Explosion
The refinery had been in operation since 1934, but had not been well maintained in several years. Consulting firm Telos had examined conditions at the plant and released a report in January 2005, reporting of "broken alarms, thinned pipe, chunks of concrete falling, bolts dropping 60ft and staff being overcome with fumes", and the report's co-author stated "we have never seen a site where the notion 'I could die today' was so real". The refinery had also had five managers in the six years since BP inherited it in its 1998 merger with Amoco.
The U.S. Chemical Safety and Hazard Investigation Board investigating the incident found that operators had started up the raffinate splitter tower (which separates light and heavy gasoline components) of the ISOM unit (which increases the octane rating of gasoline) and begun filling it with hydrocarbon fluid (i.e., gasoline components) without beginning timely discharge of product. The operators started the tower while ignoring open maintenance orders on the tower’s instrumentation system. An alarm meant to warn about the quantity of liquid in the unit was disabled.
Once the lack of draw-down from the tower was recognized, operators opened the discharge valve. This worsened the problem, because the hot discharges passed through a heat-exchanger that pre-warmed incoming fluids. The resulting increase in temperature caused the formation of a bubble of vapor at the bottom of the raffinate tower that was already overly full and overheated. The tower burped the vapor bubble and the liquid above the bubble into the overhead relief tube of the tower.
The relief tube was connected to a disposal system for relieved discharges. The particular type of disposal system serving the raffinate tower was a blowdown drum with an atmospheric vent stack, rather than an inherently safer and more environmentally sound knock-out tank and flare system. Because of the overfilling of the raffinate splitter tower and the burp of both vapors and liquids to the undersized blowdown drum with an atmospheric vent stack, a “geyser-like” emission of hot flammable vapors and liquids was expelled from the vent stack.
A new white diesel pick-up truck, owned by a contractor, was parked near the blowdown stack. While BP operators were running to turn off furnace burners, to remove sources of vapor cloud ignition, the truck's owner returned to his truck and proceeded to crank the engine, in an attempt to move his new truck out of the area. Due to a high hydrocarbon content above the Upper Explosion Limit (UEL), the truck would not start. As the man continued to crank the engine, operators ran to him in an attempt to get him to stop. Once the hydrocarbon content in the surrounding air came down to the UEL, the truck provided the source of ignition for the Vapor Cloud Explosion.
The people in the trailer located near the process unit's battery limit were holding a meeting, and were unaware of the ISOM's unit startup condition. The people on the side of the meeting table with their backs to the process unit were killed, due to blunt-force trauma. A number of people on the side of the table facing the unit survived the blast.
Read more about this topic: Texas City Refinery Explosion
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