Red flags have been raised about the possibility of lithium ion tool batteries catching fire in industrial settings, such as mines.
Newmont Goldcorp’s Red Lake Gold Mines reported that an underground fire took place Dec. 6 when three workers went to get their tools on the 4400 level storage area.
“When the workers arrived, they smelled smoke,” said mine rescuer Loye Halteman at a recent safety conference in Sudbury.
One of the workers was sent back to a refuge station to notify security to “stench the mine,” thus releasing stench gas, a foul-smelling gas used to alert miners of impending danger.
The two other workers entered the storage area with a couple of 10-pound fire extinguishers to investigate. They discovered a large area of flame by one wall.
“The workers attempted to extinguish the fire with the fire extinguishers. It increased the smoke and they couldn’t put it out,” said Halteman.
The fire was inside a storage bay behind an eight-foot-high steel partition wall. It was being fuelled by a stack of lithium batteries and chargers used for hand-held power tools.
He said the workers retreated to the refuge station to wait for help and shut off all the power in that area. Mine rescuers arrived shortly after and, using a thermal camera, discovered there were significantly high heat indicators in the storage area. A ventilation door was opened to help clear the air.
The first rescue team returned to surface. The second team arrived to use water hoses to cool down the area.
The fire was knocked down by 2:10 a.m. It was nearly 3 a.m. – more than eight hours after the fire was discovered – before the heat had dropped to a safe level.
Halteman said it was eventually decided to ask an outside investigation team – forensic consultants Origin and Cause – to determine what had happened.
Newmont Goldcorp mine safety supervisor William McCleary said lithium fires are something new, but mines don't want to abandon the use of lithium batteries because portable tools are so useful and convenient.
“You can’t just throw all these tools out of the industry overnight just because of one specific incident.”
Going back to the day of the fire, McCleary said, investigators discovered that several workers had borrowed tools during the day and returned the tools and the batteries to the storage area at the end of the shift. Two lithium batteries were placed on charge.
The charging station was a wall-mounted steel frame device with wooden shelving.
There were four charging devices on the top shelf. The second shelf held a supply of 30 to 40 lithium batteries.
McCleary said it was learned that if a lithium battery is dropped, it could force internal metal contacts to touch each other, causing the battery to overheat and catch fire within 30 minutes to an hour.
It could not be determined if that had happened.
Investigators could not specifically determine whether it was a malfunctioning charger, a malfunctioning battery, or the fact that the charger was connected to power bar, which had an extension cord plugged into a wall outlet.
“It was a disaster waiting to happen, basically, when you have something like that where all those components start to make heat as it's charging,” McCleary said.
“They know the origin was that location. The fire had started in the charging station, either (with) a battery, a charger, or a power strip or a plug-in or an extension cord.”
The fire began on the top shelf and burned down through the second shelf where the stacks of batteries continued to fuel the blaze, said McCleary.
It was concluded that if the batteries had been stored separately from the chargers, it likely would have lessened the impact of the fire.
Among the investigators’ recommendations is that mine sites should have custom-built steel storage cabinets, with a built-in power breaker that will shut off if there is any excess heat.
Another concern is that a normal dry-chemical ABS extinguisher will not work. The fire would flare up bigger, McCleary said.
The solution is to purchase additional Class-D extinguishers, which will cut off the oxygen supply immediately.
McCleary said all mine sites and mine rescue stations need to be made aware of the possibility of lithium battery fires.