Designing efficient screw feeders
Screw feeders are one of the industry's most useful feeding devices: they use relatively simple components and can be designed to reliably feed many kinds of bulk solids in a variety of applications. Unfortunately, the mechanisms governing the operation of these feeders under bin outlets aren't well understood. As a result, many existing screw feeders don't operate properly. This often leads to excessive power consumption, abrasive wear, particle attrition, or worse, unreliable material flow. Such problems can be avoided. This article reviews design procedures that can help you improve screw feeder performance. It also discusses the interaction mechanisms between proper bin design and optimum screw feeder design.
Feeders are used to control the rate of material discharge from a bin, hopper, silo, or bunker outlet. They shouldn't be confused with conveyors, which simply transport material from one location to another without controlling the flow rate. Common mechanical feeding devices include screw, belt, chain, rotary vane, rotary plow, rotary table, vibrating pan, and vibrating louver feeders. These feeders are typically used in a volumetric mode, where the volume of material being discharged per unit of time is varied by changing the speed, amplitude, or frequency of the feeder. Several of these devices can be designed to operate in a gravimetric mode, where the mass flow rate of material is actually measured and controlled.