Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
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UNDERGROUND HAULAGE The latest version of the Kiruna truck concept, the 50-mt-capacity Electric Minetruck EMT50 is part of Atlas Copco's new Green Line. (Photo courtesy of Atlas Copco) The Green Line includes two new electric underground trucks, the Electric Minetruck EMT35 and EMT50, with load capacities of 35 and 50 mt, respectively. There is, of course, some history here, since Atlas Copco acquired the former Kiruna Electric truck with its acquisition of GIA at the end of 2011, with the Kiruna Electric truck concept having been available since the 1980s. Now Atlas Copco claims that the new versions are about twice as fast as any diesel truck in these capacity ranges, making them the world's most productive underground haul trucks. At the time of the Green Line launch, Product Manager Erik Svedlund said, "Looking at the cost per ton, using an electric underground truck can almost double the productivity while decreasing the total cost of ownership by up to 50%." According to Atlas Copco, the electric trucks reduce energy consumption by up to 70%. High-efficiency electric motors drive the axles directly, minimizing transmission losses, while regenerative braking returns energy to the grid—meaning that about 30% of the energy consumed up the ramp is regenerated going back down. The EMT trucks operate from fixed trolley lines with a small diesel engine 60 E&MJ; • JUNE 2013 used to maneuver the vehicle when it is out of reach of the main power supply. The truck draws its power through a patented trolley arm and trolley car, which automatically connects to or disconnects from the trolley line. The arm is flexible enough to allow the center of the truck to deviate by up to 2 m from the center of the line. Looking specifically at the EMT50, auxiliary power is provided by a 107-kW (145-hp) Mercedes engine, while the truck itself can be supplied with 17, 21, 24 or 28 m3-capacity boxes, depending on the characteristics of the rock being handled. Atlas Copco points out that the advantage gained by using an electric truck over its diesel counterpart increases as the ramp depth—and hence length of haul—increases, with an electric vehicle needing a power input of around 3 kWh/mt over a 400-m vertical lift compared with around 8 kWh/mt for a diesel truck. The company told E&MJ; that an EMT50 was being delivered to a mine in Canada in May. Caterpillar's Radical Approach As featured in this year's Best of Germany supplement to the April edition of E&MJ;, Caterpillar's Germanbased underground mining equipment operations have been working on a rad- ical new concept for handling ore in block-caving operations. The Rock Flow system essentially transfers armored face conveyor concepts from coal mining to the hard rock sector, offering mines the opportunity to do away with LHD operations completely in the block-cave production system. The concept centers on the use of an RF300 Rock Feeder beneath each drawpoint, each with a capacity of up to 300 mt/h, to push broken ore on to a 900-mt/h RM900 Rock Mover conveyor. This in turn moves the ore to a primary crusher, with belt conveyors being used for rock transport after that. Caterpillar said the Rock Feeder replaces the LHD at the drawpoint, so personnel are not exposed to the hazards of the loading area, even where remote control of the vehicle is being used. Major benefits claimed for the system include higher production, lower costs, a high level of automation, and a better working environment since all of the equipment is electric-powered. In addition, Caterpillar said the Rock Feeders are easy to remove for maintenance or clearance work, while the system has low maintenance requirements and high resistance to wear. One Rock Flow unit has been on trial at Codelco's Salvador mine since 2007, with a second, more extensive system scheduled for installation at the company's Andina operation this year. Caterpillar suggests that by using the Rock Flow system, mining companies can cut development costs for drawpoint-level infrastructure in block-cave operations, then achieve continuous, high-performance production that is supervised from a surface control room without the need for on-site operators. An Award for Thinking Outside the Box In May, the Canadian company RailVeyor received the 2013 Bell BEA Innovation Award. Sponsored by NORCAT (the Northern Center for Advanced Technology) and Cambrian College of Applied Arts and Sciences, the award recognizes Rail-Veyor's innovative approach to bulk materials handling in underground operations. As described in detail in E&MJ; (December 2012, pp.86–87), RailVeyor is an electrically powered series of two-wheeled interconnected mini rail www.e-mj.com