Introduction of the Release Incident at Hydrogen Refueling Station in South Korea

In this conference, the investigation results of a recent incident at Dowon HRS is presented. The release of compressed hydrogen from the high-pressure storage vessel of volume 487 L was detected on August 4th, 2020, and the hydrogen is immediately vented out for safety measure. There is no injury, fatality or property damage. For the investigation, the vessel was disassembled. And it is found that there are significant difference in thread length between the plug and the neck; and that the o-ring and the back-up ring ruptured. The investigation was extended to other vessels from different sites. They are manufactured by one maker but in different facilities. The vessels made in a specific facility showed, in common, 1) the difference in thread length between the plug and the neck, 2) the difficulty in removal of the plug from the neck, and 3) the damage in threads. And the structural analysis for the neck assembly demonstrated that the metal parts were designed with sufficient strength but the margin of safety for the back-up ring decreased to negative value, which can cause to a plastic deformation and a rupture in the end.