LH2 tank cracking

During transfer of LH2 from a 200,000 gallon (760 m3) storage vessel to a road trailer, loss of vacuum was detected due to a crack in the outer vessel. The crack was located below an elbow of the 6” diameter pressurisation line. The probable cause of the crack was the formation of liquid air dripping onto the outer vessel.

The INITIATING CAUSE was the failing of outer thermal shield of the vessel, due to thermal cold shock.
During the transfer operation liquid air formed on the vertical run of the pressurisation line, ran down the pipe and then dripped of the elbow onto the vessel. The vertical run did not have drip trays to collect liquid air and the crack formed where the liquid air dropped.
Probable ROOT CAUSE was an installation error (a missing drip tray supposed to be there) or a design error (a not-foreseen safety component).

connection, LH2 vessel

The report does not specify the application. It is highly probable that it was a loading of a road tanker at the hydrogen production facility.

It is unknown if the vessel had to be vented, or mitigting actions were availale to continue the transfer without loosing the whole stored quantity.

The LH2 was transferred and the inner vessel purged with hot N2 gas. also positive and vacuum pressures were applied. The annular space was brought up to atmospheric pressure and filled with N2 gas. The crack was then repaired.

The consequence of the loss of thermal insulation capacity on the cryogenic vessel are unknown. The most probable immediate effect would have been the increased boil-off and internal pressure, with the need to vent. However, it is unknown if the whole vessel content had to be vented, or mitigating actions would have allowed to repair the crack and re-install the vacuum without major content loss.