what's the difference between circular and linear vibrating screen? jxsc rock crusher
Both crusher production line and sand production line basically use vibrating screen. There are many kinds of vibrating screen, which can be divided into circular vibrating screenand linear vibrating screenaccording to the movement track of materials. These two types of screening equipment are usually used in daily production. Whats the difference between circular vibrating screen and linear vibrating screen? The following weteach you to distinguish between circular vibrating screen and linear vibrating screen.
There is no essential difference in style and structure between circular and linear vibrating screen. Through the screen surface vibration screening materials, but the different vibration trajectory will directly affect the purpose of screening.
The motor drives the eccentric block of the vibration exciter to rotate at high speed through the V-belt, which generates a large centrifugal inertia force, thus stimulating the circular motion of the screen box with a certain extent. The material on the screen is transferred through a screen frame on the sloping screen surface. A given pulse produces a continuous throwing motion. When the material meets the surface of the sieve, the particles smaller than the hole of the sieve can pass through the sieve to realize the classification.
The vibrating motor is used as the vibration source to make the material thrown on the screen and move forward in a straight line at the same time. The material evenly enters into the feed port of the screening machine from the feeder and passes through the multi-layer screening. The upper and lower screen sizes are discharged from their respective outlets.
Generally, the plate used for the production of circular vibrating screen is thicker, while the boxes are made of manganese steel to resist the impact of materials during screening. The materials used for the production of linear vibrating screenare mainly light plate or stainless steel plate.
For circular vibrating screen, because the exciter is arranged above the center of gravity of the screen box, the long ellipse axis at both ends of the screen box is in the shape of lower octagons, while the upper end of the long ellipse is oval. The axis of the feed end is toward the discharging direction, which is conducive to the rapid flow of materials. The upper end of the elliptical long axis is opposite to the discharge direction, which will reduce the moving speed of the material, and it is beneficial to the materials difficult to screen, while the arc screen surface increases the area of the effective screen, thus increasing its effective areaand In addition, for materials that are difficult to screen, the circular vibrating screen can reverse the spindle, make the vibration direction opposite to the moving direction of the material, reduce the moving speed of the material along the screen surface and improve the screening efficiency.
The material of circular vibrating screen moves in parabola shape on the surface of screen surface, which makes the material as scattered as possible to improve the materials bounce force, and the material stuck in the sieve hole will also beat to reduce the hole blockage.
According to the particle size of the material, the circular vibrating screen can change the inclination angle of the screen surface, thus changing the velocity of material moving along the screen surface and improving the productivity of the screen machine. Generally speaking, linear vibrating screen has a small screen angle in the production process.
Circular vibrating screenis also called single axis vibrating screen, because the exciter is an axis working with the inertia motor. Linear vibrating screen consists of two shafts and works according to the excitation principle of vibration motor, so it is also called double shaft vibrator.
Circular vibrating screen is mainly used to screen materials with large ratio, large particles and high hardness.It is widely used in mining industries, such as mines, coal and quarries. Linear vibrating screen mainly selects fine particles, light weight and low hardness materials. It is mainly used in dry powder, fine particle or micro powder material. It is commonly used in the food, chemical, construction materials and pharmaceutical industries.
The most widely used in the field of mine crushing is circular vibrating screen. In practice, the selection of circular orLinear vibrating screendepends on the type of material and application field that the user processes.
Jiangxi Shicheng stone crusher manufacturer is a new and high-tech factory specialized in R&D and manufacturing crushing lines, beneficial equipment,sand-making machinery and grinding plants.
vibrating screen working principle
When the smaller rock has to be classified a vibrating screen will be used.The simplest Vibrating Screen Working Principle can be explained using the single deck screen and put it onto an inclined frame. The frame is mounted on springs. The vibration is generated from an unbalanced flywheel. A very erratic motion is developed when this wheel is rotated. You will find these simple screens in smaller operations and rock quarries where sizing isnt as critical. As the performance of this type of screen isnt good enough to meet the requirements of most mining operations two variations of this screen have been developed.
In the majority of cases, the types of screen decks that you will be operating will be either the horizontal screen or the inclined vibrating screen. The names of these screens do not reflect the angle that the screens are on, they reflect the direction of the motion that is creating the vibration.
