A screw conveyor is a machine that uses rotating helical screw blades called "flighting"
affixed to a central shaft and supported at either end by bearings. This assembly
can be mounted within a ‘U’ trough, ‘V’ trough or a Tube. They are used in many bulk
handling industries. A variation on this is a heavy duty "shaftless spiral", supported
and driven at one end and free at the other, which runs on a specially designed wear
plate or wear bars. Screw conveyors can be used horizontally or at an incline as
an efficient way to move semi-solid materials, including cement, aggregates, cereal
grains, wood chips/pellets, animal feed, boiler ash, bone meal, municipal waste,
and many, many others. Inclines are up to 45 degrees although as the angle of inclination
increases, the capacity of a given unit rapidly decreases. In certain applications
they can be vertical. The rate of volume throughput is proportional to the rotation
speed of the shaft. Feed rates can be controlled by varying the rotational speed
of the shaft to deliver a measured quantity of material into a process. The rotating
part of the conveyor is sometimes simply called an auger.