AbstractFeeders and Discharge Aids. Feeders and discharge aids have an influence on the flow behaviour of bulk solids in silos. Together with the geometric form of the silo, they are responsible for the operating conditions of a silo. Therefore, feeders and discharge aids have to be chosen and installed under consideration of the flow properties of the bulk solid to be stored. The necessary information is obtained by using the silo design method due to Jenike. This method yields the geometrical data of the hopper (wall steepness, outlet diameter) necessary for a troublefree operation (no doming and ratholing; mass flow; no segregation; uniform flow). Furthermore, the design of feeders and discharge aids plays an important role in determining their function. For example, stagnant zones will build up and cause flow problems on protruding edges and on walls which are not steep enough. For the correct function of the hopper/feeder combination it is important to make sure that the feeder fully activates the hopper outlet and stagnant zones cannot build up. This can be ensured by an appropriate feeder design (increasing capacity in direction of conveying). The driving power of a feeder has to be calculated also on the basis of the flow properties of the bulk solid to be stored.