Vibrating screen is a kind of very important auxiliary equipment in crushing plants. The screening efficiency of vibrating screen has important influence on the further processing. So knowing the factors affect vibrating screen working efficiency and knowing how to improve the efficiency of vibrating screen means a lot. Here, we focus on the factors affect vibrating screen working efficiency.
The working efficiency of vibrating screen is related with various factors, which includes the raw material properties, structural parameters of screen deck, motion parameters of vibrating screen etc.
Raw material properties are the important factor affects the working efficiency of vibrating screen. In the production process of vibrating screen, the screen mesh is easily blocked, making the effective screening area reduces, so does the working efficiency. The block of screen mesh is related with the component type of raw material, density of raw material and the size of raw material and so on.
Different types of raw materials have different physical properties. The type of raw material can be divided into friability and viscosity. The adhesive raw material may easily form dense adhesion, blocking the screen mesh and reducing the efficiency. But for brittle material, the working efficiency of vibrating screen can be assured. Also, the particle shape of raw material will also affect the efficiency of vibrating screen. Cubical and spheriform particles are easier to go through the screen mesh while the flaky particles are easy to stock in the screen mesh.
Generally, the raw materials are layered and screened according to their sizes. In other words, the density of raw material directly affects the production capacity of vibrating screen. Particles with large density can easily go through the screen mesh, so the working efficiency is also high. On the contrary, particles with small density or powders are difficult to go through the screen mesh, so the working efficiency is also low.
If the raw material has high moisture content, they will easily form adhesion. Besides, in the vibrating process, the particles squeeze each other, making the adhesion more dense, which will increase the resistance of raw material movement. In this case, it will be difficult for the raw materials to go through the screen mesh. Also, the adhesion of raw material will reduce the size of screen mesh, making it easy to be blocked, reducing the effective screen area. Some raw materials with high moisture content even cannot be screened. So when the raw material contains much moisture, we should do some measures to deal with it, such as adopt a dryer to dry the raw material etc.
Generally, the width of screen deck directly affects the production rate and the length of screen deck directly affects the screening efficiency of vibrating screen. Increase the width of screen deck can increase the effective screen area, improving the production rate. Increase the length of screen deck, the residence time of raw material on the screen deck also increases, and then the screen rate is high, so the screening efficiency is also high. But for the length, it is not the longer the better. Too long length of deck screen will reduce the working efficiency. So choosing proper length and width of screen deck can improve the screen efficiency of vibrating screen. Actually, the match of width and length of screen deck is also very important.
Even the shape of screen shape is mainly decided by the particle size of products and the application requirements of screened products, but it still has certain influence on the screening efficiency of vibrating screen. Compared with screen mesh with other shapes, when the nominal sizes are the same, particles go through the circular screen mesh have smaller sizes. For example, the average size of particles goes through circular screen mesh is about 80%-85% of the average size of particles goes through square screen mesh. So, in order to get high screening efficiency, we should adopt different shapes of screen mesh according to different raw materials.
Size Of Screen Mesh And Opening Rate Of Screen Deck
When the raw material is fixed, the size of screen mesh has great influence on the working efficiency of vibrating screen. The larger the screen mesh size, the stronger the through screening ability, so the production capacity is also larger. And the size of screen mesh is mainly decided by the raw material to be screened.
The opening rate of screen deck refers to the ratio of the opening area and screen deck area (effective area coefficient). The high opening rate increases the possibility for materials to go through the screen mesh, so the production capacity is also high. Or, the capacity will be reduced. So in order to improve the working efficiency of vibrating screen, we should adopt screen deck with relatively larger effective area coefficient.
Material Of Screen Deck
Non-metallic screen deck, such as rubber screen deck, polyurethane woven deck, nylon screen deck etc. has properties to produce second high-frequency vibration in the working process of vibrating screen, making it difficult to block. In this case, the working efficiency of vibrating screen with non-metallic screen deck is higher than vibrating screen with metal screen deck.
The included angle between screen deck and horizontal plane is called screen angle. The screen angle has close relation with the production capacity and screening efficiency of vibrating screen. When the screen angle increases, it will strengthen the throwing strength of raw materials on the screen deck. In this case, movement speed of raw material on the screen deck will be faster, making the production capacity increase. But at this time, the residence time of raw materials on the screen deck reduces, so does the screening efficiency. Otherwise, the production capacity will reduce and the screening efficiency will increase. In order to keep the screening efficiency in ideal range, the screen angle of circular vibrating screen is generally between 15-25буand the screen angle of linear vibrating screen is between 0-8бу.
Vibrating direction angle refers to the included angle between vibration direction line and upper layer screen deck. The larger the vibrating direction angle, the shorter the distance that the raw material moves, the slower the forward movement speed of raw materials on the screen deck. In this case, raw materials can be fully screened and we can get high screening efficiency. The smaller the vibrating direction angle, the longer the distance that raw material moves, the faster the forward movement speed of raw materials on the screen deck. At this time, the vibrating screen has large production capacity, but raw materials cannot be fully screened. So we should choose proper vibrating direction angle. For raw materials that are difficult to screen, the vibrating direction angle should be larger. For raw materials that are easy to screen, the vibrating direction angle should be smaller.
Increasing the amplitude can greatly reduce the blocking of screen mesh and be helpful for grading the raw materials. But too large amplitude will damage the vibrating screen. And the amplitude is chose according to the size and properties of the screened raw material. Generally, the larger the scale of vibrating screen, the larger the amplitude should be. When the linear vibrating screen is used for grading and screening, the amplitude should be relatively large, but when it is used for dewatering or desliming, the amplitude should be relatively small. When the screened raw material has large size, we should adopt large amplitude, but when the screened raw material has small size, we should adopt small amplitude. Generally, the amplitude of linear vibrating screen is between 3.5-6mm.
Increasing the vibration frequency can increase the jitter times of raw material on the screen deck, which will improve the screening possibility of raw material. In this case, the screening speed and efficiency will also increase. But too large vibration frequency will reduce the service life of vibrating screen. For raw materials with large sizes, we should adopt large amplitude and low vibration frequency. For raw materials with small sizes, we should adopt small amplitude and high vibration frequency.
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