Top 6 Mistakes To Avoid When Optimizing Your Fine Material Washer

Fine Material Washers are vital pieces of equipment for wet aggregate processing, used for washing, classifying and dewatering sand. Fine Material Washers come in single or double screw configurations depending on the application.

As material is fed into the Fine Material Washer, heavier material settles to the bottom and finer fractions overflow the weirs. The material that has settled to the bottom of the pool is conveyed up an inclined tub by a screw shaft. The tumbling action of the screw agitates and cleans the material for washing, and dewatering occurs as the screw conveys the material up the incline toward the discharge end.

While the basic operating principles of Fine Material Washers are simple to follow, you must consider various factors when optimizing these pieces of equipment. Proper operation is key for efficient classification and dewatering with Fine Material Washers.

To ensure the most out of your operation, try to avoid these mistakes.

At first glance, it may seem that a faster screw speed will produce the best results for your operation, but that’s not always the case. If you’re producing a finer

product like mason sand, asphalt sand or manufactured sand, losing those fines is losing you money.

Fine material takes longer to settle out in the wash tub and needs a slower screw speed to do so. Excessive speed can cause valuable fines to overflow the weirs with the wastewater, which means you’re missing out on a saleable product.

Along those same lines, if the fines accumulate in the wash tub and remain in suspension, an excess concentration of fines can occur. This fine sand concentration builds up in the wash tub, eventually overloading and stalling the screw shaft and inevitably leading to downtime.

Refer to this chart to help determine the optimal speed for the size of your equipment.

In order to optimize your Screw Washer correctly, the proper amount of water is necessary for your operation. Typically, 50 gallons of water per minute is needed to remove 1 ton per hour of silt.

Supplying too little water to your Fine Material Washer can cause loss of fines. Too little water can also cause a buildup of material in the pool area of the Fine Material Washer.

Every part of a Fine Material Washer’s operation is interconnected. As shown on the chart below, the amount of water supplied to your Screw Washer and the size of the machine will both need to be considered to determine the mesh of the material retained.

The adjustable weirs on a Fine Material Washer help allow the water and silts to have the slowest possible velocity when overflowing the tub. A typical Fine Material Washer has two weirs on the sides and one on the back of the washer tub. Adjusting the height of the weirs yields different results in terms of fines retention.

In order to achieve maximum retention of fines, all three weirs should be at their highest position. In contrast, lowering the back weir helps remove additional fines. Depending on your operation, some weir height combinations are better than others.

Improperly feeding your Fine Material Washer – whether it’s how you’re feeding it or how much you’re feeding it – can cause numerous problems. From material build-up to poor classification to loss of fines, improper feeding is an easy mistake to avoid.

Overfeeding the washer can cause sand to build up in the washer’s backflush channel, creating a wetter end product. To avoid this, make sure to feed your Fine Material Washer based on its capacity and size.

If there is too much turbulence in your feed area of the washer tub, you can lose excess minus 200 mesh fines and even plus 200 mesh fines. To lessen turbulence in the feed area, consider a feed chute or flume with a velocity break box.

A calm pool area is key to retaining the maximum amount of fines. If your pool is too turbulent, your fines can overflow with the wastewater leaving the Fine Material Washer.

Routine maintenance and regular inspections are important to maintain the efficiency of a Fine Material Washer. If you’re not performing these routine checks, things can go overlooked and cause problems.

Periodic checks are recommended to ensure your equipment is operating at an optimum level. Simple issues like improper V-belt drive belt tension; loose bolts, supports and other parts; and screw shaft wear are all examples of key maintenance problems that can negatively impact the efficiency of your operation.

Adding rising current water to your operation can help the classification process of your Fine Material Washer operation. If your feed material is high in silt, the higher specific gravity of the slurry can cause retention of undesirable silts.

Adding fresh water helps to lower the specific gravity, removing ultra-fines. Adding rising current water also helps to improve the classification process by allowing product-sized particles to settle out and be conveyed by the screw, while ultra-fines remain in suspension.

When it comes to ensuring optimal operation of your Fine Material Washer, avoiding these common errors will help you get the largest amount of saleable product and avoid key maintenance issues.