The isomerization unit, a gasoline octane booster that exploded, should not have been started up on March 23, according to the Chemical Safety Board (CSB), because of a history of problems and a malfunctioning level indicator, level alarm, and a control valve. In addition, the raffinate splitter tower that overflowed on March 23 had a history of abnormal startups that included recurrent high liquid levels and pressures. BP management was aware of these incidents and malfunctioning equipment, but had never acted on that knowledge.
The Board held a hearing in Texas City this evening. According to CSB Lead Investigator Don Holmstrom
"The first rule of oil refinery safety is to keep the flammable, hazardous materials inside piping and equipment. A properly designed and sized knockout drum and flare system would have safely contained the liquids and burned off the flammable vapors, preventing a release to the atmosphere." Mr. Holmstrom said investigators found evidence that BP evaluated connecting the raffinate splitter to a flare system in 2002 but ultimately decided against it. After the March 2005 incident, BP said it would eliminate blowdown stacks that vent directly to the atmosphere at all U.S. refineries.Earlier this week, the CSB issued an "urgent recommendation" to the American Petrleum Institute and the National Petroleum Refiners Association, calling on them to revise their guidelines to prohibit unsafe siting of office trailers. Most of the workers who died in the explosion were in a temporary office trailer only 100 to 150 feet away from the vent stack that exploded.
Investigators presented new details on the 16 previous startups of the raffinate splitter from 2000 onward. They found eight startups with tower pressures of at least double the normal value, and thirteen startups with excess liquid levels. These abnormal startups were not investigated by BP. "Investigations of these incidents could have resulted in improvements in tower design, instrumentation, procedures, and controls," Mr. Holmstrom stated.
In his presentation, Mr. Holmstrom said that there was no supervisor with appropriate experience overseeing the startup at a critical time on March 23. Operators did not follow the requirements of startup procedures, including opening the level control valve for the splitter tower. This omission allowed the tower level to rise rapidly for three hours, to fifteen times its normal level. Operators were misled by the malfunctioning level indicator on the tower and a separate high-level alarm which failed to activate. The training and experience of the operators remains under investigation.
Investigators stated that a variety of equipment problems made it unsafe to start up the raffinate splitter on March 23. "Proper working order of key process instrumentation was not checked as required by the startup procedure. Managers turned away technicians and signed off on the instrument tests as if they had been done," Mr. Holmstrom said. Investigators also found that BP's traffic policy allowed vehicles unrestricted access near process units. On the day of the incident, there were running vehicles including a diesel pickup truck as close as 25 feet from the blowdown drum. A total of 55 vehicles were located in the vicinity of the drum, investigators determined, and one likely served as the ignition source for the explosions.
As a result of the March 23 explosion and other incidents at BP refineries, the Board issued the first "urgent recommendation" in the Board's history last August, calling on BP to establish an independent panel to review a range of safety management and culture issues in its North American operations. BP announced the panel's members earlier this week.
More on the CSB report and meeting here and here.
More BP stories here.