Circular vibrating screen is composed of screen box, exciter, supporting device and other components.
Screen box is composed of screen frame, screen surface and tensioning device. The vibration exciter is composed of two side plate vibration motors connected by a universal coupling in the middle. The screen box is supported by 8 springs.
The vibration force generated by the vibration source of circular vibrating screen is an inertial force that changes in a positive direction around a fixed axis, and its essence is a centrifugal force formed by the rotation of the eccentric mass around the fixed axis.
The working principle of the circular vibrating screen is that after the vibrating screen is started, the vibrating screen exciter drives the vibrating screen box to make a directional jumping motion, during which the material smaller than the screen surface aperture falls to the lower layer through the screen hole and becomes the under-sieve material, and the material larger than the screen surface is discharged from the discharge port after continuous jumping motion, and finally the screening work is completed.
Selection of Circular Vibrating Screen Parameters
(1) Throwing index
In general, according to the use of the screen, the circular vibrating screen generally takes KV=3～5, and the linear vibrating screen should take KV=2.5～4. The difficult-to-screen material takes a large value, and the easy-to-screen material takes a small value. When the sieve hole is small, take the larger value, and when the sieve hole is large, take the small value.
(2) Vibration strength
The choice of vibration strength K is mainly limited by the strength of the material and the stiffness of its components. The current mechanical level K value is generally in the range of 3 to 8, and the vibrating screen is generally in the range 3 to 6.
(3) The inclination angle of the screen surface
For circular vibrating screen, the inclination angle of the screen surface generally take 15°~25°, take the small value when the amplitude is large, and take the large value when the amplitude is small.
(4) The amplitude of the screen box
Screen box amplitude A is an important parameter for designing vibrating screen and its value must be appropriate to ensure adequate stratification of materials, reduce blocking, and facilitate the screening process. Usually A = 3 ~ 6mm, the larger the sieve hole takes the larger value, and the smaller the sieve hole takes the smaller value.
Tips for Selection of Circular Vibrating Screen
The main factors to consider when choosing the type of screening machine are:
- Characteristics of screening materials (grain content of materials under screen, content of difficult-to-screen particles, moisture and clay content in materials, shape of materials, specific gravity of materials, etc.);
- The structure of the screening machine (screen area, the number of screen layers, the size and shape of the screen holes, the area ratio of the screen holes, the movement mode of the screen machine, the amplitude and frequency, etc.);
- Requirements of beneficiation processing technology (processing capacity, screening efficiency, screening method, inclination angle of screening machine), etc.
In addition to considering the above factors, the following basic principles should be observed:
(1) After determining the screening area, the width of the screen surface should be at least 2.5 to 3 times the size of the largest piece of material to prevent the screen from being blocked by large pieces of material.
(2) In order for the vibrating screen to be in good working condition, the ratio of the length to the width of the screen should be selected within the range of 2 to 3.
(3) Reasonable screen material and structure suitable for working conditions should be selected.
(4) Determination of mesh size
When fine screen, arc screen, linear vibrating screen are used for fine particle screening, the size of the screen gap is 2 to 2.2 times the separation particle size, and the maximum is not more than 3 times;
For vibrating screen used for medium particle size material screening, its screen mesh size is 1.2 times of the separation particle size;
When used for screening coarse-grained materials, the screen size should be 1.05 times of the separation particle size;
For probability screen, the screen size is generally 2 to 2.5 times the actual separation particle size.
(5) Determine whether to choose double-layer or multi-layer screen
When the particle size range of the material to be screened is wide, the double-layer screen can be used as a single-layer screen, which can improve the processing capacity of the screening equipment, protect the lower screen, and prolong the service life of the lower screen. The selection of the screen size of the upper screen of the double-layer vibrating screen should generally be determined according to the characteristics of the raw material. The particle size of 55-65% of the raw material can be considered as the mesh size.
(6) Determine the effective working area of the screen
The screening area calculated according to the requirements of the production process is the effective area of the screen, and the specification of the screen is the nominal area of the screen.
For the vibrating screen used for screening medium-sized materials, the effective screening area should be 0.8 to 0.85 times the nominal area of the screen. Of course, this is closely related to the screen opening rate on the screen surface.
(7) For materials above 200mm, heavy-duty vibrating screens are mostly used; for materials above 10mm, circular vibrating screens are mostly used; linear vibrating screens and high-frequency vibrating screens are mostly used for desliming, dehydration and classification.
(8) When conditions permit, the seat screen should be preferred to facilitate inspection and maintenance. When a suspended screen must be selected, the suspending height should be minimized to reduce the swing amplitude of the vibrating screen and facilitate production operations.
When choosing screening equipment, you cannot only consider one reason, but fully consider various factors to ensure that you choose the equipment that suits your working conditions.