Release from a LH2 tanker during transfer

The incident happened during a liquid hydrogen delivery at a customer site. When the drivers were pressurising the tanker preparing for hydrogen transfer, the safety relief system rupture disc failed prematurely. The released gaseous hydrogen ignited.
The drivers quickly activated the vent system fire abatement system and extinguished the flame and allowed the venting pressure to reduce. When the pressure was stabilised, they switched the pressure control system to the secondary pressure relief system and continued their product delivery without any further incident. The primary rupture disc was replaced upon return to the home terminal.

The INITIAL was an a premature burst of the pressure relief burst disc.
The drivers were able to mitigate consequences by following the procedure for these cases. They were clearly well trained and the procedure was effective.
It unknown if the burst disc was damages, aged, wrongly installed or of the wrong materials.
Therefore is the ROOT CAUSE unknown.

burst disc