A Warman MC mill circuit slurry pump on trial at First Quantum Minerals’ Frontier mine in the Democratic Republic of Congo (DRC) has increased the mill throughput significantly and almost doubled the lifespan of the pump wear parts. Rui Gomes, Product Manager – Slurry Pumps at Weir Minerals Africa, says that the pump was installed and commissioned in March 2010, with a mill throughput of up to 1,200 t/h. “The Warman mill circuit pump has been engineered for arduous operating conditions and manages the large particle sizes of the raw product as well as scats and foreign material so often found in the dense abrasive slurries in a mill discharge application,” he says.
“While the pump set-up is similar to that of the original installation, the Warman MC pump is equipped with a larger impeller which allows the unit to be run slower, resulting in reduced wear,” Gomes says. “The expeller vanes on the pump have also been engineered to reduce recirculation and this further minimises wear while at the same time improves pump efficiency.”
Gomes says that as at the end of July, the pump components were entering week 22 without having been replaced. “This can also be attributed in part to the pump’s adjustable throat bush and back liner,” he says. “By adjusting the front and back liner, the gap between the liner and impeller is kept to a minimum reducing recirculation and this further improves the wear life of the components.”
Wear on the pump components is monitored at Frontier mine through visual inspections by both Weir Minerals Africa and mine personnel during scheduled or unscheduled maintenance shutdowns. Sadly now, the mine has been shut by a dispute with the DRC government. The mine has been responsible for monitoring the actual pump performance and this data includes, amongst others, current draw, tonnage throughput, relative density, water consumption and operating hours.
“Following the success of these initial field trials, the next step which started in August, is to test a trimmed impeller to match the output speed of the pump with the speed of the gearbox,” Gomes says. This trial will run for a period of 10 to 12 weeks with the impeller which was manufactured in South Africa by Weir Minerals Africa.
Commenting on mill discharge applications, Gomes says that the Warman MC pump incorporates the latest in hard alloys and elastomer technologies. Weir’s proprietary R55 rubber has successfully outlasted and outperformed metal in many mill discharge applications worldwide, and there are numerous Warman MC pumps operating effectively in both South America and Australasia in this type of harsh application.
“An additional advantage of having a rubber lined pump over an unlined unit is that the liners can wear fully without compromising the integrity of the pump casing,” Gomes says. The pump easily manages the large sized particles in dense abrasive slurries for which it is specifically designed, including ball mill and SAG mill cyclone feeds and water flush crushing in mineral processing plants.
“It is an ideal slurry transfer unit for exacting applications, like gravel dredging or coarse coal cyclone feeds, because it has a large open passage that reduces internal velocities, resulting in less wear,” he says. The large diameter shaft, with its short overhang and heavy duty roller bearings housed in a removal bearing cartridge, extends bearing life. Shrouds that extend beyond the periphery of the impeller, together with expelling vanes, improve the flow and reduce wear at the expelling vane tips.
Commenting on the choice of mine for the trial of the Warman MC pump, Gomes says that one of the main motivating factors was transfer of skills and knowledge. “A Weir Minerals mill pump specialist has been intimately involved with the commissioning and installation of the pump and is responsible for on-site training for Weir Minerals Africa personnel based in Zambia, as well as mine personnel.”