Evaluating a natural gas pipeline steel for blended hydrogen service

An X70 natural gas pipeline steel that is being considered for blended natural gas/hydrogen gas service was evaluated in a high-pressure hydrogen gas environment. Fracture toughness testing and fatigue crack growth rate testing were conducted according to ASTM standards and the results are presented in the context of ASME B31.12 qualification. While a reduction in fracture toughness was observed, the fracture toughness and fatigue behavior were within acceptable bounds for hydrogen service.