Working Mechanism of powder flow instruments?

Powders are a type of granular material, the study of which has intrigued many a physicist and led to some fascinating and important observations about the nature of this material which is composed of solid particles, but exhibits powder flow properties like liquids and yet isn’t quite like either solids or liquids in nature. Though this behavior sounds simple, they exhibit a lot of complex behavior much of which isn’t fully understood yet. This much we know that temperature does not affect the macroscopic particles and the particles are in constant inelastic collisions with each other with loss of energy due to friction. Also, that stress is not distributed uniformly in the granular material. Flowability is defined as the ability of a powder to flow. Though the flowability can be said to extend across a range from free flowing to nonflowing, this is a simplistic view, whereas actually, powder flow is complex and multidimensional. Hence it cannot be expressed as a single value. It is not an inherent property of the material but is a combination of the physical properties of the powder and the powder handling equipment. It is to understand and predict the flow of powders that flow instruments have been designed with flow measurement devices. This has relevance and implications in the food and pharmaceutical industries which are of particular interest to us. What is the relevance of flowability in the industry? - The flow of powder during the manufacturing process determines the final quality of the product in terms of weight and content uniformity. - Flow also affects the manufacturing efficiency as it determines the kind of powder handling equipment to be used, and the parameters to be fixed in the development of formulations (mixing of powders). Flow also has a bearing on powder segregation issues. Flowability Testers There are many different types of powder flowability testers available in the market. Manufacturers can match the unique flowability concerns they have in their manufacturing processes to those powder flow testers which actually imitate those processes and thus predict their behavior in the factory settings. The tests and the properties examined are given below:rnShear cell test – which determines the interparticle friction The uniaxial compression test – which measures the compressibility of the powder The wall friction test – which tests the friction between the powder and the wall of the roller or container. Some commonly used test methods are the Standard Shear Testing Method for Bulk solids using the Jenike Shear Cell, the Standard Test Method for Bulk solids Characterization by Granutools.