LH2 leak from a stationary tank

A leak occurred near the bottom of a stationary liquid hydrogen tank with a capacity of a 6,000-gallon. The leak was localised on a valve and was visible due to the air condensation forming white clouds rosing upward and dissipating. Ignition did not occur.

Fire fighters tested hydrogen concentration in air around the leaking place and determined it to be safe. After which, plant workers shut off a secondary valve, isolating the leaking valve.
Preliminary investigations indicated that a faulty O-ring may have been the cause.

Nothing is known on the ROOT CAUSE. The fact that the leak was identified first at the bottom of the tank, and later also from the top of the tank (see reference), suggest a possible degradation of the thermal isolation capacity of the external shell of the tank. But it cannot be confirmed by unavailability of the investigation report.

tank

the quantity of hydrogen in the tank during leak is unknown.

The original emergency strategy of the company was to let the tank bleed. Eventually, the company called the local fire department. The onsite building, a neighbouring business and a residence were evacuated, and police blocked nearby streets. Major concern was the possibility to produce ignition source able to ignite the leaking hydrogen.