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.
Ideal for dry or wet screening, Carriers vibratory screeners can handle up to 1500 tons per hour, with many deck design options that deliver maximum efficiency. Our vibratory screeners can be manufactured to meet your needs, with customizable construction and configuration.
There are two types of screeners that are commonly used in the production of bulk solid materials, leanearvibrating screeners and gyratory screeners or sifters. Most linearvibrating screeners use a linear or elliptical motion to convey the material down the screen surface. Gyratory sifters use a more gentle sifting motion, utilizing primarily horizontal motion to convey the material.
Lets start with the linear vibrating screeners. There are both advantages and disadvantages to using an linear screener. The first advantage is that they are relatively inexpensive. The other advantage is that linear screeners can handle high tonnages of product. Industrial screening equipment can get rather costly, but linear screeners will allow the processing of high amounts of material for a relatively low cost.
However, along with those advantages come some disadvantages. The first disadvantage is that linear screeners allow for poor spreading of material as it is fed to the screen. linear screens do not have any side-to-side motion. Thus, when material is dropped onto the screen it tends to run in a straight line down the length of the screen. Consequently these machines often require the use of a separate feeding device that spreads the material so that it can be dropped into a full width inlet. This feeder adds cost, complexity, and vertical height to the overall height of the machine. Without the spreader, the material wont spread properly and much of the screen surface area may be underutilized. Additionally, the screens will wear out much quicker in the highly used areas, resulting in early screen failure.
The other disadvantage to linear screeners is that they produce inaccurate separations. Because of the incline of the screen deck, the material is exposed to two different openings the actual measured opening and the effective opening. The actual measured opening is the true opening size of the screen mesh. For example, a 30 U.S. standard sieve has an actual measured opening of 600 microns. The effective opening results from the effect of gravity influencing how particles impact the screen. Therefore, if you put a 30 US screen on an linear screener, the effective opening size of the mesh is smaller than the actual opening size due to the screen angle (see exhibit A).
Accordingly manufacturers of linear screeners have to cheat on the screen selection, using a larger opening than the particle size distribution requires. To give you a couple of examples, in a fines removal application an linear screener may use an 18 market grade mesh (980) screen to make a 30 US (600) separation. In the process of travelling down the screen, some of the good near-size product (600-980) is lost to the fines fraction. If they try to prevent that product loss by going to a finer mesh, they will not be able to achieve adequate fines removal performance. In a scalping application, you typically cannot cheat on the opening. A 600 scalp requires the use of a 600 screen opening. Use of such a screen on an linear vibrating machine will result in significant tail-over of good product as the ~400-600 particles race down the screen and are lost to the oversize fraction.
As with linear screeners, gyratory sifters have their advantages and disadvantages. Gyratory sifters have a tendency to be more expensive than your typical linear screener, and they have lower throughput in the same basic footprint as compared to linear screeners. However, gyratory sifters are more efficient, producing cleaner, more accurate cuts. Additionally, the gyratory motion of the sifter tends to spread the material out on the screen for more effective use of the screen area.
There are several attributes that must be considered when choosing a gyratory sifter. First, the motion of the sifter needs to be considered. Keep in mind that gyratory sifters utilize only horizontal motion. Some sifters have a fully gyratory circular motion; others have a gyratory-reciprocating motion. The gyratory circular motion produces the same motion across the entire screen area, creating equal efficiency throughout the screen deck. This motion is possible because the drive system is located at the center of gravity of the machine. Its this type of motion that helps to spread the material evenly on the screen. The motion also helps to produce more effective ball action on the self-cleaning ball decks. The gyratory-reciprocating motion is a combination of circular and straight-line motions. This occurs when the drive is located at the feed end of the machine. The screen deck is moving in a circular path at the feed end of the machine and moves in a linear motion at the discharge end. The circular motion allows for even spreading of the material, but the linear motion is not as effective for the ball action in the ball decks, causing screen blinding at the discharge end, which in turn lessens efficiency and throughput.
Another attribute that must be considered is stroke and speed of the sifter. Some sifters have a short stroke and higher speed motion, which is optimal for fine particle separation. Other sifters have a longer stroke with a low speed motion, which produces a motion that is too active for fine particle separation. This type of motion is better suited for coarser applications like grain screening. Both motions can be effective in different applications. Its just a matter of what works best in your process.
Finally, screen deck length needs to be considered when choosing a gyratory sifter. Screen deck lengths vary from manufacturer to manufacturer and are typically available in screen sizes of 7 to 12 ft in length. Sifters with shorter screen decks have a more compact footprint, but they also have shorter retention time for the material on the screen (see exhibit B).
More retention time for the material results in better exposure of near-size particles to the screen apertures and more accurate screening. Additionally, longer screen decks are more beneficial when youre screening with multiple screen deck configurations (see exhibit C).
As the material travels down the length of the top screen deck, the smaller material falls through to the next screen deck and begins its journey down that screen. This continues to occur until the smallest of the material reaches the bottom-most screen and falls through to the bottom pan. On shorter screen decks, the smaller material often does not have enough retention time on the screen to fall to the bottom pan. This leads to screening inefficiencies or undersized product mixing in with the larger material fractions. The only way to remedy this would be to slow the rate of the feed, which leads to a reduction in capacity. The longer deck lengths can handle this more easily since they have longer screens and more screen area.
As you can see, there are many factors to consider and options from which to choose when purchasing screening equipment for your process. When determining which screening motion is best for your process, keep in mind that gyratory motion is far superior to linear or elliptical motion when efficiency and accurate cuts are a requirement. Additionally, the gyratory circular motion will aid in the spread of the material over the screen area while promoting superior screen cleaning.
When choosing which gyratory sifter is right for you, keep in mind that the stroke and speed of the machine impacts fine particle separation, and the deck length is critical when dealing with multi-deck applications.
To make your life easier and to aid your equipment manufacturer in supplying the right equipment for the application, there are three rules to consider. One, know your process. What are you trying to accomplish? What is your rate requirement? What is your product specification? What happens before and after the screening operation? Two, know your product. Is it free flowing? What is the moisture content? What is the bulk density? If possible, know the particle size distribution (PSD) of the feed material. And three, require and participate in laboratory testing. Having all of the process and product information along with testing will ensure that you are on the right track when selecting screening equipment. Involve your screening equipment supplier as early as you can in the process and follow these rules, and you will greatly improve the probability that you will end up with a successful installation.
