multiple collisions involving a CGH2 tube trailer

Motorway accident which involved a large quantity of vehicles and a gaseous tube trailer which transported gas hydrogen in pressure. Some cars were burning under the back part of the gaseous tube trailer. (for details see source).
The fire brigade team used a thermo-camera to assess the situation, finding that in proximity of the valves of the lowest containers there was flame, and there was an hydrogen release which was burning (jet-fire). One of cylinder was deformed in correspondence of tractor’s wheels. To reduce explosion risk the fire brigade team decide to cooling deformation point with maximum priority.

By monitoring the flame evolution with the thermo-camera, and identifying when the jet-fire was reduced, the fire brigades decided to proceed to the definitive turning off of the releasing valve.
This operation of was performed with the aid of two crossed water throws. The definitive extinction of the flame could be verify by means of a thermo camera.

The ROOT CAUSE was the development of a fire due to a road accident.
This damage of one or more cylinders of the hydrogen trailer, and the release of hydrogen from the a valve and from a crack on the cylindrical side of one cylinder.

tube trailer, Compressed hydrogen cylinders, multiple vehicles

One cylinder cracked and an additional one deformed.

(as issued by the first responders):

1. Lack of equipment to evaluate pressure inside the cylinder gaseous tube trailer.
The knowledge of the pressure inside the cylinders is critical in case of accident, to assess the gas quantities involved and the filling of the storage system. The present gaseous tube trailer design does not allow for, due to the fact that the manometers installed on the cylinders’ heads are the most fragile elements and therefore are the first equipment that break. Even when still functioning, they are difficult to be read at a certain distance, and are often shadowed by other components.

2. Lack of protection in the back part of the tube trailer.
All the valves for the load/unload of the gas were installed at the back of the trailer. They consist of connecting pipes, collector final valves of a pneumatic valve for The remote control of all manometers. These components are not well protected in case of road accident. There is only a steel plate protecting the components from meteorological phenomena. Mechanical accidents at the rear can cause damage to the valves with consequent possible release and prevention of their confinement function. Fires can further damage the functioning of these components.

3. Lack of a mechanical system allowing the simultaneous closing of all the valves.
Every cylinder had with a manual closing system by means of a proportional valve with bolt in brass and joint elements in Teflon. All the valves were connected via piping to two manual valves. According to the ADR normative all the valves during the transport must be in closing position. There is however no control system which allows to check automatically that the valves are really closed.

4. Lack of protection among the trailer wheels in rubber and the cylinders.
The trailer/tractor components with the greater fire potential are the tires and the fuel. In case of road accident with fire, the heat develops quicker and more heavily around the anterior parts of the cylinders of tube trailer. This may cause the pressure increase in the cylinders beyond their burst pressure value.