An eccentric shaft is used in the inclined vibrating screen. There is an advantage of using this method of vibration generation over the unbalanced flywheel method first mentioned. The vibration of an unbalanced flywheel is very violent. This causes mechanical failure and structural damage to occur. The four-bearing system greatly reduces this problem. Why these screens are vibrated is to ensure that the ore comes into contact will the screen. By vibrating the screen the rock will be bounced around on top of it. This means, that by the time that the rock has traveled the length of the screen, it will have had the opportunity of hitting the screen mesh at just the right angle to be able to penetrate through it. If the rock is small enough it will be removed from the circuit. The large rock will, of course, be taken to the next stage in the process.
Depending upon the tonnage and the size of the feed, there may be two sets of screens for each machine.
The reason for using two decks is to increase the surface area that the ore has to come into contact with. The top deck will have bigger holes in the grid of the screen. The size of the ore that it will be removed will be larger than that on the bottom. Only the small rock that is able to pass through the bottom screen will be removed from the circuit. In most cases the large rock that was on top of each screen will be mixed back together again.
The main cause of mechanical failure in screen decks is vibration. Even the frame, body, and bearings are affected by this. The larger the screen the bigger the effect. The vibration will crystallize the molecular structure of the metal causing what is known as METAL FATIGUE to develop. The first sign that an operator has indicated that the fatigue in the body of the screen deck is almost at a critical stage in its development are the hairline cracks that will appear around the vibrations point of origin. The bearings on the bigger screens have to be watched closer than most as they tend to fail suddenly. This is due to the vibration as well.
In plant design, it is usual to install a screen ahead of the secondary crusher to bypass any ore which has already been crushed small enough, and so to relieve it of unnecessary work. Very close screening is not required and some sort of moving bar or ring grizzly can well be used, but the modern method is to employ for the purpose a heavy-duty vibrating screen of the Hummer type which has no external moving parts to wear out ; the vibrator is totally enclosed and the only part subjected to wear is the surface of the screen.
The Hummer Screen, illustrated in Fig. 6, is the machine usually employed for the work, being designed for heavy and rough duty. It consists of a fixed frame, set on the slope, across which is tightly stretched a woven-wire screen composed of large diameter wires, or rods, of a special, hard-wearing alloy. A metal strip, bent over to the required angle, is fitted along the length of each side of the screen so that it can be secured to the frame at the correct tension by means of spring-loaded hook bolts. A vibrating mechanism attached to the middle of the screen imparts rapid vibrations of small amplitude to its surface, making the ore, which enters at the top, pass down it in an even mobile stream. The spring-loaded bolts, which can be seen in section in Fig. 7, movewith a hinge action, allowing unrestricted movement of the entire screening surface without transmitting the vibrations to the frame.
One, two, or three vibrators, depending on the length of the screen, are mounted across the frame and are connected through their armatures with a steel strip securely fixed down the middle of the screen. The powerful Type 50 Vibrator, used for heavy work, is shown in Fig. 7. The movement of the armature is directly controlled by the solenoid coil, which is connected by an external cable with a supply of 15-cycle single-phase alternating current ; this produces the alternating field in the coil that causes the up-and-down movement of the armature at the rate of thirty vibrations per second. At the end of every return stroke it hits a striking block and imparts to the screen a jerk which throws the larger pieces of ore to the top of the bed and gives the fine particles a better chance of passing through the meshes during the rest of the cycle. The motion can be regulated by spiral springs controlled by a handwheel, thus enabling the intensity of the vibrations to be adjusted within close limits. No lubrication is required either for the vibrating mechanism or for any other part of the screen, and the 15-cycle alternating current is usually supplied by a special motor-generator set placed somewhere where dust cannot reach it.
The Type 70 Screen is usually made 4 ft. wide and from 5 to 10 ft. in length. For the rough work described above it can be relied upon to give a capacity of 4 to 5 tons per square foot when screening to about in. and set at a slope of 25 to 30 degrees to the horizontal. The Type 50 Vibrator requires about 2 h.p. for its operation.
The determination of screen capacity is a very complex subject. There is a lot of theory on the subject that has been developed over many years of the manufacture of screens and much study of the results of their use. However, it is still necessary to test the results of a new installation to be reasonably certain of the screen capacity.
A general rule of thumb for good screening is that: The bed depth of material at the discharge end of a screen should never be over four times the size opening in the screen surface for material weighing 100 pounds per cubic foot or three times for material weighing 50 pounds per cubic foot. The feed end depth can be greater, particularly if the feed contains a large percentage of fines. Other interrelated factors are:
Vibration is produced on inclined screens by circular motion in a plane perpendicular to the screen with one-eighth to -in. amplitude at 700-1000 cycles per minute. The vibration lifts the material producing stratification. And with the screen on an incline, the material will cascade down the slope, introducing the probability that the particles will either pass through the screen openings or over their surface.
