Explosion and fire in a fertiliser plant

The explosion occurred in the compressors unit of the plant. Witnesses reported a cloud of yellow smoke and a fire ball at its bottom.
This first event was followed by a fire fed by a hydrogen pipe (5.5 t of hydrogen was present in the system). The fire brigade confined it until its natural extinction.

A negligible amount of ammonia was probably released to the environment. No injured but a considerable materials damage: the plant remained closed for one week and specialised work had to be done for the removal of asbestos contained in a wall which was destroyed by the explosion.
It is suspected that the cause of the first incident was a weld on the hydrogen pipe which failed due to fatigue.

The INITIATING (or the contributing) cause is suspected to be the failure of the welding of the hydrogen pipe.
Nothing is known on the root cause, but the organisation has continued the operation, while not able to identify the original of the incidents.

compressor, hydrogen pipe, ammonia reactor

other small incidents had occurred during the preceding 7 days : the plant was shut down one week before due to the malfunctioning of a compressor and a boiler. When restarting a small explosion had occurred. The plant was restarted 2 days later and stopped again the next day due to the malfunctioning of an other compressor. After one day of control, the plant is again restarted and the main explosion occurred.

Asbestos was released by the destruction of a wall. Analysis were made to determine if welded part were strained.

14.30 detection of the leak. Area secured,
19:15 Isolation of the pipeline section
20:00 Start controlled emptying
23:00 Pipeline pressure at zero, start of nitrogen injection
Day after: repair of the leak