By OGJ editors
HOUSTON, May 18 -- A BP PLC investigative team concluded that personnel failures before and during start-up of an isomerization (isom) unit in the 446,500 b/cd Texas City, Tex., refinery led to the Mar. 23 explosion and fire that killed 15 workers and injured more than 170 others (OGJ Online, Mar. 23, 2005).
BP Products North America Inc. on May 17 issued an interim fatal accident investigation report by a team of BP executives, BP refining and safety experts, salaried employees, and union employees.
The team concluded that isomerization unit managers and operators overfilled and overheated the unit's raffinate splitter.
The tower's fluid level was nearly 20 times as high as it should have been, the report said. The presence of water or nitrogen in the tower at start-up also might have contributed to a sudden pressure increase that forced a large volume of hydrocarbon liquid and vapor
into the adjacent blowdown stack, exceeding its capacity. An unknown source ignited a resulting vapor cloud.
"If isom unit managers had properly supervised the start-up or if isom unit operators had followed procedures or taken corrective action earlier, the explosion would not have
occurred," the investigation team said.
The number of deaths and injuries was increased by the presence of workers in temporary trailers near the stack and the failure to evacuate personnel when it was apparent that pressure was building in the isom unit, the report said.
The decision to place trailers near the stack was preceded by hazard reviews that did not recognize the possibility that multiple failures by isom unit personnel could result in such a flow of fluids and vapors to the stack, the report said.
The investigation team also concluded that the use of a flare system, instead of a blowdown stack, would have reduced the severity of the incident.
"The mistakes made during the start-up of this unit were surprising and deeply disturbing," said Ross Pillari, president of BP Products North America. "The result was an extraordinary tragedy we didn't foresee."
The company intends to "provide fair compensation without the need for lawsuits or lengthy court proceedings," he said. Company attorneys have started contacting attorneys for the families of the deceased to begin evaluating and settling claims.
The investigation team published an interim report because pending fluid sample analysis and computer modeling are not expected to change the causes or recommendations.
"We have accepted the report and its findings, and we will implement the team's recommendations," Pillari said. "Some will take time to complete. However, refinery management did not wait for this report to take action."
Managers clarified and reinforced roles, responsibilities, and expectations around start-up, operating, and evacuation procedures, he said. They prohibited the occupancy of trailers within 500 ft of blowdown stacks and flares. Nonessential personnel are being moved out of process areas.
In addition, the company will commission a third party-led facility study to make recommendations for the safe placement of temporary structures.
"Our goal is to eliminate or greatly reduce the need for temporary buildings at the refinery by limiting the workforce in process areas to operators and people involved in hands-on maintenance," Pillari said. "We are assessing space needs for workers whose jobs require them to be located at the refinery."
BP will modify or replace all blowdown systems that handle heavier-than-air hydrocarbon vapor or light hydrocarbon liquids (gasoline and lighter). Meanwhile, the company has instituted additional operating requirements to ensure those systems are safely operated until they can be modified or replaced.