In anticipation of an economy increasingly reliant on the transportation of gaseous hydrogen, API’s SC6 recently prepared a new Annex M titled “Valves in Hydrogen Gas (H2) Service” to supplement API Spec 6D “Specification for Valves.” Unlike pipeline-grade natural gas, transporting H2 may lead to environmental hydrogen embrittlement (HE) for susceptible materials. To minimize the risk of environmentally induced HE, proper material selection is critical when either retrofitting existing equipment and/or manufacturing new isolation valves (or other critical components) for hydrogen service.

The material requirements listed in Annex M are written for valves operating in gaseous hydrogen service with a design temperature limitation of 175 °C and for total pressures up to 43.1 MPa (6,250 psig). Based on consensus, the material requirements listed in Annex M refer to material specifications defined in NACE MR0175/ISO 15156 and API 6ACRA. In support of the committee’s recommendations, this article provides a comprehensive literature review of publicly available material performance data in gaseous hydrogen for carbon and low alloy steels, austenitic stainless steels, and nickel-based alloys. Based on our investigation, materials that are suitable for sour service to at least 0.1 MPa H2S at 25 °C are also suitable for manufacturing API 6D isolation valves for gaseous hydrogen service.

Subject
Test methods, Atomic hydrogen, Materials, Fracture toughness, Valves, Nickel based alloys, Sour environments, Isolation, Steel, Sulfide stress cracking, Yield strength, Hydrogen, Low alloy steel
Keywords:
Hydrogen embrittlement, gaseous H2, isolation valves, hydrogen standards, sour service, plastic deformation, NACE MR0175/ISO 15156, API 6ACRA, carbon and low alloy steels, alloys
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2025
Association for Materials Protection and Performance (AMPP)
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