Fire from a CGH2 tube trailer just loaded

A compressed hydrogen tube trailer was fully loaded and parked in the sun. The heat caused a pressure build-up, so that a burst disc failed prematurely venting hydrogen, which ignited.
13,360 cu ft (approximately 32 kg) of hydrogen were released.

[Zalosh and Short, 1978]

The INITIATING CAUSE was the premature failure of the burst dis.

A CONTRIBUTING CAUSE was the increase of hydrogen pressure in the tubes of the trailer caused by heat flow from direct sun exposure
The fact that the a common environmental condition such as sun exposure was enough to cause a disc to one, suggests CONTIBUTING or ROOT CAUSE possibly related to (i) not fully respecting operative instructions , or (ii) lack of attention to the over-heating aspects in the operative instructions (shortcoming in accidental scenarios setting and risk assessment).

burst disc

The emergency measures were taken effectively. The fire was completely extinguished approximately 1 hour after its start.

The safety procedure (automatic pressure-relief due to over-pressurisation) worked as designed, preventing the pressure inside the tubes to increase beyond the maximal allowed values.
Although the source does not provide any detail, the fact that only 32 kg of hydrogen were released suggests that only one of the tube vented and emptied, while the others did not experienced a pressure excess. (30-35 kg is the usual capacity of a steel tube used typically for the transport of hydrogen in the period when the event occurred).