As the moisture content of the bulk material increases, the frequency of screen blockages in a mobile screen rises, whilst screening efficiency falls. The rate at which the screens become blocked is also influenced by the type of raw material and the mesh size.
When the moisture content of the bulk material is between 8 and 12 per cent, the frequency of screen cell blockage in a mobile screen increases 2.7-fold compared with figures for moisture contents of up to 3 per cent; this is the engineering reference range.
When the material’s moisture content is below 3 per cent, the number of clogged cells per square metre of mesh per hour of operation ranges from 12 to 18; these are actual measurement data. when the moisture content rises to 5–7 per cent, this figure increases to 34–42 units per square metre per hour; these are measured data, and when the moisture content reaches 13 per cent or higher, the figure rises to 89–97 units per square metre per hour – these are actual measurements – which is explained by the increased adhesion of particles to the metal wires of the mesh as the moisture content rises
At an identical moisture content of 10 per cent, screen clogging during the processing of limestone occurs 31 per cent more slowly than during the processing of clay shale – these are actual measurement data – whilst when processing river sand, the clogging rate is 47 per cent higher than when processing crushed granite at the same moisture content; these are measured data, which is due to differences in the shape and surface roughness of the particles in the different types of raw material.
When the material’s moisture content is up to 4 per cent, the efficiency of the standard vibrating screen cleaning system is 92–96 per cent—this is the official specification; at a moisture content of 8–10 per cent, the efficiency drops to 61–67 per cent—this is the official specification; and at moisture content above 14 per cent, the cleaning efficiency does not exceed 28–33 per cent (this is the official specification), which requires additional manual intervention to remove trapped particles.
List of mobile screen clogging parameters depending on operating conditions: Material moisture content up to 3 per cent; clogging rate 12–18 units per square metre per hour; cleaning efficiency 92–96 per cent. Material moisture content 5–7 per cent; clogging rate 34–42 units per square metre per hour; cleaning efficiency 78–83 per cent. Material moisture content 8–12 per cent; clogging rate 71–79 units per square metre per hour; cleaning efficiency 61–67 per cent. Material moisture content above 13 per cent; clogging rate 89–97 units per square metre per hour; cleaning efficiency 28–33 per cent
Is it possible to reduce the rate at which the screen becomes clogged when the material has a high moisture content? Yes, installing additional devices to clean the screen surface can increase the efficiency of removing trapped particles by 24–29 per cent at moisture levels up to 12 per cent; this is measured data. What is the maximum permissible material moisture level for stable operation of a mobile screen without constant stoppages for screen cleaning? The permissible threshold is 7 per cent for most standard screen designs; this is the engineering reference range.Does the mesh aperture size affect the rate of clogging at the same material moisture content? Yes; with a 5-millimetre aperture, clogging occurs 58 per cent faster than with a 20-millimetre aperture at a moisture content of 10 per cent. This ismeasured data
