AMETEK Brookfield Page 5
Manual No. M09-1200-F1016
I. INTRODUCTION
There is a need throughout industry to characterize powder flow properties and flow behavior.
The Brookfield Powder Flow Tester (PFT) is a precision instrument of robust design that satisfies
this need and can be used to measure, display and print out flow results at specified compaction
loads. Potential users include R&D Departments, QC laboratories, Incoming Inspection for raw
materials, and government/university organizations.
The principal of operation of the PFT is to drive a compression lid vertically downward into a
powder sample contained in an annular shear cell. The powder sample has a defined volume
and the weight of the sample is measured before the start of the test. A calibrated beam load
cell is used to control the compaction stress applied to the powder. The annular shear cell is
then rotated at a defined speed and the torque resistance of the powder in the shear cell moving
against the powder in the stationary lid is measured by a calibrated reaction torque sensor. The
geometries of the lid, shear cell, rotational speed of the cell, and the compressive loads applied
to the powder all contribute to the calculations which determine the “flowability” of the powder.
The intended uses for the PFT include:
• Pass/fail tests to certify material quality prior to shipment
• Providing meaningful numbers that guide how powder will flow in silos, hoppers, feeders,
filling machines and similar equipment
• Benchmarking for daily production lots or for comparing flow behavior of new
formulations against existing product
• Creating databases for choice of production lines, sourcing, formulation and second source
suppliers
• Producing quantitative results that can be used for design of processing plants and
equipment
There are several powder flow properties which the PFT measures to categorize flowability.
Note that these properties, which may vary with changes in temperature and humidity, include:
• Unconfined failure strength
• Major Principal Consolidating Stress
• Time Consolidation
• Angle of internal friction
• Angle of wall friction
• Cohesive strength
• Bulk density
The most recognized indication of powder flowability is the unconfined failure strength when
viewed as a function of the consolidating stress, known as the flow function. Wall friction, internal
friction, and bulk density are also commonly used to relate measurements to flow behavior.
Appendix A provides a more detailed explanation of these properties and how they are measured.
