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vibrating screen | crushing & mining screen - jxsc mine

vibrating screen | crushing & mining screen - jxsc mine

Vibrating screen is a rectangular single-, double-, and multi-layer, high-efficiency new screening equipment. It does circular trajectory, so also known as the circular vibratory screen. The screen machine is ideal equipment in rock crushing and screening plant.

JXSC vibrator screens adopt the cylindrical eccentric shaft exciter and the partial block to adjust the amplitude. The long material sieve line and the screen specifications are many. Specifical design for the quarry plant, stone crusher plant and also appropriate for mining, coal and mineral preparation. Our screening installation has advantages of reliable structure, strong excitation force, durability, and low vibration noise.

The vibratory screening machine is to utilize reciprocating vibration of the vibration generator produced. The processing of the screen separates the different size material by a single- or triple-deck screen. That is, according to the size of particles to separate. The underlayer is a small material, and the upper layer is coarse particle material. In the end, the coarse and fine particles are separated and the screening process is completed.

Types of vibrating screens According to motion theory, screening machines can divide into linear, circular, horizontal, eccentric shaft vibratory screens and inclined screen. The single deck, double deck, and multilayer vibrating screen is the basis of the numbers of the layers. Because of the different screening materials, we also call it gravel screen, sand screen machine, aggregate screening, wet vibratory screens.

Performance characteristics: 1. The material screen drip line is long and has many screening specifications. 2. The eccentric block as an exciting force, a strong exciting force. 3. Sieve beams and sieve box connected by high strength bolts, no welding. 4. Sieve machine has the advantages of simple structure and convenient repair. 5. The small amplitude, high frequency, high dip structure, so this machine is of high efficiency, maximum, long life, low power consumption, low noise.

1. The shape of the particle and screen size Most screening material is cylinder or anomaly, and the screen size has both circular and rectangle. The shape of the material granule touch screen for particle whether passed has a big effect. The rectangle screen is good for the circular particle, and the circular screen for irregularity.

5. The peculiarity of the material All the size, humidity, friction and flowability of material will affect the screen. The humidity higher, friction bigger, flowability too bad, so the passing rate lower.

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. Read More

vibrating screen - mineral processing

vibrating screen - mineral processing

Separate crushed materials and gravel into different sizes through large screens or industrial screens. As part of the crushing operation, coarse screens called grizzly bears or oxen are used to separate too large or too small materials from raw materials.Screens have static, horizontal and cylindrical screens, but today, most factories use inclined vibrating screens. The screening equipment determines the clear and reliable material separation, which provides the basis for the subsequent mineral processing.

Main parts of high frequency vibrating screen are mainframe, screen, electric vibrators, electric motor, rub spring and coupler.The screening decks are capable of single to triple decks, greatly improve the screening efficiency and capacity. Besides, providing a thin and loose bed of particles, which as well as do a good effect on the screen.Sieving is one of the oldest and most widely used physical size separation methods and is widely used in industry. In the continuous screening process, high frequency and low amplitude features lead to the vertical elliptical movement, the particles that fall from the feed hopper and reach the surface of the screen are sorted under the action of gravity. Oversized particles rebound along the screen, and most undersized particles pass through the holes.

High frequency vibrating screen is the most important screening machine mainly used in the beneficiation industry. They are used to separate materials containing solids and crushed ores with a particle size of less than 200 m. Wetting or drying materials can be sieved.Unlike the ordinary vibrating screen, the frequency of high-frequency screening is controlled by an electromagnetic vibrator installed above the surface of the screen and directly connected to the surface of the screen, and the vibration frequency is adjustable.High-frequency vibrating screens are usually operated at an angle of inclination, traditionally varying between 0 and 25 degrees, up to 45 degrees. In addition, it should operate at a low stroke with a frequency range of 1500-7200 RPM. Before using a high-frequency screen, it is usually necessary to pretreat the feed, because the holes in the screen are easily blocked.

The limitation of the high frequency vibrating screen is that the fine screen is very fragile and easily blocked. As time goes by, the separation efficiency will decrease and the screen needs to be replaced.

