Stirring Devices in Screw Metering Equipment - Action and Design Strategy. The accurarcy of metering by screw dosage equipment with or without gravimetric control depends primarily on the flow of material to the discharging screw. In the case of cohesive solids, stirring devices are generally required to prevent bridging. Experimental observations show that flow conditions correlate directly with the intensity of stirring. Mass flow in the metering container and hence optimum constancy of metering are attainable only from certain stirring efficiencies upwards. Cases of interference to metering due to poor flow of solids can be explained and overcome by modified dimensioning. The effects of the principal parameters - geometry and speed of rotation of the stirrer - are studied with the aid of two stirrer configurations - viz. overhead and concentric. Straightforward model calculations provide a mathematical method of estimation for optimum and reliable stirrer dimensioning also applicable to strongly cohesive solids.