ISO 11439:2013

Overview - ISO 11439:2013 for CNG on-board cylinders

ISO 11439:2013 specifies minimum requirements for light‑weight, refillable high‑pressure gas cylinders intended for the on‑board storage of compressed natural gas (CNG) as a fuel for automotive vehicles. The standard covers cylinders made from seamless steel, seamless aluminium alloy and non‑metallic materials (including fully or partially wrapped/composite constructions). It uses 200 bar as a reference working pressure (other pressures can be applied) and designates cylinders as Type 1, Type 2, Type 3 and Type 4. Stainless steel cylinders are excluded. ISO 11439 applies to normal service conditions and does not address external loadings from vehicle collisions.

Key topics and technical requirements

• Materials and construction: Requirements for seamless steel, aluminium alloy and non‑metallic liners and for hoop‑wrapped and fully‑wrapped composite designs (Types 1–4).
• Design and calculations: Design criteria for pressure containment, allowable stress ratios and working pressures (reference 200 bar).
• Prototype, batch and per‑cylinder testing: Mandatory prototype testing, batch acceptance tests and tests applied to every cylinder (including pressure, leak and proof tests).
• Inspection and NDE: Non‑destructive examination (ultrasonic, visual, other NDE) and fracture performance evaluation; defect size assessment and acceptance criteria are covered.
• Type approval and documentation: Type approval procedures, required design/manufacturing data, statement of service and certificates.
• Marking and lifecycle: Cylinder marking, expiry/service life considerations, manufacturer’s handling and inspection guidance.
• Service conditions and limits: Temperature range, gas composition, number of filling cycles and external surface protection; excludes collision loading scenarios.
• Annexed methods: Normative and informative annexes provide test methods, ultrasonic examination guidance, NDE defect sizing, report forms and suggested working pressures.

Applications - who uses ISO 11439

• Cylinder manufacturers designing and producing CNG on‑board storage vessels (Type 1–4).
• Automotive OEMs integrating high‑pressure CNG cylinders into vehicles.
• Certification and testing laboratories performing type approval, prototype and batch testing.
• Regulators, fleet operators and safety engineers assessing compliance, lifecycle and inspection regimes.
• Composite and materials engineers developing lightweight, high‑pressure fuel storage solutions.

Related standards and references

ISO 11439 references several test and materials standards used in verification and testing, for example ISO 148‑1 (Charpy impact), ISO 306 (Vicat softening), ISO 527‑2 (tensile for plastics) and standards for coating and hardness testing. It was developed by ISO/TC 58 (Gas cylinders) and replaces earlier editions to clarify change‑of‑design and approval requirements.

Keywords: ISO 11439, CNG cylinders, high pressure cylinders, on‑board natural gas storage, Type 1 Type 2 Type 3 Type 4, CNG vehicle fuel storage, type approval, cylinder testing.