NASHVILLE, Tenn. (AP) -- A federal agency investigating a fatal fire at a Middle Tennessee chemical plant said a corroded pipe leaking hydrogen gas caused an explosion that ignited combustible iron dust there.
A total of four workers have died this year after being critically burned in fires at the Hoeganaes (HAY'-gan-eez) plant in Gallatin, with the latest one occurring last week.
On Friday, the head of the U.S. Chemical Safety Board said the plant needs to be completely redesigned before the company restarts the manufacturing of metal powder for automotive and industrial uses. The CSB does not have the power to close the plant, which employs about 180 people, and can only make recommendations.
Board Chairman Rafael Moure-Eraso likened the flash fires at the Hoeganaes plant to the explosion at an Imperial Sugar factory near Savannah, Ga., that killed 14 workers in 2008.
That factory was completely redesigned and rebuilt after it "basically blew up, disappeared," Moure-Eraso said. "Rather than wait for a total, catastrophic failure here, we are advocating systematic changes. For us, it is catastrophic enough that four people have been killed."
He emphasized that simply cleaning up the combustible dust that inspectors have found covering surfaces all over the plant is not enough.
"Without design and engineering improvements, dust will quickly accumulate back to its former levels," he said.
Asked whether he would work there under current conditions, Moure-Eraso said, "No. Absolutely not."
Two days earlier, Hoeganaes Vice President of Human Resources Mike Mattingly said production was shut down after the May 27 accident and would not restart until the Cinnaminson, N.J.,-based company completes what he called "a comprehensive safety review" of the entire facility, expected to last about two weeks.
Mattingly did not immediately return a message left for him on Friday.
This is the third serious accident at the Gallatin plant this year.
Two workers died after a flash fire in January and another worker was injured in a March flash fire. The CSB investigation found both of those fires occurred when flammable dust became airborne and exploded.
Last week's explosion and fire occurred after hydrogen gas leaked from a corroded pipe, and the CSB plans to expand its investigation to include the maintenance of those pipes, but Banks said he thinks flammable dust also played a role.
Witnesses reported seeing burning dust raining down after the explosion and the dust was so thick in the air that some workers told investigators they could only see for 3 or 4 feet in front of them.
The Tennessee Occupational Safety and Health Administration last week issued $42,900 in citations to Hoeganaes after an investigation into the January and March accidents found 12 serious violations. But neither TOSHA nor its federal counterpart, the U.S. Occupational Safety and Health Administration, have rules governing combustible dust.
The Chemical Safety Board in 2006 recommended that OSHA develop those rules and the agency is currently in the process of doing so.
Asked about how long the regulations were taking, Moure-Eraso said OSHA was following its normal procedure, which takes years to complete.
"That, for us, of course, is not a satisfactory approach."