Investigators detail fatal ComDust blast at Hoeganaes
Three combustible dust explosions at the
Hoeganaes atomized metal dust plant in
Gallatin, TN, this year, including two in which
workers were killed, are under investigation by
the Chemical Safety Board.

NASHVILLE, TN  -- A combustible iron dust explosion, believed to be fueled by hydrogen gas that killed two workers and seriously injured a third May 27 at the Hoeganaes facility in Gallatin, TN, is under investigation by the Chemical Safety Board (CSB).

It was the third serious accident linked to ComDust at the plant this year, including the second that resulted in two employees' deaths.

CSB Chairman Rafael Moure-Eraso and Johnnie Banks, CSB investigator in charge, held a press conference on June 3 to discuss the CSB's ongoing investigation into the lates explosion and fire at the Hoeganaes plant.

The Hoeganaes facility in Gallatin was also the site of a flash fire on January 31 that fatally burned two workers. A similar flash fire occurred on March 29 and caused one injury.

Moure-Eraso said CSB tests show that finely powdered iron 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.

Banks noted that the Hoeganaes facility employs approximately 180 workers and manufactures "atomized" iron powder that is sold to the automotive and other industries for the production of metal parts using powder metallurgy.

"During all three of our trips to the Hoeganaes plant my team observed alarming quantities of metal dust within close proximity to the incident locations. This was of particular concern as metal dust flash fires present a greater burn injury threat than flammable gas or vapor flash fires."
 
Banks added that according to witness interviews of the May 27 incident, "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 the gas leak was thought to have occurred.

"After several attempts to lift the cover with a pry bar were unsuccessful, a call went out to get a forklift. The cover was attached to the forklift with a metal chain and raised. As the cover was pried 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, we now know, involved hydrogen gas that had been leaking into the trench from a large hole in the vent pipe. However, the witness statements as well as the physical evidence leave no doubt that combustible iron dust was also involved in the aftermath of the explosion," Banks said.

Moure-Eraso, noting that Hoeganaes has suspended production at the Gallatin plant, said, "It is my view as the chairman of the Chemical Safety Board that Hoeganaes and its corporate parent, GKN, need to make significant safety improvements to this plant before resuming the manufacturing of iron powder. Without such improvements, there is too great a risk that additional tragic accidents will occur here in the future."

Read Chemical Safety Board Hoeganaes press conference comments.

Posted by Rich Christianson

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