Zirconium Dust Explosion
An employee was egaged in the manufacture of zirconium (Zr) products. She would take samples from the Zr products after they were heat treated. She would grind and polish and then etch the samples and then examine and document the microstructure. A specific microstructure had to be attained to ensure the desired degree of corrosion protection had been achieved on the Zr. This overall process of grinding, polishing and etching metal samples is sometimes referred to as metallography.
The grinding and polishing involved in the metallography produces Zr fines, powder and dust. These fine particles are sometimes called "swarf." Since Zr is a flammable solid, it is well known that Zr swarf is highly flammable and explosive under certain conditions. This is true for most metals when they are in a fine particulate form that produces a high surface-to-volume ratio.
On the day of the incident, the employee was not performing her normal job. The plant had been shut down for about a week for routine maintenance and cleaning. She requested to work during that time and had been assigned to clean the metallography area where she regularly worked. Per OSHA reports, there was one year's worth of swarf accumulation that was being addressed.
The worker obtained a wet/dry shop vacuum that was alledgedly the only vacuum available for cleaning. Unfortunately, the vacuum was not explosion-proof and the hose was not grounded. She testified that she had been vacuuming less than one minute when there was a flash explosion that originated from within the vacuum. The most likely explanation was that the vacuuming process initiated a pyrophoric ignition of the finely divided Zr swarf, meaning that it could self-ignite when mixed with air.
The worker was subsequently transported to a hospital where she was treated for second degree burns over 25% of her body area. She filed lawsuits against the manufacturers of the Zr raw material and the shop vacuum. They were primarily "Failure to Warn" in nature.
The focus of the Chemaxx investigation was the adequacy of the MSDS and labeling for the Zr raw materials. The case settled prior to trial.
Dr. Fox is an explosion expert, fire expert, and chemical expert with extensive experience in OSHA chemical regulations and chemical safety.
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