Introduction of the Technical Document in Japan for Safety Use of Type2 Pressure Vessels in Hydrogen Refueling Stations

We considered the Type2 pressure vessel (hereinafter, Type2) used in hydrogen refueling stations (hereinafter, HRS), a stational Composite Reinforced Pressure Vessel (hereinafter, CRPV) in which a metal layer made of high-strength low-alloy steel is wrapped with a carbon fiber reinforced plastic (hereinafter, CFRP) layer in the circumferential direction. Because Type2 is lightweight and has a long life, installation in HRS is expected. However, since no technical standards concerning design for safe use of Type2 for HRS currently exist, few Type2 have been installed in HRS in Japan. Based on these circumstances, we are developing a Technical Document on the safe use of Type2 (hereinafter, TD) to promote the installation of Type2 at HRS. In this paper, we introduce the current discussion on issuance of the TD as an industrial standard, focusing especially on the following: Type2 shall be considered a two-layer pressure vessel in which the CFRP layer shares the circumferential stress of the metal layer. The wall thicknesses of the metal layer and CFRP layer of Type2 are calculated by Design by Rule approach, but when necessary, Design by Analysis (stress analysis and fatigue analysis) can be applied. Design specification tests such as the burst test and hydraulic pressure cycle test using an actual Type2 should not be required. The hydrogen compatibility and fatigue life of the low-alloy steel used in the metal layer are evaluated in accordance with our previously-proposed methods [1]. In the fatigue analysis, the effect of autofrettage can be considered.