Principles of Table Feeder Operation

The basic principles behind the operation of table feeders are simple, as illustrated in the following experiment:

A straight walled cylinder is filled with a fine powder and covered with a flat plate. The cylinder is then inverted and placed on a flat surface. Lift the cylinder slightly and observe the flow of powder between the partially lifted cylinder and the plate. Powder flows out from the clearance between the cylinder and the plate surface as it forms an angle of repose along the entire periphery of the plate.

Now insert a thin rigid wire through the powder between the clearance and the plate, then slowly rotate the wire horizontally in a clockwise direction. As the wire is rotated, powder flows out the cylinder successively around its periphery. Note that the level of powder drops evenly across the whole surface area of the cylinder allowing for mass flow conditions. It is important to note that the powder flows from the inside to the outside of the cylinder, where no powder pressure is exerted. Additionally, the slow movement of the wire helps move the material radially to the outside.

Circle Feeder (Mass Flow Feeder) Design

The Circle Feeder consists of a stationary bottom plate, flow adjusting ring (weir), central rotating vanes, peripheral rotating vanes encased by a cylindrical ring, drive shaft/speed reducer/motor, and a discharge port. A holding bin is mounted on top of the Circle Feeder. The central and peripheral rotating vanes are attached. The drive shaft runs up through the center of the bottom plate, and is attached to the peripheral vanes which consist of four evenly distributed flat blades.

Inside the flow adjusting ring, powder pressure is imposed. Because of the natural collapse of the material being fed and the slow rotation of the central vanes, the material flows out to the periphery where no powder pressure is exerted. At the periphery, the rotation of the peripheral vanes carry the material to the discharge port.

The two parameters that control the Circle Feeder discharge rate are shaft rotation and the height of the flow adjusting ring (weir). The rotation of the central vanes is controlled by a variable speed motor and inverter.

Features of the Circle Feeder

• The large inlet exceeds most materials' critical arching diameter, preventing bridging.
No ratholing!

• The slow rotating vanes move the material radially from the center to the outlet ensuring "first in – first out" mass flow

• Superior turndown ration (30:1)

• Low maintenance

• Both discharging and metering functions

• Wide range of discharge rates are possible by variable motor speed and the height of the flow adjusting ring

• The larger diameter opening between the holding bin and the feeder allows for large bin capacity

• Excellent as a powder feeder or for feeding a wide variety of bulk solids