August, 2008

This is a repeating event

200828AugAll DayBayer Cropscience Explosion 2008Bayer CropScience Institute (US-WV) Origin: CSB Lessons:Competency,Emergency Preparedness,Operational Readiness,Process Knowledge,Risk AssessmentIndustry:ChemicalsCountry:United StatesLanguage:ENLoC:Operator error

Summary

On August 28, 2008, at about 10:35 p.m., a runaway chemical reaction occurred inside a 4,500 gallon pressure vessel known as a residue treater, causing the vessel to explode violently in the methomyl unit at the Bayer CropScience facility in Institute, West Virginia. Highly flammable solvent sprayed from the vessel and immediately ignited, causing an intense fire that burned for more than 4 hours. The fire was contained inside the Methomyl-Larvin insecticide unit by the Bayer CropScience fire brigade with mutual aid assistance from local volunteer and municipal fire departments.

The incident occurred during the restart of the methomyl unit after an extended outage to upgrade the control system and replace the original residue treater vessel. Two company employees who had been dispatched by the control room personnel to investigate why the residue treater pressure was increasing were near the residue treater when it ruptured. One died from blunt force trauma and burn injuries sustained at the scene; the second died 41 days later at the Western Pennsylvania Burn Center in Pittsburgh, Pennsylvania. Six volunteer firefighters who assisted in the unit fire suppression activities and two contractors working at the facility were treated for possible toxic chemical exposure.

KEY ISSUES:
• PROCESS HAZARDS ANALYSIS
• PRE-STARTUP SAFETY REVIEW
• PROCESS SAFETY INFORMATION & TRAINING
• EMERGENCY PLANNING & RESPONSE

ROOT CAUSES:
1. Bayer did not apply standard Pre-startup Safety Review (PSSR) and turnover practices to the methomyl control system redesign project. The equipment was not tested and calibrated before the unit was restarted.
2. Operations personnel were inadequately trained to operate the methomyl unit with the new distributed control system (DCS).
3. Malfunctioning equipment and the inadequate DCS checkout prevented the operators from achieving correct operating conditions in the crystallizers and solvent recovery equipment.
4. The out-of-specification methomyl-solvent mixture was fed to the residue treater before the residue treater was pre-filled with solvent and heated to the minimum safe operating temperature.
5. The incoming process stream normally generated an exothermic decomposition reaction, but methomyl that had not crystallized due to equipment problems greatly increased the methomyl concentration in the residue treater, which led to a runaway reaction that overwhelmed the relief system and over-pressurized the residue treater.


Image credit: CSB

Origin

CSBUS Chemical Safety Board

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