An open-pit mine reduces conveyor failures and maintenance with a new drive configuration

^{First published in "Coal Age" September 2018 issue}

The pilot project established the feasibility of installing GCDs on mobile mining machines and shows the suitability of permanent magnet torque motors to drive conveyors. The results reveal that on both productivity and energy efficiency metrics, GCDs are viable alternatives to conventional geared drives. The potential for energy savings, reduction of failure rate and maintenance have also been demonstrated. The gearless solution has performed better in regard to dynamic accuracy and overall efficiency than the existing traditional solution.

Leadership at Lausitz Energie Bergbau AG (LEAG), owner of the Jänschwalde mine, which staged the project, lauded the solution. “The interest of LEAG in this pilot project mainly lies in the expectations related to higher efficiency, lower wear and hence less expenses for repairs and maintenance,” Peter Scholze, head of services, open pit mines, LEAG, said. “Since commissioning has taken place, the drive has been running smoothly.”

Further, Jänschwalde’s operations and maintenance team found the new system to be easy to learn, understand, and use, without any major difference in operation or handling when compared with the existing systems.

The proof, according to Ulf Richter, product manager, GCD, mining, ABB Process Industries, is in the numbers. “So far, during the one year of operation, we measured 6% energy saving and 100% availability of the drive with just two hours inspection,” he said.

The development amounts to historic precedent, Richter said. “This had not been possible to-date from technical and commercial points of view with the existing solution based on synchronous motor technology,” he said. “The key point for success was the decision to use permanent magnet motors.”

Tracing back to research and development initiated in 2013, the GCD package adopted by LEAG in June 2017 also included a frequency converter and a transformer. “The new gearless solution was installed on a high-capacity (15,000 metric tons per hour) discharge conveyor of a bucket chain excavator,” ABB reported.

The low-speed synchronous electric motor is controlled by a variable-speed drive to produce a shaft rotational speed of typically 50 to 150 rpm.

Enabling exact benchmarking, the GCD system runs in parallel to the existing geared drive” on the 2.5-meter-wide belt “located at the end of the discharge boom. Both drives connect to the same pulley shaft. The belt moves sand and large rocks (ice-age foundlings) that give rise to mechanical shock and vibration.

Ambient temperatures reportedly range from -25° to 40°C. And that is what the technology was built to handle, Richter said. “The drives are out in the field without any additional protection” from temperature swings, he said. Mobile or semi mobile conveyors generate higher shock and vibration stress than stationary equipment, he said. And contaminant “ingress must be avoided,” Richter said. “This has all been incorporated in the design of the drive assembly.”

White paper: Gearless drives for medium-power belt conveyors