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On a unanimous vote of 5 to 0, the U.S. Chemical Safety Board (CSB) on October 31 issued new safety recommendations calling on the U.S. oil industry to improve safety practices for refinery pressure relief systems, eliminating the type of atmospheric vent that caused the hydrocarbon release and explosions that killed 15 workers and injured 180 at the BP Texas City refinery on March 23, 2005.
The accident occurred during the startup of the refinery's octane-boosting isomerization (ISOM) unit, when a distillation tower and attached blowdown drum were overfilled with highly flammable liquid hydrocarbons. Because the blowdown drum vented directly to the atmosphere, there was a geyser-like release of highly flammable liquid and vapor onto the grounds of the refinery, causing a series of explosions and fires that killed workers in and around nearby trailers.
The announcement followed by one day the release of new preliminary findings in the CSB's ongoing, independent federal investigation of the accident. The board's final report is expected in March 2007.
The first recommendation calls on the American Petroleum Institute (API), a leading oil industry trade association that develops widely used safety practices, to change its Recommended Practice 521, Guide for Pressure Relieving and Depressuring Systems. The revised guidance should warn against using blowdown drums similar to those in
Further recommendations call on the U.S. Occupational Safety and Health Administration (OSHA) to establish a national emphasis program promoting the elimination of unsafe blowdown systems in favor of safer alternatives such as flare systems. OSHA should also emphasize the need for companies to conduct accurate relief valves studies and use appropriate equipment for containing liquid releases, the board said. A national emphasis program results in a concerted inspection and enforcement effort around a specific safety hazard.
CSB chairman Carolyn W. Merritt said, "Unfortunately, the weaknesses in design, equipment, programs, and safety investment that were identified in
Lead investigator Don Holmstrom noted that the ISOM unit blowdown drum at the BP Texas City refinery had a number of safety problems.
"This drum simply wasn't large enough to hold all the liquid released from the distillation tower if it flooded. Not only could the blowdown drum not hold enough liquid, but it could not assure safe dispersion of flammable vapors through the vent stack," Holmstrom said.
He added that safe dispersion of flammable vapors would require a high exit velocity that could never be guaranteed when handling multiple discharges through a complex piping system.
That design weakness resulted in unsafe conditions in
Prior to the 2005 accident, BP operated 17 blowdown drums for disposal of flammable materials at its five
In 1992, the
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in safety management systems. The board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. For more information, visit www.CSB.gov.