Measure flow properties on all raw powders and blends to determine if there are differences in their flowability and whether these correspond with plant experience
The classic problem when working with powders is their failure to discharge reliably from bins, hoppers, silos, feeders, dosing machines, packing machines, etc. Their unpredictable nature causes interruptions in the production process and at times requires complete plant shutdown in order to correct flow restrictions and stoppages. Failure to flow reliably also leads to variations in pack weight, mixture, performance, and sensory properties of powder products.
A Powder Flow Tester eliminates flow problems with a Flow Function test; a proven scientific method used to analyze powder flow behavior. ASTM D6128 describes the Flow Function test procedure, which consists of compressing and shearing powder samples in a defined annular shear cell, using an established well-defined methodology. The Flow Function test enables you to:
In addition to measuring the flow function, the powder flow tester also measures the angle of internal friction, angle of wall friction, cohesive strength, and bulk density all of which help to eliminate potential flow problems.
For Newtonian fluids, the resistance to shear (viscosity) is independent of the normal pressure but dependent on the shear rate. In powders, the effect of these factors is reversed so that the shear stress of a powder is strongly dependent on the normal stress but independent of the shear rate. Hence, when characterizing powders, tests are undertaken at a single speed but over a range of normal stresses. The other key difference is that powders are anisotropic so the stresses are not equal in all directions and are frictional so that they can generate shear stresses at wall boundaries.
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