McLanahan Shaker Screens, also known as Sand Dewatering Screens, are designed for dairy producers looking to remove excess water from recycled sand bedding. Dewatering the sand leads to a faster turnaround time while also reducing bacterial growth and improving overall freestall bed quality.
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Recycled sand from a separation system will contain about 20% moisture, which is too wet for freestall bedding. Stacking the sand into piles and conditioning it for several weeks or months allows the water to leach out, but that inventoried sand can tie up cash. With a Sand Dewatering Screen, the water is immediately reduced, yielding a sand that is drip-free and requires minimal conditioning.
A Sand Dewatering Screen can be supplied as part of a sand separation system or added later as a final dewatering step. It’s also used on many dairies to dewater sand removed from a sand lane. In every case, the sand produced from these systems is cleaner, drier and requires less conditioning than a system without it.
To dewater recycled sand effectively, the washed sand is fed onto the steep, downward inclined screen surface at the feed end of the Sand Dewatering Screen to achieve rapid drainage. A pool of water forms in the transition area as material builds up on the slightly upward inclined surface. Two counter-rotating vibratory motors create a linear motion at an angle to the screen surface. This rapid motion accelerates the solids upward and forward, forcing the liquid and small organic fibers to drain through the sand and through the screen surface. The sand is conveyed up the screen toward the discharge by this linear motion. The uphill slope of the screen, along with a discharge weir, creates a deep bed of sand that acts as a filter medium, allowing material much finer than the screen openings to be retained. Water and sand that pass through the screen’s surface are typically recycled back to the source or captured again in a Hydrocyclone system. This allows the process to attain recovery rates well over 90% while yielding a clean, dry sand product. In a sand separation system, the water held in the sand contains a small amount of organic material that acts as food for bacteria. As the water is pulled from the sand in a Dewatering Screen, it drags with it a portion of those small fibers, which exit with the water. This yields a cleaner sand without the use of additional fresh water. Screens can be fitted with a Derocker to remove oversize and tramp material from the bedding sand before it is dewatered. This Derocker removes large rocks, plastic, wood and other debris that can be problematic if it ends up in the sand bedding.
McLanahan Sand Dewatering Screens were originally developed for the aggregate and mining industries for dewatering, rinsing, scrubbing, sizing and washing sand and other materials. They are designed to produce a consistent drip-free product. Dewatering Screens have been adapted to the dairy industry for dewatering recycled sand bedding, but they still maintain the integrity of design and the consistency of the product they produce.
All the Sand Dewatering Screens are built with side panels that are secured to cross supports with Huck bolts. This heavy-duty structure provides the support for all the longitudinal stringers that attach to the screen panels. The screen panels, which are available in a variety of opening sizes, snap into the longitudinal stringers, allowing them to be quickly and easily replaced when necessary. The side panels are protected from wear by rubber panels that are attached to the inside surface.
The machine uses rubber buffers to isolate the supporting structure from the heavy vibrations that the motors produce to separate the water and sand. These buffers are perfect for wet, corrosive environments.
Sand Dewatering Screens have been tested and proven to remove up to 40% of the water and up to 80% of the organic material that remains in the recycled sand. In all cases, this creates a drier, cleaner product that can be reused more quickly with less conditioning.
A Sand Dewatering Screen can save you money in several ways. Sand that is drier and cleaner requires less conditioning, which means less loader and operator time. Less conditioning means smaller stockpiles of sand. Click here to see how much money can get tied up in sand inventories. v
Screens work best when a bed of sand can build up during the dewatering process. If the sand bed is too big, it will eventually build up and plug the screen. If the sand bed is too small, a larger percentage of fines will escape with the water. Each screen is sized for the specific application into which it will be installed. This chart shows the different screen sizes that are available and the tonnage that they can process.
The first dewatering screen used for recycled sand underwent extensive testing and sampling. Here are the results from those tests.
There are several ways to configure a Sand Lane System, but basically it involves cleaning the sand from the lane and dumping it into a hopper, which feeds the dewatering system. Click here to see a video of a Dewatering System installed into a Sand Lane.
Sometimes the sand is still dirty when it enters the Sand Dewatering Screen. If the manure fibers are larger than the screen openings, then they cannot be washed out. In some cases, though, it’s possible to install a spray bar and add some clean water to rinse out the dirty manure water. When doing this, it’s important to install a weir partway up the deck to create a break in the sand bed through which the water can go. McLanahan's engineering team will be able to help with setting up a rinse bar on your screen.
McLanahan Shaker Screens produce cleaner, drier bedding sand that can be reused much quicker.
