MULTIPLE SIEVE SIFTER PERFORMANCE USING VARIOUS COMBINATIONS OF FEED RATES, CIRCLES AND SPEEDS1

Wheat was ground on a rollermill then sifted into several size classifications to determine how certain sifting characteristics changed when the material was subjected to changes in feed rate, sifter circle or throw and sifter speed. The travel speed of the stocks over the sieves decreased with a decrease in average particle size. Changes in the rate of feed to the sieves had no effect on the stock travel time. Travel speed was increased for all stocks when the linear cloth speed of the sieve was increased. Sifter efficiency, as defined by the percent of undersize material removed by each sieve in a series of sieves having the same cloth aperture, compared to the amount of undersize material going to the first sieve of the series was influenced by changes in feed rates and in sifter dynamics. Particle size analysis of individual sieve throughs showed that when the stocks were sifted on a series of sieves having the same aperture opening size, the finest material was sifted out on the first sieve with subsequent sieve throughs becoming progressively coarser.