The automated log washer from Columbus, Neb.-based GreyStone Inc. increases efficiency and lowers labor costs for aggregate producers, keeping the quality of aggregate consistent while saving operators time and money. GreyStone recognized the need for log washer operators to keep output quality consistent without having to make frequent manual adjustments to the angle of inclination. Working closely on the unit’s design with one of the company’s long-time customers, GreyStone manufactures an automated log washer with a hydraulic support system tied to a PLC sensor that detects the tonnage going through the unit. When the tonnage decreases, the system detects this and increases the angle of inclination — also increasing the material retention time in the unit — until the sensor detects the proper tonnage. If tonnage increases, the hydraulic system automatically decreases the angle of inclination, which decreases material retention, until the proper tonnage is detected. Upper and lower limit switches are employed to prevent excess inclination or damage to the unit.

Log washers remove tough plastic clays from coarse aggregate by scrubbing the material with paddles, causing an abrading action. These units break down clay and liquefy it by causing rock to grind against rock. It is important to have enough material in the log washer at any given time to create the desired rock-on-rock action. Log washers typically operate at inclinations between 5 and 10.5 degrees.

As the angle of inclination increases, output capacity of the unit decreases, with a corresponding increase in retention time. Decreasing the angle has the opposite effect: increased capacity and a decrease in retention time. This makes the angle of inclination vital.

In most applications, the feed rate is set and the angle of inclination can only be adjusted through a costly trial-and-error method until the desired output (clean rock) is achieved.

By automating the variable incline section of the log washer, GreyStone’s unit removes the need for human input beyond an initial calibration by the operator. The resulting increase in efficiency and elimination of unnecessary labor costs solve the problem of inconsistent feed rate and uneven product quality — which in the past typically forced many operators to split the difference between clean material and lowered tonnage output, according to the manufacturer.

For more information, call 888/346-9274 or visit www.greystoneinc.com.

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