ISO 20766-19:2025

Road vehicles - Liquefied petroleum gas (LPG) fuel system components - Part 19: Gas-tube pressure relief valves

This document specifies general requirements and definitions of liquefied petroleum gas fuel (LPG) components, intended for use on the types of motor vehicles as defined in ISO 3833. It also provides general design principles and specifies requirements for instructions and marking. This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) that use gaseous fuels in accordance with ISO 9162. It is not applicable to: - fuel containers; - stationary gas engines; - container mounting hardware; - electronic fuel management; - refuelling receptacles. Miscellaneous components not specifically addressed in this document can be examined for conformity with the criteria of any applicable part of the ISO 20766 series, including testing to the appropriate functional tests. All references to pressure in this document are considered gauge pressures unless otherwise specified. This document applies to devices that have a service pressure in the range of 110 kPa (butane rich at 20 °C) and 840 kPa (propane at 20 °C). Other service pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio).

Véhicules routiers — Équipements pour véhicules utilisant le gaz de pétrole liquéfié (GPL) comme combustible — Partie 19: Soupape de sécurité à tube de gaz

General Information

• Status: Published
• Publication Date: 05-Mar-2025
• ICS: 43.060.40 - Fuel systems
• Technical Committee: ISO/TC 22 - Road vehicles
• Drafting Committee: ISO/TC 22 - Road vehicles
• Current Stage: 6060 - International Standard published
• Start Date: 06-Mar-2025
• Due Date: 17-Jan-2026
• Completion Date: 06-Mar-2025

Overview

ISO 20766-19:2025 specifies requirements for gas-tube pressure relief valves used in liquefied petroleum gas (LPG) fuel systems for road vehicles (as defined in ISO 3833). Part 19 of the ISO 20766 series covers definitions, design principles, marking, instructions and mandatory conformity tests for valves that protect LPG tubing from overpressure. The standard applies to mono-fuel, bi-fuel and dual-fuel vehicles using gaseous fuels in accordance with ISO 9162, and excludes fuel containers, stationary engines, container mounting hardware, electronic fuel management and refuelling receptacles.

Key topics and technical requirements

• Scope and applicability: Devices with service pressures in the approximate range of 110 kPa (butane-rich at 20 °C) to 840 kPa (propane at 20 °C); other pressures accommodated by ratio adjustments.
• Marking and traceability: Manufacturer/agent name, part number, discharge pressure (and temperature range), flow capacity, and flow direction; recommended additional markings include fuel type, certification symbol, type approval number and serial/date code.
• Design and installation: Mounting must ensure unobstructed discharge and avoid directing discharge toward enclosed areas, air intakes or exhausts.
• Prescribed discharge settings:
  • 3 200 ± 100 kPa if pipe working pressure (WP) is < 3 MPa;
  • 1.07 × WP ± 100 kPa if WP > 3 MPa.
• Leakage limits: No leakage up to 3 000 kPa (if WP < 3 MPa) or up to the pipe working pressure (if WP > 3 MPa).
• Mandatory tests (referenced to ISO 20766-2 test methods):
  • Hydrostatic strength: test at 2.25 × working pressure.
  • Leakage tests: at specified temperatures and pressure factors (see Table 2 in the standard).
  • Continued operation (endurance): 200 cycles of opening and reseating; leakage re-check after cycling.
  • Operational tests: start-to-discharge and resealing pressures (within set tolerances) and flow capacity tests (conducted at 120% of maximum set pressure; capacity must fall within 10% of highest observed).
  • Creep, corrosion, vibration and material compatibility tests where applicable.

Applications and users

• Manufacturers of LPG pressure relief valves and fuel-system components - to design, test and mark components for vehicle use.
• Vehicle OEMs and system integrators - for specifying compliant safety devices in LPG fuel systems.
• Test laboratories and certification bodies - to perform hydrostatic, leakage, flow capacity and endurance tests for type approval and production checks.
• Regulators and safety engineers - to set procurement and inspection criteria for LPG vehicle safety equipment.

