Use these dewatering tips to keep your sand operation flood free.

by John Bennington

When fine material screws fail to remove enough moisture from their material, many sand operations decide to introduce a dewatering screen into their material flow.

The producers who own them already know that dewatering screens typically require little maintenance. While some dewatering screens resemble traditional sizing screens that use eccentric shafts to induce their shaking motion, the majority of dewatering screens use high-frequency vibrators and have few moving parts. The screens are designed for an operator to simply flip a switch and run them, day in and day out. However, even low-maintenance machines still require some care, and the necessary maintenance is essential to their successful operation. In addition, operator error can affect both capacity and drying capability on these simple screens.

Opportunity for error

With either dewatering screen type, the theory behind water removal is the same; as the wet sand feed creates a deep material bed on the screen deck, the combined material weight and motion of the screen’s throw work to squeeze water through tiny apertures in the screen media. At the same time, the throw moves the material down the screen’s length. The desired result is that sand coming off the end of the screen should have a moisture content of 10 percent or less.

The most common complaints noted among dewatering screen operators – those of wet material and decreased capacity – are usually the result of not feeding enough material. If the screen cannot form a deep bed of sand, it will not be able to retain the product on the screen to remove the moisture and will also have trouble effectively moving the sand down the length of the screen. It is the vertical/diagonal vibrating motion of the screen, along with the inertia of the sand, that work to squeeze the water through openings in the screen media. The thinner the bed depth, the lower the inertia, resulting in lost and wet material – ultimately defeating the purpose of a dewatering screen.