8 Reasons To Use A Dewatering Screen In Your Application

Alan Bennetts
By: Alan Bennetts February 1, 2019
The Dewatering Screen may have started in the coal industry, but it has really found a home in the aggregate world. Since being introduced to the North American market in the late 1970s, the Dewatering Screen has become the go-to piece of equipment for the economical removal of water from sand. Here are eight reasons why Dewatering Screens play such a large role in the production of clean aggregate material.

1. Produce a drier material

Several pieces of equipment are used to reduce moisture content in sand. A Separator™ or siphon-assisted Hydrocyclone produces an underflow material that is in the range of 22-35% moisture. The material can be stacked on a drainage field or discharged to a Dewatering Screen for additional moisture removal. Discharging the material directly onto a conveyor belt usually creates a housekeeping issue due to the remaining free water.

A Fine Material Screw Washer produces a discharge with a moisture content of 15–30%. While the product can discharge onto a conveyor directly, material can cling to the belt and create a significant housekeeping issue.

The Dewatering Screen achieves 8-20% moisture, depending on the physical characteristics of the material. Despite the range of retained moisture, the Dewatering Screen discharge is classified as drip-free and can be easily conveyed, loaded into a truck or placed in a bin.

When feeding dryers, putting material on conveyors, loading trucks or discharging to other equipment that requires the lowest percent moisture, a Dewatering Screen is a low-cost solution.

Dewatering Screen_drip-free sand

Dewatering Screens are a low-cost solution for producing a drier material.

Check out this case study to see how Dewatering Screens are helping Kilgore Companies increase their product yield by producing a sand that is 85% solids.

Download Case Study

2. Can handle multiple products

The use of longitudinal dividers allow as many as three products to be dewatered on one screen. Many applications feature a two-stream process where a fine stream and a coarse stream can be kept separate or blended to create specialty products. Utilizing one Dewatering Screen for multiple products reduces the overall footprint of equipment and can lower both capital and operating costs.

Longitudinal divider

The longitudinal divider allows up to three sand products to be dewatered on one screen.

3. Integrate with surrounding equipment

Dewatering Screens fit well into many applications to yield a drier product, capture ultra-fine material or allow better control in the process.

Wash Plant

The combination of a Hydrocyclone or Separator™ with a Dewatering Screen creates a wash system with a higher level of efficency and yield with a drier product. The screen underflow can be recirculated back into the Hydrocyclone feed for recovery or removed as undesired. 

Ultra Fines Recovery Plant

Generally, a screen is set up to make a classification based on the media openings. When trying to capture material that would normally pass through the media, a Dewatering Screen can be used in combination with a Hydrocyclone to recover ultra-fine material before it goes to a settling pond. Even though some of the fines will pass through the screen media, they will remain in the system. The Hydrocyclone overflow is the only exit point for the fine material, and it is operated at a high pressure to retain the material. 

Feed preparation for downstream equipment

Equipment such as Attrition Scrubbers will not operate at optimal levels when the material is too wet. A Dewatering Screen will produce a predictable moisture, which will allow better control in the process. The material can be adjusted to the correct percent moisture through the addition of water at a controlled rate.

Integration with downstream equipment

Dewatering Screens integrate with downstream equipment.

4. Usable with a wide range of size gradations

Since the main purpose of a Dewatering Screen is to reduce the percent moisture in material, it can handle a wide range of particle sizes. From as large as 0.5” down to 400 mesh fines, a Dewatering Screen can be configured to handle the material in the size that is needed. Because the Dewatering Screen is designed to blind off the media openings, material that would normal pass through is retained while the water flows through. Especially when used in combination with a Hydrocyclone or Separator™, a Dewatering Screen is extremely effective in retaining material and producing a dry product.

5. Media can be adjusted to make sizing cuts

A Dewatering Screen is specifically set up to blind the screen media in order to retain material to the overs and allow the water to report to the unders. With this mind, it is still a screen, and the media can be adjusted to perform the sharp size classification for which screens are known. The inclined discharge continues to promote the removal of water from the material. The media does not have to be continuous in purpose. One section can be configured for size classification, while others are configured for the dewatering requirement. Spray water can be used to increase the size classification efficiency, like with other wet screens.

6. The addition of spray water will remove fines from the product

While it is preferable to address fines removal upstream in the process, there are situations when fines remain in the product. Adding water to a Dewatering Screen may seem like a counterproductive approach, but it can have a significant impact on removing the unwanted fines. The media will retain the desired material, while the fines will travel with the water and report to the underflow of the screen. The amount of water and the location it is added will have an impact on the effect, but generally speaking, water is added at the feed end.

spray bars

The addition of spray bars can help remove additional fines from the product.

7. Low horsepower

Fitted with two vibrating motors or a single motor to drive exciters, Dewatering Screens utilize significantly lower total horsepower for similar capacity equipment. With the recommended percent moisture in the feed of 50% or higher, a Dewatering Screen can accept a variety of feed sources. Under some circumstances, the feed can go below 50 percent solids, but it can affect the final product dryness or the total capacity. When the feed is too high in water content, it may require additional equipment, such as a Hydrocyclone, to decrease the percent moisture prior to introducing the material to the Dewatering Screen. 

8. Low maintenance

The screen media and springs/buffers are the main items that will need replaced. These items, along with the sideliners and discharge lip, are the only wear parts, and they all have a long lifespan. Motors and structural components are designed for heavy-duty applications and have a low rate of failure. 

For these eight reasons, a Dewatering Screen can be a welcome addition to an aggregate plant when looking remove moisture and improve housekeeping. 

Tags: Mining, Screening, Fines Recovery, Dewatering
Alan Bennetts

Alan is the Global Product Manager for Washing and Classifying at McLanahan Corporation. He provides leadership, direction and oversight to the evaluation, design, development, engineering, training and support needed for McLanahan’s extensive washing and classifying equipment line. Alan has nearly 25 years of experience in the mineral and aggregate industry, having served in a wide array of roles with equipment manufacturers and mining companies throughout the United States. Alan is a 1996 graduate of the University of Montana, where he received his Bachelor of Science degree in metallurgical engineering.