Fire on a liquid hydrogen tanker

A LH2 trailer was delivering at a customer’s site. Just after having terminated the transfer to the stationary tank approximately 13000 gallons (3500 kg) of liquid hydrogen, the pressure relief valve on the trailer activated at a tank pressure of approximately 120 psig (8.4 bar). The tanker was rated for 150 psig (9.7 bar). The venting hydrogen ignited.
The two tanks were still connected with the transfer hose. The driver immediately isolated the trailer and the customer storage tank and then called 911. The local fire department put in place an extensive emergency area, by evacuating residents and shutting down traffics.

The INITIAL CAUSE was the premature opening of the pressure relief valve.
ROOT CAUSE is unknown. It would require a detailed investigation on the cause of material failure.

PRD

The tanker had just terminated the transfer of LH2 to the customer's stationary tank.

[Note of HIAD event validator: the PHMSA individual report has a wrong value of 126,000 cubic feet of LH2 delivered, but the correct value appears in the column dedicated to tank capacity]

Over 300 local residents were evacuated, but no one was injured.
Approximately 30 kg of hydrogen were vented to the atmosphere.

Over 300 local residents were evacuated in a a radius of 800 m. The traffic on the nearby highway stopped for 2 hours and the railway traffic was reduced, to allow the fire fighters to intervene using that area. The emergency management was performed using the EPA software CAMEO (https://www.epa.gov/cameo).
Nothing is known on how that leak was stopped. Since the tanker was almost empty, it can be assumed that it was decided to let the fire extinguish by itself, and then simply driving away.

Premature activation of pressure relief devices is a regular cause of hydrogen release. It is usual due to ageing of the devices material, which could have several causes: wrong choice of the design materials, lack of inspection/maintenance, error in replacing sub-components, by not using the ones certified/specified.