Sand Washing/Dewatering

Sand washing and dewatering equipment is used to process fine materials typically less than 0.25" (6.35 mm) that includes passing 200 mesh (75 micron).

When washing or separating, this equipment uses hydraulic separation and large amounts of water to separate 200 mesh material or coarser from the product. Therefore, the relative buoyancy of different grain particles and their setting rates under specific conditions of water flow and turbulence are critical factors in the AggFlow DM calculations.

When dewatering, the equipment uses a mechanical action to separate the product from excess water.

This equipment operates using similar inputs in the setup. Material that enters the equipment will be divided into 2 flows, being a product and an overflow. As material passes through the equipment, the flow separation is determined by the split point settings which are related to the amount of water in the feed and added, and the water retained in the product.

Sand screws are limited in the amount of material smaller than the #50 (0.297 mm) that can be raked up the incline. As spiral speed increases, more turbulence in the weir reduces the settling rate of the fines and the ability of the sand screw to move those fines up the incline.

To Adjust Sand Washing/Dewatering Equipment

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Sand Washing/ Dewatering equipment is set up from the Adjust Set up panel. The panel is organized with different sections as follows:

Feed material - Shows the manufacturer limits for the equipment if available. The red flag limits can be set or modified.
Define Water Flow - Depending on the equipment selected, manufacturer limits will be shown. If the equipment is generic or manufacturer limits are not available, the water flow limits can be set for the equipment. Water can be added to the equipment in define water flow, and for sand screws the split can be automatically calculated by changing the water flow.
Define Material Split - Material split is adjusted for the equipment by setting the % in overflow. For Sand Screws, manufacturer split based on the water flow can be calculated by selecting Always calculate split based on input.
Define water in Product- Changing one of the inputs will recalculate the others.
Results - Based on the settings, results will be automatically calculated using the feed results from the latest run.

To set up the equipment, follow these steps

Select the equipment on the worksheet (it will turn blue).
Double click the equipment or right-click and select Adjust Setup.
Set the water flow, material split points and water in product for the equipment
Review the data available on the Input, Output and Overflow tabs
Use the Power tab to record and track details of the machine.

Additional Sand Screw Settings

Spiral Speed: Adjust the spiral speed of the sand screw by moving the slider or entering a value. The corresponding Spiral RPM is calculated based on the speed. Modifying this automatically adjusts the raking capacity.

Raking Capacity:

Maximum %: Displaces the maximum percent passing #50 mesh (0.297 mm) that the screw can take at the current spiral speed.
Current Material Passing %: Displays the percentage of incoming material that is passing #50 mesh.

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To operate a sand screw properly, the Current % value must be less than the Max % value.

Set Tonnage Based Water Requirements

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To set water requirements based on feed, click on the Set Tonnage Based Water Requirements, enter the values and save, this will modify the minimum water required for the machine to operate.

Water Requirement to Operate the Machine: Specifies the amount of water required for each ton of material input.
Water Requirement for Fine Material: Specifies the amount of water required for each ton of material input that is smaller than #200 (0.074 mm).