Technical ArticlesPowder Flow Studies IV: Uniformity of Flow: Instrumentation and Applications

Use of the recording powder flowmeter for the qualitative evaluation of nonuniform flowing formulations and additional instrumentation for the quantitative measurement of the variation are described. This additional refinement prints out the time, in hundredths of a minute, for preselected weight increments of powder to flow from a hopper. The variation in time is a measure of the uniformity of flow. To illustrate the utility of the instrument, two formulations having similar average flow rates but differing in their uniformity of flow were tableted. The nonuniform flowing formulation tableted on a single-rotary press had a higher coefficient of intertablet weight variation and did not conform to USP standards. Both formulations were tableted on a double-rotary press equipped with induced die feed and low coefficients of variation were obtained in both instances indicating that the die feed mechanism was effective in minimizing intertablet weight variation of an irregularly flowing formulation.