Related standards

• ISO 20766-1 (general requirements and definitions)
• ISO 20766-2 (performance and general test methods)
• ISO 3833 (vehicle types)
• ISO 9162 (gaseous fuels for vehicles)

Keywords: ISO 20766-19:2025, LPG, gas-tube pressure relief valves, road vehicles, pressure relief valve testing, flow capacity test, hydrostatic strength, leakage test, LPG fuel systems.

Standards Content (Sample)

International
Standard
ISO 20766-19
First edition
Road vehicles — Liquefied
2025-03
petroleum gas (LPG) fuel system
components —
Part 19:
Gas-tube pressure relief valves
Véhicules routiers — Équipements pour véhicules utilisant le gaz
de pétrole liquéfié (GPL) comme combustible —
Partie 19: Soupape de sécurité à tube de gaz
Reference number
© ISO 2025
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.
ISO copyright office
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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 Markings . 2
5 Construction and assembly . 2
6 Tests . 3
6.1 Applicability .3
6.2 Hydrostatic strength .3
6.3 Leakage .3
6.4 Continued operation (endurance) .4
6.5 Operational test .4
6.5.1 General .4
6.5.2 Test procedure.4
6.5.3 Test No. 1: Start-to-discharge and resealing pressures of pressure relief valves .4
6.5.4 Test No. 2: Flow capacity .5
6.5.5 Test No. 3: Recheck start-to-discharge and resealing pressures .6
6.6 Creep test.6
7 Production batch inspection and acceptance testing . 6
Bibliography . 7

iii
Foreword
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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
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this may not represent the latest information, which may be obtained from the patent database available at
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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.
A list of all parts in the ISO 20766 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 20766-19:2025(en)
Road vehicles — Liquefied petroleum gas (LPG) fuel system
components —
Part 19:
Gas-tube pressure relief valves
1 Scope
This document specifies general requirements and definitions of liquefied petroleum gas fuel (LPG)
components, intended for use on the types of motor vehicles as defined in ISO 3833. It also provides general
design principles and specifies requirements for instructions and marking.
This document is applicable to vehicles (mono-fuel, bi-fuel or dual-fuel applications) that use gaseous fuels in
accordance with ISO 9162. It is not applicable to:
— fuel containers;
— stationary gas engines;
— container mounting hardware;
— electronic fuel management;
— refuelling receptacles.
Miscellaneous components not specifically addressed in this document can be examined for conformity with
the criteria of any applicable part of the ISO 20766 series, including testing to the appropriate functional tests.
All references to pressure in this document are considered gauge pressures unless otherwise specified.
This document applies to devices that have a service pressure in the range of 110 kPa (butane rich at 20 °C)
and 840 kPa (propane at 20 °C). Other service pressures can be accommodated by adjusting the pressure by
the appropriate factor (ratio).
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 20766-1, Road vehicles — Liquefied petroleum gas (LPG) fuel systems components — Part 1: General
requirements and definitions
ISO 20766-2:2018, Road vehicles — Liquefied petroleum gas (LPG) fuel systems components — Part 2:
Performance and general test methods
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20766-1 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

— IEC Electropedia: available at https:// www .electropedia .org/
3.1
discharge pressure
pressure at which the pressure relief valve opens to release the pressure
3.2
flow capacity
relieving capacity of a gas-tube pressure relief valve measured at the flow-rating pressure
Note 1 to entry: Flow capacity is expressed in m /min of air at a temperature of 15 °C and at a pressure of 100 kPa.
4 Markings
Marking of the component shall provide sufficient information to trace:
a) the manufacturer or agent’s name, trademark or symbol;
b) the model designation (part number);
c) the discharge pressure or discharge pressure and temperature range;
d) the flow capacity;
e) the direction of flow (when necessary for correct installation).
The following additional markings are recommended:
— the type of fuel;
— electrical ratings (if applicable);
— the symbol of the certification agency;
— the type approval number;
— the serial number or date code;
— a reference to this document.
NOTE This information can be provided by a suitable identification code on at least one part of the component
when it consists of more than one part.
5 Construction and assembly
The gas-tube pressure relief valve is a device used to prevent the build-up of pressure in the tubes above a
pre-set value. The gas
...