On a unanimous vote of 5 to 0, the U.S. Chemical Safety Board (CSB) issued Tuesday new safety recommendations and called on the U.S. oil industry to improve safety practices for refinery pressure relief systems.
These new measures would eliminate 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 in March of 2005.
The explosion 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 first recommendation calls on the American Petroleum Institute (API), a leading oil industry trade association that develops widely used safety practices, to change its Guide for Pressure Relieving and Depressuring Systems. The revised guidance should warn against using blowdown drums similar to those used in Texas City, urge the use of inherently safer flare systems, and ensure companies plan effectively for large-scale flammable liquid releases from process equipment.
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.
CSB is also suggesting OSHA should emphasize the need for companies to conduct accurate relief valves studies and use appropriate equipment for containing liquid releases.
Lead Investigator Don Holmstrom noted that the ISOM unit blowdown drum at the BP Texas City refinery had a number of safety problems.
Design weaknesses in the system resulted in unsafe conditions in Texas City prior to the explosion. The CSB documented eight previous releases of vapor from the same blowdown drum from 1994 to 2004.
Prior to the 2005 accident, BP operated 17 blowdown drums for disposal of flammable materials at its five U.S. refineries. BP has since pledged to eliminate all the drums and use safer alternatives, such as flare systems.
In 1992, the Texas City refinery, then owned by Amoco, was cited by OSHA for operating an unsafe blowdown drum. Amoco did, however, succeed in having the citation and fine withdrawn, asserting that the drum complied with accepted industry standards embodied in API Recommended Practice 521.