Release of LH2 during transfer

During preparations for off-loading of a commercial tanker, the trailer experienced an overpressure causing the 50 psig (ca. 3.5 bar) relief valve to open and also the rupture of the 70 psig (ca. 4.8 bar) burst disc. Hydrogen was vented through the vent valve and the disc. A vapour cloud of about 25 feet in diameter resulted. Examination later also showed cracks in the carbon steel vent line.

[Ordin, NASA (1974)]

The liquid phase valve into the trailer transfer build-up coil was opened prior to opening the gas pressurization valve. Opening the pressurization valve resulted then in unrestricted large flows into the tank causing excessive pressures which opened the relief valve and ruptured the burst disc. Vibrations during transit may have caused the liquid phase valve to open. The trailer was almost completely full of liquid hydrogen which contributed to the accident. The flow of cold fluid caused the cracks in the carbon steel vent line.

PRV; burst disc