Iron dust is a huge safety hazard and after the January 31, 2011 a fatal flash fire at Hoeganaes Corp. plant in Gallatin, TN, the Chemical Safety Board issued a video showing the dangers of the substance.
The flash fired fatally injured a one worker and seriously burned another at the facility twenty miles outside of Nashville, TN. The plant produces powdered iron.
The video shows two different tests, the first clip is at normal speed followed by the two tests filmed in slow motion at 1,000 frames a second.
“The Hoeganaes facility in Gallatin was also the site of a flash fire on January 31 that fatally burned two workers, said CSB Chairman Rafael Moure-Eraso. “A similar flash fire occurred on March 29th and caused one injury.”
“To date, CSB and its experts have done extensive testing on the metal dust from the facility,” Moure-Eraso. “Tests show that powder samples collected from the sites of both the January and March accidents were combustible and could be exploded under test conditions. These test results largely agree with results obtained by Hoeganaes itself prior to the January accident.”
Combustible dust is a huge workplace hazard when it accumulates on surfaces, especially elevated surfaces.
The Hoeganaes facility employs 180 workers and makes atomized iron powder for the automotive and other industries for the production of metal parts using powder metallurgy.
The plant collects scrap iron, which they melt and then spray into powder form. They then anneal it using hydrogen gas using a large continuous furnace. This powder is then further milled, packaged, and eventually sold as a final product.
Following the May 27 accident, the CSB arrived at the Hoeganaes facility at 11 a.m. on May 28. According to witnesses, the incident took place on May 27 between 6:30 and 6:40 a.m. At 6:10 am, two annealing operators heard a hissing sound in a trench that housed a number of process pipes carrying hydrogen, nitrogen, and cooling water. When the operators heard the hissing sound, they summoned plant maintenance personnel to lift a cover over the area where they thought the gas was leaking.
After several attempts to lift the cover with a pry bar were unsuccessful, a call went out to get a forklift. Workers attached the cover to the forklift with a metal chain and raised it. As the cover opened, an explosion occurred. Some witnesses saw a flash of light; some heard a muffled boom and felt the building shaking from the explosion. The building filled with dust and the lights went out. Witnesses saw burning dust raining down from above.
The initial explosion involved hydrogen gas that had been leaking into the trench from a large hole in the vent pipe, CSB officials said.
Witnesses as well as the physical evidence leave no doubt that combustible iron dust was a culprit in the aftermath of the explosion.
Examining the scene following the incident, CSB investigators observed splatterings of burned iron dust.
A hydrogen fire, described as three to four feet high, continued until an operator in the area closed a valve on the hydrogen piping.
Emergency workers life-flighted three of the victims to the Vanderbilt Hospital Burn Unit. Two have since died and a third remains in critical condition.