Performance and general test methods for LNG components.
• ISO 3833: Defines road vehicle types relevant to the LNG fuel system applications.

Together, these documents provide comprehensive guidance on the design, testing, and maintenance of LNG fuel system components, promoting safe adoption of LNG as a sustainable alternative fuel for road transport.

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Keywords: ISO 12614-7, pressure relief valve, PRV, liquefied natural gas, LNG fuel system, road vehicles, LNG safety standards, LNG fuel pressure testing, ISO LNG standards, LNG vehicle components, LNG fuel pressure valves, automotive LNG systems.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 12614-7
Second edition
2021-06
Road vehicles — Liquefied natural gas
(LNG) fuel system components —
Part 7:
Pressure relief valve (PRV)
Véhicules routiers — Équipements pour véhicules utilisant le gaz
naturel liquéfié (GNL) comme combustible —
Partie 7: Soupape de sécurité à la pression
Reference number
©
ISO 2021
© ISO 2021
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.
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Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Marking . 2
5 Construction and assembly . 2
6 Test . 2
6.1 Applicability . 2
6.2 Hydrostatic strength . 3
6.3 Leakage . 3
6.4 Continued operation . 3
6.5 Operational test . 3
6.5.1 General. 3
6.5.2 Test procedure . 3
Bibliography . 5
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 41,
Specific aspects of gaseous fuels.
This second edition cancels and replaces the first edition (ISO 12614-7:2014), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— editorial changes.
A list of all parts in the ISO 12614 series can be found on the ISO website.
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