ISO 15500-20:2015

Overview

ISO 15500-20:2015 specifies requirements and test methods for rigid compressed natural gas (CNG) fuel lines made of carbon steel (materials other than stainless steel) for road vehicles. It applies to vehicle types defined in ISO 3833 and is intended for CNG systems with a service pressure of 20 MPa (200 bar) at 15 °C. All pressure references are gauge pressures. ISO 15500-20 is one part of the ISO 15500 series covering CNG fuel system components.

Key topics and technical requirements

• Scope and exclusions
  • Applies to seamless carbon-steel rigid fuel lines for CNG (20 MPa service pressure).
  • Does NOT apply to LNG upstream components, fuel containers, stationary gas engines, container mounting hardware, electronic fuel management, or refuelling receptacles.
• Marking and labelling
  • Components must be traceable: manufacturer name/trademark, model/part number, and working pressure or pressure–temperature range.
  • Marking should be indelible and repeated at intervals ≤ 0.5 m.
• Construction and compatibility
  • Rigid fuel line must be seamless carbon steel and compatible with fittings to prevent electrochemical corrosion.
• Mandatory tests and acceptance criteria
  • Hydrostatic strength: tested per ISO 15500-2, at 4× the working pressure.
  • Continued operation (endurance): 100,000 cycles, followed by the hydrostatic test.
  • Corrosion resistance: 500 hours (tested on the bare rigid fuel line, without protective sleeves).
  • Bending: line is bent over a mandrel (mandrel diameter per RFLE diameter rules) to a U-shape, subjected to corrosion testing, then pressurized to 4× working pressure - no leaks allowed.
  • Additional applicable tests from ISO 15500-2 (leakage, vibration, ageing, fluids compatibility, etc.) are referenced where relevant.

Applications and users

• Who uses it
  • Automotive OEMs and Tier-1 suppliers designing or manufacturing CNG fuel system piping.
  • Component testing laboratories and certification bodies evaluating CNG rigid fuel lines.
  • Fleet integrators, retrofitters, and safety engineers implementing CNG systems in vehicles that comply with ISO 15403-1 fuel quality requirements.
• Practical use cases
  • Designing carbon-steel rigid fuel lines for mono-fuel, bi-fuel, or dual-fuel vehicles.
  • Verifying durability, corrosion resistance and pressure integrity of CNG piping under vehicle operating conditions.
  • Ensuring traceability and compatibility of components for regulatory approval and type-approval processes.

Related standards

• ISO 15500-1 (General requirements and definitions)
• ISO 15500-2 (Performance and general test methods)
• ISO 3833 (Vehicle types - terms and definitions)
• ISO 15403-1 (Natural gas fuel quality for vehicles)

Keywords: ISO 15500-20, CNG fuel line, rigid fuel line, carbon steel, hydrostatic strength, corrosion resistance, bending test, ISO 15500, compressed natural gas standards.