Explosion on a test bench for rocket engins

An explosion of hydrogen gas occurred on a test bench at a factory manufacturing rocket engins. The effect was perceived several kilometres away.

The explosion was caused by the release of 8 kg of H2 (equivalent to 100 m³ of gas) from a section of gas line a under maintenance. A 6-inch flange had been left open, in addition a remotely-controlled valve was opened accidentally. The explosion was followed by a jet flame fed by additional 16 kg of hydrogen gas (200 m³).

The protrective panels were blown off, and debris was scattered within a 100-meter radius of the bench. No injuries were reported, even among the six employees working within a 10- to 50-meter radius of the explosion.

THE INTIATING CAUSE was an accidental release from a compressed hydrogen supply system under maintenance.
The fact that to achieve this, two independently operated valves were opened, suggests that the ROOT CAUSE was not only due to a human error, but to shortcoming in the operative procedures prescribing what to do before and during maintenance. In fact, the hydrogen supply system affected by the explosion had just been used to a pupose different from its main application. it was probably not in the status expected by the team performing maintenance.

valves, test bench

During the day, the damaged test bench, mainly used for testing turbopumps and generators, had been used for one of its secondary functions: supplying gaseous hydrogen at 200 bar to another test bench. To this purpose, liquid hydrogen was first evaporated and then compressed to 800 bar.