Abstract
Low alloy, quenched and tempered Cr-Mo and Ni-Cr-Mo steels are commonly used for construction of seamless pressure vessels for hydrogen gas storage. Designing such vessels for high-pressure gaseous hydrogen service requires knowledge of fatigue crack growth rates and fracture toughness in the service environment at the design pressure. Measurement of these properties is challenging, and only a few laboratories in the world are equipped to make these measurements at very elevated pressure up to 103 MPa (15,000 psi) which are of interests for pressure vessels to be used as buffers in hydrogen refueling stations. In recent years, these properties for common low alloy steels were published in the ASME Boiler and Pressure Vessel Code Case 2938-1, therefore allowing design and construction without the need for dedicated testing. However, the fatigue crack growth rate curves published in the CC were determined from test data at 100 MPa and above and may be over-conservative for lower pressure applications. Prior publication PVP2019-93907 ([1]) in fact, already proposed a correction factor of fatigue crack growth rates based on hydrogen fugacity. Since then, new data were generated at lower pressures i.e. 55 MPa (8,000 psi). This paper presents the new findings and discusses the applicability of the previously proposed equation, which could allow reducing conservatism in current design of pressure vessels.