Its compatible with excavators with an operating weight ranging from 60,000 to 90,000 pounds. Its the only shafts screener to have 5 interchangeable shafts that can be replaced on the spot in a few minutes. Maintenance also happens on site, thanks to the centralized greasing system.
The perfect tool for quarries, large trenching projects, and any construction site that requires powerful and tough machinery. The shaft's position in the bucket ensures a greater production rate and processing speed.The "V Shaft System" 's design creates a simultaneous screening process and increases production while the two motors ensure consistent and quick performance.
RSM Series volumetric screeners from Cleveland Vibrator are compact, self-contained units, incorporating a bulk supply hopper with a vibrator and vibratory screener or scalper. The all in one unit enables production efficiencies for easily dumping material from an inexact process and getting a controlled and uniform product output. Common Applications Include: Simultaneously screening or scalping bulk materials while feeding into bins, hoppers, packaging or conveyors Benefits of the RSM Volumetric Screener Include: All in one unit for low cost of maintenance Improved production rates and product quality Faster, more streamlined production lines Features and options of the RSM Volumetric Screener include: Controls for managing flow rate through vibration intensity, force and frequency Designs for loads up to 30 tons per hour available Screener or scalper options for multi-deck configuration, dust control and product contact surface materials Click on the button at left to request a quote, or contact us now for more information on our full line of vibratory screeners. See this product in action on our YouTube Channel!
The vibrating Inclined Screen is the most popular type of screen. There are various types of Inclined Screens, including two and four bearing, high-speed, and high-frequency screens. The overwhelming majority of installations today are either two or three decks, though there are single and four deck varieties available as well.
The two bearing, circle throw Inclined Screen from McLanahan utilizes a counterweight on a shaft to move the screen. Screen throw varies inversely with the shaft speed, which generally runs between 800 and 950 rpm. The screen is mounted on springs and is usually powered by an electric motor. The inclination of this type of screen runs from 15 to30 degrees.
McLanahans MAX Series Vibrating Screens are designed to meet and exceed the demanding applications and specifications required of screening equipment. MAX Series Vibrating Screens provide a solution for all heavy-duty applications, including minerals, aggregates and more.
Capable of separating coarse feed material from finer materials, these vibrating screens are a low-headroom design. Each screen is built with maximum strength steel to withstand heavy loading and with the durability to give you longer wear life. MAX Series Vibrating Screens are available in a range of sizes from 6 x 16 (1.8m x 4.8m) to 8 x 24 (2.4m x 7.3m). They are designed to fit into any existing structure and operation with no rework. Backed by McLanahans years of industry experience, we work with each customer to make sure their MAX Series Vibrating Screen meets the specific requirements of their application.
MAX Series Vibrating Screens were designed with operator safety in mind. Side plates feature cross beam inspection ports that allow you to inspect the inside tubes for failures when the tube is not visible due to abrasion-resistant lining, thus eliminating the need for operators to crawl between decks for inspections. Foreign material that can corrode or abrade the inside of the cross members and cause premature failure can be flushed out via cross beam inspection ports. The eccentric mechanism features jacking bolts in the mechanism tube to support the eccentric shaft during bearing change-outs, eliminating the need for a crane to suspend the shaft or the chance of the shaft tipping over and injuring workers, creating a safer work environment and decreasing downtime.
Many of the features of the MAX Series Vibrating Screen improve maintainability for increased uptime. Independent cross members allow you to replace only worn tubes and not the complete deck frame. The direct drive system eliminates the requirement for a pivoting motor base to keep belt tension on startup, which can be troublesome to maintain and eventually fail over time. Speed can be adjusted by simply replacing the motor sheaves and can be varied from 700 to900 rpms without a change to the driven sheave.
The MAX Series Vibrating Screen is designed to be durable for the longest useful wear life and with maximum strength steel to withstand heavy loading. Side plates are a fully bolted construction that reduces/eliminates crack propagation due to stress risers in the steel caused by welding and provide the ability to quickly replace worn components without cutting. The eccentric mechanism is a custom one-piece machined eccentric shaft for maximum strength and force output. It features a labyrinth seal to deter oil contamination and eliminate the need for a standard breather, which is prone to plugging and failure. The quick change spring kit allows the removal of the spring pack with only minimal vertical clearance and no overhead crane required. This saves the customer money, as well as reduces downtime and increases worker safety while changing out the springs.
In an Inclined Screen, the vibratory motion is circular. Vibration lifts the material, aiding stratification, while the combination of vibration and angle of incline provides the travel speed of the material over the deck.
Screens are used throughout materialprocessing to separate and size material prior to and following crushing stages. At the primary stage, large scalping screens remove fine material before the feed enters the primary crusher, helping to protect the crushers wear parts from abrasive stone or sand material that has already been sized. Without scalping, the primary crushers liners wear down faster, requiring more frequent changes and maintenance downtime.
Following the primary crushing stage, screens with two or three decks and different opening sizes are used to separate the material into different size categories, with conveyors transporting the sized material for further crushing or for stockpiling as a saleable product. Usually this screening is accomplished through dry screens. Wet screens may help to remove debris from material before stockpiling, as clean stone is often required for concrete and asphalt specifications.
Depending on the process stage, the material to be screened is fed to the screen either from a loading device such as a wheel loader (intermittent feed) or from a hopper or conveyor (continuous feed). The screen box vibrates via shafts with counterweights or exciters, causing the material bed to vibrate as well.
The reason you might run the screen uphill is to slow the rate of material travel, increasingthe amount of time the material stays exposed to the deck, providing better odds of the material falling through. Running the screen uphill also changes the exposure of the particles to the openings themselves. Quite often the choice of running a screen uphill is made in finer screening applications where efficiency can be tough.
You will not do any harm to the screen or the mechanism itself by running it uphill. Just make sure you do not increase your bed depth too much or you will have a negative effect rather than a positive one.
McLanahan MAX Inclined Vibratory Screens provide a screening solution for heavy-duty applications, including minerals, aggregates and more. Capable of separating coarse feed material from finer materials, each screen is built with maximum strength steel to withstand heavy loading and with the durability to give you longer wear life. McLanahan MAX Inclined Vibrating Screens are designed to fit into any existing structure and operation with little to no rework.
