Fire from a CHG2 trailer during filling

The incident occurred at the site of a gas production company.
During the filling of a compressed hydrogen trailer, an end plug thermal pressure relief device (TPRD) had an unplanned activation. The released hydrogen vented through a leak in the vent manifold of the TPRD venting system, which appeared to be improperly assembled.
The ignition of the hydrogen caused significant damage to the trailer and damage to the another trailer which was being filled alongside the affected trailer.

The INITIATING CAUSE was the unexpected activation of a thermal pressure relief device. The reason for this failure is not reported.
The hydrogen released by the PRD would have been vented without further consequence, if the venting system would not have failed at the manifold.
Therefore, the ROOT CAUSES were a combination of a material failure and a wrong installation of the venting system manifold.

TPRD, vent manifold

Two other trailers experienced TPRD failures in a similar fashion before, but on separate occurrences and no resulting fire or damage.

DESCRIPTION OF THE UNIT
The trailer consisted of 50 tubes of type 3, with a composite external shell and a metallic liner.
Specification According to the manufacturer:
nominal pressure 520 bar / 7,500 psig
Cylinder Water Volume 315 litres / 11.1 scf
Total Water Volume 15,750 liters / 555 scf
Hydrogen Capacity 501 kgs / 211,690 scf
(source: https://bayotech.us/bulk-hydrogen-transport-trailers/).
According to PHMSA, the quantity were lower:
Capacity 780 gas-pound (350 kg)
Quantity (300 kg)

Significant damage to the trailer and damage to the another trailer which was being filled alongside the affected trailer.

Recommended actions: 1. Recall all valves and end-plug TRPDs related to the production lot(s) that have failed to prevent reoccurrence.
2. Valve manufacturer needs to implement a verifiable quality control program for all future valves.
3. Vent manifolding should be pressure tested by the trailer manufacturer before shipping to customers, to identify and fix possible vent manifold leaks.