Screen capacity is dependent on the type, available area, and cleanliness of the screen and screenability of the aggregate. Belowis a general guide for determining screen capacity. The values may be used for dried aggregate where blinding (plugged screen openings), moisture build-up or other screening problems will not be encountered. In this table it is assumed that approximately 25% of the screen load is retained, for example, if the capacity of a screen is 100 tons/hr (tph) the approximate load on the screen would be 133 tph.
It is possible to not have enough material on a screen for it to be effective. For very small feed rates, the efficiency of a screen increases with increasing tonnage on the screen. The bed of oversize material on top of the marginal particlesstratification prevents them from bouncing around excessively, increases their number of attempts to get through the screen, and helps push them through. However, beyond an optimum point increasing tonnage on the screen causes a rather rapid decrease in the efficiency of the screen to serve its purpose.
Two common methods for calculating screen efficiency depend on whether the desired product is overs or throughs from the screen deck. If the oversize is considered to be the product, the screen operation should remove as much as possible of the undersize material. In that case, screen performance is based on the efficiency of undersize removal. When the throughs are considered to be the product, the operation should recover as much of the undersize material as possible. In that case, screen performance is based on the efficiency of undersize recovery.
These efficiency determinations necessitate taking a sample of the feed to the screen deck and one of the material that passes over the deck, that is, does not pass through it. These samples are subjected to sieve analysis tests to find the gradation of the materials. The results of these tests lead to the efficiencies. The equations for the screen efficiencies are as follows:
In both cases the amount of undersize material, which is included in the material that goes over the screen is relatively small. In Case 1 the undersize going over the screen is 19 10 = 9 tph, whereas in Case 2 the undersize going over is 55 50 = 5 tph. That would suggest that the efficiency of the screen in removing undersize material is nearly the same. However, it is the proportion of undersize material that is in the material going over the screen, that is, not passed through the screen, that determines the efficiency of the screen.
In the first cases the product is the oversize material fed to the screen and passed over it. And screen efficiency is based on how well the undersize material is removed from the overs. In other cases the undersize material fed to the screen, that is, the throughs, is considered the product. And the efficiency is dependent on how much of the undersize material is recovered in the throughs. This screen efficiency is determined by the Equation B above.An example using the case 1 situation for the throughs as the product gives a new case to consider for screen efficiency.
Generally, manufacturers of screening units of one, two, or three decks specify the many dimensions that may be of concern to the user, including the total headroom required for screen angles of 10-25 from the horizontal. Very few manufacturers show in their screen specifications the capacity to expect in tph per square foot of screen area. If they do indicate capacities for different screen openings, the bases are that the feed be granular free-flowing material with a unit weight of 100 lb/cu ft. Also the screen cloth will have 50% or more open area, 25% of total feed passing over the deck, 40% is half size, and screen efficiency is 90%. And all of those stipulations are for a one-deck unit with the deck at an 18 to 20 slope.
As was discussed with screen efficiencies, there will be some overs on the first passes that will contain undersize material but will not go through the screen. This material will continue recirculating until it passes through the screen. This is called the circulating load. By definition, circulating load equals the total feed to the crusher system with screens minus the new feed to the crusher. It is stated as a percentage of the new feed to the crusher. The equation for circulating load percentage is:
To help understand this determination and the equation use, take the example of 200 tph original or new material to the crusher. Assume 100% screen efficiency and 30% oversize in the crusher input. For the successive cycles of the circulating load:
The values for the circulating load percentages can be tabulated for various typical screen efficiencies and percents of oversize in the crusher product from one to 99%. This will expedite the determination for the circulating load in a closed Circuit crusher and screening system.
Among the key factors that have to be taken into account in determining the screen area required is the deck correction. A top deck should have a capacity as determined by trial and testing of the product output, but the capacity of each succeeding lower deck will be reduced by 10% because of the lower amount of oversize for stratification on the following decks. For example, the third deck would be 80% as effective as the top deck. Wash water or spray will increase the effectiveness of the screens with openings of less than 1 in. in size. In fact, a deck with water spray on 3/16 in. openings will be more than three times as effective as the same size without the water spray.
