About the FT4 Powder Rheometer

Confined and Unconfined Flow

Two types of flow pattern are typically employed for quantifying flowability: -

Forced (or confined) Flow

A measure of the powder’s flowability when forced to flow, such as through a screw feeder or in an active feed frame. This property is defined as the Basic Flowability Energy, BFE, and is measured during the downward blade movement. The powder is confined by the closed bottom end of the test vessel.

Dynamic Powder Testing - Confined Flow

Low Stress (unconfined) Flow

A measure of the powder’s flowability when unconfined, such as during low stress filling, or low shear blending. This property is defined as the Specific Energy, SE. In this measurement, the resistance to flow is measured as the blade traverses from the bottom of the vessel to the top. As there is no solid surface at the top of the vessel preventing the powder from dilating and moving upwards, the powder is unconfined during this test.

Dynamic Powder Testing - Unconfined Flow

The regimes of confined and unconfined flow are very different and so it is important, when correlating data with process performance, to identify which regime is most representative of the process being considered.

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