Quantifying Density (Porosity) of a Mixture

The SPECTester has been specifically developed to assess and measure the segregation potential of individual components, and also the whole mixture in a product comprising of up to six distinctive components. Moreover, the potential of the machine can be extended to examine the density (porosity) of any material, irrespective of the number of ingredients present in the mixture.

Basically, during the review of the pile formed in the test hopper, the SPECTester quantifies the amount of material present in the pile when compared to the void space existing between all or any particles in the pile.

To put it in simply, the density (porosity) of the material can be determined at particular points in the process by comparing the presence of material to air in the pile. The steps for determining the density or porosity of a mixture using the SPECTester are as follows:

  • Using just two component trays, the top tray is filled with the material mixture and the bottom (second) tray is left empty
  • The tester hopper is filled in a normal manner with approximately 2 liters of the material to be analyzed
  • On the touch-screen, the SPECTester program is started
  • The name of the test to be run is entered once the SetUp1 screen appears
  • ‘Component Mode’ is selected to obtain density
  • ‘2’ is entered as the number of components
  • The number of data points to be collected by the SPECTester is added. For the majority of materials, 15 to 20 data points are recommended.
  • The height of the left side of the material pile is entered by referring to the pile height gauge.
  • The percentage of concentration as well as the names of the two components is entered. The names are random to the user’s preference. Yet, the percentage concentration of the two components (air and material) should be defined as 50% each, or a 50/50 mixture.
  • The standard 0.5 inch window with a four- or five sided matrix is selected on the SetUp2 screen.
  • The ‘CurveSelect’ screen demonstrates the material spectra as a white curved line and the void or air spectra as a flat blue line.
  • On the ‘RunTest’ screen, all the entered data is checked for accuracy and then ‘Get Data’ is selected. The time taken for data collection and analysis will range from several seconds to a few minutes.

The segregation profile portrays the density (porosity) of the mixture at the different locations in the pile, which simulates the process. Both the white and blue line can be exactly horizontal, overlapping one another, providing that the density remained constant through the material run. The density of the material will be greater where the white line appears above the 0.5 line.

Similarly, the density of the material will be less and the packaged material may be lightweight where the white line appears below the 0.5 line. It is important to note that if the process has typical funnel flow hoppers that make the sides of the bin empty last, then the material at the extreme end of the production cycle is likely to be slightly out-of-spec, as signified by the large dip in the density profile.

The Material Segregation Intensity number is the number of primary interest on the ‘Results’ screen. For the example shown (which refers to the segregation profile graph above), the product’s overall density throughout the process is good.

Both the Segregation Intensity Number and the Segregation Profile graph should be considered for the proper assessment of a material’s density using the SPECTester. Collectively, this data offers the information required to explain the porosity or density segregation of a sample mixture.

This information has been sourced, reviewed and adapted from materials provided by Particulate Systems.

For more information on this source, please visit Particulate Systems.


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