A government investigation into the June 29 explosion at Bonnell Aluminum that injured five workers turned up no violations of federal safety regulations and didn’t result in any fines, but the company was advised on multiple precautions.
The U.S. Occupational Health and Safety Administration released the 100-plus page report of its investigation Wednesday to The Newnan Times-Herald.
The explosion, which caused significant damage to the casting area of the aluminum-extrusion plant located off Temple Avenue, was the result of a loss to power to certain components of the aluminum casting operation.
Alarms and a sump pump that should have activated did not, as a result of the power outage, according to the report.
During the casting operation, molten aluminum leaves the furnace and runs down troughs to a “sow pan” and then to the molds, which are set on a hydraulic table above a 26-foot-deep pit. Aluminum flows into the molds and becomes “billets.” Water is then sprayed on the billets to help cool and harden the metal.
Typically in the event of a power outage, the operator aborts the casting process, stopping the flow of molten aluminum. “Emergency water” flows to clear out the metal from so that the metal does not harden, according to the OSHA report.
There are alarms that are supposed to go off when water levels in the pit go over 16 feet. There are two pumps in the pit – one to make sure water is always available, and one to remove water when it reaches 14 feet.
Though the alarms, both audio and visual, are powered by battery backups, they did not activate.
The power outage was limited to the circuit that controls the casting process – the overhead lights and the furnaces continued operating, according to the report.
“There were no indicators of loss of power unless the operator was watching the control panel screen,” the report states.
The casting process had begun shortly before the explosion. An employee had just opened the gate that allows the liquid aluminum to flow into the sow pan. But because the water in the pit had overflowed, due to the failure of the sump pump, there was water in the pan. The water was encased by the molten metal and turned to steam, causing the explosion.
OSHA did recommend that Bonnell take three actions: ensuring that the cast operator continuously monitors the control panel and does not engage in tasks that draw attention away from the operation, installing a gravity drain in the pit at 20 feet to ensure water stays at a safe level, and installing a backup sump pump to keep the water level below 14 feet in the event of a power outage.
When asked if Bonnell had acted on those recommendations, spokesman Brian Ellis said in an emailed statement, “as we work to rebuild our casting operation, we remain committed to a safety-first approach, and have integrated the recommendations from OSHA and our own investigation, which further build on our strong safety systems and training.”
“The findings of the investigation indicated that there were no violations of any OSHA requirements, demonstrating that we have strong safety systems in place, and that our employees are well-trained and follow those guidelines,” Ellis said in the statement. “This event also reminds us of the importance of focusing on safety every single day.”
Interviews with employees which were included in the OSHA report show that employees were aware of the need for a drain in the pit.
“I think we need our own generator, also a drain to let the water out so it doesn’t get too high,” said one employee.
“Casting department needs a backup generator. Emergency drain would help as well,” said another.
Another employee said he’d never heard the alarms go off during a power loss, and that the pumps have required repairs “quite a bit.”
“The pump has been an issue,” the employee said. He said that a new pump system had been ordered but had not arrived. He said there is a need for upgrades and an emergency drain.
An upgrade to the casting pit was done in 2007.
Two employees stated that a worker has other things to do besides just watching the control panel during the casting process.
The explosion blew a hole in the roof of the casting area, sending fire brick and molten aluminum into the sky, striking neighboring buildings and even starting a small fire in a boat at Sewell Marine.
Included in the report is the narrative from an employee who was injured and taken to a hospital by air ambulance. The man said he had taken a break and was in the nearby smoking area. At the time of the explosion he started running and tripped. Then something hit him in the back. Everything had been normal when he went on break, he said.
As part of the company’s investigation, Bonnell conducted “non-destructive” testing of the casting pit control system and the “uninterruptible power supply” backup system.
The explosion destroyed the roof above the casting pit and a portion of the end walls, according to an engineer’s report. The main building structure sustained little damage. There was roof damage in adjacent areas. The roof areas remained structurally sound but not capable of withstanding storm force winds because of broken tension rod bracing. Falling debris punctured the roof in some other areas of the plant.
Bonnell was given the go-ahead to begin repair of the casting area in early July. That work is ongoing.
“They hope to reopen sometime mid-year,” Ellis said.
Other than the casting house, the plant has been operational since the day after the incident, Ellis said. Because casting isn’t being done on site, raw materials are being brought in, “which is quite normal in the industry,” he said.
All casting house employees have been reassigned, and there have been no layoffs related to the explosion, he said.
In addition to the OSHA and Bonnell investigations, one was done by the United Steelworkers, which represents union members at the plant.