Lessons Learned from a Medium Pressure Tank Leak at Nrel's Hydrogen Refueling Station

Safe and reliable hydrogen systems are critical to the expansion and widespread utilization of hydrogen as an energy storage mechanism. Hydrogen component failures leading to external leaks create a hazard which could lead to fire or explosion. Leaks with the most potential energy are those which cannot be isolated from the bulk hydrogen storage system. In 2021 a leak occurred on a union connected to the end plug of a medium pressure tank at the National Renewable Energy Laboratory’s Hydrogen Fueling Station. The failure of an O-ring in the union created an external leak which could not be isolated. There was no ignition or any injuries as a result of this leak event. Here we outline the potential cause of the leak, the lessons learned, and the improvements to the hardware design. NREL’s highly instrumented station provides a clear indication of the leak with pressure, temperature monitoring, and ultrasonic leak detection instruments. Post failure analysis provides insight as to why the O-ring failed and informed the redesign of the medium pressure gas manifold. This leak occurred during the recommissioning of the medium pressure system following extended downtime and rebuild of a system that had been originally installed at a different facility. Sharing this experience informs the greater hydrogen community and hopefully can be utilized to inform and improve other hydrogen systems.