Particle size measurement of dry, free-flowing powders and granules in the range from 0.5 µm to 8,750 µm with laser diffraction

The system configuration comprising the laser diffraction sensor HELOS/KR, gravity disperser GRADIS/L and dosing unit VIBRI/L is the first choice for the analysis of free-flowing particles from 0.5 µm to 8,750 µm that require only low dispersing forces. The gentle dispersion in the free fall shaft of the GRADIS is recommended in particular for metastable particles and coarse grained samples with a low fines content. With the long optical bench, the system is ideally suited to samples with a mean particle size in the medium micrometre range to several millimetres and can be used for sample amounts from a few grams to the kilogram range.

The dosing of the dry sample is performed with the precision vibratory feeder VIBRI/L, which guarantees optimum concentration of the sample in the measuring zone with a uniform, controlled product supply. In the GRADIS free fall shaft, the acceleration under gravity and the integrated impact-plate cascade ensure gentle dispersion with slight particle-to-wall and particle-to-particle collisions. Replaceable slot apertures with sizes of 2, 4 or 10 mm are used to adapt the free fall shaft outlet to the sample material. Extraction generates laminar flow conditions in the free fall shaft and in the measuring zone. The free fall shaft can be disassembled into two halves for cleaning. For special applications, the free fall shafts can also be optionally supplied with PTFE coating (conductive or non-conductive).

GRADIS is designed both for use in the HELOS laser diffraction sensors and for dynamic image analysis with the QICPIC sensors and can therefore be used alternatively for the analysis of particle size and particle shape of dry, free-flowing products.

  • Particle size and particle size distribution
  • For coarser or even metastable powders and granules
  • For analyses in the quality or production laboratory | Also process-oriented
  • Sample amount per analysis < 10 g to 1,000 g
  • 6 high-resolution measuring ranges from 0.5 µm to 8,750 µm | R3 to R8T
  • Gentle dispersion under the force of gravity in a free fall shaft
  • GRADIS dry dispersion can also be used with QICPIC image analysis

The modular concept of the HELOS laser diffraction sensors allows this configuration to be systematically expanded with numerous dispersion units and dosing options to open it up to many more product-appropriate measuring applications.