ISO 20766-6:2019

Overview

ISO 20766-6:2019 specifies requirements for pressure relief valves (PRV) used in LPG fuel systems for road vehicles. It is part of the ISO 20766 series covering LPG fuel system components and focuses on definitions, design principles, marking, construction and testing to ensure safe, reliable venting of overpressure in vehicle LPG systems. The standard applies to mono‑fuel, bi‑fuel and dual‑fuel vehicles (as defined in ISO 3833) using gaseous fuels per ISO 9162, and addresses devices with service pressures from 110 kPa to 840 kPa (gauge pressure).

Key topics and technical requirements

• Scope and exclusions
  • Applicable to LPG PRVs for vehicle use; not applicable to fuel containers, stationary gas engines, container mounting hardware, electronic fuel management, or refuelling receptacles.
• Marking
  • Components must be marked to allow traceability: manufacturer/agent, model/part number, and working pressure (and recommended additional markings such as flow direction, fuel type, certification symbol).
• Construction and assembly
  • PRVs should be mounted in the vapour phase and designed with a discharge pressure ≤ 1.0 × working pressure (WP).
• Testing and performance
  • PRVs must meet the applicable provisions of ISO 20766‑1 and ISO 20766‑2 and pass specific tests in Clause 6, including:
    • Hydrostatic strength: tested at 2.25 × WP to verify body strength (moving parts may be blocked).
    • Leakage: evaluated at specified temperatures and fractions of WP.
    • Continued operation: capable of 600 cycle operations (open/vent and re‑seat cycles within 10 s ± 2 s), followed by leakage test.
    • Operational test: opening and re‑seating pressures verified on samples; opening pressure within ±5% of manufacturer’s set pressure; re‑seating ≥ 90% of set pressure and within ±5% of average; temperature tests require minimum percentages of reference values (e.g., opening ≥ 85% at temperature extremes).
    • Additional tests: corrosion, vibration, material compatibility, temperature cycling, etc.
• Production quality
  • Manufacturers must implement a production batch inspection and acceptance testing program to ensure consistent safety performance.

Applications and who uses it

• Target users:
  • PRV and LPG component manufacturers
  • Vehicle OEMs integrating LPG systems
  • Test laboratories and conformity assessment bodies
  • Regulatory authorities, safety engineers, and aftermarket component suppliers
• Practical uses:
  • Designing, certifying and validating PRVs for automotive LPG systems, ensuring compliance with international safety and performance expectations.

Related standards

• ISO 20766‑1: General requirements and definitions
• ISO 20766‑2: Performance and general test methods
• ISO 9162: Gaseous fuel characteristics and requirements
• ISO 3833: Vehicle type definitions

Keywords: ISO 20766-6, pressure relief valve, PRV, LPG fuel systems, road vehicles, hydrostatic strength, operational test, LPG safety, production inspection.