Switching from a wheel-mounted to a tracked crushing and screening system has revolutionised the Dutra Group quarry and recycling operations.
For the past 12 years, The Dutra Group of Richmond, CA 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 mile 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 tonne 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 costs 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,” he added.
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 a 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 set-up, 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. The 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 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. 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 3/4” drain, which is clean—no dirt. We also make manufactured sand by using the jaw, cone and screen in closed circuit.”
“We feed 3/4” clean material directly into the cone from the jaw. No other cone can handle a direct all-in-feed. 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,” Guglielmini added.
“When we first started investigating tracked equipment, Paul Campbell, owner of Powerscreen of California, the state-wide dealer for Powerscreen and Pegson, told us the Pegson 1300 cone could make sand from 3/4” material. I was very, very skeptical. But I’ve dealt with Paul Campbell since 1995, and he’s always been straight up in everything he says. So when Paul volunteered to bring in the jaw, cone and screen plants for a test in closed circuit, of course I agreed — and guess what — he was absolutely right. I was amazed. I’m still amazed. We put the whole system through every kind of gruelling test we could think of, and it came through with flying colours,” Guglielmini said, shaking his head. “We actually tried to prove the equipment couldn’t perform as claimed, but we couldn’t do it. The 1300 cone can actually make sand from 3/4”, 1/2” and 3/8” clean material.”
“The new tracked system is also much more efficient. This is equipment that likes to be fed constantly. When we do, we can get production of up to 360 tonne per hour in the quarry. Our daily goal is at least 3,000 tonne, and we normally achieve 3,200 with the new system. With old system, we might have gotten 3,000 tonne three times in 12 years.” Dutra had a lot of unplanned downtime for repairs with the old system. A major problem was with mesh and rebar clogging and tearing up the conveyors and chutes. And the old system had eight wear points, that is, where material drops from one piece of equipment to another. The new system has only four.
The new system runs like a charm, according to Guglielmini. The manufacturer’s maintenance recommendations are followed, and the equipment is checked periodically for wear. This has resulted in very dependable service from all the new equipment. The old wheel-mounted system took three times as much maintenance time and work. “I will go so far as to say that I believe tracked crushing and screening equipment, with its versatility and mobility, is the only way to go in California’s aggregates and recycling industry,” Guglielmini averred. “Nothing else makes as much sense to me. But making the decision to purchase a tracked system was only the beginning. Purchasing six pieces of new equipment is expensive. We still had to convince our corporate management people that the payback would be well worth the cost, helping us to better compete in this tough business and still earn an acceptable profit.”
“To make that recommendation, we had to stick our neck out pretty far. But I was convinced that tracked equipment was the way to go. Before going to management, we considered a number of factors: purchase cost, equipment efficiency, fuel consumption, equipment durability, parts, anticipated maintenance downtime — it’s the unexpected downtime that can kill your profits. In other words, what is it going to cost to buy the equipment, the cost to operate and maintain it annually over a period of years, and what can you reasonably expect it to be worth in resale value down the road? Powerscreen of California was a big help to me in determining these things.”
Guglielmini concludes, “Lastly, I literally crawled under, over, around and through each piece of equipment to examine it for construction design and quality. Then we went to management with all our ducks in a row: facts, figures, features and benefits of all the tracked equipment. It was really a major change in philosophy for our company. But we decided to go ahead with the purchase, and it has been a very smart decision. Management is happy with the outcome. It’s all just one huge improvement.”