Additionally, he explains that another incentive for the modular approach is the ability to economically relocate the primary circuit within the pit. “In about 15 years, we will move the modular primary to the face and convey to the surge pile of the secondary plant,” LeClair says.

When it came time to assemble the plant, the process was simple and straightforward. In addition to the plant and manufacturer teams, a contracting company — with no previous experience in erecting a plant — handled the assembly. Detailed drawings allowed the process to be handled seamlessly. “For the entire structure, we never had one anchor bolt out of place, which is remarkable in itself,” LeClair recalls.

Design goals

The top goals of the new crushing system design were locating both the primary and secondary circuits nearer to the face; meeting a minimum production throughput goal of 1,200 tons per hour; eliminating any bottlenecks throughout the crushing system; and minimizing fines production.

Due to the previous blasting pattern and the operation of the older gyratory crusher, the operation produced in excess of 300,000 tons of fines annually, which had no viable market at that time. Furthermore, the operator had no opportunity to remove excess fines until the material went through both processing operations and was put into the stockpiles. “So we had all the cost of processing the fines, and then had to recover them as well,” LeClair says. “Now we have the ability to remove the excess fines right at the quarry face with a two, triple-deck screen setup on the discharge side of the secondary circuit.”

The modular primary crushing station includes a 60-inch by 30-foot step-deck vibrating grizzly feeder; the largest jaw crusher currently available in the U.S. market; and a 175-ton live storage dump hopper. A 3,000-foot-pound breaker breaks up any large oversize before it hits the crusher.

The new plant has reduced monthly energy costs by more than $50,000.

“We could have gone with a smaller crusher, but to get the minimum of 1,200 tons per hour, we would have been at the top end of the capacity of that crusher — and we wanted room for growth,” LeClair says. “We would never want the first circuit, especially, to ever be a bottleneck.” He estimates that the unit can comfortably process up to 1,600 tons per hour. As such, the conveyors are sized to handle higher tonnage, and the screens are also sized for excess capacity with triple-deck versus double-deck models.

Material is conveyed from the jaw to the surge tunnel which features pan feeders to control the feed to the secondary circuit. “The tunnel was delivered to us in pre-assembled sections with lights, feeders, and conveyors actually hanging inside the tunnel. We could just lift it right off the trucks, set it on the concrete, and just bolt it up, establish all the connections, and never have to touch it again,” LeClair says. The surge feeds a modular scalping screen station with an 8-foot by 20-foot, triple-deck, inclined vibrating screen.

The modular secondary crushing station includes a 600-horsepower cone with an automated crusher control system. LeClair likes the anti-spin system on the cone, as it stops the head from spinning and reduces liner wear, while the automation program allows operators to monitor wear and allows adjustments on the fly. “We’re getting up to 1,300 tons per hour from the secondary, and that is exceeding goals,” he says.

As to the programming and PLC-controlled operation of the plant, LeClair says that the manufacturer assigned one of its in-house electrical engineers to interface with the Carmeuse electrical engineer. Either in the control house or remotely, LeClair can monitor and track every process at the facility, including transfer points, conveyors, motors, and sensors, as well as material flow and tons per hour. Diagnostics can be run on site, remotely, or by the manufacturer.

Meeting design goals resulted in significant operating cost reductions. In energy costs alone, LeClair estimates a savings of more than $50,000 monthly, in part due to the use of properly sized, high-efficiency motors throughout the plant. The operation also eliminated one 150-ton haul truck that burned more than 250 gallons of fuel in a single two-shift day and had an annual maintenance operating cost that averaged $25 per operating hour (not including labor costs).

LeClair says that Carmeuse is fortunate to have retained its seasoned employees throughout the recession, with nearly 60 being on staff today. “Through attrition, we lose some personnel, and with the new plant, we can operate without hiring replacements,” he says.