Explosion in the hydrogenation reactor of a chemicals manufacturing plant

Explosion in a chemical manufacturing plant for the pharmaceutical and cosmetics industries, classified as Seveso high level,

The explosion occurred in the hydrogenation reactor, when opening two buffer tanks to clean the reactor the after hydrogenation using a catalyst (ruthenium on coal).

Following the explosion, the operator initiated the emergency plan, evacuated personnel and secured the area. Two operators were injured.

According to the ARIA source, the explosion was probably be due to the presence of hydrogen in the reactor, because the nitrogen purging was not performed despite the procedures in place. The flammable mixture created by the entrance of oxygen at the opening of the buffers, was then ignited by a hot spot formed by a catalyst deposit which probably had become pyrophoric after activation.

INITIATING cause of the explosion was the presence of hydrogen when opening to air the tank.

Intermediate cause was the failing to apply the procedure to purge the tank with nitrogen.

ROOT CAUSE is unknown, because it is not known why the procedure was no followed.

hydrogenation reactor, buffer tank

The incident started when tanks for cleaning.

Two operators in the vicinity of the reactor at the time of the explosion were injured.
The system was not damaged.

An additional measure, not mentioned in the ARIA report, would come from answering the question on why the procedure was not followed, and what can be put in place to guarantee/monitor that they are followed in the future.

The operator introduced the following two improvements
1. Review and re-assessment of the operative procedures
2. new training of the workers.