Volumetric dosing efficiency in relation to the bulk, flow and shear properties of powders |
Removing a small, precise volume or mass of powder from a bulk is commonplace in many industries where items such as tablets, vials, pellets, blister packs and inhalation products are manufactured. In the majority of cases the dosing operation is volumetric and based upon achieving a consistent fill and bulk density of powder. The efficiency of the operation is usually measured in terms of the mass variability of the dosages. Relatively free flowing powders are the most efficient regarding dosing, but are vulnerable to de-blending and to the release of dust. For these reasons dosing powders are usually more cohesive and this makes the prediction of their flow performance more difficult.
Powder flowability is complex and behaviour is difficult to predict, but there are many bulk, flow and shear properties that in combination provide increased understanding of how powders flow in everyday processes.
This study examines the efficiency of volumetric dosing for a number of different powders and shows how the results correlate with the powder properties measured using a powder rheometer. These properties include bulk density, compressibility, permeability, dynamic flowability and shear properties with particular emphasis on behaviour in the loosely packed or un-consolidated state.
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