Aggregate material is separated into sizes through the use of screens. In most crushed-stone operations, this process occurs after the shotrock has been processed by a primary crusher. The role of screening in the processing flow is to size and separate material ahead of secondary and tertiary crushing circuits, and/or to size and separate material in preparation for final product stockpiling. The bottom line is that crushers produce the material; screens separate the material; and screening efficiency affects the operations overall performance.
Screening is both art and science. The art of screening lies in the meticulous fine tuning, tweaking and synchronizing of screen setups within a near-limitless number of applications. Its science is stratification. In other words, the vibration of the screen deck agitates the material causing it to stratify, allowing the larger particles to remain on the top deck and the smaller particles to fall through the openings of the screening surface. Screening efficiency is calculated as the percentage of the undersize materials passing through the openings divided by the percentage of undersize in the feed. For example, if a screen is only 75 percent efficient, then 25 percent of the material within the desired product range is being rejected with the oversize material.
Vibrating screens must be properly selected and designed, or they will be the biggest bottleneck within an operation. Todays trend is toward larger screens to increase capacity within larger plants. While most producers want more tons per hour across the screen, the key to optimum screening is maximizing capacity without losing efficiency. This may involve a good amount of trial and error, as there are many operating parameters to consider.
Maximum screening efficiency results from proper adjustments in speed, stroke, rotation (or throw) direction and angle of inclination. Each of these parameters affects one of the most important facets in screening proper depth of bed.
As feed material is a mixture of varying sizes, oversize material will restrict the passage of undersize material, which results in a build-up, or bed depth, of material on the screen surface. Bed depth diminishes as the undersize material passes through the screen openings. For efficient screening, the material bed should not reach a depth that prevents undersize from stratifying before it is discharged. The industry rule of thumb is this: Depth of bed (in dry screening) should not exceed four times the opening size at the discharge end of the screen. Consequently, with a -in. opening, the depth of bed at the discharge end should not exceed 2 in.
Loading screens too heavily is a common practice, and one that leads to a carryover problem and less screening efficiency. Operators should consider these four parameters to fine tune screening performance.
Increasing speed has its trade-offs. Greater speed may decrease depth of bed, but also increases the G-force, which decreases bearing life. Using the proper opening size for the desired particle separation, along with increased speed, will leave a minimal percentage of desired product size in the oversize. Alternatively, combining increased speed with a slightly larger opening size may allow a percentage of oversize in the desired product specification.
Increasing stroke delivers a higher carrying capacity and travel rate, while reducing plugging, blinding and enhancing stratification. However, it can create some inefficiency when lightly loaded decks lead to material bouncing. Generally, coarse separation requires increased stroke and less speed, while fines separation needs less stroke and higher speed.
Rotation direction can dramatically impact incline screen performance. Running counter flow, or uphill, increases material retention time and action on the screen, potentially giving the particles more opportunity to find an opening and ultimately increasing efficiency. Direction of rotation has little effect on a linear-type horizontal screen.
Increasing the angle of inclination causes faster material travel, which can be advantageous in certain dry screening applications. Although, there may be a point where too much incline will hinder efficiency as fines may roll over the media rather than pass through. Consider adjusting both linear and triple-shaft horizontal screens for inclination as well. One can realize some gain in capacity, rate of travel and productivity by adding some incline to the horizontal screen.
There are a limited number of applications where a horizontal screen is more suitable than an incline screen. These may include portable applications or plants where proper clearance for an incline is not available or applications with heavy water use, such as a dredge-fed screen.
An incline model is less prone to plugging and uses gravity to reduce its energy and horsepower requirements. There are differences in rate of travel between an incline and horizontal unit. At 45 to 50 ft. per minute (and at a specific tonnage), a horizontal screen will experience diminished capacity due to a greater depth of bed. Alternatively, on a 20-degree incline and at 70 to 75 ft. per minute travel rate, an incline screen will deliver up to 25 percent more capacity than a linear-stroke horizontal machine. Unlike the latter, the circular motion of an incline screen results in less stress to the vibrating frame.
Most of the processes for separation and classification consume large amounts of water. Different types of machinery and equipment have been developed to recover the water used for processing and to produce a final product that is easy to transport and store. One such device is a dewatering screen.
The purpose of the dewatering screen is to remove the water content down to 14 percent or less so the material can be conveyed and stacked. Dewatering on a vibrating screen produces a dense, compact filter cake that moves to the screen deck. Polyurethane and profile wire are the best media options for dewatering screening.
Typically, the screen deck is minus-3 degrees (negative slope). The filter cake traps smaller particles and allows water to pass through to the screen deck openings. Dewatering in mineral processing is normally a combination of the sedimentation and filtration methods. The bulk of the water is removed in the first one-third of the machine by sedimentation. This thickening of the material produces a pulp of 55 to 65 percent solids by weight. Up to 80 percent of the water can be separated at this stage. Filtration of the thickened pulp then produces a moist filter cake of between 80 and 90 percent solids. Filtration is the process of separating solids from liquid by means of the porous filter cake that retains the solid but allows the liquid to pass.
Specifying the right screen involves making sure the manufacturer understands the production goals and is supplied with complete application data, which includes information such as tons per hour, material type, feed gradation and top particle size, particle shape, application type (wet or dry), type of screen media and deck opening, and the method of material feed. Armed with accurate information, the manufacturer can customize the screen setup for maximum performance. For example, with a known feed gradation, the manufacturer can analyze the loading on each deck. If a deck has a heavier depth-of-bed ratio relative to the opening, that deck may be specified at a steeper angle than an accompanying deck. Therefore, one might have an incline screen at 20 degrees on the top deck, and up to 24 degrees on the bottom deck where its more heavily loaded.
Plugging happens when near-size particles become lodged, blocking the openings. Solutions may include increasing stroke, changing media wire diameter or opening shape, using urethane or rubber media, and adjusting crusher settings.
Blinding occurs when moisture causes fine particles to stick to the surface media and gradually cover the openings. In this case, changing stroke and increasing speed may help. Also, if changing the screen media does not improve the situation, consider ball trays or heated decks. Ball trays incorporate rubber balls into pockets beneath the screen cloth. As the machine vibrates, the balls strike the media to free collected material. Heated decks have an electric current in the wire that heats and dries material, so that it easily knocks itself loose as the screen vibrates.
Carryover occurs when excessive undersize particles fail to pass through the openings. Solutions may involve changing stroke, speed or reversing screen rotation; changing wire diameter or the shape of the opening to increase open area; changing the angle of inclination; changing feed tonnage; controlling feed segregation; and centering feed on the screen.
