Overview
EN ISO 11439:2013/A1:2021 is Amendment 1 to ISO 11439 (adopted as a CEN European Standard) covering high‑pressure gas cylinders for on‑board storage of natural gas (CNG) as a fuel for automotive vehicles. The amendment (approved August 2021) updates test methods, material and design verification requirements, and adds guidance for corrosion testing and specific composite cylinder conditions. It is used where safe, durable, and certifiable on‑vehicle CNG storage is required.
Key topics and technical requirements
- Scope: Applies to design qualification and production testing of high‑pressure CNG cylinders (including type 2, 3 and 4 designs). Some tests are explicitly not intended for in‑service inspection.
- Normative references: Several ASTM and NACE references (e.g., ASTM D1308, D2794, D3170, G154, NACE/TM 0177) are updated by removing dates so they are treated as current editions.
- Material strength / sulfide stress cracking: Tensile strength limits for steels tested for sulfide stress cracking are restricted so actual tensile strength shall not exceed tested values by more than 5% (applies in several clauses).
- Polymer resin requirement: Glass transition temperature (Tg) of resin measured per ASTM D3418 shall be not less than 102 °C.
- Composite and load‑sharing designs: Where glass or aramid fibre provides load sharing, one finished cylinder must pass the dedicated A.18 test (260 bar at ≥100 °C for ≥200 h, followed by volumetric expansion, leak and burst tests).
- Pressure cycling and durability:
- Cycling between ≤20 bar and ≥1.5× or ≥1.3× working pressure at controlled rates (e.g., ≤10 cycles/min for certain tests).
- Environmental pressure cycling (A.14): hydraulic cycling ≤20 bar to ≥260 bar for 3 000 cycles, then hold at 260 (+10) bar for a minimum of 24 h (total environmental exposure = 48 h).
- Long‑term hydrostatic conditioning (A.19): for type 2–4, hydrostatic pressurization to 260 (+10) bar at 65 (+10) °C for 1 000 h, then burst must exceed 85% of minimum design burst pressure.
- Leak and natural gas cycling: Type 4 leak tests can be done with compressed natural gas or nitrogen with detectable tracer (e.g., helium). Natural gas cycling for type 4 validates end boss/liner interfaces (1 000 cycles).
- Corrosion resistance (Annex H): Accelerated cyclic corrosion testing - 100 cycles for underbody/outdoor exposed cylinders; 20 cycles for other expected conditions.
Applications and users
- Cylinder manufacturers and composite overwrap suppliers - design qualification, materials testing, production acceptance.
- Automotive OEMs and system integrators - selecting and certifying on‑board CNG storage systems.
- Test laboratories and certification bodies - implementation of updated test protocols (e.g., Tg, pressure cycling, corrosion).
- Regulators and fleet managers - understanding performance and safety validation requirements for CNG vehicles.
Related standards
- ISO 11439:2013 (base standard)
- ISO 14130 (resin coupon testing referenced)
- ASTM D3418, ASTM D1308, D2794, D3170, G154; NACE/TM 0177 (referenced test methods)
Keywords: EN ISO 11439:2013/A1:2021, gas cylinders, CNG cylinders, high‑pressure cylinders, on‑board storage, natural gas fuel, automotive, composite cylinders, corrosion resistance, pressure cycling.