The fatigue failure analysis of SUS316L flexible hose of the hydrogen station which was demonstrated during EXPO 2005 in Nagoya was carried out. The fatigue fracture surface where hydrogen leakage was detected showed clear striations which revealed a unique evidence of hydrogen effect on the ratio of striation height and spacing. The number of striations observed on the leakage fracture surface was 270. Considering that the number of hydrogen supply to the fuel cell buses was 280, it can be concluded that the fatigue fracture process during the demonstration is completely controlled by microplasticity resulting ductile fracture contrary to the conventional concept expressed with a term of decohesion or hydrogen embrittlement. The striation data were used to make the fatigue crack growth rate equation which was applied to the life prediction and structural integrity assessment for a new hydrogen station. The fatigue crack growth data showed the evidence of a strong frequency effect of fatigue crack growth rate of SUS316L used in the hydrogen environment with 8 minutes hydrogen supply time at the hydrogen station.
