Explosion on the pressure release device of a hydrogen supply unit

The explosion followed a hydrogen leak on a unit conditioning hydrogen.
The accident was caused by the mechanical rupture of a pressure regulator diaphragm on a section of a hydrogen line that included the dual-stage regulator, shut-off valves, and connecting flanges.This section of the hydrogen line had the purpose to reduce the hydrogen pressure from 220 to 50 bars and further to 3 bar and to supply it to an area for the conditioning of semi-trailers.
The fire was extinguished by powder-based fire estiguishers and by stopping the supply of hydrogen. FInally, the nitrogen was injected in the system..

The INITIATING CAUSE was the mechanical failure of a pressure reduction device.
The ROOT CAUSE is unknown.

hydrogen supply line, pressure reducer, hydrogen conditioning unit

The damage was confined to the pressure reduction unit of the hydrogen line, on a ground surface of 4 m².

A deflagration occurs following a hydrogen leak and its inflammation on a unit conditioning hydrogen. The fire is extinguished by the workers and hydrogen feeding is closed. The installation is stopped and placed under nitrogen.