For efficient wet or dry screeningHi-capacity, 2-bearing design. Flywheel weights counterbalance eccentric shaft giving a true-circle motion to screen. Spring suspensions carry the weight. Bearings support only weight of shaft. Screen is free to float and follow positive screening motion without power-consuming friction losses. Saves up to 50% HP over4- bearing types. Sizes 1 x 2 to 6 x 14, single or double deck types, suspended or floor mounted units.Also Revolving (Trommel) Screens. For sizing, desliming or scrubbing. Sizes from 30 x 60 to 120.
TheVibrating Screen has rapidly come to the front as a leader in the sizing and dewatering of mining and industrial products. Its almost unlimited uses vary from the screening for size of crusher products to the accurate sizing of medicinal pellets. The Vibrating Screen is also used for wet sizing by operating the screen on an uphill slope, the lower end being under the surface of the liquid.
The main feature of the Vibrating Screen is the patented mechanism. In operation, the screen shaft rotates on two eccentrically mounted bearings, and this eccentric motion is transmitted into the screen body, causing a true circular throw motion, the radius of which is equivalent to the radius of eccentricity on the eccentric portion of the shaft. The simplicity of this construction allows the screen to be manufactured with a light weight but sturdy mechanism which is low in initial cost, low in maintenance and power costs, and yet has a high, positive capacity.
The Vibrating Screen is available in single and multiple deck units for floor mounting or suspension. The side panels are equipped with flanges containing precision punched bolt holes so that an additional deck may be added in the future by merely bolting the new deck either on the top or the bottom of the original deck. The advantage of this feature is that added capacity is gained without purchasing a separate mechanism, since the mechanisms originally furnished are designed for this feature. A positivemethod of maintaining proper screen tension is employed, the method depending on the wire diameter involved. Screen cloths are mounted on rubber covered camber bars, slightly arched for even distribution.
Standard screens are furnished with suspension rod or cable assemblies, or floor mounting brackets. Initial covering of standard steel screen cloth is included for separations down to 20 mesh. Suspension frame, fine mesh wire, and dust enclosure are furnished at a slight additional cost. Motor driven units include totally-enclosed, ball-bearing motors. The Vibrating Screen can be driven from either side. The driven sheave is included on units furnished without the drive.
The following table shows the many sizes available. Standard screens listed below are available in single and double deck units. The triple and quadruple deck units consist of double deck units with an additional deck or decks flanged to the original deck. Please consult our experienced staff of screening engineers for additional information and recommendations on your screening problems.
An extremely simple, positive method of imparting uniform vibration to the screen body. Using only two bearings and with no dead weight supported by them, the shaft is in effect floating on the two heavy-duty bearings.
The unit consists of the freely suspended screen body and a shaft assembly carried by the screen body. Near each end of the shaft, an eccentric portion is turned. The shaft is counterbalanced, by weighted fly-wheels, against the weight of the screen and loads that may be superimposed on it. When the shaft rotates, eccentric motion is transmitted from the eccentric portions, through the two bearings, to the screen frame.
The patented design of Dillon Vibrating Screens requires just two bearings instead of the four used in ordinary mechanical screens, resulting in simplicity of construction which cuts power cost in half for any screening job; reduces operating and maintenance costs.
With this simplified, lighter weight construction all power is put to useful work thus, the screen can operate at higher speeds when desired, giving greater screening capacity at lower power cost.
The sting of the positive, high speed vibration eliminates blinding of screen openings.
The sketches below demonstrate the four standard methods of fastening a screen cloth to the Dillon Screen. The choice of method is generally dependent on screen wire diameters. It is recommended that the following guide be followed:
Before Separation can take place we need to get the fine particles to the bottom of the pile next to the screen deck openings and the coarse particles to the top. Without this phenomenon, we would have all the big particles blocking the openings with the fines resting atop of them and never going through.
We need to state that 100% efficiency, that is, putting every undersize particle through and every oversize particle over, is impossible. If you put 95% of the undersize pieces through we in the screen business call that commercially perfect.
how to identify circular and linear vibrating screen | m&c
Screening is to separate materials with different properties, which is an essential part of the aggregate production line. Screening machines are classified into different types according to their structure and motion characteristics, among which circular vibrating screen and linear vibrating screens are the most commonly used mining equipment. In this article, will introduce top 9 tips differences between linear vibrating screen and circular vibrating screen.
