In Screw Feeder only a controlled amount is carried to the discharge.In Screw  feeder the inlet portion of the trough is made to flooded with the material and by means of a shroud in the trough or by the use of tubular trough.

  Several factors should be established before  selecting  a screw feeder, these being:
1. Kind and Character of material being handled.
2. Density of the material as conveyed
3.Maximum rate at which material is handled
4.Overall length of feeder  

Type of Screw Feeder :-

Single Screw feeder

Multiple Screw Feeder