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Chemical Mixing Plant Explosion

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Areas of Expertise

Michael Fox, Ph.D.



Chemical Mixing Plant Explosion

A violent explosion occurred at a chemical mixing plant that resulted in the death of five employees, many injuries and significant property damage. In addition, numerous residents were evacuated and fire-fighting efforts created contaminated water that ran into the streets and a nearby river.

The plant was using a large V-shaped blender to mix a dry chemical product that consisted mostly of sodium hydrosulfite, aluminum powder and potassium carbonate.

A problem developed in the addition of a small amount of a final ingredient. The exact nature of the problem adding the final ingredient was never determined with certainty. However, this problem resulted in extending a 1-hour mixing process to about 24 hours and the generation of odorous fumes. As a result, the management evacuated the plant. They then made the decision to have five men re-enter the facility to off-load the product from the V-blender into 55-gallon drums. After several drums were off-loaded, there was an explosion that killed five men and injured many others.

This chemical accident was of such a magnitude that a Joint EPA/OSHA Task Force also separately investigated the explosion as did the United States Chemical Safety Board. Chemaxx was asked to investigate this chemical explosion with an emphasis on the adequacy of the Material Safety Data Sheets or MSDSs.

The cause of the accident was believed to be contamination by water (via water-cooled bearings) during the prolonged mixing. During his investigation, Dr. Fox conducted many experiments that showed that the mixture and its ingredients generated heat when exposed to water. However, in Dr. Fox's small-scale experiments, there were limits to the amounts of heat generated and the maximum temperatures reached. No runaway-exothermic, explosion, or fire was observed. Furthermore, the maximum temperatures reached would not be expected to ignite combustible materials and flooding the mixture with water immediately cooled the mixture and stopped the generation of heat. The instruction to vent and flood with water was part of the MSDS for the final product. A similar warning was part of the MSDS for sodium hydrosulfite.

Dr. Fox's experiments demonstrated that this instruction, to vent and flood with water, was a safe and immediately effective means to control and stop the exothermic reaction. Additionally, Dr. Fox exposed the mixture and its individual ingredients to a sustained butane torch. Neither the mixture nor its individual ingredients would ignite or burn in air.

Based on reviews of the subject MSDSs and numerous experiments, it was concluded that the MSDSs for the individual ingredients and the final product provided adequate safety information with respect to fire hazards and reactivity hazards expected under the end-use conditions for the product.

The case settled prior to trial.

Dr. Fox has his Ph.D. in Physical Chemistry and specializes in the reconstruction of complex industrial chemical accidents, fires and explosions as well as chemical-related consumer product accidents. He is also OSHA Certified as a Process Hazard Analysis (PHA) Team Leader and a Certified Fire & Explosion Investigator (CFEI). In addition, Dr. Fox began developing a Chemical Risk Assessment and Prevention Program, known as CHEMRAP, in the mid-1980's when the OSHA Hazard Communication Standard was initially enacted and expanded. As a result, Dr. Fox is intimately familiar with this OSHA standard and its requirements for Material Safety Data Sheets (MSDSs).