Fire on a heat exchanger at refinery

The event occurred at a petrochemical plant, which was temporary shut down due to a staff strike. A visual inspection detected fumes under the heat insulation of a heat exchanger operating under hydrogen pressure. The unit, usually operated under a mixture of butane and hydrogen, was filled with hydrogen only, as prescribed according by supplier's instructions.
Since the smoke was an indication of an underlying fire, the first responders’ team was mobilised, and the unit was stopped, then depressurised and cooled down. A risk analysis was conducted before erecting a scaffold, removing the thermal insulation and inspecting the leaking component (a flange) under safe conditions. After having defined the fire protection and fire prevention strategy, the operator decided to put the unit back under pressure.
During this rise in pressure, a new fire on a flange justified the triggering of the emergency plan. The first responders’ team managed the fire.

No injuries or damage inside and effects outside the site.

The INITIATING CAUSE was a leaking seal on a flange. The ARIA report does not mention the conclusions of the inspection executed after the first fire. It is plausible to conclude from the text that no evident reason for the leak was found and was decided to bring back the unit to an operative status.
The report mentions a risk assessment, but it does not explain it, and misses the technical details needed to understand the unit operative status (why was the heat exchanger kept ‘warm’? And at which temperature?) and to perform a root cause analysis (was the leak due to differential thermal expansions?).

heat exchanger operating under hydrogen pressure

At the time of the accident, the plant was shut down due to a staff strike. The unit, usually operated under a mixture of butane and hydrogen, was filled with pure hydrogen according to supplier's recommendations.

No injuries or impacts outside the site are to be deplored. At the time of the accident, the plant was shut down due to a staff strike.

16:00 Fumes detected during a visual inspection. First intervention team is mobilized, the unit is stopped for depressurization and cooling.

Risk analysis performed, safety inspection executed,. A fire protection and fire prevention strategy defined and operation restarted by pressurising the system.

21:30 the emergency plan is put in place due to the restart of the fire
The intervention team manages the fire.

The action plan put in place to reduce the probability of re-occurrence of the accident implied:
1. A study of the possibility of cooling and re-pressurising the heat exchanger under helium or nitrogen,
2. A preventive replacement of all connections under hydrogen.
3. regular technical inspection.