Rock Products

FEB 2018

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Page 26 of 85 ROCK products • February 2018 • 23 production requirements," said Malcolm Bennett, plant manager for Sequatchie Concrete's Sand Switch Plant. Bennett said that after the installation of the new washing and screening circuit, they have increased throughput at the wash screen by at least 20 tph; and have increased overall production through the plant by more than 10 tph. "Our products are cleaner, our gradations are better, and as far as maintenance and downtime, we have cut that by more than half," said Bennett. The new washing and screening cir- cuit was initiated by Robert Kelly, the territory manager for Alpharetta, Ga.- based 1 st Quality Equipment, a regional aggregate equipment dealer who rep- resents both Deister and Polydeck. Kelly examined the existing circuit and made several recommendations, followed by onsite consultations with Joe Schlabach, Deister vice president of marketing and sales; and Tommy Daniel, Polydeck Southeast regional manager. The Vibrating Wash Screen A new heavy-duty 6- x 16-ft. Deister triple-deck wash screen was installed in August 2017. "We weren't shedding water very well on our previous screen and it had such a rough vibration. The new screen has such a smooth and quick vibration. In fact, it's so smooth that you can hardly tell that it's running," said Bennett. "Deister set the machine up according to our tonnage-per-hour requirements. Once we hooked the electric motor up to it, and turned it on, it was ready to roll. We're putting about 170 tph through it, while our previous screen could barely make 150 tph," he said. Schlabach explained that optimum screening efficiency results from proper adjustments in speed, rota- tion (or throw) direction, and angle of inclination. Each of these parameters affect proper depth of bed and greater throughput. As to the unit's vibrating mechanism, he said that it's located between the decks. On this model, Schlabach adds, its "Type O" vibrating mechanism produces a uniform circular movement of the vibrating frame and screening surface. "The spray equipment on the wash screen is also key to throughput. Deis- ter wash screens are provided with a pre-assembled manifold and spray system from the factory that is attached to the machine and is ready to be hooked up," said Schlabach. He explained that the nozzles fan out water jets into sheets, which provide broad bands across the screen, giving complete coverage under each header. The nozzles are staggered to provide two solid sheets of water per header. "The spray should hit the screening surface at 30- to 45-degrees. Depend- ing upon the desired washing/rinsing efficiency and material properties, the nozzles can be positioned to spray against or with the flow of material; and for most applications, a pressure of approximately 40 psi is desired at the nozzles," said Schlabach. Synthetic Screen Media Polydeck Regional Manager Tommy Daniel said that 38-mm Rubberdex mod- ular rubber screen panels are installed on the top deck of the wash screen and 16-mm Polydex modular polyurethane screen panels on the middle deck. "We've placed polyurethane panels with 5-mm slotted openings on the bottom deck, and also utilize panels with inte- grated dams to slow the material and increase washing efficiency," Daniel said. One of the reasons why the screen is so quiet during operation, said Daniel, is the fact that rubber and polyurethane media (versus wire cloth) can reduce noise levels by as much as 9 decibels, which is a 50-percent reduction as per- ceived by the human ear. "That means that plant personnel can work nearby for longer periods of time without dam- aging their hearing," he said. Maximum open area is built into the screen with the use of the Polydeck PipeTop II stringer frame system. "This framework system features unique REDUCE

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