Oil industry urged to improve safety at U.S. refineries

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 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. 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 Texas City are not unique either to that refinery or to BP. Federal regulators and the industry itself should take prompt action to make sure that similar unsafe conditions do not exist elsewhere. Taken as a package, the new CSB safety recommendations we issued today will provide for effective guidance, outreach, and regulatory enforcement to reduce the risk of similar tragedies in the future."

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 Texas City prior to the March 23, 2005, accident. The CSB documented eight previous releases of vapor from the same blowdown drum from 1994 to 2004. In six cases, dangerous flammable vapor clouds formed at ground level but did not ignite; in two other cases, the blowdown stack caught fire.

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. A properly designed flare system includes an adequately sized vessel for containing liquids and a stack with a flame for safely burning flammable vapors, preventing an uncontrolled fire or explosion near personnel. Flares are the most commonly used disposal system for flammable releases in refineries.

In 1992, the Texas City refinery, then owned by Amoco Corporation, was cited by OSHA for operating an unsafe blowdown drum. However, Amoco succeeded in having the citation and fine withdrawn, asserting that the drum complied with accepted industry standards embodied in API Recommended Practice 521. Today's recommendation from the CSB would strengthen that guidance document so that it would explicitly warn against such unsafe blowdown systems.

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.