A need to adopt more efficient mining methods after a downturn in the coal price led management at the New Acland Mine (NAC), located adjacent to the Queensland township of Acland, to trial a Wirtgen 4200 SM surface mining machine.
Previously, coal and interburden were extracted by bulldozers fitted with ripper teeth and assisted by wheel loaders.
Wirtgen says the 4200 SM is suited to the challenging geological conditions in the mine, which comprises up to 27 mostly thin coal seams interspersed by layers of hard interburden.
It says that, compared to conventional methods, the selective surface mining technology simplifies the mining process, thus reducing operating costs and supplying coal of higher quality to the neighboring processing plant.
The companies agreed on a six-month trial phase with defined target performance levels. The 4200 SM’s point-attack cutting tools were subjected to in-depth trials and optimised to cut both coal and interburden.
The surface miner achieved the projected cutting performance of up to 3,000 tonnes per hour, and NAC made the call to buy it.
To maximize exploitation of the coal deposits, the 4200 SM cuts and loads the material in a single machine pass, producing an even and easily trafficable surface in the process.
Previously, NAC had two dozers and a wheel loader performing the work now done by the 4200 SM. The resulting savings, mainly in labor and fuel, have led to a significant reduction in operating costs, Wirtgen says.
The company says the operators cab on the 4200 SM has significantly reduced vibration, noise levels and emissions which work together to ensure operator health.
The cutting drum has been specially designed for operation in soft rock and is ideally suited to mining coal (20 MPa) and the significantly harder interburden layers (50 MPa). A camera system enables the machine operator to conveniently differentiate between the two layers, thus significantly improving coal quality.
The 4200 SM mines coal in a selective process at exactly the specified cutting depth, producing a clean cutting surface and guaranteeing high degrees of purity, Wirtgen says.
As a result, fewer truck passes are needed to transport the material to a special coal-washing plant for further processing and to return the separated tailings to the mine.