Granudrum

GranuDrum

Granular material flow analyzer

Automated cohesive index and rheology measurements
  • Principle

    Granudrum is an automated instrument able to measure quickly and precisely granular materials flowing properties. This instrument provides powder cohesive index and powder flowing angles for different shearing rates.

    It works on the rotating drum measurement principle associated with a customized image treatment algorithm.

  • Key Benefits

    Measurement is simple, fast and intuitive.

    Delivered with intuitive software, both average and variance are easy to access and allow the comparison of the results. Accessibility is password protected. All pictures and data are automatically collected and stored for post processing. Easy data transfer and automatic report generation.

    Closed system for safety requirements.

    Size compatible with hood or confined enclosure.

    Recorded standard operating procedures increase the repeatability of measurements.

    Through the simplicity of its design, Granudrum maximizes uptime. It is made out of modules, each of them can be swapped to avoid extensive diagnostics.

  • Description

    GranuDrum instrument is an automated powder rheometer method based on the rotating drum principle. A horizontal cylinder with transparent sidewalls called drum is half filled with the sample of powder. The drum rotates around its axis at an angular velocity ranging from 2 rpm to 60 rpm.  A CCD camera takes snapshots (30 to 100 images separated by 1s) for each angular velocity. The air/powder interface is detected on each snapshot with an edge detection algorithm.

    Afterwards, the average interface position and the fluctuations around this average position are computed.

    Then, for each rotating speed, the flowing angle (also known in the literature as ‘dynamic angle of repose’, much relevant than “Avalanche Angle”) αf is computed from the average interface position and the dynamic cohesive index σf (much more relevant than the so-called “Avalanche Angle”) is measured from the interface fluctuations.

    In general, a low value of the flowing angle αf corresponds to a good flowability. The flowing angle is influenced by a wide set of parameters: the friction between the grains, the shape of the grains, the cohesive forces (van der Waals, electrostatic and capillary forces) between the grains. The dynamic cohesive index σf is only related to the cohesive forces between the grains. A cohesive powder leads to an intermitted flow while a non-cohesive powder leads to a regular flow.

    Therefore, a dynamic powder cohesive index closes to zero corresponds to a non-cohesive powder. When the powder cohesiveness increases, the cohesive index increases accordingly.

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