Circular vibrating screenThe multi-layer vibrating screen is specially designed for screening stones in quarries. It can also be used to classify products in coal preparation, mineral processing, building material production, power and chemical industries.The main advantages of the circular vibrating screen are as follows.(1) By adjusting the excitation force, the flow rate can be changed easily and steadily.(2) The circular vibrating screen has stable vibration, reliable operation and long service life.(3) Simple structure and reliable operation. The relatively light weight and small volume make maintenance easier.(4) The closed structure of the screen effectively prevents dust pollution.(5) Low noise intensity and small power consumption are generated during the operation of the vibrating screen.High frequency vibrating screen(1) Light, durable structure. The compact high-power vibration exciter is used as the drive. No belt or other accessories are required. The screen is very light but durable.(2) Adjustable flow rate. The screening capacity can be adjusted with ease because the stroke can be varied by adjusting the unbalanced weight with the most suited number of poles.(3) Screening capacity can be easily adjusted by adjusting the stroke, frequency, etc.(4) Stable performance. The high power of vibration makes screen run stable, even when screening adhesive materials.(5) Accurate screening. According to the specific materials and flow rate, single-layer to triple-layer deck-type groove can be designed according to the screening requirements to achieve accurate and efficient screening.(6) Simple start, stop. Press the controller button to easily control the start or stop of screening.

In the beneficiation line of various ores, the high-frequency sieve plays a vital role. The high-frequency sieve sifts out the coarse particles and sends them back to the crusher for crushing. At the same time, the fine-grained materials are discharged in time to avoid excessive crushing caused by re-grinding.The sieved materials can enter the next stage of beneficiation process. The use of high-frequency sieve can not only meet the requirements of mineral fineness, but also achieve smaller particle size separation, thereby reducing the capacity and overall energy consumption required in the crushing stage. Therefore, the grade of the final product is improved, and a better recovery rate and screening efficiency are provided.

dewatering screen

dewatering screen

The material is usually introduced as slurry. On an inclined dewatering screen the accelerations along with a portion of the gravitational force will cause the material to travel towards the discharge end while the water is being screened out by means of proper screening media.

The resulting force for material travel is indicated as the yellow arrow. The force causing the water to separate from the solids is gravity enhanced by the vertical vector of the G-forces produced by the screen.

In order to improve dewatering one would have to decrease the inclination of the screen which in return will also decrease the material travel rate drastically. In other words the dry product will end up quite wet.

This can raise a couple of problems. A customer could be quite hesitant to pay for a high amount of water in the product. A product w ith high water content w ill flow back on a conveyer belt and will cause severe damage to the rollers of the belt by washing fine solid product into the bearings. Finally the amount of w ater in the product is a loss if the customer doesnt pay for it just as well as it is a loss if the plant runs a closed water circuit.

As for the applications discussed above the material is usually introduced as slurry. Other then on inclined machines the only force resulting in material travel is the g-force produced by the screen. This g-force is aligned a 45 and transports the material uphill. The gravitational forces enhanced by the vertical portion of the acceleration of the machine arc fully utilized towards dcwatcring.

In operation those forces w ill build a material layer on the screen that is pushed out of the wet zone towards the discharge end. A back dewatering field is used to reduce the amount of water right after feeding the screen. The thick layer of material acts as a filter cake and not only presses water out but traps fine particles that would be lost in a thin layer screening process.

The purpose of this investigation was to determine the advantage of using either a conventional sieve bend ahead of a vibrating screen or of attaching a sieve-bend screen surface onto a vibrating screen to serve as a scalping deck when dewatering or draining dense medium from fine coal.

In dewatering, use of either the sieve bend or scalping deck increased the capacity of the vibrating screen tenfold and the recovery of coal finer than 0.5 mm threefold, with no sacrifice in the moisture content of the over-size product. In dense-medium drainage, either the sieve bend or the scalping deck reduced the amount of magnetite retained on the product of the vibrating screen, particularly when the medium was as dense as that characteristic of the underflows from dense-medium cyclones.

The sieve bend was slightly superior to the scalping deck in dewatering, but the scalping deck was clearly superior in dense-medium drainage. Additional advantages of the scalping deck are lower cost and a substantial saving in headroom.

