Material Matters - Fall 2012 - (Page 15)

FOCUS ON SCREENING By Carol Wasson for Deister Machine Company Breaking the Bottlenecks Efficient Screening is Key to High-Quality, Multiple-Product Output AS DEISTER MACHINE Company looked for a showcase project to highlight its 100th year of industry service, they didn’t have to search too far. Callanan Industries recently undertook the relocation of its Ravena crushing operation to South Bethlehem, and the company seized an opportunity to make key upgrades to an 18-year-old plant. Now the relocated facility is on track to produce up to a million tons of crushed limestone annually with its beefed up crushing, screening and washing operations. “We needed to eliminate some bottlenecks, increase efficiencies, 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 Company. Onboard with Deister is its East Schodack, NY-based representative, Dibble Equipment. Owner Rod Dibble worked closely with Clemente, and Plant Manager Steve Akers, to specify the most cost-effective solutions while meeting stringent specifications. Ultimately, the team decided to capitalize on the reliability of five existing screens, while upgrading four strategic screening locations with new Deister screens. While everyone wants more tons per hour across the screen, the key to optimum screening is maximizing capacity without losing quality and efficiency. Vibrating screens must be properly selected, designed, and applied – and must be operated under the correct parameters. If not, screening circuits may become big bottlenecks. Do the math. A screen operating at 75 percent of total efficiency allows 25 percent of material within the desired product size range to be rejected with the oversize material. Bottom line, that means that production goals and profit margins are falling through the cracks. Perhaps the most important upgrade, says Akers, was the replacement of two older single-deck high-speed pre-screens with two 6’ x 12’ double-deck high speed pre-screens. “These high-speed pre-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 uphill for more efficient stratification. “Uphill is for quality and downhill is for quantity,” he stressed. According to Dibble, the two high-speed pre-screens pull out the 1/8-inch-minus sand product before the material is fed directly onto dual 8’ x 20’ triple-deck finishing screens. “The high-speed screens run at approximately 1200 rpm, and operate with a very short 1/4-inch stroke and at a steep incline of 30 degrees. Dibble further explained that the double-deck approach on the high speed screens allows greater stratification of the  feed  material between the decks. “The load is reduced on the bottom deck, which in turn reduces the depth of bed 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 optimal size and type of openings needed,” he said. Material Matters • Fall 2012 15

Table of Contents for the Digital Edition of Material Matters - Fall 2012

Breaking the Bottlenecks
Glacial Materials Goes Emerald Green
The System Works
Giving HMA Driveway Advice
Promotion Doesn’t Cost – It Pays
Exposed Aggregate Pervious Concrete
Stuyvesant Falls Hydroelectric Plant: Steel Fiber Reinforcement in Action By Dan Casale

Material Matters - Fall 2012