Hydrogen release from a liquid hydrogen tank

The release affected a cryogenic vessel used for liquid hydrogen storage at a manufacturing facility. The burst disc opened releasing hydrogen through a vent stack located between approximately at 5-6 m above ground.
The cryogenic hydrogen storage tank had an insulation jacket, but it had been idle for a long time. Therefore, the heat transfer through the tank insulation had caused the evaporation of liquid hydrogen enough to increase the pressure beyond the design pressure of the burst disc.
After the opening of the burst disc, the hydrogen was released to the environment through the stack without further consequences. It did not ignite.
Approximately seven months after the replacement of the burst disc, the new burst disc prematurely ruptured for the same reason.

The INITIATING CAUSE was a natural increase of the internal pressure of the cryogenic tank.
The burst disc and the venting system operated safely and as expected .
The fact that the tank was left idling without inspection suggests that operator thought that the vacuum jacket eliminated the heat transfer, while in reality, it only reduced it.
The ROOT CAUSE is probably related to lack of maintenance and/or of knowledge of the operation of a cryogenic tank.

burst disc

The ambient temperature was approximately 16 °C (60 °F), the cryogenic hydrogen was approximately at −250 °C (−418 °F)

No injuries or damage. The hydrogen safety venting equipment functioned properly.

No injuries or damage. The hydrogen safety venting equipment functioned properly. A technician of the gas supply contractor was called and found the tank pressure at zero and the burst disc blown. He switched the three-way diverter valve to the other safety relief device and replaced the burst disc when the line defrosted.

A cryogenic vessel will always produce some boil-off gas even with the insulation jacket. This requires frequent inspection and, potentially, manual venting. Moreover, a pressure relief device able to release the excess this boil-off gas and to maintain the internal pressure below the design value should be always present.

(specific)
After a second burst disc opened seven month later, the cryogenic storage was equipped with some modifications with a system (not further specified) which eliminated the building of pressure on the burst disc.

(general)
(1) Liquid hydrogen installations should be inspected by facility personnel on a regular basis and according to existing regulations, standards and guidelines.
(2) Also the manufacturing of liquid hydrogen storage systems should follow the related requirements from existing technical regulations and standards.
(3) Hydrogen safety training should be provided to local emergency responders.