ISO 20766-19:2025

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.