Road incident CGH2 tube trailer

This accident happened on the SS66 road and involved a trailer transporting compressed hydrogen cylinders. The 50 l cylinders were in packages of 16 cylinders each.

Due to the breaking of fixing straps, cylinder packages fell on the middle of the road.
The damage to the gas collector of the package and to some cylinders valves caused a gas release with consequent deflagration, with consequent damage to the first vehicle following the truck and to the glass door of house in the vicinity

The INITIATING CAUSE was the breaking or loosing of the fixing strap, which caused one or more H2 cylinder packages falling from the truck.
Damage to some the cylinder heads caused release and consequent ignition.
The ROOT CAUSE lies in the design of the design supposed to guarantee the integrity of the transport. It is not only about the shortcoming of the strapping system, but also about protecting critical safety elements of the cylinders packaging.

Truck, cylinders rack

The truk was travelling on a city road.

DESCRIPTION OF CARGO
Each package had a capacity of approx. 12 Kg. Assuming that they were all full, full damage to one package would have released its total quantity. it is however not possible to deduce from the photo how many cylinders' valves failed.

Considerable damage to the first vehicle following the truck and to the glass door of house in the vicinity.
The photo in the reference shown three packages of 16 cylinders each fallen from the truck. Only one having lost all its cylinders.

The fire brigade cooled the cylinders with by nebulized water. At the same time, they evacuated two persons that were working in the vicinity and closed the road to the traffic.
A thermal camera allowed to assess the temperature of the cylinders, therefore assisting the cooling of the hot spots.
The last operation was the emptying of the of the cylinders under jets of nebulized water.

The analysis of this accident has revealed the followings critical points which shall be used as recommendations:
1. Lack of a system indicating the pressure inside the cylinders.
The knowledge of the pressure is critical for the formulation of the correct rescue procedures.
2. Lack of a system visualising/confirming that all the cylinder valves are closed.
All valves should be closed during transport. If however a valve was forgotten open, a damage to the gas collector will be enough to release the whole content of that cylinder.
3. The package design did not offer the structural resistance required to protect the cylinders in case of fall-off the trucks.