A Type 2 pressure vessel for hydrogen storage, which is made of a combination of a seamless linepipe steel liner and carbon fiber reinforced plastic (CFRP), was developed for hydrogen refueling stations operated at over 70 MPa hydrogen. This newly developed vessel was designed based on various standards such as ASME Sec. VIII Div. 3. However, a leak before break (LBB) methodology has not yet been established for hydrogen. The current study assessed LBB of the Type 2 vessel by a cyclic pressure test in a hydrogen gas atmosphere. The vessel with an artificial flaw was subjected to a cyclic test at pressures between 35 and 93 MPa hydrogen. Hydrogen gas leaked at 7,973 cycles. Eventually, LBB failure was confirmed. This number of cycles to leak was in good agreement with the simulated number, of 9,082 cycles using the crack growth properties in the presence of hydrogen and stress distribution of the thickness direction of the liner calculated by a finite element method. It is suggested that the fatigue crack growth behavior of the pressure vessel can be accurately estimated by using the fatigue crack growth properties in the presence of hydrogen, which correspond to the crack-tip stress-intensity range of an actual pressure vessel.

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