For feeders comprising a single screw throughput can be influenced by: the volumetric efficiency of the screw; the bulk solid's bulk density and its variability; whether the bulk solid is free-flowing or cohesive; the clearance between the screw and the casing.

Predicting the throughput of a multi-screw feeder has additional complicating factors including: whether the screw are overlapping or not; the distance between non overlapping screws; screw rotational directions; trough (casing) geometries.

This paper will consider these issues in relation to predicting the throughput of single and multiple screw feeders.