Brookfield PFT Powder Flow Tester Operating Instructions Manual page 56

The standard classification of powder flowability uses the flow factor index ff, as shown
above:
ff<1
1<ff<2
2<ff<4
4<ff<10
10<ff
Anticipated uses of the Brookfield Powder Flow Tester:
Benchmarking - 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.
New materials - Test new ingredients/blends versus existing ingredients/blends to determine
whether the alternative material is likely to be easier, more difficult or no different to handle.
This potential material handling cost can be factored into the purchasing decision.
Reverse engineering - If you have plant experience with powders that flow easily or poorly on a
given process line, you can use the PFT to determine the flow properties of each powder and
determine over time a flowability window required for flow on a given line.
Design - Design the geometry (converging angle and outlet size) of new hoppers/silos for reliable
flow.
Alternative methods of displaying the flow function test results
To demonstrate powder flowability, the flow function can be presented graphically (as in Figure
A-5) to describe behavior over the stress range of approximately 0.6kPa to 10kPa. This stress
range is representative of that experienced by the powder in small to intermediate sized silos.
However, describing flowability with a function may complicate the analysis as it is sometimes
found that the flow functions of two different materials cross over one another, so that their
relative ranking changes with stress levels. Alternatively, flowability rankings for specific stress
levels can be determined by calculating the following parameters:
AMETEK Brookfield
ff=1
Non
Very
flowing
cohesive
Major Principal Consolidation Stress σ
Figure A-5: The powder flow function
Non flowing
Very cohesive
Cohesive
Easy flowing
Free flowing
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ff=2
Cohesive
ff=4
Easy flowing
ff=10
Free flowing
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Manual No. M09-1200-F1016