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Pesticide Chemical Runaway Reaction

Pressure Vessel Explosion

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Background

Bayer CropScience is one of the world's leading innovative crop science companiesin the areas of seeds, crop protection and non-agricultural pest control.

On August 28, 2008, at about 10:35 p.m., a runaway chemical reaction occurredinside a 4,500 gallon pressure vessel known as a residue treater, causing the vessel toexplode violently in the methomyl unit.

This highly flammable solvent sprayed from the vessel and immediately ignited,causing an intense fire that burned for more than 4 hour.

The incident occurred during the restart of the methomyl unit after an extendedoutage to upgrade the control system and replace the original residue treater vessel.

Incident resulted in fatal incident of two company employees, toxic chemicalexposure to six volunteer fire fighters and evacuation of about 40,000residents up to12 km of area.

Primary reasons of the runaway chemical reaction and loss of containment of theflammable and toxic chemicals resulted from deviation from the written start-upprocedures, bypassing of critical safety, inadequate pre-startup safety review,

inadequate operator training on the newly installed control system and insufficienttechnical expertise available in the control room during the restart.

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Incident Details

Date : 28 August 2008, 10:35 p.m.

Location : Bayer CropScience , Virginia, US

Incident : Runaway Reaction & Explosion

Consequences : 2 company employees fatal, 6 volunteerfire fighters toxic exposures, 40,000 residents evacuation and7500 liters of toxic and flammable liquid sprayed inatmosphere.

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Bayer CropScience Runaway Reaction

CSB Video

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Residue treater vessel after explosion

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PSM Element Failures

Operating procedures & Safe Work Practices:

o Several required SOP steps were not completed during the methomylunit startup like The residue treater was not pre-filled with solvent. The solvent was not circulated and heated to the minimum operating

temperature. Daily residue treater liquid sample was not collected and analyzed

for methomyl concentration. Safety interlocks bypassed on the residue treater bottom feed valve

allowing concentrated methomyl.

Training & Competency:

o Operations personnel were inadequately trained to operate themethomyl unit with the new DCS control system.

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Process Hazard Analysis:

o The residue treater layers of protection to prevent a runaway reactionwere inadequate.

o PHA team failed to validate critical assumptions used in theiranalyses. (e.g. PHA team concluded that a high residue concentrationin the flasher feed was an operations issue having no consequence.)

Pre-Startup Safety Review:

o The PSSR did not include a formal process of involving multiplediscipline member team.

o The PSSR did not verified the completion of modifications in the field,

including toxic gas monitoring system which were not in service,verification of the functionality of critical DCS control andinstruments installed before the restart.

PSM Element Failures

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Practice Consistence with Procedures:

o Non adherence to safe operating practices & safety interlocks

Active Lines of Communication:

o

Inadequate operator awareness on newly installed DCS systemo A number of key items were inadequately addressed in the shift

changeover log book.

Leadership By Example:

o Inadequate safety checks before start upo Failure to identify protection factors for chemical runaway

reaction

OD Element Failures

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Take home for Reliance

InherentlySafer: The Future of RiskReduction

Bayer has taken specific action to reduce the risk of MIC.

The company did not rebuild the damaged methomyl unit anddiscontinued production of two of the MIC based pesticides.

The company also made an investment of more than $25 million toredesign and modify the MIC production unit to significantly reducethe on-site inventory.

The company announced it would eliminate the production of the tworemaining Carbamate pesticides, Aldicarb and Carbaryl, during 2012

and end all production, use, and storage of MIC.

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