Cost Effective Powder Flow Characterization For Formulations, Mixes And Blends

By Vinnie Hebert, Senior Sales Engineer, Brookfield Engineering Laboratories, Inc.

Characterizing powder formulations, mixes and blends for flowability is a necessity that is sometimes elusive and frequently done with archaic methods. The reason? There has really been no cost effective way to test and characterize powder flow properties. In some cases this is merely guesswork. Some common tests, such as “smear” tests, angle of repose, and flow through a funnel have one commonality: They are subjective and do not provide a number or value that correlates consistently with behavior on the production floor.

Another common method, the “tap” test, calculates values known as the Hausner Ratio and Carr Index; these tests use the measurements for the freely settled bulk density and tapped bulk density to determine flowability. These indices have been criticized as not having a strong theoretical basis. Legacy types of tests like these can be fraught with errors due to the operator procedure and sample preparation technique, thus making the data that results seem subjective as well.