Screening for Top Production
Screen machines and their accompanying media can mean the difference between finer production and unsaleable products. Here’s a guide to what’s on the market.
by Tina Grady Barbaccia, Senior Editor
Generates 50 Gs of acceleration
The Liwell screen from Allmineral creates a flip-flow or trampoline-like action in order to generate 50 Gs of acceleration, which allows wet, sticky material to be screened at small cutpoints without using water. The screen uses two sets of sideplates that are connected to alternating cross beams, both of which are connected to slider crank mechanism with an eccentric bearing — when one system is drive uphill, the other is drive down. A polyurethane screen mat is connected to crossbeams and is stretched to achieve the flip-flow type motion. This tenses up and overstretches the mats, and the overstretching slightly changes the holes size to allow the screen to self clean the deck. The combination of the high G forces and self-cleaning ability enables the screen to be resistant to both blinding and pegging. The screen is available in sizes up to 10 by 30 feet. According to the company, this screen is particularly useful in applications using a very fine hole size — down to a cutpoint at 50 mesh — and for removing unwanted 200-mesh dust.
Five force amplitude settings
The Prosizer 2612V closed-circuit mobile plant from Astec Mobile Screens features a PEP Vari-Vibe 2612V double-deck, high-frequency screen and horizontal impact crusher. The screen is a 6- by 12-foot top and bottom deck driven by five variable-speed hydraulic vibrators ranging from 0 to 4,200 rpm that are mounted below the screen for directly induced vibrating action. All the vibrators have five force amplitude settings on adjustable slip counterweights, hydraulic controls for variable angle operation, and a rotary tension device for quick screen cloth changes. The top- and bottom-deck discharge chutes are lined with UHMW, aggregate spreader, and a fixed access ladder with a wraparound walkway for easy screen access. According to the company, this is the only self-contained plant on the market today that’s designed to fractionate RAP with a high-frequency screen for higher percentages in hot-mix asphalt designs.
The Vari-Vibe and Duo-Vibe family of high-frequency screens come are available in multiple configurations in stationary and portable structures and in mobile screening plants.
‘No-bearing’ changeout environment
The IS Inclined Vibrating Screen from Metso Minerals combines the company’s Modular Vibrator (MV) with an extra-heavy screen body and was designed with finite element analysis. The screen’s huckbolt construction creates a connection and durability without stress points created by traditional screen-welding methods, according to the manufacturer. It has four bearings per shaft line, which are protected from contamination with the MV unit. The MV unit has a lightweight aluminum end cap that can be removed by hand facilitating counterweight adjustments and inspections and can be easily removed and replaced with a new unit, which has created a “no bearing” changeout environment.
Heavy-duty polyurethane decking
The Density Separator and Intensive Dewatering Screen wet classification system from CFS works well as a sizing screen for 0.5-, 0.75-, 0.85-, 1.0-, and 1.5-mm separations. The 1,200- and 1,800-rpm 45-degree strokes are said to be ideal for these fine separations, and the heavy-duty polyurethane decking is excellent for long life and low wear, according to CFS. The company also makes a step deck screen with two footsteps down the screen, tumbling the material bed at each step. These are used in combination to make coarse and fine sands, which can be blended together by blend gates or percent gates to make specification manufactured sand or concrete sand.
High-wear, tear-resistant wire
W.S. Tyler introduces Ty-Ger Wire, a high-carbon, industrial wire available for high-wear screening applications. Typically, this hard steel wire is only available in larger diameters, however the company says it can now weave these smaller diameter wires in this unique high-carbon alloy. The product is engineered with a special patented drawing process resulting in a high-wear, tear-resistant, and extremely elastic wire.
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