Circular vibrating screen makes use of centrifugal force produced by the rotation of the eccentric block in the vibrator to make the screen box, vibrator and other parts make a forced continuous circular or approximate circular movement. The materials on circular vibrating screens move with screen boxes in a round movement trajector.
The material of the circular vibrating screen moves in parabola shape on the screen panels, which makes the material disperse as much as possible, and the material stuck in the screen hole can also jump out, and the plugging is less.
While the exciter of circular vibrating screen is arranged above the center of screen box gravity, which is conducive to the rapid spread of materials, and the treatment capacity is higher than that of the linear vibrating screen.
Linear screen is mainly used to screen fine particles, materials with light specific gravity and low hardness, mainly inclede dry powder, fine particles or micro powder, which are usually used in food, chemical, building materials and pharmaceutical industries.
Circular vibrating screen is mainly used for screening materials with large ratio, large particle size and high hardness, which is widely used in mines, coal preparation plant, quarries, etc. In addition, circular vibrating screens can also be used for some materials that are not easy to be screened.
Circular vibrating screen can turn the spindle, so that the vibration direction is opposite to the material movement direction, and the material movement speed along the screen surface is reduced, thus the screening efficiency is improved.
In the field of mine crushing, circular vibrating screen is widely used.In the actual production, the choice of circular vibrating screen or linear vibrating screen mainly depends on the types of materials and application fields handled by users. The purpose of screening is different, the selection of equipment is also different.
circular-motion screening machine - siebtechnik tema
A SIEBTECHNIK circular-motion screening machine is the classic solution for process requirements in screen classification. It is a freely vibrating screening machine that vibrates in a circle and is mounted on air springs or helical compression springs. Screen box and unbalance mass are optimally coordinated in their mass ratios. This enables a harmonious vibrating motion to be transmitted to the screened material at all points on the machine. Speed and vibration amplitude of the machine can be varied specifically to suit the product and so ensure a lastingly perfect screening result. The robust construction using and combining standard component parts ensures high flexibility and enables customer-focused solutions. Moreover, machines can be constructed with a low-maintenance running time and a long service life.
Our REKORD V (shaft with unbalance mass), VZ (cell drive) and VR (unbalance motor) series screening machines offer separation sizes of between 0.8 and 300 mm and a screening area of between 0.5 and approx. 60 m. These machines can be set up for a vibration amplitude of between 2 and 14 mm, depending on the product. The screen panel tilt can be between 10 and 30, and the screen set-up can comprise between one and three screen decks according to requirement.
The screen box is set up to hold lengthways or crossways tensioned screen panels or for level screen decks and naturally also for system screen cloths by different screen cloth manufacturers. For dusty screening material we supply on request circular-motion screens with a dust cover or a closed dust protection box. Individually adapted screening aids in the form of beating devices or spraying systems are also available.
SIEBTECHNIK circular-motion screening machines are freely vibrating machines, that is, the vibration circle diameter adjusts itself freely in accordance with the mass ratio of screen box and unbalance mass. Circular-motion screens have a steep throw angle and therefore require a screen panel tilt of between 10 and 18. Exceptions to this are dewatering screens with a tilt of between 3 and 5 and steeply tilted screens, e.g. sand screens, with a tilt of between 25 and 40.
The screen box, consisting of side walls and cross-members, can withstand all static and dynamic forces. The drive shaft with the unbalance masses runs in two rolling bearings that are arranged at the centre of gravity of the screen box. The screening machine is drive by V-belts or by a flexible coupling. Larger screening machines are additionally fitted with an intermediate transmission shaft. Bearings are either oil- or grease-lubricated. The screen box is elastically supported against the substructure on 4 spring elements. It is optionally set up to hold lengthways or crossways tensioned screen panels or for level screen decks. For dusty screening material we supply on request circular-motion screens with a dust cover or a closed dust protection box.
There is a comprehensive range of accessories available for all SIEBTECHNIK TEMA screening machines. Whether its a spraying system, wear protection, counter-vibration frame, air suspension, dust guard, dust covers, drive consoles, double unbalance gear units, hybrid suspension or special screen cloths thanks to its decades of experience SIEBTECHNIK TEMA gets you the best result for your requirement
feed & food archives | oli vibrators
For the foodstuff sector, the application of OLIs solutions, such as external electric motovibrators, pneumatic vibrators, hydraulic vibrators and aerator pads, facilitates the production process of a vast range of products, among the most consumed, from pasta to industrial baking products, biscuits to convenience food, to sugar, salt and coffee.