The particle size distribution depends on the screen surface, which is available in three types: grate screens, plate screens, and mesh screens. Grate screens are suitable for screening large particles; the grate opening should be 1.1 to 1.2 times the diameter of the material passing through the screen, and generally should not be less than 50 mm. Plate screens are made of perforated steel plates with round, square, or rectangular holes, typically 10–80 mm in diameter. They have a long service life, are not easily clogged, and are suitable for screening medium-sized particles. Mesh screens are made of woven or welded steel wire with square, rectangular, or elongated holes, commonly 6–85 mm in diameter. Elongated holes are suitable for screening moist materials. The advantage of mesh screens is their large effective area.
Screening machines operate on two principles: rotary screens and vibrating screens. Rotary screens include shaft screens, drum screens, solid screens, spiral roller screens, and blade roller screens. Vibrating screens include banana screens, high-speed screens, and tension screens. Rotary screens utilize forced conveying, reducing the likelihood of material clogging the screen surface. Vibrating screens are prone to clogging when screening sticky or wet materials (generally with a moisture content of 6% or higher) due to their inherent characteristics, and they require a relatively high power consumption.