Vibration analysis, the acquisition and analysis of data regarding the vibrational characteristics of the machine, is one of the tools for ensuring optimum vibrating screen performance. Vibration analysis collects data on parameters such as natural frequencies, displacements and stroke amplitude, and the operation of bearings and gears. It typically involves using a hand-held analyzer connected to a series of accelerometers. The analyzer electronically records the vibrational data. This data can be immediately examined on the analyzer or downloaded onto a computer for a more detailed analysis.
Tests are conducted both at the factory and in the field. Baseline readings are taken at the factory on every machine while they are on the test stand for quality control. More readings should be taken shortly after start-up once the machines are operational in the field. Readings should be taken while the machine is empty and when it is fully under load. They should also be taken any time a speed or stroke change is made, when significant screen media changes occur, when applications change, and importantly, when and if there are any major support tower upgrades or rebuilds.
Vibration analysis benefits from the additional technologies of impact testing and operating deflection shape (ODS) analysis. Impact testing is used to determine natural frequencies that could cause issues at run speeds, or would require structural changes. A baseline reading is taken on each machine at the factory and is used to confirm the accuracy of engineering models. ODS analysis is used to animate and check new equipment and new concepts, while also confirming engineering models for accuracy. ODS identifies how a machine moves in actual operation and at specific frequencies. The analysis compares mode shapes to determine the most effective structural modifications to the machine.
At the primary stage, large scalping screens remove fine material before the feed enters the primary crusher, helping to protect the crushers wear parts from abrasive stone or sand material that has already been sized. Without scalping, the primary crushers liners wear faster, requiring more frequent changes and maintenance downtime.
Following the primary-crushing stage, screens with two or three decks and different opening sizes separate the aggregate material into different size categories with conveyors transporting the sized material for further crushing or stockpiling as a saleable product. Usually this screening is accomplished through dry screens. Wet screens may help to remove debris from material before stockpiling, as clean stone is often required for concrete and asphalt specifications.
Depending on the process stage, the material to be screened is fed to the screen from an intermittent-feed loading device like a wheel loader or from a continuous-feed device like a hopper or a conveyor. The screen box uses shafts with counterweights or exciters to cause the material bed to vibrate. Through the vibration, larger particles work their way to the top of the material bed, while the smaller particles make contact with the screening surface.
Because they are inclined, circular-motion screens provide a high travel rate. They generally accept a continuous feed very well. Screens using circular motion are best suited for larger material, as finer material tends to blind on this style of screen. Also, wet, sticky material does not screen well with this type of screen, unless water spray is also used.
Linear-motion horizontal screens typically generate less blinding and pegging of material on screen media because their straight-line motion, with high G-forces, can both dislodge material and convey it forward across the screen. This motion can be more effective than circular- or elliptical-motion screens, resulting in a high-efficiency screen that also operates at a fairly high speed. The operator is able to better control the material travel rate across the screen, further improving screening efficiency. Linear-motion screens also benefit producers through a lower installed cost because they require less headroom than circular- or elliptical-motion screens.
Elliptical-motion horizontal screens offer some of the efficiency of linear-motion screens and the tumbling effect generated by inclined circular-motion screens. They also work to speed material travel rate at the feed end, while slowing it at the discharge end. However, this type of screen does not exert the high G-forces that linear-motion screens do.
There are formulas to help select screens based on many factors, including feed tonnage, screening area and desired efficiency. There are enough variables involved in the formula that it is best to work with manufacturers who understand the complete parameters of the application.
It is important that the manufacturer knows the feed method, size, gradation, moisture content and rate. Existing equipment and mounting structure, total plant production needs and efficiency requirements are also part of the equation. Manufacturers can help to specify not only the best screen unit for the application, but also the best screen media.
Choosing the proper screen media for a given application is the key to delivering screen-sizing accuracy and maximum throughput, which also greatly impacts the performance of upstream and downstream equipment. In its most basic definition, screen media can be described as a surface with openings on a vibrating screen deck that allows undersized particles to pass through, and oversized particles to carry over. A vibrating screen can have anywhere from one to four decks, with each deck having a different sized opening, or mesh, for the separation of various particle fractions. Every application is a unique screening challenge, and thus the type of screen media selected is critical for success.
Screen media is a replaceable wear surface that can be made up of one or more removable panel sections on a single deck. There are a vast number of screen media configurations based on material types, aperture sizes and styles, fixing systems and surface features, to name a few. As a result, manufacturers are constantly striving to differentiate their products by varying these specifications to dial in a functional and often customized solution for producers.
To get the best possible screen media solution, it is imperative that the producer supplies the manufacturer with complete and accurate application data up front. Vibrating screen inside box dimensions, a particle-size distribution, moisture content and desired final products are some of the minimum requirements to properly select screen media. Further questions that should be asked of the producer include:
Is it a wet or dry screening process? Will blinding or plugging be a problem? How abrasive is the material? Will there be much impact on the screening surface? What is the top size and the bottom size feed to the screen deck? How much screening area is there? Does the material need to be washed? Is noise a concern?
The two most important factors for screen media selection are the screen panel life expectancy and open area. Producers should examine the issue of maximum open area versus maximum wear life there has to be a tradeoff between the two in designing the configuration of screen panel openings. In general, wire cloth will provide the maximum open area with a sacrifice to wear life, and the reverse is true for polymer screen media. However, recent and ongoing developments in material compounds and hybrid solutions (such as urethane-encapsulated wire) have helped to expand the spectrum of this sweet spot and enable producers to enjoy more of the best of both worlds.
Ultimately when making a decision on screen media, the producer needs to consider the benefits realized and the overall costs over the life of the media panel. A panel with a higher upfront cost may provide significant wear life or throughput benefits, compared with one offered at a fraction of the cost. Therefore, cost per ton of material processed is a more accurate gauge of the cost of screen media.
Screen media originated with the steel options of wire and plate. Now, the choices include wire, perforated and flame-cut plate, polymers (polyurethane and rubber), and hybrid media. Heres a closer look at each of those options.
Wire cloth is the best option for an operation with frequent media change outs as a result of varying product specifications. The most common wire cloth options are high-carbon, oil-tempered and stainless steel wire, each with its own application benefits. Stainless steel, for example, is beneficial for corrosion prevention and is effective as an anti-blinding solution.
