Weba Chute Systems has provided a turnkey solution including investigation, design, manufacture, installation and commissioning of the BK9 conveyor transfer chute at Debswana’s Damtshaa mine in Bostwana. After eight months of continuous operation, the installation has proved to be trouble and maintenance free. The challenge for Weba was for an equal split feed between the two vibrating screens with the complete wetting of the ore before it entered the screen deck.
The new system, which is apparently the only recorded slurry screen splitter distributor system, provides for a belt capacity of 600 t/h (nominal) with water and effluent addition of 1,080 m3/h. During normal operation, each leg operates at 50% capacity and during maintenance one leg will perform 100% of the duty cycle while the other one is shut down and checked.
Debswana elected to replace conveyor BK9’s previous transfer chute, which was supposed to convert the dry ore to slurry and distribute it equally between the two vibrating screens. The chute, however, was prone to blocking, requiring regular maintenance and did not split or distribute evenly.
“The previous third-party design resulted in a consistent build-up on the apex and the head pulley was too close to the chute. Other problems included excessive wear rates and no allowance for scraper fines,” Mark Baller, Managing Director of Weba Chute Systems, says.
“We chose a Weba slurry arrangement with multiple changes of direction, comprising four levels of flood box along the 11 m descent into the transfer chute, which would result in a full width weir overflow onto the slurry,” Baller explains. “We also made selective use of micro ledges to minimise parent metal wear and supplied a relatively shallow trouser leg chute at an angle of 40˚ to vertical.” Baller added: “Because of the careful planning we instituted prior to the installation, there has little need for after-sales support after handover.”
“A reference check was performed by WorleyParsons for Debswana in May 2009 and the feedback was extremely positive,” Baller says. “The Weba Chute System has achieved all of the requirements laid down by the client at the outset and there is no wear evident in the chute. The recommendation is that Debswana considers installing Weba technology at all problematic or challenging transfer chute sites at the mine in future,” he concludes.