ISO 12614-15:2021

Overview - ISO 12614-15:2021 (Capacitance fuel content gauge)

ISO 12614-15:2021 specifies tests and requirements for the capacitance fuel content gauge, a component of liquefied natural gas (LNG) fuel systems for road vehicles (types defined in ISO 3833). It applies to vehicles using natural gas per ISO 15403-1 (mono‑fuel, bi‑fuel, dual‑fuel). The standard covers construction, marking, functional description and a set of applicable tests for the gauge and its electrical interfaces. It excludes fuel containers, stationary gas engines, container mounting hardware, electronic fuel management and refuelling receptacles.

Keywords: ISO 12614-15, LNG fuel system, capacitance fuel content gauge, LNG gauge, road vehicles.

Key topics and technical requirements

• Construction and components

  • Capacitance transmitter (mounted adjacent to fuel tank), fuel content indicator (dashboard), capacity transmission cables and signal cable.
  • The gauge measures capacitance between the tank outer vessel and the inner-vessel sensor cable and converts it to an electrical signal (e.g., 4 mA to 20 mA) compatible with the dashboard indicator.
  • The fuel content indicator is an automotive-type gauge calibrated to the transmitter and is not itself tested under this part.

• Marking and traceability

  • Mandatory markings: manufacturer/agent name or trademark, model designation (part number), and temperature range.
  • Recommended: flow direction, fuel type, electrical ratings, certification symbol, type approval number, serial/date code, and reference to ISO 12614-15.

• Testing requirements

  • Lists applicable functional and durability tests (referencing ISO 12614-2 for methods), including:
    • Excess torque resistance, bending moment
    • Corrosion resistance, oxygen ageing
    • Electrical overvoltages, vibration resistance
    • Brass material compatibility
    • Insulation resistance: apply 1 000 V d.c. between a connector pin and housing for at least 2 s; minimum allowable resistance 240 kΩ.
  • All pressure references are gauge pressures; nominal working pressure is 1.6 MPa (16 bar). Other pressures are accommodated by proportional scaling (e.g., 2 MPa → multiply pressures by 1.25).

Applications and who uses this standard

• Component manufacturers designing or certifying LNG capacitance gauges
• Vehicle OEMs and integrators specifying LNG fuel-system components
• Testing and certification bodies conducting conformity and safety testing
• Fleet operators and maintenance engineers requiring compliant replacement parts
• Regulatory and type-approval authorities evaluating LNG vehicle systems

Practical benefits: ensures electrical safety, mechanical robustness, interoperability with dashboard indicators, and traceability for LNG vehicle fuel systems.

Related standards

• ISO 12614-1 - General requirements and definitions (LNG fuel system components)
• ISO 12614-2 - Performance and general test methods
• ISO 3833 - Road vehicle types, terms and definitions
• ISO 15403-1 - Natural gas quality for vehicle fuel

For procurement, design or compliance work involving LNG capacitance gauges, reference ISO 12614-15:2021 alongside ISO 12614-1 and ISO 12614-2.