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IN-PIT CRUSHING 54 E&MJ; • JULY 2017 www.e-mj.com Professionals in mineral processing know the MMD name and associate it with the sizer technology it introduced almost 40 years ago. More recently, the company has been finding more uses for its large sizers in the pit. They have recently launched two new pieces of equipment that could revolutionize truck-shovel mining, the Mo- bile Sizing Station and the Surge Feeder. About 12 years ago, MMD built an apron feeder for a Colombian coal operation that accepted loads directly from a dragline. It proved to robust enough to process the overburden and load the haul trucks. More recently, MMD installed a semimobile in- pit sizer and conveyor (IPSC) at a Chinese mine. Now they have combined the experi- ence from both of those operations to build a system that lets the shovel dig continuously. Open-pit mines constantly struggle to properly pass match trucks and shovels, David Pitchford, president, MMD Miner- al Sizing Americas, explained. "There is a lot of room for improvement as far as accuracy and efficiency," Pitchford said. "Trucks rarely reach 90% of their fill fac- tor and most shovels rarely load at 6,000 tons per hour (t/h) when they should be loading at 10,000 t/h because they are waiting on trucks." At the time, the Colombian mine could not purchase a shovel due to long lead times, so they improvised and with MMD's help developed an alternative sys- tem. "The trucks drive under a hydrauli- cally powered feeder, which can be started and stopped immediately," Pitchford said. "We could load trucks three times faster. What we also found was that we could load trucks accurately [98% fill factor]. The system also eliminated the time consumed in reversing the trucks into their loading position. The trucks fall in line and it takes about 75 seconds to load them precisely." MMD also built an IPSC installation in China where a shovel loads rock into it continuously and it sizes the material and places it on a conveyor. Reminiscing during a presentation at the 2017 Haul- age & Loading conference, Pitchford said he spent four hours on the machine one day and the shovel operator never quit loading the IPSC. "The shovel operator never needs to stop until he repositions the machine," Pitchford said. "For the first time, a shovel operator is continu- ously loading 10,000 t/h to 12,000 t/h." At that point, Pitchford knew MMD could connect trucks and shovels with a contin- uous loading system. The IPSC system in China feeds a conveyor system, but he knew mines with large truck-shovel fleets would not replace their equipment with convey- ors after making that investment, plus they would have to redesign the pits. Combining the experience in Colombia and China with the feeder and the IPSC concepts, MMD developed the Mobile Sizing Station and the Surge Feeder for loading trucks. Developing a New Continuous System To crack the nut, MMD needed to build a piece of a kit that would sit next to the shov- el, and make it mobile to move along with the shovel, so the mine can use the shovel to its maximum capacity, Pitchford reasoned. Mining ore, however, is different from moving overburden. So MMD began to work on a concept where the shovel loads the Mobile Sizing Station, which in turn feeds the Surge Loader. The Surge Loader places crushed ore into the haul truck in a very quick and precise manner. MMD flew a group of South American copper miners to China to see the IPSC in action. They wanted to mine ore in this fashion and they have now decided on a 12-month pilot program to monitor the production of the shovel working in tan- dem with the Mobile Sizing Station. A New Approach to Truck- shovel Mining Employing a Surge Feeder working in tandem with a Mobile Sizing Station, open-pit miners could soon realize the continuous mining benefits of in-pit crushing, while using the existing truck fleet for haulage By Steve Fiscor, Editor-in-Chief New mining methods would use a Surge Loader for overburden or waste (top) and a Mobile Sizer Station and Surge Loader for ore (bottom).