Release from a LH2 tanker

A liquid hydrogen tanker was travelling on a highway, when the driver noticed vapour exiting the rear tanker cabinet. The driver stopped the vehicle in a safe location and discovered that the vapour return valve was not sufficiently closed. The driver tightly closed the valve and the vapour leak was secured. The trip was completed safely without any further incident.

The INITIATING cause was the vapour return valve not properly closed, similar events have been attributed this to road vibrations.

The ROOT CAUSE was a design which did not took into account the whole range of mechanical solicitations which the pressure control system of the trailer could experiment when travelling.

valve

The driver closed the vapour return valve stopping the leak.

This incident is very similar to other, such as the 070, which attributed to road vibrations the opening of the vapour return valve.

Independently from the root cause, releases of hydrogen in the control cabinet can generate flammable mixture with explosion potential, as found out by J. Song et al., Hydrogen leakage and diffusion in the operational cabin of hydrogen tube bundle containers: A CFD study, International Journal of Hydrogen Energy 88 (2024) 986–1002.
The passive ventilation of the involved cabinet is unknown, however, the fact that the driver opened it without further precautious measures indicated a lack of attention to explosion hazards.