Perforated and flame-cut plate screens are a good alternative for secondary screening and are available in various steel types and hardness. Plate screens are ideal on top- and middle-deck applications for impact and abrasion resistance. Steel plates have seen recent improvements in quality with options available all the way up to the 400- to 500-Brinell range (a measurement of the hardness of the steel plate), providing for longer wear life and durability.
Polyurethane is available in different durometers and more frequently applied in wet applications where water is added or the feed is in slurry form. Urethane is also the best choice for dewatering screens.
Polyurethane does have its place in dry applications as well, with the development and improvement of material compounds and chemical formulations. Open-cast thermoset polyurethanes have superior wear-life performance over injection-molded urethanes, primarily due to the slow-curing manufacturing process, which creates stronger molecular bonds in the material. Polyurethane panels are often found in a modular configuration for ease of installation and replacement. However, there are large cable-tensioned polymer screens that are better suited for aggressive, high-impact applications.
Rubber media is ideal in dry, high-impact applications and can often be offered in place of plate screens, depending on the nature of the feed. Modular rubber systems combine the benefits of modular screen panels with the durability of rubber impact screens in a high, open-area design. Rubber screen media may also be recommended in a wet-screening application such as where a plant is processing only natural sand and gravel. As well, self-cleaning rubber screens are used in fine, sticky or near-size material applications to prevent blinding from fines buildup, and to gain greater sizing accuracy.
Rubber generally offers the longest wear life of any screen media in the most difficult and aggressive scalping applications. Rubber panels are effective in reducing noise levels by up to 9 decibels when compared with steel media, which is about a 50 percent reduction as recorded by the human ear.
Hybrid screens come in several different types that maximize open area and wear life. Urethane-encapsulated wire offers the advantage of urethane screen media (wear life and noise reduction) without the need to convert to a modular deck and without great sacrifice to open area. Another common hybrid screen combines wire held in place with rubber or urethane strips for greater wear life and an optimal flexing action during screening to prevent plugging or blinding.
Screen media is attached to a deck frame in any number of ways. Proper installation, which includes tightening or tensioning the screen surface against the supporting frame, is integral in prolonging the life of the screen. This is applicable both for modular screen panels that are hammered into place on some types of stringer systems and tensioned panels that are tightened against a clamp rail with rubber pads beneath the screen creating a tensioned crown. Improper screen installation is the biggest cause of premature failure on a deck, and therefore its important to check the installation at each shift to ensure the screens are secure and in place. One check at start-up and one at shutdown will be far less costly than unplanned downtime.
Modular polymer screens (stringer system and individual panels) generally have a higher initial cost per square foot compared with wire screens. However, in addition to the wear life benefits, modular panels are smaller and safer for operators to handle. They allow for selective change out of individual worn panels, as opposed to a complete wire cloth panel that would need to be changed out if one section was worn. Modular systems offer greater ease of installation (without any pins or bushings), and are better engineered for retrofitting applications.
Wear life for any type of media is largely determined by its mass the diameter of the wire or the thickness of the urethane. The media must be heavy enough to handle a given top-size material and peak feed rate. Synthetic screens (rubber or urethane) will wear far longer often more than 10 times longer than wire cloth or plate screens.
When working with wire cloth, workers typically detect excess wear when a hole is blown through the cloth, allowing oversize material to contaminate product stockpiles. Consequently, it is common to assume that the same wear pattern and result will happen with synthetic media but that is not so. Operators tend to look for a hole to weld or repair rather than looking at the actual gradations. Frequent quality-control sampling to detect sudden or gradual specification changes is the most effective method to monitor the wear life and condition of synthetic screen panels.
With modular synthetic panels, the maintenance crew can catch any wear issues early by conducting a sieve analysis. This involves examining the particle distribution of a representative sample of material, which is expressed in the percentages of a particle size group passing through or being retained on standard testing sieves. For example, if production is slightly off on a number-one sieve, the crew should start gauging its screens and checking for any wear. After this routine maintenance, they simply take a few minutes to change out a modular panel or two, and they are up and running again.
Note that polyurethane and rubber panels are available in different durometers, which is a measure of surface resistivity or the resistance of plastics toward indentation. Media manufacturers may use the Shore-A scale in selecting plastic and rubber compounds for screen panels the higher the number, the harder the material.
An aperture is an individual opening in the screening surface. Synthetic media panels are manufactured in a wide range of opening types and sizes. Both polyurethane and rubber media panels are offered with either square (the most common type), slotted, zigzag, slotted zigzag and round openings. For example, zigzag openings reduce or eliminate plugging or pegging, which is a condition where near-size particles wedge or jam into the screen openings, preventing the passage of undersize material. Round openings are highly effective in primary scalping operations to minimize plugging or pegging.
Depending upon specification requirements, decks can be composed of panels with varying opening sizes and/or types. Note that solid (with no openings) rubber or polyurethane panels can be installed at the feed end of a screen deck where heavy wear is experienced. Or, solid panels can be used as a discharge lip.
Special surface features, such as dams, skid bars and deflectors can be used to enhance performance. When produced by an injection-molding process, these features can be molded into the surface as part of the original panel construction. This seamless integration of surface feature to panel allows greater strength and longer life versus that of a laminated-on feature.
For example, dams are used in wet applications to slow material and increase washing efficiency. Skid bars are effective in scalping applications to keep oversize material off the screen panel surface, while reducing wear. And, deflectors help redirect material toward the middle of panels.
Sorting aggregate to specification piles requires accurate screen openings and high open area for optimum production capacity. Synthetic polyurethane or rubber media panels offer these characteristics, while increasing wear life over that of conventional wire cloth media. Note that for damp material typically prone to blinding, natural rubber panels are often recommended as they retain open area even in very sticky materials.
Wet sizing (usually with sprays) often increases a screens efficiency. Polyurethane media panels deliver greater wear life in this application. Rinse screens are part of the final wash to clean aggregate products prior to sale. Polyurethane media panels are a good fit for rinsing applications as they offer long service life and are available in a wide range of opening characteristics and sizes.
Dewatering involves draining the maximum amount of moisture out of a sand product or waste fines, while retaining as much solid material as possible. Manufacturers offer dewatering panels in a variety of openings from 0.1 mm (about 140 mesh) to 2 mm. Typically the panels have a heavier steel skeleton structure to withstand the very heavy bed depths and high G-forces of the application.
