Leak from a CGH2 cylinders truck

A truck transporting a pallet of 30 compressed hydrogen cylinders was traveling on a highway when gas started leaking from the welded pipe. The fire department ordered the hydrogen to be released to the atmosphere. The leak was caused by poor construction of the brazed welded pipes.

The INITIATING CAUSE was a leak from pipe welds.
The KHK report identified the ROOT CAUSE in the bad welding quality (manufacturing cause). The road vibrations as contributing factor cannot be excluded.

weld, pipe

The driver called the alarm number because he was not able to extinguish the tyre fire.
Meanwhile the LH2 tank over-pressurised, the pressure relief valve activated and the escaping hydrogen ignited.
The first responders were able to extinguish the fire by using a "helium fire abatement system'. The source does not specify what this system consists of. It may implies the use of a non-freezing inert gas system. Anyhow, they avoided the risk of blocking the pressure relief valve due to water freezing.
6 hours later, a company employee arrived to the site performed a controlled venting, to reduce the pressure to a safe level and to allow the PSV to reclose. The intervention was successful and the pressure reduced from approximately 170 psi (11.7 bar) to 3-5 psi (0.2 – 0.3 bar).

During the incident, the highway was closed in both direction. The trailer was moved off of the interstate 9 hours after the start of the incident, and the traffic resumed a couple of hours later.

The bad quality of the brazed weld of the piping system was given as root cause. Nevertheless, road vibrations cannot be excluded as contributing factor.
A welded connection can be performed well enough to operate safe in stationary applications, while not resisting to stress and stress frequency typical from road vibrations. Several en-route connection failures in the PHMSA database are attributed to road vibrations.
This incident occurred in the 60’. More recent regulations prescribe minimal resistance requirements for components exposed to mechanical vibrations.