Since the fire broke out the day before the start of a planned turnaround, the process plant was depressurised, drained and purged with inert gas.
One of the turnaround activities involved replacing the inlet separator’s internals. The fire started in connection with preparatory activities ahead of entering the separator.
Rough cleaning of the separator had been completed and it was being vented when the incident occurred. Analyses of the separator contents after the fire revealed the presence of iron sulphide.
The PSA team’s view is that the fire was caused by spontaneous combustion of iron sulphide in contact with the air, which then ignited oil deposits remaining in the separator.
It emerged from the investigation that iron sulphide was not known to be present in the separator. Nor did anyone know about the problem posed by pyrophoric iron sulphide. No measures for handling this as a potential ignition source had therefore been assessed or implemented.
The actual consequence of the incident was a fire lasting for about three hours in the inlet separator on Snorre B. Subsequent analyses show that the integrity of the actual separator had not been weakened by the fire. No personal injuries were suffered in connection with the incident. The wind direction was favourable for avoiding smoke exposure.
Where potential consequences are concerned, the fire was unlikely to spread beyond the separator. The process plant had been depressurised and drained in connection with the turnaround, and no other flammable materials were in the vicinity. However, the incident could have had more serious consequences had the fire broken out when personnel were inside the separator or the wind direction was more unfavourable, so that exposure to smoke could have been greater.
No assessment had been made of the waste as a potential ignition source, with no special measures therefore implemented to prevent spontaneous combustion when handling or transporting it. However, it emerged from interviews that this material was treated as low radioactive (LRA) waste, which means it is kept moist, and thereby also indirectly prevented the iron sulphide in the waste from igniting. The team therefore considers it unlikely that handling of the waste could have resulted in a fire elsewhere on the platform.
The investigation has identified three nonconformities related to:
- risk assessment before starting the activity
- experience transfer
What happens now
Equinor has been asked to explain how these nonconformities will be handled. The deadline for its response is set at 20 September 2019.