Sifting Through Screening Equipment
- Published: Wednesday, 01 July 2009 08:00
When asking what an aggregate professional does, the answer is often, ìI take big rocks and make little rocks.î Of course, that's a science in itself. But no matter how efficient an operation is, it can't blast all Ω-inch stone or even crush all Ω-inch stone. Hence, that material has to be sorted by screens. Unlike other aggregate equipment such as conveyors or mobile equipment, there seems to be no one right way to do this. Screens can be horizontal or they can be inclined. The media can be rubber, polyurethane or wire that might be heated or vibrating. There are wet screens, and there are dry screens. There are portable screens and stationary screens. Each of these choices offers its own set of advantages.
SCREENING TECHNOLOGY OFFERS PLENTY OF OPTIONS
The Terex Cedarapids CRS6203 portable screening plant has a new truss frame design for added stability and vibration resistance, the company says. Blending chutes and multi-section gates allow the plant to produce six products simultaneously. Heat-treated chute materials are included, and a flex-shaft screen drive maintains constant belt tension to prevent belt whip. A high G-force, 6- ◊ 20-foot triple-deck ElJay screen has an oval stroke. The CRS6203 also has flex-shaft screen drive system. Heavy AR400 blending chutes with multi-section gates provide numerous product variations. Wide cross conveyors have more horsepower, and vulcanized belts are snag resistant. Cross conveyors extend to reach transfer stacker conveyors. A fines rejection conveyor is optional.
Unified's TwinWire Screen is designed for high-impact, top-deck applications. Typically used for 11/2-inch openings and larger, this construction provides durability, while maintaining open area. High-carbon, stainless steel or Tufflex wire is recommended and can be made to fit any screening area, the company says.
Special tooling is designed for various wire diameters to ensure uniform openings with a strong lock-crimp construction. In some tested applications, field observations uncovered a ?-inch wire outperforming a ?-inch-diameter, single-wire construction.
Polydeck's PipeTop II stringer system has 1/2-inch-wide rails of the PipeTop II system, coupled with their Maxi screen panel designs that allow for more holes on the screen panel surface. It features steel ferrules with screw-in polyurethane inserts, which can be changed if they become worn, without replacing the frame. The ferrule inserts are available in several fastening options, depending on the needs of the application. The system even can be adapted to accept wire cloth for special runs, then changed back to its flat deck surface.
PipeTop II rail sections are available in three options. Individual rails are bundled and shipped directly to any OEM, to be installed in a new deck frame. Jigged assemblies, with end plates and spacers are made for onsite installation when converting an existing deck to the PipeTop II system. The third option is a complete deck frame with stringer rails, ready to be bolted into position when replacing a deck on an existing vibrating screen.
Polydeck Screen Corp.
KPI-JCI has a 14-page brochure focusing on materials separation. It features the company's line of horizontal, incline, combination, scalping and screening plants. This brochure reflects design features and specifications for each model of screen available to the industry. This includes the company's triple-shaft horizontal screens with an oval motion stroke pattern.
Screens have a huck-bolt design and an internal oil bath lubrication system with a Titan oil seal. Sizes range from 5 ◊ 16 feet to 8 ◊ 20 feet. Three-deck configurations are available for both wet and dry applications.
GreyStone offers three models of dewatering screens: the DS-488 (4 ◊ 8 feet), DS-6010 (5 ◊ 10 feet) and DS-7212 (6 ◊ 12 feet) ó to handle a variety of capacities and dewater up to 350 tons per hour. The company says the screens eliminate the need to air dry concrete and masonry sands that typically retain from 18% to 24% moisture. The GreyStone dewatering screens reportedly cut moisture to 10%. As each unit receives water-saturated fine material, it produces a dense, compact cake that rides up the belt and forms a pile without runoff or water pools.
GreyStone's high-frequency separator allows producers to adjust bed depth, table tilt and vibrator variables in order to remove up to 50% of the water from material. The plant can combine the adjustable motor force in conjunction with the adjustable bed tilt.
The dewatering screen has two vibrators that initiate a linear motion, driving particles in an uphill, downhill or horizontal direction so water is strained down through the sand bed and below the screen deck. The urethane deck has a 0.25-mm aperture for a range of particle sizes. The deck handles up to 14 inches of material depth, making use of the bottom thin layer of material to preserve fines smaller than 200 mesh. All of GreyStone's dewatering screens models are constructed of ASTM A36 structural steel.
The Metso TS, Triple Slope, creates a high G-force, which stratifies the feed material faster than other screens and results in higher capacities. The three separate deck angles create three distinct material travel rates. Higher travel rates at the feed end screen out the fines, and the slower travel speeds in the center and discharge end allow near-size material more time to screen out. The modular vibrator is standard, and overhead mounting keeps the vibrator out of the material flow and creates greater clearance between the decks for access to the screen media.