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Metal Powders

New Flow Patterns with a "Flo-Thru" Separator

Since Kason introduced the Flo-Thru Circular Screen Separator last year, customers have realized two important benefits. Flo-Thru separators provide outstanding scalping rates and fit into plant processing lines with minimal headroom. Using 30" (762 mm) diameter units, one plastic pellet manufacturer scalps at rates of 5000 to 7000 lbs/hr (2268 to 3175 kg). Another company in the same industry will scalp with a 72" (1828.8 mm) diameter Flo-Thru unit at 40,000 lbs/hr (18,144 kg) using a perforated plate with 9/32" (7.14 mm) openings.

A company that handles metal powders is using a 60" (1524 mm) diameter Flo-Thru unit with a 50-mesh screen to scalp at 1000 lbs/min (453.6 kg). Another company that processes pigment has ordered a 30 in. (762 mm) diameter Flo-Thru unit with a 3-mesh screen to scalp pigment at 7400 lbs/hr (3356.6 kg). Though all of these companies are processing powders, the Flo-Thru unit was also designed for separation of solids from liquid.

If any of these customers decide to use their Flo-Thru separators for different powders, they may need to change the vertical and horizontal motion of the screen to achieve the most efficient screening rates. The Flo-Thru's dual gyrator motors also serve as the weights which can be adjusted in two ways to alter the screen motion and subsequently the material flow patterns on the screen. Understanding the screen motion and flow pattern help Flo-Thru operators achieve single particle bed depth which is needed to reach the maximum throughput rates.

The Flo-Thru unit's material flow patterns on the screen approximate an infinite number of curved arrows that start at the screen center and end at the edge. This pattern offers good distribution of the particles across the screen and results in ultrahigh capacity scalping or dewatering. A 4" (101.6 mm) to 8" (203.2 mm) long plough blade helps direct the oversize material into the discharge spout.

In some cases, balls, rings, or wipers may be needed if the material being screened tends to blind. Experience with a variety of materials has shown that the Flo-Thru unit is suited for scalping operations in which oversize materials do not make up more than 5 to 10% of the total incoming product. If the material being screened meets this limit, then the "Flo-Thru's" benefits of ultra-high scalping rates and minimal headroom requirements can be realized.

Flo-Thru operators can adjust the flow pattern on the screen surface by mounting the motors on their brackets in one of three angular settings and/or adjusting the eccentric weights. These adjustments change the vertical and horizontal stroke, allowing the Flo-Thru operator to find the combination that gives the maximum throughput.

Adjusting the eccentric weights 

Each of the two motors has eccentric weights on dual shaft extensions of the motor. The inner one of the half-disc shaped eccentric weights remains fixed to the shaft and the outer one may move when the Allen-type set screw is removed. For safety reasons, these weights reside under airtight covers.

The Flo-Thru operator has the option of adjusting the movable eccentric weight so it completely overlaps the fixed weight, overlaps 50% or overlaps 75%. Experience shows that 50% and 75% overlap positions are ideal for continuous operation. As the overlap is increased, the amplitude of vibration is increased.

Adjusting the gyrator motors on the brackets

Each Flo-Thru unit has a mounting bracket for each of the two gyrator motors. Each mounting bracket has a series of holes drilled through the metal plate to allow for mounting the gyrator motors as 30 degrees, 45 degrees or 60 degrees to the plane of the screen. The lower the angle, the greater the vertical stroke to the screen and the lower the horizontal stroke. Or, stated conversely, the higher the angle that the gyrator motor is mounted with respect to the screen, the higher the horizontal stroke. For materials with a high bulk density and high percentage of oversize particles, it is recommended that the angle be set at 45 or 60 degrees. Kason supplies stick-on amplitude gauges to help customers achieve the point at which the ratio of horizontal to vertical stroke allows for maximum scalping rates.

Refer to the Flo-Thru unit instruction manual for maintenance procedures and schedules. Understanding how to operate the Flo-Thru unit and maintain it helps a company achieve many years of trouble-free service and contribute to profitability.

Screen Tips Volume 8, Number 2