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Significant lapses in process safety in August 2008 Bayer CropScience explosion

24 April 2009

The Bayer CropScience chemical facility explosion and fire that fatally injured two plant operators and potentially threatened plant neighbors likely resulted from a series of process safety management deficiencies that led to a runaway chemical reaction, U.S. Chemical Safety Board Chairman John Bresland told a House committee investigating the matter.

Significant lapses in process safety in August 2008 Bayer CropScience explosion
Significant lapses in process safety in August 2008 Bayer CropScience explosion

The accident occurred the night of August 28, 2008, in the Methomyl/Larvin unit of the company's pesticide manufacturing complex in Institute, West Virginia, when high temperature and pressure ruptured a Methomyl residue treater, hurling the 5,000-pound vessel up to 50 feet through a swath of piping and other equipment.

In testimony before the Subcommittee on Oversight and Investigations of the Committee on Energy and Commerce, Chairman Bresland said, “The explosion at Bayer was a very serious and tragic event that could have had additional grave consequences.”

Bresland continued, “Our investigation has revealed significant lapses in process safety management that likely contributed to causing this accident.” The accident occurred during the restarting of the Methomyl unit after a long maintenance shutdown period. Equipment was replaced, and a completely new computer control system was installed, though workers were not adequately trained on it prior to the startup. An undersized heating system for the residue treater vessel, long known to the Bayer management personnel, required operators to deviate from written procedures. To deal with the inadequate heater, operators had to bypass critical safety interlocks intended to prevent the flow of Methomyl into the residue treater until the required minimum temperature was reached.

“The practice of bypassing the safety interlocks was longstanding and was known to Bayer managers and engineers,” Bresland said. “But bypassing the safety interlocks made it much more likely to overcharge the vessel with Methomyl, which could lead to a catastrophic runaway reaction.”

Investigators also determined that operators had not pre-filled the treater vessel with heated solvent, as required by the startup procedure. The reasons for the deviation are still under investigation, but Bresland noted that operators had been working shifts of 12 hours or more up to seven days a week. As the startup proceeded, concentrated Methomyl continued to be pumped into the treater. It eventually overheated and violently decomposed, destroying the residue treater tank.

Bresland said the residue treater could have been propelled in any direction. About 80 feet from the original location of the treater, there is a 37,000-pound capacity tank of methyl isocyanate (MIC), which held 13,800 pounds of the highly toxic and volatile liquid on the night of the accident. The CSB is further investigating whether this tank is located in a safe position and whether alternative arrangements to using or storing MIC have been considered at Bayer, or should be considered in the future.

Bresland noted that Bayer, saying it was acting under the 2002 Maritime Transportation Security Act (MTSA), had marked approximately 2,000 pages of investigative documents as sensitive security information or SSI, a Department of Homeland Security designation that prevents release of the information to the public.

Bresland has urged Congress to carefully review existing information protection rules to ensure that the public's right to know about chemical accidents can be preserved in the future.

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