ISO 11114-4:2017

Overview

ISO 11114-4:2017 - Transportable gas cylinders - Compatibility of cylinder and valve materials with gas contents - Part 4: Test methods for selecting steels resistant to hydrogen embrittlement (ISO, 2017) - defines laboratory qualification test methods to identify steels suitable for manufacturing seamless steel gas cylinders (up to 3 000 L) intended for hydrogen and hydrogen-bearing embrittling gases.

The standard specifies how to evaluate steel composition and heat treatment to limit hydrogen-assisted cracking and embrittlement under service pressures and gas compositions likely to be encountered in use.

Key technical topics and requirements

• Scope & applicability
  • Applies only to seamless steel transportable gas cylinders up to 3 000 L.
  • Not required when the working pressure of the embrittling gas is < 20% of the cylinder test pressure, or when the partial pressure of the embrittling gas in mixtures is below specified limits (e.g., < 5 MPa for hydrogen, with specific lower limits for certain gases).
• Qualification approach
  • Tests are qualification tests for a given steel chemistry and heat treatment; once a steel is qualified at a design strength level, repeated testing per cylinder type is not required.
  • Test specimens are taken from representative cylinders or tube material.
• Test methods (Clause 5)
  • Method A - Disc test: rapid screening for susceptibility using rupture-pressure comparisons (hydrogen vs helium).
  • Method B - Fracture mechanics test: determines threshold parameters such as the threshold stress intensity factor (K1H) and crack-growth behavior under embrittling gas exposure.
  • Method C - Cylinder resistance test: assesses hydrogen-assisted cracking of cylinder material using precracked specimens and fatigue/crack-growth examination.
  • Tensile tests: used to determine mechanical properties relevant to embrittlement susceptibility.
• Test conditions
  • Tests are performed at room temperature and at pressures representative of the intended working/service conditions.
  • Gas compositions used must be at least as aggressive (embrittling concentration) as the intended service.

Practical applications - who uses this standard

• Gas cylinder manufacturers qualifying steel grades for hydrogen service.
• Materials engineers selecting steels and heat treatments to mitigate hydrogen embrittlement.
• Third‑party test laboratories performing standardized embrittlement qualification testing.
• Hydrogen suppliers, pressure equipment designers, and safety regulators verifying material compatibility for high-pressure hydrogen storage.

Related standards (for context)

• ISO 11114-1 - Compatibility of metallic materials with gas contents
• ISO 9809 (parts 1–2) - Design and testing of refillable seamless steel gas cylinders
• ISO 11120, ISO 7539 series - complementary tube/corrosion and precracked specimen guidance

Keywords: ISO 11114-4:2017, hydrogen embrittlement, transportable gas cylinders, seamless steel, test methods, hydrogen assisted cracking, fracture mechanics, disc test, cylinder qualification.