Fenner Dunlop’s redesigned rockbox transfer system and ongoing conveyor modifications at Yancoal Australia’s Ashton Coal underground mine are improving conveyor availability, reducing costs and minimising the potential for shutdowns usually associated with mining a narrow seam.
The current seam at Yancoal’s Ashton mine in the Hunter Valley ranges from 1.8–2.2m high against an average height of 3.6m throughout most of the region’s open cut and underground mines. The narrow seam is not unique to the Ashton mine and is generally confined to mines in the eastern half of the Hunter Valley mining zone.
According to Ashton engineering manager Barry McKay, the seam is a symptom of the challenging geology of the area and “something we have to deal with.”
With the longwall system set up to cut at 2.5m the decision was made to stay with the established cut height and have a primary separation of coal, sandstone and mudstone as the product was conveyed to the wash plant. Fenner Dunlop, as conveyor contractors to the mine, was asked to design an appropriate system.
Water became a primary design consideration. Cutting more rock meant using more water to control the dust – water that has to be separated off early to avoid damage to the conveyor system and components.
Fenner Dunlop’s solution was to redesign the existing transfer point on the trunk conveyor to include a rockbox which quickly separates excess water from the mined product.
“It’s a unique solution to something that could have been a real problem for us,” said McKay. “Rockboxes are not an established part of the underground mining de-watering landscape. It’s a credit to the design ingenuity of Fenner Dunlop, along with their understanding of the coal industry, that they could successfully adapt the rockbox technology to this project.”
The new components were all made to be installed during the mine’s weekly one-shift maintenance shutdown period and, in a nod to site safety and maintenance accessibility, the transfer point and integral rockbox were re-designed for floor mounting.
From Ashton’s point of view the project is a success and exceeding expectations.
“They have worked very closely with us to meet construction and installations time constraints and avoid any unnecessary shutdowns,” said McKay.
“Along with a 6 per cent improvement in system availability, we are seeing an improvement in overall efficiency, considerably less wear on the belts and associated installed equipment and tangible savings in the conveyor maintenance budget.”