Tapered Diameter screw conveyor

Tapered Diameter screw conveyor

Screw Feeders are used to control the flow rate of free flowing, bulk material from a bin or hopper. The inlet section of the trough is designed to be flooded (100% full). A shroud (curved cover) or tubular trough helps restrict the flooded area to only the inlet section. The screw under the inlet, and sometimes the trough as well, are modified to conveyor a metered amount of material per revolution of the screw. Modifications may include changes in the flighting diameter, pitch, pipe diameter, trough shape, etc.

Screws with uniform diameter and pitch will convey material from the rear of the inlet opening first. This can create flow issues with some materials because only a portion of the inlet is actually used so the bin or hopper doesn’t discharge evenly. Pockets of material don’t move and may clump, degrade over time, etc. The answer to this problem is to use the screw and trough modifications to create “Mass Flow” which means to draw material evenly across the full length of the inlet. This requires a screw with variable pitch flighting, cone shaped pipe and/or tapered diameter