Recent developments in feeder design and performance

Feeders are used to control the gravity flow of bulk solids from bins and stockpiles. While there are several types of feeders commonly used, their selection depends on the particular bulk solid and feed rate required. It is important that feeders be used in conjunction with mass-flow hoppers to ensure both reliable flow and good control over the feeder loads and drive powers. Correct interfacing of feeders and hoppers is essential if uniform draw of material over the whole of the hopper outlet is to be achieved. This requires the feeder capacity to progressively increase in the direction of feed. In the case of screw feeders, for example, this is achieved by using combinations of an increasing pitch, and a decreasing shaft diameter. In this chapter, an overview of feeder design and performance with specific reference to belt and apron feeders is presented. The interface geometry of the feed zone is examined in relation to the requirements for the optimum draw-down pattern in the hopper. Relevant aspects of feeder load and drive power determination is reviewed and the need for controlling feeder loads is stressed. The influence of hopper and feeder interface with respect to the shear resistance and feeder slip is outlined.