Introduction to microfeeding powders — Part I
Pharmaceutical and other industries have spurred demand for continuous, gravimetric low-rate powder feeding, where accuracy is measured in milligrams and an hour's worth of feeding might add as little as 1 teaspoon of material to a process. The lowest rates are achieved by loss-in-weight microfeeders, which can control the flow of minor ingredients at rates down to 20 g/h (0.04 lb/h) or lower. This two-part article explains how microfeeding differs from feeding at higher rates, how microfeeding can be applied, and how to select a microfeeder and specify its performance level.
Accurately and reliably controlling material flow at even normal process rates can be challenging. With loss-in-weight microfeeding, the challenge is twofold: controlling the feedrate of minor ingredients to micro levels in the range of 20 g/h (0.04 lb/h) while achieving a feeding precision that permits a sample-to-sample variation of only a few percent.