A new module for the Freeman Technology FT4 Powder Rheometer allows fast, fully automated measurement of wall friction using standard or custom materials in contact with powders under test
This new module further extends the capabilities of the FT4, a system that Freeman Technology says is rapidly becoming a universal powder tester.
Wall friction is an important consideration both in the design of processing plant and in predicting how a powder will process in a given plant.
In all processing machinery, powder is required to flow within containing surfaces such as hoppers, chutes and pipes.
The frictional resistance between a given surface and the powder moving over it can be important in determining the smoothness or consistency of the powder transfer process.
This frictional resistance depends on the powder characteristics, the material from which the surface is made, its finish and any surface treatments.
The FT4's new wall friction module allows experimental measurement of frictional resistance with a total test time of around ten minutes.
A 48mm diameter disc of the appropriate material and finish is used to compress a powder sample through a step sequence of predetermined normal stresses.
At the same time, the disc is rotated and the shear stress is determined from measurements of the frictional torque at each stress level.
The wall coefficient of friction is then calculated from the slope of the shear stress versus normal stress data.
The wall friction module comes with a set of four grade 304-stainless steel discs with various surface finishes.
The simplicity of the disc design means that additional discs featuring specific materials and surface conditions can be produced easily.
