Rush to Restart Cause of Bayer Explosion

Wednesday, January 26, 2011 @ 07:01 PM gHale

Bayer CropScience workers made critical mistakes as they rushed to restart a pesticide manufacturing unit in Institute, WV, leading to an explosion that killed two workers in August 2008, investigators said.

Bayer deviated from written startup procedures before the explosion blasted apart a tank filled with toxic chemicals, said investigators with the U.S. Chemical Safety Board (CSB). One worker died in the blast and a second died weeks later from burns.

Investigators also found Bayer bypassed safety devices and conducted an inadequate safety review. Bayer did not respond to a request for comment.

The report found if the trajectory of the exploding vessel had taken it in a different direction, pieces of it could have impinged upon and possibly caused a release from piping at the top of a tank of highly toxic methyl isocyanate (MIC).

The incident occurred during the startup of the methomyl unit, following a lengthy period of maintenance. The CSB found the startup was begun prematurely, a result of pressures to resume production of the pesticides methomyl and Larvin, and took place before valve lineups, equipment checkouts, a pre-startup safety review, and computer calibration were complete. CSB investigators also found the company failed to perform a thorough Process Hazard Analysis, or PHA, as required by regulation.

This resulted in numerous critical omissions, including an overly complex Standard Operating Procedure (SOP) not reviewed and approved, incomplete operator training on a new computer control system, and inadequate control of process safeguards. A principal cause of the accident was the intentional overriding of an interlock system designed to prevent adding methomyl process residue into the residue treater vessel before filling the vessel with clean solvent and heating it to the minimum safe operating temperature, according to the report.

The investigation also found the company did not install critical operating equipment and instruments before the restart. They discovered they were missing after the startup began. Bayer’s Methomyl-Larvin unit MIC gas monitoring system was not in service as the startup ensued, yet Bayer emergency personnel presumed it was functioning and said they did not release any MIC during the incident.

“The deaths of the workers as a result of this accident were all the more tragic because it could have been prevented had Bayer CropScience provided adequate training, and required a comprehensive pre-startup equipment checkout and strict conformance with appropriate startup procedures,” said CSB Chairperson Dr. Rafael Moure-Eraso. “This would have revealed multiple dangerous conditions and procedures that were occurring at a time when the company wanted to restart production of a key pesticide product. Startups are always a potentially hazardous operation, but to begin with computer control systems that have not been checked, while bypassing safety interlocks, is unacceptable.”

A major contributing factor to the accident was a series of equipment malfunctions that continually distracted operators, said CSB Investigations Manager John Vorderbrueggen.

“Human factors played a big part in this accident, and the absence of enforced, workable standard operating procedures and adequate safety systems meant that mistakes could prove fatal. For example, operators were troubleshooting several equipment problems and during the startup, inadvertently failed to prefill the residue treater vessel with solvent. A safety interlock was designed to stop workers from introducing highly-reactive methomyl, but it was bypassed as had been done in previous operations with managers’ knowledge. Once the chemical reaction of the highly concentrated methomyl started, it could not be stopped, and the temperature and pressure inside rose rapidly, finally causing an explosion.”

Board Member John Bresland, who was CSB chairman at the time of the Bayer blast, noted the confusion that resulted in the community’s emergency response following the 10:33 p.m. explosion.

“The Bayer fire brigade was at the scene in minutes, but Bayer management withheld information from the county emergency response agencies that were desperate for information about what happened, what chemicals were possibly involved,” Bresland said. “The Bayer incident commander, inside the plant, recommended a shelter in place; but this was never communicated to 911 operators. After an hour of being refused critical information, local authorities ordered a shelter-in-place, as a precaution.”

“Proper communication between companies and emergency responders during an accident is critical,” said Bresland. “The community deserved better, especially considering the amounts of hazardous chemicals, in use and being stored at various chemical facilities in the Kanawha River valley.”



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