Keep Your Sand In Spec.
Fine Material Screw Washers are the workhorses of any sand production operation. They efficiently separate unwanted silts and clays from materials up to 10 mm—typically collected from washing screen underflow—while simultaneously dewatering and conveying the clean sand out of the pool. This simple yet effective design performs three essential functions: washing, classifying, and material handling, all without slowing down the rest of your circuit.
Designed for maximum cleaning performance, our screw washers are available in single and twin screw configurations to suit a wide range of capacities and application requirements. Whether you are producing mason sand, concrete sand, or other fine aggregates, the machine ensures tight gradation control and consistent product quality.
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Frequently Asked Questions
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A fine material screw washer (also known as a sand screw, spiral classifier, or sand screw washer) is a machine that combines washing, classification, and dewatering functions into a single unit, specifically designed to process -10mm (3/8 inch) sand or fine materials. It consists of an inclined tub and a rotating screw shaft that uses hydraulic action and spiral conveying to remove clays, silts, and ultrafine particles (typically -200 mesh / 75 microns) from the material, while simultaneously dewatering the washed sand to a conveyable and stockpILABLE condition.
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Fine material screw washers have a wide variety of applications across multiple industries. Key applications include:
Construction sand production: Producing concrete sand, mason sand, asphalt sand, and other construction sands that meet strict gradation and dirt content specifications.
Mining and mineral processing: Processing iron ore fines, phosphate fines, solar evaporation salts, and other industrial minerals.
Glass recycling: Washing and classifying crushed glass materials.
Manufactured sand production: Desliming and dewatering manufactured sand to improve final product quality.
Tailings processing: Recovering valuable fine particles from tailings streams.
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A fine material screw washer operates through a multi-stage process:
Feed and classification: The sand and water slurry enters the washer through a feed box into the settling pool. Heavier, larger particles sink to the bottom, while ultrafine waste materials (silt/clay) remain suspended and overflow the weir.
Washing and scrubbing: The settled material is carried upward along the inclined tub (typically 18 degrees) by the rotating screw flights. During conveying, particle-to-particle attrition occurs, removing coatings and clays from the sand grains.
Dewatering: As the material is conveyed above the water line into the "dry deck" area, water drains from the material back into the settling pool. The final discharged sand typically contains 15-20% moisture and is ready for conveyor stacking.
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While similar in basic design, they differ significantly in particle size handling and purpose:
Fine Material Screw Washers: Designed to process -10mm (3/8 inch) sand and fines. Primary function is removing -200 mesh (75 micron) silts and clays while classifying and dewatering fine sands.
Coarse Material Screw Washers: Designed to process +5mm coarse aggregates such as crushed stone and gravel, up to 100mm (4 inches). Primary function is washing dust and soluble clays from coarse particles, often featuring paddles for enhanced scrubbing action.
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A typical fine material screw washer consists of several critical components:
Tub: Heavy-duty steel plate construction, inclined, with widened side weirs and full-length curved dewatering plates.
Screw shaft: Includes the center shaft pipe and spiral flights with replaceable wear shoes bolted to the flights.
Wear shoes: Replaceable abrasion-resistant components bolted to the screw flights, available in white iron (400+ Brinell), alloy steel (500+ Brinell), or urethane.
Drive assembly: Heavy-duty gear reducer, typically triple-reduction, with speed adjustment capability (100% down to 16%).
Feed box: Includes baffle plates to reduce feed turbulence and maintain a quiescent settling pool.
Overflow weirs: Adjustable plates on the sides and back of the tub to control pool level and fines retention.
Rising current manifold: Water injection system at the bottom of the settling area to assist in separating fines from coarse particles.
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Fines loss (overflow loss) is a common concern and can be addressed through several methods:
Optimize settling area design: Choose equipment with larger settling areas and longer weir lengths to allow more time for fines to settle rather than overflowing.
Adjust weir height: Raising the overflow weir increases water depth, extending settling time and retaining more fines.
Control feed turbulence: Ensure baffles are intact and feed is introduced smoothly to prevent turbulence from disturbing the settling pool.
Add a scavenger system: For high fines loss situations, add a scavenger system (hydrocyclones + dewatering screen) to recover fines from the overflow and return them to the product.
