What Went Wrong: Dust Explosions

Tuesday, January 10, 2012 @ 01:01 PM gHale


“It is a tragedy that five lives were lost at Hoeganaes from these accidents,” said Chemical Safety Board Lead Investigator Johnnie Banks. “The CSB believes that adhering to recommended industry practices will greatly reduce the potential of a future dust fire or explosion.”

That is one of the reactions to the three explosions and fires started last year as a result of iron dust at the Hoeganaes Corp. plant in Gallatin, TN. Over a period of five months, five people died and three more suffered injuries as a result of these explosions. A chilling new video from the CSB details just went wrong all three times at the Hoeganaes plant.

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The Hoeganaes Gallatin facility, located 30 miles northeast of Nashville, TN, employs 200 employees. Since becoming operational in the 1980s, they hiked their manufacturing capability over 550 percent from 45,000 to over 300,000 tons.

Hoeganaes receives and melts scrap steel. They add in various elements to the molten metal to meet customer specifications, but the “workhorse” product, Ancorsteel 1000, is over 99 percent iron. The molten iron cools and then gets milled into a coarse powder they process in long annealing furnaces to make the iron more ductile. They call the furnaces “band furnaces” for the 100 foot conveyor belt, or band, that runs through them. A hydrogen atmosphere exists in the band furnace to reduce the iron by removing oxides and preventing oxidation. An onsite contract provider supplies the hydrogen to the facility.

Hydrogen gets to the furnaces via pipes located in a trench under the floor and covered by metal plates.

In the process of going through the furnace, the coarse powder becomes a thick sheet called “cake.” The cake goes to the cake breaker and ultimately ends up crushed into the fine PM product. The majority of the finished PM product has a particle diameter between 45-150 microns, or roughly the width of a human hair.

The product transfers via conveyor belt to other parts of the plant. That is one area that allows the fine dust to disperse throughout the plant.

A final report released last week detailed the agency’s investigation of three fires at the Hoeganaes iron powder manufacturing plant. The CSB said new, tougher OSHA standards should include safety measures to control metal dust such as the materials associated with the Gallatin accidents.

“As I have said on numerous occasions, I believe that worker safety is a basic human right,” said board Chairman Rafael Moure-Eraso. “No worker should die or be severely injured simply trying to earn a living and provide for their families.”

The CSB will track whether the safety recommendations in the final report end up implemented.

“We are prepared to tell the public if actions were taken or not, and that is part of what we do,” Moure-Eraso said.

Effective immediately, the Tennessee Occupational Safety and Health Administration will implement one recommendation made to the agency by the CSB, which was to add the industry code for companies such as Hoeganaes to its Combustible Dust National Emphasis Program list, TOSHA Assistant Administrator Steve Hawkins said Thursday.

That means combustible dust is on the general checklist of any TOSHA inspector who visits the Gallatin facility or another factory like it.



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