June 1, 2005

'Deeply disturbing' errors led to BP plant blast

The overfilling and then overheating of a tower during the startup of the Isomerization (ISOM) process unit in BP's Texas City refinery led to a 23 March explosion and fire that killed 15 workers and injured more than 170 people, according to a BP Products North America's interim fatal accident investigation report.

"The mistakes made during the startup 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 explosion occurred because BP ISOM unit managers and operators greatly overfilled and overheated the Raffinate Splitter, a tower that is part of the ISOM unit, according to the report. The fluid level in the tower at the time of the explosion was nearly 20 times higher than it should have been.

The presence of water or nitrogen in the tower at startup may have also contributed to a sudden increase in pressure that forced a large volume of hydrocarbon liquid and vapor into the adjacent blow down stack, quickly exceeding its capacity. An unknown source ignited the resulting vapor cloud, according to the report.

If ISOM unit managers had properly supervised the startup or if ISOM unit operators had followed procedures or taken corrective action earlier, the explosion would not have occurred, the investigation team said.