Granular material heap analyzer
Automated repose angle and cohesive index measurements
Granuheap is an automated instrument able to measure quickly and precisely the repose angle (i.e. powder cohesion) of a granular material.
In addition, this instrument provides the cohesive index related to the powder flowing properties.
The instrument measures the powder heap shape with a customized image treatment algorithm.
The measurement reproducibility is optimized with the use of an automated initialization method.
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, Granuheap maximizes uptime. It is made out of modules, each of them can be swapped to avoid extensive diagnostics.
When a powder is poured onto a surface, a heap is formed.
It is well known that both the repose angle and the heap shape strongly depend on grain properties.
In particular, a cohesive powder forms an irregular heap while a non-cohesive powder forms a regular conical heap.
Therefore, a precise measurement of the heap shape provides some useful information about the physical properties of the powder sample.
GranuHeap instrument is an automated heap shape measurement method based on image processing and analysis. A powder heap is created on a cylindrical support. In order to obtain reproducible results, an initialization tube with an internal diameter equal to the circular support is installed on the support.
After filling the initialization tube by hand with a fixed volume of powder (typically 100 ml), the tube goes up at the constant speed.
Thereby, the powder is flowing from the tube to form a heap on the cylindrical support. A controlled rotation of the support allows obtaining different heap projections corresponding to different heap orientations. A custom image recognition algorithm determines the position of the powder/air interface. The repose angle refers to the angle of the isosceles triangle with the same surface than the powder heap projected image. This isosceles triangle corresponds to the ideal cohesiveness heap shape.
The repose angle is computed for each image, i.e. for each heap orientation.
Afterwards, an averaged value is computed. In general, the lower the repose angle is, the better the powder flowability is. The deviation between the real heap interface and the isosceles triangular heap provides the static cohesive index. The static cohesive index is computed for each image, i.e. for each heap orientation.
Afterwards, an averaged value is computed. This static cohesive index is close to zero for a non-cohesive powder and increases when the cohesive forces inside the powder strengthen. The next Table summarizes the empirical relation between the results obtained with GranuHeap instrument and powder flowability.