Fixed path: Drum motor withstands harsh environments

Run by the Canadian National Railway (CNR), the Two Harbours ore docks in Minnesota unloads 8 million tonnes per year of taconite iron ore pellets from rail cars, stockpiles them, and loads them onto Great Lakes Freighters bound for Chicago-area steel mills.

The key operating system that loads the cargo holds is a machine called the MX bucket wheel reclaimer. Mounted on 20-foot long tank treads, this 95-ton piece of equipment rolls along the storage yard scooping up 6,000 tonnes of ore per hour. The ore is deposited onto a boom discharge conveyor system that extends more than 30 feet. The reclaiming process kicks up dust and grit that wreaks havoc on conveyors with exposed drives causing numerous breakdowns and frequent maintenance.

Due to increasing maintenance and repair delays, CNR through JoyGlobal, a leader in high-productivity mining solutions, upgraded their conveyor systems with a drum motor that is able to withstand the extreme harsh environment without continual downtime for maintenance.

To upgrade the conveyor system, the old 300HP motor and external drive chain was replaced with two TM800 150HP drum motors in a “nested” dual-drive configuration with the conveyor belt fed into a serpentine arrangement. The compact design of the drum motor with no external moving parts eliminated motor and coupling maintenance and improved operator safety.

The lighter one-piece design of the drum motors compared to the old system, plus the weight placement to the center of the machine, increased the mechanical efficiency of the entire system. It also reduced the energy demand on the diesel generators resulting in increased savings in diesel fuel costs as well as a 250% reduction in downtime due to maintenance.

The upgrades included a dual drive for the main belt, and a single drive on a shorter feed belt. All three drives were identical and are installed using only four bolts per motor. The drives are easily accessible and the one-piece drum motor ensures simplified removal if required.

“We like the fact that they are mounted using only four bolts. If something were to go wrong with any of the motors, we could swap it out with one of the spare motors we keep on hand and have the whole system up and running again in two hours greatly reducing our downtime,” says Shawn Gramm, account manager for JoyGlobal. “The old design took around eight hours due to alignments that needed to be performed and multiple parts needing to be installed.”

Van Der Graaf
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