11 April 2005 00:01 [Source: ICB Americas]
A team of US Chemical Sa-fety and Hazard Investigation Board (CSB) investigators en-tered the BP Texas City refinery isomerization unit for the first time last week amid efforts to discover the cause of the March 23 explosion.
Investigators remained for approximately three hours using respirators to protect against residual benzene vapors, and wore fire- and biohazard- protective clothing.
A BP operator familiar with the isomerization unit assisted the CSB team. Investigators took approximately 200 photographs in the course of their examination.
“The isomerization unit equip-ment is structurally intact for the most part, but calcium silicate insulation and metal cladding litter the area and also dangle overhead,” says investigation manager Bill Hoyle.
Some areas of the isomerization unit remain unsafe for entry.
Hoyle says the team inspected the “blowdown drum” connect-ed to the atmospheric vent stack where the release is believed to have occurred. The vessel receives hydrocarbons vented from the raffinate splitter and other equipment.
Adjacent to the west of the isomerization unit is an area of debris where trailers were located at the time of the explosion.
“In the area of debris, we found the demolished remnants of approximately 6 to 10 trailers and about 30 vehicles, including cars and trucks,” Hoyle says. It is unknown how many vehicles may have been running when the vapor cloud was released from the vent stack.
The vehicles and trailers exhibit heavy blast damage, he notes, and investigators have not been able to positively identify a diesel pickup truck described by eyewitnesses as over-revving moments before the explosion.
The site examination will be an important component of the investigation, along with witness interviews and reviews of applicable regulations and company records.
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