Screens-particularly those used for fine sizing, dewatering, and recovery of dense medium-comprise a significant part of the cost of coal preparation plants. Their capacity is low in relation to space requirements; so in addition to their own cost these screens add disproportionately to building costs. Their use is increasing because of the increased proportion of fine coal in washery feed, the present trend toward removing the finest sizes of raw coal for separate treatment, and the introduction of the dense-medium cyclone for cleaning fine coal. Thus, any improvement in the capacity of screens can contribute substantial reductions in plant capital costs. This objective lead the Bureau of Mines to investigate the sieve bend shortly after its development by the Dutch State Mines. In this earlier work, use of the sieve bend for screening at fine sizes was investigated. The present work extends the investigation to cover two other important uses of the sieve benddewatering and dense-medium drainage.

In the course of a recent investigation of the dense-medium cyclone, it was found that attaching the screen surface of a sieve bend directly to the feed end of a vibrating screen to serve as a scalping deck solved a difficult medium-drainage problem; apparently because blinding of the vibrating screen was greatly reduced. Therefore, the use of such a scalping deck was included in the present investigation of the conventional sieve bend.

The test circuit used in the medium-drainage tests is illustrated in figure 1. A 26-inch by 8-foot horizontal vibrating screen divided longitudinally was arranged so that one side could be fed with the oversize product of a sieve bend. The other side was fitted with a scalping deck made by attaching the screen surface of the sieve bend directly to the feed end of the vibrating screen. When desired, the sieve bend could be bypassed so only the vibrating screen was in use. Thus, with this combination the vibrating screen alone, the vibrating screen fitted with the scalping deck, or the vibrating screen operating in tandem with the sieve bend could be used in testing. All screen underflows passed to a sump-agitator where magnetite or water was added as needed to maintain medium density, then recirculated through the system via the head tank where the coal or refuse was added.

All screen surfaces (vibrating screen, sieve bend, and scalping deck) were 0.5-mm wedge wire. In all tests, only a 4-inch width of the screens was used to hold the amount of material handled within the capacity of the auxiliary equipment. Use of such a narrow screen section might be expected to exaggerate the frictional drag at the sides of the screens and thus reduce capacity; however, comparison of the test results with the capacity of

Samples were collected at the feed and discharge of each screen in any combination of screens used so that the performance of individual screens could be assessed. These samples were wet-screened at 28-mesh, dried, and weighed; a portion of the 28-mesh to 0 fraction was analyzed for magnetic content in a Davis-tube magnetic tester.

The magnetite used was a commercial product, designated grade B, containing 90 percent of material finer than 325-mesh. The coal and refuse were -inch to 0.5-mm products obtained in the operation of a laboratory, dense- medium pilot plant. As shown in table 1, these products contained a high portion of particles (about 36 percent) in the 14- to 35-mesh size range; therefore they provided a severe test of drainage equipment.

For the dewatering tests, the sump-agitator was eliminated from the circuit. Coal and water were fed at the head tank and passed over the screens in open circuit. In most tests, samples were taken also at several additional points along the length of the vibrating screen. All samples were analyzed for moisture content and size composition. The coal used in these tests was a washed coal of -inch to 0 size, with the screen analysis shown in the last column of table 1.

One of the first steps of the investigation was to determine the influence of the inclination at which the scalping deck was mounted on the vibrating screen. Tests were conducted to determine the performance of the scalping deck at two angles of inclination-one with the feed end vertical and the other with the discharge end horizontal. Both washed coal and refuse, with medium of appropriate specific gravity, were used in these tests. When draining washed coal, the angle of inclination was unimportant; however, when draining refuse, superior results were obtained when the discharge end of the scalping deck was horizontal; magnetite retention was reduced by a third (table 2).

The medium used with the washed coal was 1.20 specific gravity, while that used with the refuse was 1.70. The thicker medium discharged with the refuse from the cyclone did not drain as fast as the thin medium that accompanied the washed coal. Reducing the slope of the scalping deck provided more retention time and hence allowed more complete drainage of the medium. However, with very thick medium, of 2.20 specific gravity for example, material sometimes compacted at the discharge end of the scalping deck when it was horizontal. With a thick medium, best results were obtained when the scalping deck was just steep enough to eliminate such compaction; therefore, the scalping deck was adjusted in this manner for all subsequent tests.

Two refuse products, both of -inch to 0.5-mm size but one much coarser than the other, were tested under similar operating conditions. The only samples collected were those of the feed and discharge of the scalping deck. The amount of magnetite retained in the discharge of the scalping deck varied in proportion to the amount of 14- to 28-mesh material in the feed; a four-fold increase in the percentage of this size caused a four-fold increase in the amount of magnetite retained (table 3). The ratio of the specific surface of these two materials was 1.8 to 1. Thus the amount of magnetite retained appears to be influenced more by the proportion of near-aperture particles (which promote blinding) than by specific surface.

