ISO 19723-2:2025

Overview

ISO 19723-2:2025, "Road vehicles - Liquefied natural gas (LNG) fuel systems - Part 2: Test methods," defines performance and general test methods for LNG fuel system components fitted to road vehicles (as defined in ISO 3833). It applies to mono‑fuel, bi‑fuel and dual‑fuel vehicles using liquefied gas per the ISO 15403 series, for both original-production and converted vehicles. The standard covers the LNG system up to and including the vaporizer; downstream components fall under CNG standards (ISO 15501).

Key topics and technical requirements

The standard specifies practical tests and acceptance criteria for LNG system safety and integrity. Key topics include:

• Tank mounting strength tests

  • Inertia and static tests to verify tank anchorages remain secure under defined accelerations/forces.
  • Use of equivalent test media (e.g., liquid nitrogen) to simulate fill mass and pressure conditions.
  • Acceptance: tanks must remain attached and not interfere with seating structures.

• Leak test

  • System pressurization and inspection (including bubble-testing) after installation.
  • Tests performed at ambient temperature, typically at a high percentage of working pressure; detected leaks must be rectified and re-tested.

• Functional automatic valve test

  • Verifies LNG/CNG automatic valves close in defined conditions (ignition off, engine stall, cranking on another fuel, or engine not running on LNG).

• Receptacle and coupling tests

  • Receptacle compliance with ISO 12617, protection against contamination, clearance checks, and mounting tests (e.g., 670 N axial pull and 200 N·m moment) with subsequent leak checks.

• Hold time test

  • Confirms tanks maintain acceptable hydrostatic pressure stability for a minimum hold time (120 hours) under specified temperature conditions.

• Venting, accumulation system checks and bonfire test

  • Procedures to validate safe venting and emergency behaviour are defined.

• Marking and documentation

  • Requirements for component identification and traceability.

Practical applications and users

ISO 19723-2:2025 is intended for:

• Automotive OEMs and component manufacturers designing or validating LNG tanks, valves, fittings and receptacles.
• After‑market converters and retrofitters of LNG propulsion systems.
• Test laboratories and certification bodies performing conformity and safety testing.
• Fleet operators and integrators seeking documented proof of LNG system performance and safety.

By following these test methods, stakeholders can demonstrate compliance with internationally recognized procedures for LNG fuel system safety, reliability and interchangeability.

Related standards

• ISO 19723-1:2025 (Safety requirements)
• ISO 12991 (On‑board LNG tanks)
• ISO 12617 (LNG refuelling connector)
• ISO 15501 (CNG components downstream of vaporizer)
• ISO 15403 series (Liquefied gas specifications)
• ISO 3833 (Vehicle categories)
• ISO 6487, ISO 898-1 (test instrumentation and fasteners)

Keywords: ISO 19723-2:2025, LNG fuel system test methods, road vehicles, tank mounting strength, leak test, hold time test, receptacle test, LNG safety standard.