The vibrating screen generally has a harsh working environment, such as high temperature and high dust. In order to maintain the normal operation of the vibrating screen under this condition, it puts forward higher requirements on the process parameters of the vibrating screen. The process parameters of the vibrating screen are What? How to choose and calculate these parameters? All we need to understand. Reasonable process parameters can also ensure the normal operation of the vibrating screen, and in some respects also extend the service life of the screen.
Process parameters of vibrating screen
1. The inclination angle of the vibrating screen
The inclination angle of the screen surface refers to the angle between the screen surface of the vibrating screen and the horizontal line. The size of the inclination angle will affect the moving speed of the material on the drying surface. When the inclination angle of the screen surface is too large, the moving speed of the material will also increase. Although it can increase the production volume, it will reduce the screening efficiency. On the contrary, if the inclination angle is too small, the screening efficiency will be increased, but the production capacity will be reduced. Linear screens are generally installed horizontally with a zero inclination angle. Horizontal linear screens are generally only suitable for the screening of materials with a particle size of 40mm or less, or for the dehydration, desliming and removal of coal. If it is used for screening materials with a particle size of 50mm or more, the linear screen should have an angle, and the inclination angle is about 5º~10º.
2. Vibrating screen amplitude and frequency
Vibrating screen amplitude refers to the range and intensity of the box vibration, and frequency refers to the number of vibrations per minute of the screen box. When the amplitude is larger, the frequency of screening is higher, and the movement speed and acceleration of the screen box are also greater. When sieving coarse particles, it is recommended to adopt a larger amplitude and a lower frequency; conversely, when sieving fine particles, a smaller amplitude and a higher frequency should be maintained.
3. The length and width of the vibrating screen
When the other conditions of screening are the same, the productivity mainly depends on the width of the screen surface, and the screening efficiency is mainly determined by the length of the screen surface. But it does not mean that the width of the screen surface is as wide as possible, because when the screen surface is too wide, the feeding will be uneven and the rigidity will be poor. The screen surface is too long and can not increase the efficiency of screening, so the screen surface of the appropriate length and width should be selected. Therefore, the aspect ratio is generally 2:3. For the screening of coarse materials, the screen surface length is 3.5~4m. For the screening of medium and fine-grained materials, the screen surface length is 5~6m; the pre-screened screen surface can be shorter than the final screen surface It should be longer.
4. Throwing angle of vibrating screen
The throw angle of the vibrating screen refers to the angle formed between the direction of the box body and the screen surface when the box is moving, that is, the direction angle that the material on the screen surface is thrown by force. The larger the throwing angle, the slower the material movement speed, which will be adequately screened, which is suitable for difficult-to-screen materials. The smaller the projection angle, the faster the material movement speed, which is suitable for easy-to-screen materials.
Selection and calculation of vibrating screen parameters
1. Throwing index
According to experience, depending on the nature of the material to be processed, the theory and production practice for sieving have proved that the particle size is less than 3/4 of the mesh size, called “easy sieve”; the particle size is larger than the mesh size 3/ 4, called “difficult to sieve granules”; the closer the diameter of the granules is to the sieve size, the more difficult it is to penetrate the sieve. Most use medium-speed throwing index 1.75-3.3.
2. Installation inclination
The installation inclination angle is related to the processing capacity and screening efficiency of the vibrating screen.
(1) Material classification and separation, etc.: Installation angle=0°;
(2) Linear vibrating screen: dewatering: installation angle = 0°, negative if necessary; when the material is above 50 mm, the installation angle = 5~10°; when the material is below 40 mm: installation angle = 0°; For mud, de-intermediation, and dehydration: Installation angle = -5°~0°.
3. Installation vibration direction angle
The value of linear vibrating screen is 30~60°, for linear vibrating screen, generally β=45°. The reason is that it has good adaptability, high movement speed and high productivity.
4. The length and width of the screen surface
Calculate the required area according to the actual production use of the sieve, productivity, and the particle size of the material to be screened. If it is a multi-layer screen, it should be calculated layer by layer, and the calculated peak value should be taken, and it should be rounded according to the standard.
(1) The length of the screen surface: below 3.6mm, the interval of each stage is 0.6m; above 3.6mm, the interval of each stage is 0.9m;
(2) Screen width: below 3.0mm, the interval of each step is 0.3m; above 3.0mm, the interval of each step is 0.6m.
5. Vibration tilt angle
The vibration tilt angle is usually 45°, and the tilt angle can be as high as 60° for some difficult-to-screen materials such as crushed stone, coke, and sinter.
6. The moving speed of the screen surface and the thickness of the material layer
The moving speed of the material along the screen surface is usually 0.12~0.4m/s, not more than 1.2m/s. For a circular vibrating screen, the moving speed of the material along the screen surface is related to the inclination angle of the screen surface. The relationship between the thickness δ of the material layer and the sieve size a is shown on the right: δ≤(3~4)a; the relationship between the thickness and the average particle size d0 of the material on the screen is shown on the right: δ≈(2~2.5)d0.
7. Vibrating screen amplitude and spindle speed
The amplitude is generally between 2~8mm. When the sieve is small or used for dehydration, take the small value. When the sieve hole is larger, choose a larger value. For the spindle speed, it can be calculated as follows:
A is the amplitude (mm); n is the spindle speed (n/min)
The above content summarizes what the process parameters of the vibrating screen are, such as the inclination of the screen surface, the amplitude and frequency, the length and width of the screen surface, etc. The vibrating screen obtains the ideal use effect.