Specific gravity was varied from 1.80 to 2.20, which is approximately the range encountered in cyclone underflow. These tests were made at a feed rate of 7.5 tph/ft of coal (or refuse). When only the vibrating screen was used (fig. 2), the amount of magnetite in the screen product increased rapidly with increase in the specific gravity of medium. With either the sieve bend or the scalping deck, the rate of increase was much lower. At specific gravities above 1.85, both the sieve bend and the scalping deck were distinctly superior to the vibrating screen. Vastly improved results were obtained when either the sieve bend or the scalping deck was used in combination with the vibrating screen. At a specific gravity of 2.20 for example, the product of the vibrating screen when used alone contained over 1,900 pounds of magnetite per ton of coal, but adding the sieve bend or scalping deck reduced the amount of magnetite to about 600 pounds per ton. The scalping deck was clearly superior to the sieve bend, either when considered as a separate unit, or when considered in combination with the vibrating screen.

The three screen arrangements were tested also with washed coal and medium of 1.20 specific gravity. The advantage of the sieve bend or scalping deck was not as spectacular as that achieved in draining refuse, but the amount of magnetite in the discharge of the vibrating screen was reduced by nearly 50 percent (see table 4). When the yield of washed coal is high, drain-and-rinse screens have to handle a much higher tonnage of washed coal than of refuse; therefore, the improvement afforded by the sieve bend or scalping deck, although of smaller percentage, could greatly reduce the amount of magnetite entering the medium-recovery circuit.

The first step in the investigation of dewatering was to establish the capacity of the vibrating screen when used alone. In these tests a water-to-coal ratio of 3 to 1, simulating the washed-coal product of concentrating tables, was used. At a feed rate of 5 tph/ft of screen width, a pool of free water on top of the bed of coal rapidly progressed all the way down to the discharge end of the screen. The screen was obviously overloaded. At 3 tph/ft dewatering appeared to be satisfactory at first, but by 90 minutes of operation the water pool above the coal had again extended to the screen dis- charge. Progressive blinding had gradually reduced the open area of the screen below the minimum required to achieve effective dewatering in the retention time available.

This coal contained 15 percent of material in the 20- to 35-mesh-size range and an additional 25 percent of material finer than 35-mesh; thus, it was more prone to cause blinding than a coarser coal would have been. With another coal of more favorable size composition the feed rate of 3 tph/ft might have been satisfactory. A feed rate of 3 tph/ft is only about half of that often used with commercial screens, but commercial screens are of 16- to 20-foot length in comparison with the 8-foot length of the experimental screen.

When the feed rate was reduced to 1.5 tph/ft dewatering was satisfactory. The water pool did not extendto the end of the screen,and samples of the screen discharge taken at10-minute intervals showedno increase in moisture content after 20 minutes of operation.In addition to sampling the discharge of the screen, samples were taken at two pointsalong the length of the screen. After 10 minutes of screenoperation, dewatering was substantially complete inthe first 3 feet of screen length (fig. 3).Blinding rapidly increased the length of screen requiredto remove the bulk of the water. Although the moisturecontent of the screen discharge did not increase after 20 minutes, the

family of curves in figure 3 demonstrates that equilibrium was not reached until the screen had operated for an hour; all corresponding samples taken between 60 and 90 minutes of operation had constant moisture values.

In the next two series of tests, the sieve bend and the scalping deck were used to relieve the load on the vibrating screen. Both of these devices greatly increased the tonnage of coal that could be handled with satisfactory dewatering. The lower two curves (fig. 4) show that with either the scalping deck or the sieve bend a feed of 8 tph/ft was dewatered as completely on the first 2 feet of the vibrating screen as was a feed of 1.5 tph/ft in the full 8-foot length of the vibrating screen when used alone. Increasing the feed rate to 16 tph/ft caused only a modest increase in the moisture content of the finished product. In fact, at this tonnage either combination of screens gave as low a moisture content in the finished product as was achieved by the vibrating screen when used alone at 1.5 tph/ft.

