Fire on a hydrogen cylinders rack

A release of hydrogen occurred during the filling of a 28 bottles rack. A worker decided to move the rack from one station to another, due to works ongoing nearby. This movement, even though the hose had remained connected to the rack, caused the bracket to break and the compressed hydrogen to leak. The jet was directed against the barrel of cylinders.

Hydrogen sensors triggered the shutdown of the installation, including the closure of the feeding valve.
The worker detached the flexible and started moving the rack towards the water supply. During its route around the building, the leak ignited. He secured the rack on the ground and gave the alarm.

The INITIATING cause of the hydrogen release was the pulling away of the rack during filling.

According to the ARIA report (see references), the formal accident investigation found out that the configuration of the filling station did not provide a clear view of the filling hose connection (see lesson learned for corrective actions).

compressed hydrogen storage, cylinders rack, flexible connection

A 28 bottles rack was being filled with compressed hydrogen on a secondary station. The principal station was closed due to works in the surroundings.

A) Following the alarm given by the worker, the safety crew began by sprinkling the rack with the fire hose, notified external first responders and manually activated the emergency shutdown: H2 production was halted and nitrogen purging of sensitive installation parts was initiated.

B) When fire-fighters arrived 15 min later, the rack had emptied and the fire had stopped burning. Nonetheless, sprinkling was continued due to the very high temperature of the bottles, whose barrel remained incandescent until an infrared pyrometer became available on-site to evaluate the bottle wall temperature. The entire facility was evacuated. An hour later, with the rack temperature dropping to 25°C, the alarm was lifted..

The ARIA report (see references) mentions the following corrective actions:
0) the secondary station must be eliminated;
1) the connection between the station and the compressed hydrogen cylinders has to be made visible;
2) Creation of a safety zone where to isolate defective racks or pallets in case of accidents;
3) Purchase of an infrared pyrometer;
4) Installation of a restraint cable fixing ring to the racks;