There are a whole range of factors that affect the flow properties of powders and thus the screening process: particle size, particle size distribution, particle shape and surface structure, porosity, bulk density and tapped density and moisture content are also included. The less capable of flowing, the more difficult to screen the product. The flow behavior is also crucial for the throughput and thus a key factor for assessing the quality of sieving.
Also products with low bulk density, high product moisture, highly variable particle shape and surface texture and small grain size are considered to be difficult to screen. To assess the fractionation quality, one must consider the components involved in the screening process, especially the mesh.
It is available with round, square- and trapezoidal shapes. Square shapes are sharp-edged in the peripheral areas, which can lead to a shift in the particle spectrum in fragile products and influence the behavior of the particle granules in the mesh.