Efficiency is gauged by product throughput or product yield. It is the ratio of the percentage of material passing through the screen surface to the percentage of undersize material in the feed that is available to pass through.
Some assume that wire cloth offers greater open area versus synthetic media. However, when considering maximum open area, it is important to understand that the percentages of open area listed in conventional wire cloth media catalogs are based on all the openings in a section of the screen. Yet, a good portion of those openings are blocked by bucker bars, crown rubber, clamp rails and center hold-downs, causing actual open area to be compromised by as much as 40 percent.
In the case of synthetic media, the open area is sometimes calculated by ignoring the border. In many cases, the traditional synthetic screen panel has a large border or dead area around the perimeter that often is not taken into account, and thus the open area percentage is overstated. To avoid the specification of undersized vibrating screens, open area needs to be calculated by taking the total number of openings in the screen panel, and determining the percentage of actual open holes versus the complete surface of the panel itself. End users should compare the open area between two different screen panel brands of the same aperture by merely counting the number of holes on each screen panel.
While the use of synthetic screen media definitely reduces maintenance labor, it does not eliminate it. Producers may wish to specify and stock certain modular synthetic screen panels that can be used in multiple applications as operations may be able to get a useful life out of a panel in one location, and then move it to another application where it will function for a period of time.
If the media supplier has provided a diagram of the deck layout, post it as a reference tool for the maintenance crew. This is especially important if the deck layout is made up of different panel types and opening sizes. This will ensure that the correct layout is maintained as panels are replaced and will ensure that the deck design remains accurate for the given application.
Portable screening plants are a major part of the business for aggregate producers, road builders and contractors. Any of these operators can tell you how important quality screeners are to a business, but whats right for one operator may lead to production issues for the next.
From small, highly customized design modifications to the overall type and size, there are a multitude of factors to sift through. Selecting the right screener takes time, research and clearly outlined goals for the operation. Here are six key considerations.
Analyze everything from output capacities to business goals before buying. The first thing to do is size the equipment to match the operation. This is not an option. Understanding the application and materials will help determine the ideal production, capacity and number of end-size products. The screen must be aligned with the goals of the operation.
Next, fully understand the companys goals and projected sales to determine what size screen is needed. For example, if an operation can sell 500,000 tons per year, its screens need to sort nearly 42,000 tons per month. If the screen is in operation two days each week (about eight days each month), 10 hours each day, the operation will require a machine capable of screening around 525 tons per hour. A screen that processes 300 tons per hour would limit profits and cap growth potential. A machine with a potential output of 900 tons per hour would come with extra expenses and no added value.
Scalping and screening have several main differences. Standard screens are often considered finishing screens because theyre capable of producing specific-sized end products. Operators can adjust the speed of the feeder belt to help produce a clean, sized, finished product. These units typically have two or three screen decks and are ideal for use in sand and gravel pits, on asphalt jobs and in quarries.
Scalping screening plants are built to handle the toughest materials but are not as precise as standard screening plants. Material is fed directly onto the screen. Scalpers are ideal for sorting materials before crushing, processing scrap metals and recyclables, and to extract rock from dirt on construction sites.
Hopper size is typically 12-ft. wide with an option to upgrade to a 14-ft. wide. Those extra 2 ft. can capture more product and prevent spillage. The size of the hopper is perhaps most pertinent when pairing the screener with the loading machine, especially when using a large wheel loader.
A tipping grid or live head can be added to a screener above the hopper for additional sizing. While they perform a similar duty, they are very different. A tipping grid is essentially a hinged grid that blocks larger materials from entering the hopper. This is an affordable option but can become a chore, particularly in wet or dirty applications where the tipping grid may become plugged frequently.
A live head is essentially a vibrating screen that attaches to the hopper and is ideal for heavy-duty, dirty, wet and sticky applications. The unit can be used for two purposes: to scalp dirty material off and eliminate the need for manual cleaning, or to size material going into the machine so operators can produce an additional sized product.
While these are generally very efficient, operators should know that screeners with 14-ft. hoppers would not be used to the full potential. A typical live head measures 12 ft., making 2 ft. of the hopper unusable.
Apron feeder versus belt feeder is another key element to evaluate, as different products vary in durability. The standard belt feeder is perfect for sand and gravel operations, but is likely to tear or break when working with metal, large rock or extremely abrasive material. An apron feeder, which is essentially a belt made of metal, is durable and can handle nearly anything an operator throws at it.
Stockpiling offers little mystery. The higher the stockpile, the less time it will take operators because theyll be able to run for longer periods without having to move material. Even an additional 8 to 10 in. of stockpile height can make a significant difference.
Aside from all the proper adjustments and operating parameters required to gain the most in screening efficiency, the need for good preventative maintenance practices is a must for longer-lasting screens and reliable performance. Here are eight key components to a solid maintenance program.
Establish an oil-sampling program. Although a commonly overlooked practice, a regularly scheduled oil sampling is an operators best insurance against catastrophic component failure and costly downtime. The valuable insights provided by samplings such as detecting a worn bearing allow operations to schedule maintenance downtime around periods of prime production. Scheduled sampling and analysis establishes a baseline of normal wear and can help indicate when abnormal wear or contamination is occurring. Oil that has been inside any moving mechanical apparatus for a period of time reflects the exact condition of that assembly. Thats because oil is in contact with mechanical components as they wear, trace metallic particles enter the oil. These particles are so small that they remain in suspension. Particles caused by normal wear and operation will mix with the oil. Any externally caused contamination also enters the oil. Identifying and measuring these impurities, indicates the rate of wear as well as any excessive contamination. Importantly, an oil analysis will also suggest methods to reduce accelerated wear and contamination.
Employ recommended lubrication practices. Always consult the owners manual for the manufacturers recommended lubrication practices. Install the correct amount of oil, and use the recommended type of oil. Change the oil at the proper intervals, making sure that the oil in storage is clean and that clean containers are used to transport the oil. Make sure that the machine is completely level so that oil does not pool at the low side of the machine.
Maintain proper belt tension. Belt tensioning must be right on target for optimum screen performance not too loose and not too tight. Ideally, the belts should only be tight enough so as to not slip during start-up. If necessary, use a belt gauge to set the correct tension. If belts squeal during start-up or operation or whip excessively this may indicate insufficient belt tension.
