There are many types of screening equipment. It is very necessary to give details and correct classification to the screening equipment before understanding it. Unified comprehensive classification methods of the screening equipment were scanty in the past. The screening equipments were usually divided into bar screen, grid screen, roller screen, cylindrical screen, inertia vibrating screen and resonance screen.

While you select the screening equipment, you should consider these following factors. First, the properties of the screening material(such as content of the grain size of the material under screen, the grain size content of the particle that is difficult to screen, the shape and density of the material) should be considered. Second, the structure of the screening machine( such as the area of the screen surface, the surface layers of the sieve, the sieve and shape, the rate of sieve openings, movement type of the screening machine, the amplitude and frequency, etc.) should be considered. Third, the process requirements (such as processing capacity, screening efficiency, screening methods and the inclination of the screening machine)should be considered. The selection should follow the following basic principles. 

First, after the screening area is determined, the screen surface should be at least 2.5-3 times the material of the largest block so that the sieve will not be blocked by the large lump materials. Second, in order to make the sieve be in good working conditions, the ratio of the length and width of the sieve should be in the range of 2 to 3. Third, you should select reasonable material and structure of the screen surface which is suitable for working conditions. Forth, for the fine screen, curved screen, liner vibrating screen for screening the fine materials, the size of the sieve slit should be 2-22 times particle separation not more than 3 times. For the vibrating screen that used for the medium-grained material, the sieve size should be 1.05 times particle separation. For the probability screen, it should be 2-2.25 times. Fifth, if the particle size of the screening material is too wide, you use the double-layer to replace the single layer, which can not only improve the handling capacity of the screening machine, but also protect the lower screen surface and extent its service life. The mesh size of the upper screen surface should be determined based on the particle size characteristics of the raw materials. The undersized amount can be 55%-60% of the total feeding amount. Sixth, when the vibrating screen is used to sieve the medium-grained materials, the effective screening area is only 0.8-0.85 time the  nominal area. Seventh, the screening of the materials more than 200mm mainly use heavy vibrating screen. The circular motion vibrating screen is often used for the material with 10-200mm. The liner vibrating screen, high-frequency vibrating mech screen and the high-frequency vibrating fine screen are often used for dehydration, desliming and classification.