At 6:58 a.m., a fire broke out on a refinery’s thermal cracking unit after hydrocarbon residues leaking from a pump had ignited. The unit’s emergency stop was activated. The refinery’s firefighters, who had arrived a few minutes earlier because of the leak, extinguished the fire at 7:15 a.m. The unit was offline for 51 days.

The unit’s fractionating column can be supplied with hydrocarbon residues by two pumps (referred to here as ‘A’ and ‘B’). The fire followed a series of malfunctions that occurred on these pumps:

• At around 4:40 a.m., pump B’s ‘low oil level’ and ‘high temperature’ alarms went off while it was running. The column’s supply was switched to pump A.
• At around 5:00 a.m., a technician noticed that pump A was vibrating. Its ‘high temperature’ alarm went off at 5:17 a.m.
• At 5:47 a.m., the column’s supply was switched to pump B. A leak was found on its mechanical seal, but was deemed acceptable.
• At 6:40 a.m., the column’s supply was switched to pump A because the leak on pump B became too large. Hydrocarbon residues began leaking from pump A at 6:48 a.m.

The operator identified multiple failures:

• The mechanical seal on pump B did not match the technical specifications.
• The coolant on pump A’s mechanical seal had not been cleaned often enough. It was fouled and clogged.
• The maximum oil temperature for starting the pumps was not defined.
• The lack of a sensor made it difficult for technicians to detect abnormal vibrations.

The operator replaced the pumps’ seals, reshaped them, and added a ‘very high temperature’ alarm and a vibration sensor. He plans to fit them with double seals by 2020.