Fire caused by tube trailer roll-over

A tube trailer was returning to the basis after having delivered compressed hydrogen to a customer site. The vehicle was operated by two drivers taking turns in driving.
While traveling on a highway, a light four-wheeled vehicle overtook the vehicle from the rear on the right and entered the path of the container transport vehicle, so the tube trailer had to brake and perform a sudden change of direction to avoid the other vehicle. It collided with the shoulder of the embankment, rolling-over and crashing into the riverbed.
The mechanical impact with the ground shock caused the blind flange of the tubes manifold to break, releasing hydrogen which first exploded and then produced a fire , which burned most of the vehicle.
The blast damaged the windows of several dozen houses about 30 m away.
The fire caused injuries to the two drivers.
There was only about 40 m3 of gas in the trailer. If the incident would have happened when transport a full load, the consequences would have been worse.

The INITIATING CAUSE was a traffic accident causing a roll-over of the trailer.
The ROOT CAUSE had two components: a human error causing the traffic incident and a lack of efficient protection of the pressure control system of the trailer, which was not designed for these of foreseeable impacts.

manifold valve,
tubes

The hydrogen transport consisted in 15 tubes, each with a capacity of 270-liter. This gives a max capacity of approximately 58 kg of hydrogen.
The gas volume at time of filling was approximately 610 m3, at a pressure of 150 bar (51 kg).
However, on the return journey there was only about 40 m3 of gas remaining in the trailer (3 kg).

A road accident causing a heavy duty vehicle to roll-over is a regularly reported event. Several administrations and also international global technical regulations require on the type-approval of a vehicle to pass a roll-over tests without major consequence. In this incident, the protections provided to the on-board pressure control system were inadequate to protect it from mechanical impact coming from a roll-over. Nevertheless, this incident occurred in the years 60’s, when the return of experience from this type of incidents could not have been developed yet. On the contrary, It is probable that the collection of these incidents contributed to the development of a better safety design.