Wharf Resources, an asset of Canada-based Goldcorp, is the only operating gold mine in South Dakota, U.S., and expects to produce 60,000–65,000 oz of gold in 2014. Production typically runs smoothly at the open-pit mine, but winter weather is harsh, with snow accumulations of up to 4 ft possible from just one storm. The plant usually processes 500–700 tons per hour (t/h) of hard porphyry ore, but in wet ground conditions its former screen media was likely to blind, significantly impacting daily production.
Goldcorp’s Wharf Resources mine in the northern Black Hills region of South Dakota currently works the American Eagle Pit, shown here, using conventional loader/truck methods. Processing consists of crushing followed by heap leaching and recovery of the gold using activated carbon columns. A third-party refiner completes further processing. The mine’s processing plant often encountered screen blinding problems during wet winter weather before switching to a different type of media.
During those periods Wharf Resources would fight—often unsuccessfully—with the wet, sticky material to get it to pass efficiently through the existing screen media. “We get a lot of rain and snow, which creates mud and clay,” said Dave Austin, crusher maintenance foreman for Wharf Resources. “The mud and clay would blind the screens over. When that happened, we couldn’t get much throughput or screening efficiency.”
General Equipment & Supplies Inc., Wharf Resources’ local supplier, recommended using Major Wire’s Flex-Mat 3 High Performance screen media to eliminate the blinding. It took some convincing to get Austin to go with wire screen media, however. “I’m a big believer in polyurethane and rubber screens because of their longevity,” Austin said. “When General Equipment started talking about Major Wire screens, I didn’t listen at first because my experience with wire screen media has been that they wear incredibly fast.”
After installing a new twin-deck screen and Flex-Mat 3 media, Wharf Resources has been able to pull the mud out of the existing circuit, reducing the load on the tertiary circuit by 30%.
Major Wire said Flex-Mat 3’s design allows right sized material to pass through instead of sticking to the wires and blinding the screen.
Wharf Resources installed a new twin-deck screen plant in the tertiary circuit, fitted with Flex-Mat 3 Tensioned Series S screen media. This new combination made it possible to continue producing in any type of weather, even during the wettest times of the year. “We’ve had no problems with the Major Wire screen media. I was really surprised that they last so long and so was everybody on my team. We didn’t think a wire screen media was capable of lasting as long as these are. It’s amazing when you consider that other locations of the plant using a basic wire screen media are wearing out in just a week,” Austin added. With the current plant, the Flex-Mat 3 screens are lasting three weeks before having to be changed, saving downtime and man-hours.
With the aid of the new screening plant and Flex-Mat 3, Wharf Resources has been able to pull the mud out of the existing circuit, reducing the load on the tertiary circuit by 30%. “With the new screen plant the entire operation is much more efficient and productive. We started the plant, out with Flex-Mat 3 so we aren’t sure how much of the increase we can attribute to the screen media, but we’re happy to say that weather conditions no longer affect production and Flex-Mat 3 has solved our blinding problem,” said Austin.
Major Wire’s Flex-Mat 3, with its independently vibrating wires and lime-green polyurethane strips, is available for both tensioned and modular screen decks. It is constructed using polyurethane strips that bond the individual wires together while allowing them to vibrate independently at different frequencies. The increased screening action allows right sized material to fall through instead of sticking to the wire, virtually eliminating blinding, pegging and clogging.
Flex-Mat 3 is manufactured with abrasion-resistant OptimumWire, which features a combination of ductility, hardness and tensile strength resulting in the longest lasting wire available, providing service up to four times longer than traditional woven wire, with up to a 40% increase in material throughput. It also provides up to 30% more screen capacity than traditional woven wire screen media and minimizes downtime spent cleaning or replacing screens.
This article was written by Gary Pederson, vice president of sales for Major Wire Industries Ltd., Candiac, Quebec, Canada.
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