Investigation of the hydrogen release incident at the AC Transit Emeryville Facility.

Abstract

This report summarizes the investigation of the release of approximately 300kg of hydrogen at the AC Transit Facility in Emeryville, CA. The hydrogen release was avoidable in both the root cause and contributing factors. The report summarizes the findings of the incident investigation and metallurgical analysis of the failed valve. Hydrogen embrittlement, manufacturing quality as well as miscommunication played significant roles in the event. No injuries or fatalities resulted from the incident.

Pressure Relief Devices for High-Pressure Gaseous Storage Systems: Applicability to Hydrogen Technology

“…Once diffused, the hydrogen forms areas of embrittlement, such that it weakens or "embrittles" the metal by reducing ductility and promoting cracking. Three main factors that can affect the magnitude of hydrogen embrittlement are material, environmental conditions, and mechanical loads or stresses [11]. Higher-strength steel alloys, which are typically used in high-pressure applications for other gases, are known to experience a greater loss in ductility when used in hydrogen service than lower strength steels do.…”

“…Minimizing stresses in the element will prevent failure resulting from hydrogen embrittlement, as the metal will still retain some level of ductility. Materials recommended for hydrogen service include 300-series stainless steels, copper, and brass, as they are the least susceptible to hydrogen embrittlement when exposed to the gas for prolonged periods [11].…”

A probabilistic visual-flowcharting-based model for consequence assessment of fire and explosion events involving leaks of flammable gases

“…1 The dominant root causes of those leakage incidents in the U.S. HRS were fatigue of filling hoses and pipe welds, use of nonconforming material for components such as pressure relief valves, and poor maintenance of filling hoses, etc. The AC transit HRS in Emeryville, California was a good example of material incompatibility as the root cause of H 2 leakage incident (Harris and San Marchi, 2012).…”

Review on the effects of hydrogen at extreme pressures and temperatures on the mechanical behavior of polymers.

“…There are already approximately 500 light-duty, 250 heavy-duty, and 3000 industrial (hydrogen) fuel cell powered electric vehicles operational today 1 . In addition, there are 58 active hydrogen fueling stations in the U.S. and 143 fueling stations worldwide 2 .…”