Power needs of screw feeders

Empty and running conditions may be generally ignored when sizing the power requirements of a screw feeder because the main load to be faced is starting conditions, where the screw has to commence rotating in a settled bed of confined bulk material. 

The shear strength, /s, then equals to Cl x tan 5, where 5 is the internal angle of friction of the bulk. 

The torque, T, required to turn a pitch section of a feeder screw is therefore  

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