The Aggre-Dry® FMW Screen — GreyStone Inc.'s innovative sand dewatering unit — combines a fine material screw and dewatering screen to produce sand and gravel products with moisture content as low as 8 to 13 percent, by weight, while using only 30 horsepower to wash and dewater up to 100 tons-per-hour.
A standard GreyStone inclined single-spiral fine material washer (FMW) initially dewaters the material, doing the bulk of the work. At the same time, the rotation of the dewatering screw scrubs the material to help remove surface dirt. The action of the screw flights sends the sand up the inclined tub, and ensures that the dewatering screen located at the top of the flights will be evenly fed. The vibratory dewatering screen further removes moisture from the sand. This combined process produces a caked, dry sand product that neither an inclined dewatering screw nor vibratory screen can separately achieve.
The GreyStone dewatering screen, curved around the spiral flights on the Aggre-Dry FMW Screen, has several unique features. A 0.25-mm screen opening reduces the amount of material that can fall through the screen. The feed from the screw allows the material to build to a bed depth of 14 inches on the screen, squeezing additional moisture from the sand as the vibratory motors move it along the length of the screen cloth, further reducing moisture content.
In its most innovative feature, this GreyStone unit re-introduces the throughs from the screen back into the screw's washing process, where the screw portion of the unit again pushes it to the unit's dewatering screen, increasing the amount of salable product. This process eliminates the need for costly pumps and cyclone sand separation systems — along with the additional horsepower this equipment requires. The Aggre-Dry FMW Screen should use less than half of the horsepower required to process the same tonnage of spec product on a traditional screen/cyclone system. In addition, the company has increased the water handling capacity of these units, making the Aggre-Dry even more versatile for aggregate producers
As production of these units increase, they will be offered in all of the company's standard fine material washer sizes, from 36 inches by 28 feet to 84 inches by 38 feet.