Because the performance of dewatering screens is influenced by the amount of water in the feed, a series of tests was made at various water-to-coal ratios, using the several screens singularly and in combination. Results of these tests, which were made at a feed rate of 8 tph/ft of screen width, are shown in figure 5. When the feed contained about 35 percent solids, the vibrating screen was able to reduce the moisture content to about 36 percent. As the feed became wetter, the vibrating screen was unable to cope with the greater amount of water and thus the moisture content of the product rose rapidly. Adding either the sieve bend or scalping deck to the circuit improved dewatering greatly. A final product of 26 to 28 percent moisture was obtained from the vibrating screen, regardless of the amount of water in the feed. With the wetter feeds the sieve bend eliminated more water than the scalping deck, but the difference was too small to be reflected in the moisture content of the final product.

Actually, figure 5 does not show the full advantage offered by the sieve bend or scalping deck, because the curve for the vibrating screen does not represent equilibrium conditions. The product of the screen was so sloppy, and dewatering obviously so unsatisfactory, that the samples were taken after only a few minutes of screen operation rather than after attempting to establish equilibrium conditions. At equilibrium the performance of the vibrating screen would have been poorer, and hence the improvement afforded by the auxiliary screens would have been even greater.

The loss of fine coal that inevitably occurs on dewatering screens is a function of feed rate and of the moisture content of the feed. When the feed to the vibrating screen was reduced to 1.5 tph/ft to achieve equilibrium dewatering conditions (in treating a feed of 25 percent solids), only 15 percent of the coal finer than 28-mesh was recovered in the screen oversize (table 5), When the scalping deck was added to the vibrating screen and the feed rate increased to 8 tph/ft, the recovery of material finer than 28-mesh increased to 37 percent. The sieve bend was even more effective; it increased recovery to 49 percent. At 16 tph/ft, maximum feed-rate recovery was even further improved.

As shown in figure 6, which depicts operation at 8 tph/ft, both the sieve bend and the scalping deck afforded minimum recovery of undersize coal when the feed was of intermediate moisture content. This is consistent with the observation that the sizing action of the sieve bend is best at intermediate feed moisture. The conditions that are ideal for sizing are, of course, the poorest for recovery of solids. Over most of the moisture range examined, the sieve bend was more effective than the scalping deck in improving overall recovery of fine coal. This superiority probably can be attributed to the fact that the sieve bend effects a separation at a size equaling about half of the net bar spacing. When the sieve bend deck is vibrated on the vibrating screen, this relationship no longer holds.

The improvement in both dense-medium drainage and dewatering that occurred when the sieve bend or the scalping deck was used in conjunction with the vibrating screen is attributed to two factors. First, these auxiliary devices eliminated enough of the near-aperture size particles to substantially eliminate blinding of the vibrating screen. Thus the degree of improvement that can be expected because of this factor depends on the size- shape characteristics of the coal. The two coals used in this investigation were both prone to cause blinding, and therefore the improvement observed was substantial. With coals of more favorable size-shape composition, the degree of improvement would be less.

The second factor responsible for the improvement observed when the sieve bend or scalping deck was used is that either of them removed a substantial proportion of the liquid, thus relieving the load on the vibrating screen. Under most of the test conditions employed, these auxiliary devices removed about as much liquid as did the vibrating screen. This factor would be substantially independent of the size composition of the coal.

Although the scalping deck was somewhat superior to the sieve bend in draining dense medium, on balance, the performance of the two was much the same. The scalping deck offers the advantage of requiring less headroom, which often is a critical factor in installations in existing plants. It also is less costly, because no housing or additional piping is required. Screen life and maintenance are equally important factors, but they cannot be evaluated readily in a laboratory investigation because of the comparatively short operating time.

vibrating screen working principle

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.

top 10 vibrating screens of 2021 | screening materials - rethinkrethought

top 10 vibrating screens of 2021 | screening materials - rethinkrethought

A vibrating screen is a machine made with a screening surface vibrated precisely at high speeds. It is utilized particularly for screening mineral, coal, or other fine dry materials. The screening execution is influenced essentially by different factors, for example, hardware limit and point of inclination, in which the performance can estimate by screening effectiveness and flux of the item. While this type of machine is doesnt use for DIY purposes, you may require this for industrial purposes. It is especially essential in the mineral processing industry. If you are considering buying one, check out this article and learn which vibrating screen machine may be perfect for you and your project.

