ISO 19723-2:2018

Overview

ISO 19723-2:2018 - 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 motor vehicles (as defined in ISO 3833). It applies to mono‑fuel, bi‑fuel and dual‑fuel vehicle systems using LNG per the ISO 15403 series and covers the LNG system components up to and including the vaporizer. Downstream components are treated as CNG components (ISO 15501). All pressure references are gauge pressures.

Key topics and requirements

This part of ISO 19723 specifies practical laboratory and on‑vehicle tests and acceptance criteria for LNG system components. Major test areas include:

• Tank mounting strength tests
  • Inertia test: vehicle/tank mounted on test trolley with deceleration measurements (ISO 6487) and liquid nitrogen load simulation.
  • Static test: applied traction force based on tank mass and LNG equivalent load; hold and release procedure and acceptance (no detachment or interference with seats).
• Leak test
  • System pressurization to 90% working pressure; bubble test (no bubbles for 3 min or leakage < 20 Ncm3/h) with procedures for detected leaks.
• Functional LNG/CNG automatic valve test
  • Verify valve closes when ignition is off, engine stalls, cranking occurs on non‑LNG fuel, or engine not running on LNG.
• Receptacle tests
  • Compliance with ISO 12617; cap protection; clearance and mounting strength (670 N axial pull, 200 N·m moment) and subsequent leak check.
• Hold time test
  • Verifies tank can maintain hydrostatic pressure stability for a minimum of 120 hours with specified fill and ambient conditions; tank must remain bubble‑tight.
• Venting and accumulation system checks
  • Vent routing, protection from fouling/ice, sizing to avoid pressure drops, and safe discharge locations.
• Additional checks
  • Bonfire test, marking requirements and engineering guidance for tank mounting (Annex A).

Applications and who uses it

ISO 19723-2 is essential for:

• Vehicle OEMs and after‑market converters designing or installing LNG systems (except original‑production and converted vehicles as noted).
• Component manufacturers (tanks, valves, fittings, receptacles) validating product performance.
• Test labs, certification bodies and compliance engineers performing type‑approval or in‑service testing.
• Fleet operators and integrators specifying safe LNG fuel systems and refuelling interfaces.

Practical benefits: ensures consistent test procedures, improves safety and interoperability of LNG components, and supports regulatory compliance and type‑approval processes.

Related standards

• ISO 19723-1:2018 - Safety requirements (companion document)
• ISO 12991 - On‑board LNG storage tanks
• ISO 12617 - LNG refuelling connector (3.1 MPa)
• ISO 15403 series - Natural gas fuel quality
• ISO 15501 - CNG system components (downstream of vaporizer)

Keywords: ISO 19723-2, LNG fuel systems, test methods, tank mounting, leak test, hold time, venting system, road vehicles, LNG standard.