This paper is concerned with the design criteria of screw conveyors and feeders based both on a theoretical approach and experimental tests. Screw conveyers are conveying devices suitable for handling a wide variety of materials that have good flowability characteristics. The screw conveyor has a helicoidal surface fitted on a shaft that rotates inside a fixed tube. The material fed into the conveyor is pushed by the helicoid flight along the base of the tube in the direction of transport (Figure 1). The advantages of the screw conveyor include the possibility of having different openings, each with its own shut-off organ for adjusting the flow, for feeding and unloading the material. It is thus possible to supply and receive different quantities and different types of materials using the same screw conveyor. The screw conveyors are also ideal for being used as screw feeders. Incorrect design and selection of this device, which is present in a large part of industrial processes, could mean poor performance, excessive power consumption, severe wear of plant and degradation of the conveyed material. A PC code has been developed to predict the performance of screw feeders and conveyors of any specific geometry. An overview and comparison between screw devices and the other mechanical feeding/conveying systems has been presented together with a selection of the most important international patents.
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