Rock Products

DEC 2012

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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���We needed to eliminate some bottlenecks, increase effciencies, and continually improve the quality and consistency of our products,��� said Mark Clemente, Callanan vice president of operations. Screening circuit upgrades were planned in consultation with Deister Machine Co., a manufacturer which is cur��� rently celebrating its 100th year of industry service. On��� board with Deister is its East Schodack, N.Y.���based representative, Dibble Equipment. Owner Rod Dibble worked closely with Clemente and Plant Manager Steve Akers to specify the most cost���effec��� tive solutions, while meeting stringent specifications. Ulti��� mately, the team decided to capitalize on the reliability of five existing screens, while adding four new screens in strategic locations. that maximum screening efficiency results from proper adjustments in speed, stroke, rotation (or throw) direc��� tion, and angle of inclination. Each of these parameters af��� fects one of the most important facets in screening ��� proper depth of bed. As feed material is a mixture of varying sizes, said Schlabach, oversize material will restrict the passage of undersize material, which results in a build���up or bed depth of material on the surface of the screen. Bed depth diminishes as the undersize material passes through the screen openings. For efficient screening, the material bed should not reach a depth that prevents undersize from stratifying before it is discharged. He says that the industry rule of thumb is this: ���Depth of bed (in dry screening) should not exceed four times the opening size at the discharge end of the screen.��� The first initiative was the replacement of a secondary 8��� x 20���ft. double���deck scalping screen with an 8��� x 24���ft. double���deck screen. ���The 8��� x 20���ft. screen was good in its day, but after we upgraded our secondary crushing circuit (from a cone/VSI to a cone/cone setup), we needed more screening capacity,��� said Akers. ���We also replaced our double���deck wash screen with a new 8��� x 20���ft. triple��� deck wash screen so that we could achieve three product sizes.��� However, the most important upgrade, said Akers, was the replacement of older single���deck high���speed screens with two Deister 6��� x 12���ft. double���deck high���speed screens. ���These high���speed screens allow us to be steps ahead by cleaning our material before it reaches our finishing screens. In the end, it���s about quality, not quantity,��� said Akers who adds that the operation runs all the screens up��� hill for more efficient stratification. ���Uphill is for quality and downhill is for quantity,��� he stressed. According to Dibble, the high���speed screens pull out the 1/8���in.���minus sand product before the material is con��� veyed to dual 8��� x 20���ft. triple���deck finishing screens. ���The high���speed screens run in excess of 1200 rpm, and operate with a very short �����in. stroke and at a steep incline of up to 30 degrees. Dibble further explains that the double���deck approach on the high���speed screens allows greater stratifi��� cation between the decks. ���The load is reduced on the bot��� tom deck, which in turn allows more open area for greater throughput,��� he said. As to this integral circuit, Dibble tapped the expertise of Joe Schlabach, vice president of marketing and sales at Deister. ���Together we determined the exact operating parameters, and we also conducted the necessary screen cloth calculations to determine the opti��� mal size and type of openings needed,��� he said. The high-speed screens run in excess of 1200 rpm, and operate with a very short ��-in. stroke and at a steep Consequently, with a �����in. opening, the depth of bed at the incline of up to 30 degrees. discharge end should not exceed 2���in., for example. Proper Depth of Bed When specifying screening circuits for operations such as the Callanan South Bethlehem Plant, Schlabach explained www.rockproducts.com ROCKproducts ��� DECEMBER 2012 19

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