There are many factors that must be considered when sizing a Fine Material Screw Washer

Fine Material Screw Washers retain more fine solids than cyclones, are simple to operate and require less electric power to run than other classifying and dewatering methods. However, sand washers must be properly sized to ensure proper fines retention.
There are many factors that must be considered when sizing a Fine Material Screw Washer. These include feed gradation, desired product specification and capacity required (if in a water-based system).
Simple structure
Originally based on Archimedes screw, this simple piece of equipment is capable of cleaning and washing most types of raw materials. It consists of a main body with a single welded box, holding the various parts of the machine together. Each sand washer has a rubber coated steel screw shape that is welded to the main shaft and driven by the drive motor.
These rotating screws conform to the curved section of the washer box tub, efficiently conveying and washing (through tumbling) the material while also dewatering. An overflow channel allows water to drain away from the washer box tub, and return back into the washing process.
Sand screws can be used as a standalone solution or combined with our wet wash systems, such as a Scavenger System and Hydrocyclone/Separator(tm). It is essential to properly size a Fine Material Screw Washer to achieve the desired product specification. A variety of factors must be reviewed, including feed solids, feed gradation and the amount of water in the feed slurry (if any). McLanahan offers two charts to assist in the proper sizing of the machine.
High washing efficiency
A Screw sand washer is a device that combines washing, classifying and dewatering to create a more consistent product. It removes impurities such as clay, mud, vegetation and rock coatings from coarse aggregates. It also reduces water consumption and improves the quality of the finished product.
A screw sand washer has many advantages, including the simple structure and low maintenance costs. It has a small floor space and is easy to operate. Its main body forms a single welded box, which holds all the parts together. Its screw is rubber coated and welded to the shaft. A drive motor is installed at the end of each screw line.
Screw Washers can be used as a stand-alone solution or as part of a larger wet processing system. They are highly efficient compared to other similar technologies. They are also relatively inexpensive compared to hydrocyclone and dewatering screen plants. In addition, they require less horsepower and kilowatts per ton of solids feed.
Low production cost
The sand washer screw has a low production cost and is easy to maintain. The operator should pay close attention to the overflow weirs to ensure the correct water flow, roughly 1". Too much or too little can overflow into ponds or not clean the sand to specification. It is also important to check for "sandbars" in the corners of the overflow, which indicate the shaft is running too fast or there isn't enough water to dilute the silt.
Easy maintenance
A Screw sand washer is a simple piece of equipment to maintain. Regular maintenance checks can prevent costly repairs and extend the service life of the screw. The machine is equipped with a water discharge tube that can easily remove excess water, reducing loss of the product.
Sand screws operate much slower than cyclones, and they handle irregular feed particularly well. If a large piece of oversize material enters a cyclone, it may get stuck in the apex or the overflow and halt production. But if an oversize particle enters the feed of a sand screw, it will simply be washed away and conveyed up the 18-degree incline toward the discharge.
The sizing of a Fine Material Screw Washer is based on the size of the coarse sand and the desired product specification, capacity required and the amount of water volume in the feed slurry (if applicable). McLanahan offers several charts to guide the process.