Leak from a CGH2 trailer

A CGH2 trailer-tractor arrived at a customer’s site for delivery. When stopping at gate and coming out of the cab, the driver noticed a noise coming from the rear of the trailer. The driver opened the rear cabinet door and found a pigtail line cracked. Hydrogen was leaking from the shut-off valve and to a minor extent from the crack. The emergency team on the customer site washed the rear of cabinet until the delivery company expert arrived on the scene. The expert cut and crimped the cracked line. He then placed a block in the valve to secure the leaking tube. The driver did not execute the delivery and returned the full trailer to the home site without incident.
The investigation revealed that road vibration had caused the line to the pigtail to crack. The pigtail and valve seat were replaced and the trailer was brought back to service.

The INITIATING CAUSE were road travel vibrations damaging a pigtail connection in the trailer pressure control cabinet.

The ROOT CAUSE was shortcoming in the design, and possibly also in the installation of the pigtail – valve connection.

pigtail, valve

The traffic was closed.
An employee of the company responsible for the hydrogen transport visited the site with a thermal imagining camera to make sure that the site was safe and that there would be no further fires or explosions

Simulation studies have shown that a leak inside the trailer control cabinet could cause the formation of a flammable atmosphere. In this case, it is probable that the hydrogen flow of the leak was very small and allowing dispersion in place of formation of a flammable gas mixture.
Nevertheless, the cabinet should be handled as an explosive atmosphere zone and preventing/mitigating measures have to be taken into account in its design. Moreover, a procedure should be in place, which allow the driver to understand what is happening in the cabinet without having to open manually the cabinet door, an action which could provide the ignition energy to a hydrogen-air mixture.