Fit for duty: Screens increase aggregates production at large quarry
March 1, 2008 By: Carol Wasson Pit & QuarrySituated around an iron ore mine that dates back to the days of George Washington, the Mount Hope Quarry is as rich in history as it is in resources – as once the site supplied ore for cannon shot and shovels used by the Continental Army, while today it boasts a granite deposit exceeding 300-million tons in permitted reserves.
Owned by Tilcon New York Inc. and located in Wharton, N.J., about 35 miles west of New York City, its 4-million-ton-per-year output of high quality aggregate is integral to the region's infrastructure. As such, the site is often the recipient of innovative operational upgrades to ensure the maximum in ongoing production efficiency.
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Products are quite plentiful at Mount Hope Quarry. Running round the clock and averaging 2,000 tons per hour, the operation processes more than eight sizes of crushed stone, plus manufactured sand, and a number of base materials. As to asphalt aggregate, the quarry produces at least five products for Marshall Mixes and another six products meeting Superpave specifications – so it's not surprising that Plant Manager Clifton Morris said, "Screening is a huge part of our operation."
Screening upgrades
To increase capacity and throughput, Mount Hope Quarry recently upgraded its screening circuits by replacing older single-drive units with new dual-drive screens manufactured by Deister Machine Co. and customized specifically for the plant and its applications. In 2007, four new Deister finishing screens were added – three triple-deck, 8 ft. x 20 ft. units and one single-deck 8 ft. x 20 ft. screen. Five additional screens are being installed, as primary and secondary scalpers, prior to spring startup this year.
"Screening upgrades were required as our previous single-drive screens couldn't handle the tonnage and keep a consistent stroke, so we were getting a lot of carryover," Morris said. "On the smaller-opening screens particularly, it was tough to get the material clean, and the inconsistency could put the product out of spec, which would cost some tonnage."
 These two photos show new screens in place at the Tilcon operation. At right, two new Deister 8-ft. x 20-ft., triple-deck, dual-drive screens are installed on Tilcon's tower, with a Deister H-beam fitting up with Tilcon's tower beam. |
With the four new Deister finishing screens, improved gradation has been one of the most favorable results, Morris said. "We're able to use smaller openings in our screens and still get the finished material as clean, if not even cleaner than expected. That gives us more options as to the cuts we can make – and we can make adjustments to the screen to really fine-tune the gradation. But bottom line, the product is cleaner and more consistent – that's the key – and we're getting consistent tonnage across the screen," he said.
Morris explained that the five additional screens being added to the primary and secondary circuits include four triple-deck 8 ft. x 20 ft. units and one single-deck 7 ft. x 20 ft. screen – again, all dual-drive units replacing less efficient single-drive models. Plus, the upgrade to triple-deck screens, particularly in the primary position, will allow increased throughput as the middle deck acts as a "relief deck" between the top and bottom deck, preventing the bottom deck from overload.
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