Quarrying
Track impressions Switching from a wheel-mounted to a tracked crushing and screening
system revolutionised The Dutra Group quarry and recycling operations
For the past 12 years, The Dutra Group, of Richmond, CA has been using a portable, wheel-mounted, electric-powered crushing/screening/conveying system that it transported about four times a year between its 300-acre basalt (blue rock) quarry at San Rafael and its concrete recycling yards at Richmond as well as two former sites. All are located in the San Francisco Bay area and range from 15 to 35 miles apart. When sufficient material stockpiles were built up at the quarry, the equipment was moved to one of the recycling yards to crush anywhere from 60,000 to 80,000 tonnes of rubble; then on to another yard or back to the quarry. Each move required four or more men and 11 truckloads, including towing two crushers and a screen, and took 11 days.
In February 2010, Dutra switched to a diesel-powered, track- mounted Powerscreen crushing and screening system that requires only two men, four trucks and two days for each move. In addition, the new system has substantially increased material production at all sites and has dramatically reduced costs overall. “The old system was too complicated, cumbersome, and was costing us too much in lost production time, maintenance time and expense, and moving costs,” said quarry manager Jon Guglielmini “Each move cost about $25,000 one way, or $100,000 for four annual moves. In addition, we lost a total of 44 production days for four moves. With the new Powerscreen system, each move costs about $10,000, or $40,000 total for four moves, and we lose only eight production days total. “Sometimes we want to move the crushing and screening system from place to place within the quarry, to follow the face or put the equipment down in the pit. Moving the old wheeled system took two days. Moving the new tracked system takes
two men about three hours.” The old system included a jaw crusher, apron feeder, cone crusher, a side conveyor, a return conveyor to the cone, a screen-feed conveyor, a screening plant, two 60’ land conveyors, a 125′ radial stacker, several chutes, and a generator. The new Powerscreen system includes an 1180 Premiertrak jaw crusher, two 1300 Maxtrak Automax cone crushers, a Chieftain 2100X double-deck dry screen, a Chieftain 2100X triple- deck dry screen, and a track conveyor. The 1180 Premiertrak jaw is designed for high output in quarrying and recycling applications. It features excellent reduction, low fuel consumption, high mobility, plus simplified setup, operation and maintenance. The 1300 cone excels in production of sub-base and aggregates, with excellent cubicity, throughput and reduction ratios. The Chieftain 2100 is designed for large volumes of high specification products. The three-deck version has a patented hydraulically folding re-circulating conveyor, eliminating the need for a crane on site. At the quarry, the jaw feeds the primary cone directly (all-in- feed), with no need for a screen plant in between. Material then goes to the two-deck screen, with oversize going on to the secondary cone under the reject side to be re-crushed and go back to the two-deck screen. The rest goes to the three-deck screen for distribution to four stockpiles: 3/4″, 1/2″, 3/8″ and quarry dust (3/16x0).
“The old wheel-mounted system was much too labour intensive and time consuming to set up and tear down,” Guglielmini said. “It was electric powered; so we had wires and connections to deal with and a generator to transport. We had to jack up the jaw seven feet to get the apron feeder under it. We had to jack up the cone about three feet. Everything was mounted on blocks and hydraulic jacks. We had to build ramps. If you tried to tow the equipment, the wheels sank into soft or muddy ground. It was all a problem—an expensive one. “We have none of that with the new system.
The new Powerscreen system consists of a Premiertrak 3244 jaw, two 1300 Maxtrak cones, two Chieftain dry screens, and a track conveyor
34 Solids & Bulk Handling • March 2011
Tracks don’t get mired in mud. We just drive the equipment into place and start the engines. The most we might have to do in addition is to build a ramp a foot high to the jaw plant sometimes. When we move the system, the tear-down and cleanup are quick and simple; we drive the equipment onto lowboy trucks, and off we go. “Also, the new system is much more versatile,” Guglielmini said. “At the rock quarry, we use all six pieces of equipment. But we need only four at the recycling yard: the jaw, the cone, the 2100 double-deck, and a stacker conveyor. At the yard we produce 3/4″ base material and
www.solidsandbulk.co.uk
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