17 May 2005 21:19 [Source: ICIS news]
HOUSTON (CNI)--BP Tuesday attributed a deadly explosion at its ?xml:namespace>
“The mistakes made during the startup of this unit were surprising and deeply disturbing. The result was an extraordinary tragedy we didn’t foresee,” said Ross Pillari, president of BP Products North America. “We regret that our mistakes have caused so much suffering. We apologise to those who were harmed and to the
BP said it is firing or otherwise disciplining supervisory and hourly employees who were directly responsible for operation of the isomerisation unit on the day of the blast and on the previous day.
The 23 March explosion and fire killed 15 contract workers and injured more than 170 people.
According to a BP interim accident report made public Tuesday, the explosion occurred because isomerisation unit managers and operators greatly overfilled and then overheated the raffinate splitter, a tower that is part of the isomerisation unit.
The fluid level in the tower at the time of the explosion was nearly 20 times higher than it should have been, the report said. The presence of water or nitrogen in the tower at start-up may have also contributed to a sudden increase in pressure that forced a large volume of hydrocarbon liquid and vapour into the adjacent blow-down stack, quickly exceeding its capacity. The resulting vapour cloud was ignited by an unknown source.
If unit managers had properly supervised the start-up or if unit operators had followed procedures or taken corrective action earlier, the explosion would not have occurred, a BP investigation team said.
The number of deaths and injuries was increased by the presence of workers in temporary trailers near the blow-down stack and the failure to evacuate personnel when it became apparent pressure was building in the unit and that vapours were being vented to the atmosphere, the report said.
The investigation team also said the use of a flare system, instead of a blow-down stack, would have reduced the severity of the incident.
BP has already prohibited occupancy of trailers within 500 feet of blow-down stacks and flares and non-essential personnel are being moved out of process areas, Pillari said.
BP said it will modify or replace all blow-down systems which handle heavier-than-air hydrocarbon vapour or light hydrocarbon liquids (gasoline and lighter).
“We will move expeditiously to modify these units,” Pillari said. “Before work can begin we must complete engineering design and obtain permits and materials.”
BP said it is taking disciplinary action against supervisory and hourly employees directly responsible for operation of the isomerisation unit on 22 and 23 March. The actions range from warnings to termination.
“As the investigation continues, and as new information is discovered, others also may be disciplined,” BP said.
“The failure of [isomerisation] unit managers to provide appropriate leadership and the failure of hourly workers to follow written procedures are among the root causes of this incident. We cannot ignore these failures,” Pillari said. Unit supervisors did not verify correct procedures were being used by unit operators and were absent from the unit during critical periods. Unit operators failed to sound evacuation alarms, contributing to the severity of the incident, BP said.
The Chemical Safety and Hazard Investigation Board (CSB) was briefed on the report. Lead CSB investigator Don Holmstrom said: “The report’s recommendations to change from an open-air vent stack system to a closed system utilising a flare to burn off any dangerous vapours, and to remove personnel trailers away from potential harm, are prudent ones, in keeping with good refinery design and practice.”
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