Over-tightened belts can cause serious damage such as pulling the vibrating frame out of square with the support frame. Operating in this twisted position introduces stresses that may lead to spring failure, metal fatigue, or cracking and broken welds. This twisting affects stroke amplitude and character, which then affects material flow and screening efficiency. Over-tightened belts also put an extra load on the mechanism bearings and may tear up motors and motor bases. Additionally, to prevent drive belts from slipping, flopping or coming off, keep belts and sheaves clean and properly aligned. Inspect sheaves for wear, and if the grooves are worn, replace the sheave.
Prevent material buildup. Accumulation of dust and stone around moving parts is one of the largest single causes of part failures, particularly for pivot motor bases, support springs, roller bearings and the vibrating frame. Impact between the vibrating frame and accumulated material may lead to tower vibrations as well as potential side sheet and support deck cracking. Note that sheaves and belts are susceptible to material jumping over the side sheets and causing damage. Where possible, use stationary skirt plates or rubber flaps to deflect airborne material. Its also important to avoid material buildup in bins, hoppers and transfer points.
Maintain proper screen media support and tensioning. Uniform tension must be maintained on the screen surface to prevent whipping and to maintain contact between the screen surface and the bucker-up rubber on the longitudinal support bars. Improper tensioning may cause severe damage to costly screen media. Also, do not operate a vibrating screen with screen cloth or other screen media sections removed as this will accelerate wear on the support frames and the longitudinal support bars.
Inspect for wear. Inspect cross members for signs of premature wear especially in wet-screen applications where wear is accelerated. Cover and protect the cross members, decking and housing tubes with rubber or urethane liners to extend their life. Prior to installing screen media sections, make sure they are appropriately square and flat so that they will seat properly on the longitudinal support bars.
Monitor spray systems. Use the required number of spray nozzles and make sure they are open and fully operational. Maintain the proper water volume and pressure. Avoid spraying perpendicular (at 90 degrees) to the screen surface as this may result in a rapid deterioration of the screening surface. The spray should strike the screening surface at approximately 45 degrees. Nozzles can be positioned to spray against or with the flow of material. This choice depends upon the desired washing/rinsing efficiency and material properties. For most applications, a pressure of approximately 40 lbs. per square in. at the nozzles is desired.
Operate with proper clearances. Maintain adequate clearances around stationary structures, and never allow vibrating frames to hit stationary structures. Wherever possible, provide a minimum of 24-in. side clearance on each side of the machine. This enables the operator to adjust screen-cloth tension and check the units condition and operation. Allow sufficient clearance in front of the screen at the discharge end, or in the rear at the feed end, for replacing screen sections. Set the clearance at least 1 ft. longer than the longest screen panel. Maintain a minimum vertical clearance of at least 5 in. between the vibrating frame and any stationary structures such as the feed hopper or discharge chutes and bins. Avoid providing places for dust and stones to accumulate and interfere with the movement of the vibrating frame.
"Our customers have shared their grievances, telling us about the difficulties they face on their job sites, and it's these problems that we've used as a stepping stone for new concepts and ideas," the company said.
"Our customers needed something more, an advantage, and an added value on other construction sites or application areas. And that's where the idea for the big sister of the MB-HDS range the MB-HDS523 shafts screener bucket was born. The biggest, strongest and toughest."
"They're meant for sectors where power and sturdiness are essential, such as in quarries, where you need to treat large quantities of material like coal and phosphate. Or to move, sift and aerate tons and tons of earth, such as excavating, earthmoving, and large trenching projects. But it's not limited to just these application areas, because regardless of the construction site or material, the new MB-HDS523 shafts screener is well-equipped and only has one goal: a high productivity rate," the company said.
The MB-HDS523 is the only HDS unit with five shafts positioned to ensure a greater production rate and processing speed. The "V Shaft System"'s design precisely creates a simultaneous dual screening effect and increases production.
Everything in the new MB-HDS523's design maximizes the results: the concealed comb allows the material to enter and flow through the rotors without jamming, and the unit comes with a removable front upper casing, giving the unit a greater closing angle and increase production.
But, power is nothing without adequate durability: the MB-HDS523 screener is solid, durable and suitable for demanding construction sites and heavy workloads, the company said. The parts that are subject to wear are protected by reinforced Hardox steel slab, and the bracket and frame are also thicker, making it a well-performing machine.
"You might think that equipment of this caliber is demanding to maintain, requiring special maintenance, expensive machine downtime, or that the shafts need to be changed in a workshop. But you would be wrong.
"MB Crusher wants to facilitate work on the job site in every aspect, especially when it comes to maintenance. A construction site that's always functioning is a construction site where the job finishes earlier, saving time and money," the company said.
The MB-HDS523 shafts screener comes with a centralized greasing system to simplify and speed up maintenance operations. Much like the others in the range, the shafts are easily switched out: they can be replaced on-site and in a few minutes. The system firmly holds the rotating system, and the rotors can be easily extracted and repositioned.
Purpose built for reliable and efficient operation in waste and scrap metal applications, the new Cat MH3022 and MH3024 material handler design provides improved performance, low operating costs and improved comfort.
Once a heavy equipment repair shop, Baschmann Services of Elma, N.Y., has grown over the past 35 years to become a substantial equipment distributor for both rolling stock and aggregate equipment in New York State.
When Michael Bercowetz approached his father, Donald, about a new role that he wanted to fill in the family business, DMR Materials, it was after several years of observing the materials production and sale industry, how their own business operated and how their competitors' businesses operated.
EvoQuip has launched the Falcon range of finishing screens to its product portfolio. The Falcon range consists of the Falcon 1220 and Falcon 1230, providing a solution for scalping, screening and stockpiling in self-contained units.
Aggregate Equipment Guide is the best source for news, how-to's and equipment for the Aggregate Industry. We list equipment in all the major aggregate categories including conveyors, feeders, stackers, crushers, magnets, screening equipment, washing equipment, and more. Our website makes it easy to find the machines you need fast. From manufacturers such as Cedarapids, Doppstadt, Extec, Kleemann, McCloskey, Metso, Nordberg, Pioneer, Powerscreen, Screen Machine, Superior, Terex, and more.
DOVE is a major manufacturer of heavy duty Vibrating Grizzly Feeders, designed for primary feeding of ore to the Minerals Processing Plants, and or Crushing Plants. These heavy duty Grizzly Feeders are designed to regulate the feed rate for various applications, including:
DOVE laboratory will assay your ore samples rapidly and analyze your raw materials and recommend the most efficient processing plant according to the ore specifications, minerals composition, and ore assay results, and your project size and the geologic and topographic conditions of your mine.
