CSB Launches Probe of Recent Texas City Accident
During a news conference Thursday in League City, Texas, two officials with the U.S. Chemical Safety and Hazard Investigation Board (CSB) announced that their agency is proceeding with a full investigation of the most recent accident at BP's Texas City Refinery.
On Jan. 14, 2008, BP supervisor Joseph Gracia was fatally injured when the top of a large steel filter housing suddenly blew off in the refinery's ultracracker unit. It was the third fatality at the refinery since the March 2005 explosion.
"The goal of this investigation is to determine as precisely as possible what happened to cause this unfortunate event and to make recommendations to BP and others to prevent similar accidents in the future," said William Wark, one of the three CSB board members. "Conducting this investigation will take a number of months."
Wark said that the CSB weighed various factors before deciding to proceed with the investigation. These criteria included the severity of the accident, the likelihood that hazardous chemicals were involved, and the "learning potential" for BP and other refiners operating similar hazardous processes. He added that CSB also considered the history of accidents at the Texas City site; since 1976, 41 people have died in workplace accidents at the facility.
The CSB board member also said that BP has cooperated with the investigation and has voluntarily provided witnesses and information.
Don Holmstrom, who is leading the CSB investigation, said that the CSB investigative team has been actively working at the facility since arriving in Texas City the week of Jan. 14. "Up to four investigators from Washington, D.C., have been at the refinery on an ongoing basis examining the scene, conducting witness interviews, identifying physical evidence, and gathering documents," he said.
Holmstrom noted that the CSB team has interviewed approximately 35 witnesses over the past three weeks, including several who were in the immediate area when the accident occurred. Cautioning that all information is preliminary and subject to change as the investigation proceeds, Holmstrom made the following observations:
- The accident that killed Gracia, an experienced BP supervisor, occurred just before 4 p.m. in a section of the ultracracker unit that was in the beginning stages of a start-up after a prolonged shutdown.
- At the time of the accident, Gracia was standing in the ultracracker unit next to a large metal filter housing whose heavy metal lid was suddenly and violently blown from the top of the filter housing.
- The filter housing was normally filled with process water and operated under a moderate pressure, and it was secured in place by 24 large steel bolts. At the time of the accident, most of the bolts were either sheared off or stripped. Bolt fragments were propelled a large distance away.
- The force necessary to blow the filter lid off in this manner was likely well in excess of the normal operating pressure.
- There is limited physical damage other than the catastrophic failure of the lid, along with no indication of any sustained fire in the area.
- Gracia likely died of blunt force trauma and also suffered thermal injuries, consistent with steam burns.
Holmstrom said that various possible scenarios could explain the sudden pressure build-up inside the filter housing. One possible scenario that CSB is investigating is an internal explosion inside the filter.
"This filter was being returned to service after a filter element change and had recently been refilled with process water, as specified by the startup procedure," Holmstrom explained. He said witness told the CSB that the process water sometimes contained hydrogen, flammable light hydrocarbons, and the toxic and flammable gas hydrogen sulfide.
"These substances are a possible fuel for an explosion, in the presence of oxygen and an ignition source," he said. "We therefore plan to test the process water to determine its composition and flammable characteristics, and also to examine historical data about the presence of hazardous materials in this process water."
CSB is also examining BP's procedures and practices to understand if air may have remained in the filtration system. "Typically in refinery service, when flammables may be present, it is critically important to remove oxygen to avoid possible fires and explosions," Holmstrom explained.
He added that CSB also plans to test the filter housing for any residues of pyrophoric materials, which are substances that can combust spontaneously on contact with air and can form in the presence of hydrogen sulfide.
Holmstrom also said that other scenarios are not being ruled out. They include a sudden pressure increase of undetermined origin within the unit equipment, causing failure of the lid.
"We are requesting a variety of documents from BP such as operating and maintenance procedures," concluded Holmstrom. "We are also examining how process design changes were managed in this unit and researching previous incidents involving similar hazards, here and at other facilities."
The CSB team expects to complete its initial field work this week and will continue its investigation from other locations throughout the country. The CSB's findings, root causes, and recommendations are final only after a vote by the board members.