Powder Flow Studies I: Instrumentation and Applications

Several methods have been used to evaluate the flow properties of pharmaceutical formulations. Although these methods give reproducible results, they often measure different factors. Consequently, it is difficult to interpret the data, and it is debatable whether correlation with actual flow of material is possible. A new approach to the measurement of powder flow is presented and involves measurement of the weight of powder per unit time flowing through a hopper orifice. The instrument, a recording powder flowometer, consists of a hopper, strain gauge balance, and recorder. The flow rate can be calculated from the recorder tracing, and in addition, the tracing serves to characterize the flow qualities of a formulation. Various sized hopper orifices with or without vibration can be used. By incorporation of an ionostat into the instrument, the static charge may also be measured concurrently with the flow rate.