WE HIGHLY RECOMMEND FORWARDING SOIL SAMPLES OF YOUR MINE TO US FOR ANALYSIS, IN ORDER TO DESIGN AND RECOMMEND THE MOST EFFICIENT PROCESSING PLANT, TAILOR MAID TO YOUR MINE REQUIREMENTS, FOR HIGHEST PRODUCTION RECOVERY.
As the number of digital assets continue growing, traders find themselves shifting through chart after chart to find good opportunities. This can not only take valuable time but also lead to missed opportunities.
In addition, crypto assets tend to move similarly to the overall crypto market, which make it even more important to find patterns that "stand out" for certain coins. There are two general ways traders can look for coins that "stand out":
Suppose we are looking for funding rates across the entire market. If coin X has an extremely high funding rate while all others are neutral, this implies that coin X has a high funding rate relative to the rest of the market. However, in some situations some coins are consistently high relative to the rest of the market, in which case relative to the market may not be as impactful. This is where users can switch to outlier mode and look for extreme data points not to the rest of the market, but instead to the coins own historical data. In other words, outlier mode can help answer the question: "How does the current value compare to all past values for this coin?", where as normal mode can help answer the question: "How does the current value compare to the current values of all other coins?"
The Coin Screener displays data in both of these formats, so that traders can find outliers or abnormalities allowing traders to identify potential opportunities by scanning all coins with a birds eye view.
The Coin Screener visualizes an indicator on all crypto assets over time. While crypto scanners exist, most focus on a current snapshot and general metrics like marketcap or change in price. We try to provide more context by by allowing traders to see change in the indicator over time as well as less mainstream indicators such as global long shorts or number of trades occurred.
In addition to the above indicators, we also display indicators based on the change or difference. Delta is the increase/decrease in the particular time period and percent change is the percentage of change of the values.
Note: all indicators are based on 5 minute granularity with the exception of Funding Rate [8hours] and Insurance Fund [24 hours]. For example, Global Accounts Longs% Delta is the increase or decrease in longs% on a 5minute candle basis.
There are many different designs that are useful for a number of different applications and industries, so it is important to know just how these vibratory screens function and how they might fit into your application. Read More
ERIEZ is a global manufacturer of an entire range of vibratory feeders and related machinery. We serve all the process industries, including food, chemical, pharmaceutical, ceramics, glass, packaging, metalworking, minerals processing and others.
Carrier Vibrating Equipment, we pride ourselves on our extensive customer base and our commitment to excellence. We know that the grizzly screens you receive from us are the best in the business. Carrier continues to bring new technology to the market, as well as new value to existing technology through its research and development lab, to make sure they remain at the front of the industry.
Founded in 1923, The Cleveland Vibrator Company offers one of the most comprehensive lines of vibrators and vibratory bulk handling equipment available today. Innovations are constantly making our vibrators more durable and more adaptable to strenuous environments. We have successfully applied vibrators to such industries as plastics, chemical, food, pharmaceutical, ceramics, and metal working.
Rodix manufactures vibratory feeder controls, inline track drives, drive bases, & bulk storage hoppers for part feeding systems. Our line of vibratory feeder controls feature variable amplitude, variable frequency, line-voltage compensation, UL/cUL Listed, CE Marked, and more. We have experience working with machine integrators, vibratory feed system builders, and manufacturers.
Our company has many years of experience in the material handling industry. We offer a variety of products, including bowl feeders, parts feeders, and grizzly screens to our customers around the world. We believe that efficient designs lead to efficient and profitable products. That is why we are dedicated to offering you nothing but the best. Find out more when you contact us today!
Our company has many years of experience in the material handling industry. We offer a variety of products, including bowl feeders, parts feeders, and grizzly screens to our customers around the world. We believe that efficient designs lead to efficient and profitable products. That is why we are dedicated to offering you nothing but the best. Find out more when you contact us today!
Vibratory Screens - Carrier Vibrating Equipment, Inc.High frequency vibrating screens and normal vibrating screens operate in the same fashion; the high frequency screens only operate at a high frequency in order to filter specific minerals.Vibratory screens offer many different advantages. They are one of the best ways to filter and separate two or more substances from each other. Vibratory screens do this by breaking down the surface tension between the particles within the substances which allow them to separate more easily.Vibratory screens often function at an angle in order to further separate materials. This angle provides what is referred to as the popcorn effect. This means that the coarser a particle is, the more likely it is going to be lifted higher while finer particles remain closer to the screen. The rate at which the screen vibrates, or the frequency, can be controlled in order to achieve the desired popcorn effect or separation.As we stated before there are a number of different applications in which you can find a vibratory screen at work. Some of these applications and industries include, processing powder in coal, metallurgy, wood pelleting, fractionated asphalt pavement, ores and minerals, food, chemical applications and the pharmaceutical industry. Because of this there are multiple designs of vibratory screens available.It is important to consult with a trusted vibratory screen manufacturer in order to determine what design is best for your application. If you do not have the correct design, or the frequency is not set correctly, you may experience inaccuracies when trying to separate particles as the process is influenced by many different factors, from vibratory equipment capacity to the angle at which the vibratory screen is placed.Vibratory Screens Informational Video
Vibratory screens offer many different advantages. They are one of the best ways to filter and separate two or more substances from each other. Vibratory screens do this by breaking down the surface tension between the particles within the substances which allow them to separate more easily.
Vibratory screens often function at an angle in order to further separate materials. This angle provides what is referred to as the popcorn effect. This means that the coarser a particle is, the more likely it is going to be lifted higher while finer particles remain closer to the screen. The rate at which the screen vibrates, or the frequency, can be controlled in order to achieve the desired popcorn effect or separation.
As we stated before there are a number of different applications in which you can find a vibratory screen at work. Some of these applications and industries include, processing powder in coal, metallurgy, wood pelleting, fractionated asphalt pavement, ores and minerals, food, chemical applications and the pharmaceutical industry. Because of this there are multiple designs of vibratory screens available.
It is important to consult with a trusted vibratory screen manufacturer in order to determine what design is best for your application. If you do not have the correct design, or the frequency is not set correctly, you may experience inaccuracies when trying to separate particles as the process is influenced by many different factors, from vibratory equipment capacity to the angle at which the vibratory screen is placed.Get in Touch with Mechanic