Application of screw conveyors:
Screw conveyors are employed for handling a great variety of materials which have relatively good flowability. Sticky and stingy materials are unsuitable for screw conveying.
Screw conveyors have a few favourable points to its credit for recommending its application in different industries. Simplicity of design, easy construction and maintenance, are the few points which are often mentioned in favour of its application. But material characteristics often dictate the choice of its selection.
Dusty, hot materials or materials having foul ordour are often conveyed by screw conveyors, because it can be easily made dust-proof by jacketing the trough.
Typical applications include grain storage plants, feed mills, cereal processing plants, chemical plants, and sand preparation shop of a foundry for delivery of clay to the mixing machines.
Screw conveyors are very suitable for being adopted as a device to control the volume of materials flow from the bottom of bins, hoppers, storage silos etc. when screw conveyors are used for this purpose they are termed as screw feeders. Screw feeders have wide applications for the operation of processing units like driers, hammer mills, oil expellers and other innumerable mills.
Screw conveyors may be used to convey materials which can be subjected to thermal operation during transit. The conveyor trough is provided with jacket through which the heating or cooling medium may be circulated to effect the thermal operation.
Screw conveyors may be operated horizontally, on an incline, or vertically. Often inclined conveyors can solve a transportation problem effectively, but otherwise a combination of horizontal and vertical units should be installed. The angle of inclination of inclined conveyors is usually 10° to 20°. Vertical conveyors are usually complex in design and should be run at faster speed.
Screw conveyors do not always get favourable consideration due to high friction of the material against screw and trough, probability of material degradation due to crushing of material and due to higher power consumption resulting from higher friction. Therefore screw conveyors have limitation in capacity and distance of conveying. They are suitable for low and medium capacities for short distance. Capacity may be as high as 100m3/hr and distance of conveying is of the order of 30 to 40m typically.