Twofold vibrating engines drive a linear vibrating screen. At the point when the two vibrating engines are turning synchronously, and contrarily, the excitation power creates by the whimsical square counterbalances each other toward the path corresponding to the pivot of the engine. Then, it covers into a resultant power toward the path opposite to the hub of the engine. So, the movement becomes a straight line.

The elliptical vibrating screen is a vibrating screen with an elliptical movement track, which has the upsides of high proficiency, high screening precision, and a wide scope of use. Contrasted with the conventional strainer machine of similar detail, it has a bigger handling limit and higher screening productivity.

A circular vibrating screen is another sort of vibrating screen with a multi-layer screen and high proficiency. As per the kind of materials and the prerequisites of clients, you can use its multiple screening plates. it were introduced in the seat type. The alteration of the screen surface edge can acknowledge by changing the position and tallness of the spring support. This screen is used for mining, building materials, transportation, energy, chemical industry.

The working surface of the roller screen is made out of a progression of moving shafts that masterminded on a level plane, on which there are many screen plates. When working, the fine material goes through the hole between the roller or the screen plate. In this way, enormous squares of materials are driven by rollers, moving to the closures and releasing from the outlets. Roller screens are usually widely used in the conventional coal industry.

High frequency vibrating screen is likewise called a high-frequency screen for short. High frequency vibrating screen is made out of exciter, screen outline, supporting, suspension spring and screen, and so on. This type of vibrating screen is the most significant screening machine in the mineral preparing industry, which is reasonable for totally wet or dry crude materials.

Rotary vibrating screen principally utilize for the grouping of materials with high screening effectiveness and fine screening precision. It features a completely shut structure, no flying powder, no spillage of fluid, no obstructing of work, programmed release, no material stockpiling in the machine, no dead point of matrix structure, expanded screen territory, etc. Any molecule, powder, and bodily fluid can screen inside its specific range. The machine usually used for characterization, arrangement, and filtration in nourishment, substance, metal, mining, and some other ventures.

Horizontal screen has the benefits of both slanted screen and straight vibrating screen. The machine has the highlights of good screen penetrability, enormous handling limit, and small installed height. The establishment point of the regular vibrating screen is 15-30, while the establishment of a flat screen is corresponding to the ground, or somewhat slanted 0-5.

Heavy inclined screen can apply to the treatment of debris from the quarry, mine, and building destruction. It can also utilize in the treatment of topsoil, the reusing of development materials, the screening of rock, the screening of gravel and aggregates, etc.

Grizzly screen regularly utilizes for pre-screening before coarse and medium pulverizing of materials. The work size is by and large>50mm, yet some of the time <25mm. This machines productivity is low, but screen efficiency is not that high. Also, quite often, the mesh tends to get a block.

The banana screen has a screen plate with various areas and diverse plunge edges. The longitudinal segment is a broken line, while the entire screen resembles a banana shape. The banana screen is, for the most part, appropriate for the arrangement of huge and medium-sized materials with high substance of fine particles. It can likewise utilize for drying out and demoralization.

While you picking vibrating screens, the material qualities should consider, including the substance of material particles under the screen, the substance of troublesome screen particles, material dampness, the shape and explicit gravity of the material, and the substance of clay. Professional vibrating screens makers could give serious vibrating screen value, assorted variety redid vibrating screen models, auspicious after-deals administration, save parts, and can keep on offering types of assistance for clients entire creation circle.

vibrating screening machine manufacturer, supplier and exporter in india

vibrating screening machine manufacturer, supplier and exporter in india

Vibrating screening machine is designed for the use in sizing of minerals, ceramics, refractories and other powders. The principle on which the Jaykrishna multi-form grader operates is equally adaptable for the handling of many ceramic products.

The unit is more than Just a screen it is a precision tool for producing accurate grades, a not merely rough grouping of sizes. It is economical of power and space; screen life is long; upkeep low. Flexible in its adaptability to widely different materials and conditions, it is unyielding in the uniformity of grades produced. Multi-Deck vibrating screens are available in different models.

Jaykrishna Magnetics Pvt. Ltd. is the leading manufacturer and exporter of Magnetic and Vibratory Equipments in India. We are established since 1978. The unique and premium structural design imparts quality and elegance to our products. Our focus is on continuously improving our process, service and products to exceed the benchmarks set by our competitors and offer better products to you.

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