The six safety issues identified by CSB in its investigation of the March 23 incident, which killed 15 workers and injured 170 others, point to an incident that could have been prevented or at least minimized.
According to CSB:
- Trailers were placed in an unsafe location, too close to an isomerization (isom) process unit handling highly hazardous materials. All the fatalities occurred in and around trailers that were as close as 121 feet from the release. One trailer located 600 feet from the explosions was heavily damaged, and 39 other trailers were either damaged or destroyed.
- The isom unit's raffinate splitter should not have been started up due to existing malfunctions of the level indicator, level alarm and a control valve.
- The raffinate splitter tower had a history of abnormal startups that included recurrent high-liquid levels and pressures.
- The day of the incident, a blowdown drum vented highly flammable material directly to the atmosphere. The drum was never connected to a flare since its construction in the 1950s. The previous owner of the refinery, Amoco Corp., replaced the isom unit blowdown drum in 1997 with identical equipment; Amoco refinery safety standards recommended connecting the drum to a flare when such major modifications were undertaken but this was not done.
- Between 1995 and March 23, there were four other serious releases of flammable material from the isom blowdown drum and stack that led to ground-level vapor clouds; fortunately none ignited.
- In 1992, OSHA cited a similar blowdown drum and stack at the Texas City refinery as unsafe because it vented flammable material directly to the atmosphere, but the citation was dropped and the drum was not connected to a flare system.
The public meeting is scheduled for 6 p.m. tonight at the Doyle Center, 2010 Fifth Ave. North, in Texas City. Following the investigators' presentation, CSB will call for comments by members of the public.
"The meeting tonight marks an important milestone in the board's independent investigation of the tragedy at BP Texas City," CSB Chairman Carolyn W. Merritt said. "The preliminary findings we present this evening should be reviewed throughout the industry, which shares the CSB's goal of safer operations in the future. I also commend BP for cooperating with our investigation. BP has provided witnesses and documents on a voluntary basis and has facilitated testing of critical equipment."
Simulations Show Huge Flammable Vapor Cloud
CSB investigators have released three detailed computer animations of the startup of the isom unit, the vapor cloud formation and the subsequent explosions. The simulations show a vapor cloud that blanketed much of the nearly 5-acre isom unit just before the cloud was ignited, most likely by an idling diesel pickup truck.
The process simulation depicts liquid hydrocarbon flows through a complex of piping connecting a heat exchanger, a furnace, the raffinate splitter tower and the blowdown drum. As the temperature and fluid levels increase inside the tower, the animation shows pressure-relief valves directing overflow to the blowdown drum and attached vent stack. The drum rapidly fills, finally causing a geyser-like release of flammable liquids from the top of the vent stack. The vaporizing liquid falls to the ground, where it forms a vapor cloud.
P>"The first rule of oil refinery safety is to keep the flammable, hazardous materials inside piping and equipment," CSB lead investigator Don Holmstrom said. "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."
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.
CSB: Abnormal Startups Not Investigated by BP
CSB investigators plan to present 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 13 startups with excess liquid levels. These abnormal startups were not investigated by BP, according to CSB.
"Investigations of these incidents could have resulted in improvements in tower design, instrumentation, procedures and controls," Holmstrom said.
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 3 hours, to 15 times its normal level.
Operators were misled by the malfunctioning level indicator on the tower and a separate high-level alarm that failed to activate. The training and experience of the operators remains under investigation.
Investigators said 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," Holmstrom said.
Investigators also have 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.
Findings Prompted Urgent Recommendations to Petrochemical Industry
Based on findings from its BP investigation, CSB earlier this week issued two new urgent recommendations to leading U.S. petrochemical trade organizations. The board called on the American Petroleum Institute (API) to develop new safety guidance that establishes minimum distances for occupied trailers away from hazardous areas of process plants.
The board also called on API and the National Petrochemical & Refiners Association (NPRA) to immediately contact their members urging "prompt action to ensure the safe placement of occupied trailers away from hazardous areas of process plants" before the new API safety guidance is completed.
An API spokesperson, in a statement, said the organization will “consider developing new industry guidance to assist companies in the safe placement of trailers located within process plants,” as CSB has recommended. An NPRA spokesperson said the association has alerted all of its members to CSB’s recommendations and added that member companies “respect CSB and take this notice very seriously.”
A final public report of the CSB investigation is expected in 2006.