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Reaping the benefits of a tracked mobile crushing and screening system

Switching from a wheel-mounted to a tracked crushing and screening system revolutionized The Dutra Group’s quarry and recycling operations

For the past 12 years The Dutra Group, of Richmond, California, had been using a portable, wheel-mounted, electric-powered crushing/screening/conveying system that they transported about four times a year between their 300-acre basalt (blue rock) quarry at San Rafael and their 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 tons of rubble; then on to another yard or back to the quarry.  Each move required four or more men and 11 lorry loads, including towing two crushers and a screen, all of which 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.

Jon Guglielmini, quarry manager, commented: ‘The old system was too complicated, cumbersome, and was costing us too much in lost production time, maintenance time and expense, and moving costs. 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 60ft land conveyors, a 125ft 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 is designed for high output in quarrying and recycling applications. Features include low-fuel consumption, high mobility, plus simplified setup, operation and maintenance. The 1300 cone is designed for sub-base and aggregates, with good cubicity, throughput and reduction ratios. The Chieftain 2100 is designed for large volumes of high-specification products. The three-deck version has a hydraulically folding re-circulating conveyor, eliminating the need for a crane on site.

At the quarry, the jaw feeds the primary cone directly, 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: 3/4in, 1/2in, 3/8in and quarry dust (3/16x0). 

‘The old wheel-mounted system was much too labor intensive and time consuming to set up and tear down,’ Jon 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 7ft to get the apron feeder under it. We had to jack up the cone about 3ft. 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. 

‘We have none of that with the new system. 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 low-loader lorries, and off we go.

‘Also, the new system is much more versatile. 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 3/4in base material and 3/4in drain, which is clean.  We also make manufactured sand by using the jaw, cone and screen in closed circuit

‘We feed 3/4in clean material directly into the cone from the jaw. No other cone can handle a direct all-in-feed and I have never before seen a cone that can handle fines going into it without plugging up.

‘With the 1300 cone we can recycle in the morning and make sand in the afternoon with just a screen change, but no liner change.’

Dutra report that the new tracked system is more efficient than the old system. They can achieve production of up to 360 tons per hour in the quarry. Their daily goal is at least 3,000 tons, and they normally achieve 3,200 with the new system.

 
 

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