high frequency screen time

high frequency screens - astec

high frequency screens - astec

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The directly-induced vibration improves screen efficiency at high production rates compared to conventional screens.A unique rotary tensioning system provides the quickest screen media changes in the market, up to 50 percent faster than competitive models. Our high frequency screens offer ideal gradation control for reclaiming fines in both wet and dry applications.

high frequency sizing screens

high frequency sizing screens

Widely used in fine wet screening applications, these high frequency screening machines comprise of up to five individual screen decks positioned one above the other operating in parallel. The stacked design allows for high-capacity units in a small footprint. The flow distributor splits the feed stream evenly to the individual polyurethane screen decks (openings down to 45 pm) where feeders distribute the stream across the entire width (up to 6 m) of each screen. Dual vibratory motors provide uniform linear motion to all screen decks. The undersize and oversize streams are individually combined and exit toward the bottom of the Stacked Sizer. Repulp sprays and trays arc an optional addition in between screen sections, which allow for increased screen efficiency.

By classifying by size-only, screens compared to hydrocyclones, give a sharper separation with multi-density feeds (for example, in PbZn operations), and reduce overgrinding of the dense minerals. Operations that replaced hydrocyclones with stackedhigh frequency screening machines in closing ball mill circuits can result in a decrease in the circulating load from 260% to 100% and 10 to 20% increase in circuit throughput.

The high capacity Stacked Sizing/screening machine consists of up to five decks positioned one above the other and all operating in parallel. Its use together with urethane screen surfaces as fine as 75 microns (200 mesh) has made fine wet screening a practical reality in mineral processing operations worldwide. The application of this technology in closed circuit grinding is demonstrated with specific application examples.

Screening is the process of separating particles by size and fine screening typically refers to separations in therange of 10 mm (3/8) to 38 microns (400 mesh). Fine screening, wet or dry, is normally accomplished with highfrequency, low amplitude, vibrating screening machines with either elliptical or straight-line motion. Various types ofwet and dry fine screening machines and the factors affecting their operation have been discussed previously.In fine particle wet screening, the undersize particles arc transported through the screen openings by the fluid andthe fraction of fluid in the slurry will therefore affect the efficiency of the separation. From a practical standpoint, the feed slurry to a fine screen should be around 20% solids by volume to achieve reasonable separation efficiency. Asmost of the fluid passes through the screen openings rather quickly, the fine screening process can be completed in ashort screen length. Therefore screen width, rather than screen area, is an important design consideration for fine wet screening.

Recognition of this concept led to the development of multiple feed point fine wet screening machines, or example, the Multifeed screen consists of three screen panels mounted within a rectangular vibrating frame and is actually three short screens operating in parallel. Each screen panel has its own feed box and the oversize from each panel flows into a common launder and then to the oversize chute. Similarly, the undersize from each of the three panels flows into the undersize hopper. The popular 1.2 m (4 ft) wide by 2.4 m (8 fl) long version has a total effective width of 3.0 m (10 fl) In general, multiple feed point machines have been shown to have 1.5 to 2 times more capacity than a single feed point machine of equivalent size and screen area.

Expanding further on this concept, the Stacked screening machine was introduced in 2001. With a capacity considerably greater than any other type of fine wet screening machine previously available, the Stack Sizer has up to five vibrating screen decks operating in parallel for a total effective width of 5.1 m (17 ft). The decks are positioned one above the other and each deck has its own feed box. A custom-engineered single or multiple-stage flow distribution system is normally included in the scope of supply to representatively split the feed slurry to each Stacked screen and then to the decks on each machine. Ample space is provided between each of the screen decks for clear observation during operation and easy access for maintenance and replacement of screen surfaces. Each screen deck, consisting of two screen panels in series, is equipped with an undersize collection pan which discharges into a common launder with a single outlet. Similarly, the oversize from each of the screen decks collects in a single hopper with a common outlet large vibrating motors rated at 1.9 kW (2 5 HP) each and rotating in opposite directions produce a uniform high frequency linear motion throughout the entire length and width of all screen decks for superior oversize conveyance.

As mentioned above, the fluid passing through the openings carries the undersize particles through the screen openings. The screening process is essentially complete when most of the fluid has passed through the openings. Any remaining undersize particles adhere to the coarse particles and are misdirected to the oversize product An optional repulping system is available for the Stack Sizer in which spray water is directed into a rubber-lined trough located between the two panels on each deck With this feature, oversize from the first panel is reslurried and screened again on the second panel. This repulping action maximizes the correct placement of undersize particles and its use will depend upon the particular objective of the screening machine.

To date, 1000s of screening machines are in operation at mineral processing plants worldwide. Dry mass flow capacity typically ranges from 100 to 350 t/h. This is roughly equivalent to 3 or 4 of the older style Multi-feed screens discussed above Like all screening machines, capacity depends upon many factors such as screen panel opening, weight recovery to oversize, the amount of near-size particles, particle shape, and slurry viscosity.

Sizers are for high capacity in a short compact machine. Generally you can make good cuts or separations with high efficiency. If you need near absolute 99.9% precision cuts, then a sizer cannot do that, and most inclined screeners also cannot. So that is why it is very important to understand what the separation goal is before selecting a screener. You cannot have high capacity and high accuracy + 99.9 in the same machine! This machine does not exist! A sizer generally can accomplish a similar separation of a single inclined screen in 2 or 3 screens, and 1/3 the length. of course a lot depends on the PSD, and how close the remaining particles are on each side of the desired cut.

mobile high frequency screen plants - astec

mobile high frequency screen plants - astec

The site navigation utilizes arrow, enter, escape, and space bar key commands. Left and right arrows move across top level links and expand / close menus in sub levels. Up and Down arrows will open main level menus and toggle through sub tier links. Enter and space open menus and escape closes them as well. Tab will move on to the next part of the site rather than go through menu items.

These screens offer ideal gradation control for reclaiming fines in both wet and dry applications. Pair that with the flexibility and mobility of the track unit and producers can quickly and easily produce the material they need.

mev screener - midwestern industries, inc

mev screener - midwestern industries, inc

The high-frequency screens manufactured by Midwestern can be utilized in many screening applications from rugged quarry and rock sizing to sand and gravel processing and high volume fine mesh screening. With a variety of sizes and screening decks, the versatile MEV Screener can fit numerous applications.

The MEV High-Frequency Screener is a rectangular screener that utilizes an elliptical motion to convey material across itsscreening surface. Available in sizes three-foot by five-foot (3 x 5), four-foot by eight-foot (4 x 8), and five-foot by ten-foot (5 x 10) with the availability of one to five screening decks gives the MEV Screener the versatility to meet your screening needs.

The MEV Screener is designed to retain material at the feed end for a longer period of time and then gently slops the material near the discharge end, assisting itoff the screening deck and into production. This is achieved by the screeners unique parallel-arc configuration. Crossbars support the end-tensioned screens tocreate a flat screening surface, thus maximizing the screening area.

The end-tensioned screens used in the high-frequency screener simplify changing screen panels. End-tensioning permits the use of square-opening and slotted screens and is accurately maintained by a spring-loaded drawbar. Users can make screen changes in 1015 minutes.

Midwesterns commitment to providing our customers with outstanding screening products continues with our full line of replacement rectangular screens. Our screens are manufactured to fit all makes and models of screeners.

vibratory screens | mclanahan

vibratory screens | mclanahan

Screens can be considered the cashbox of the operation, because while crushersmake the gradation, screens make the specification. Material must go through or over a specified size to end up in the right pile. Unlike the crushers, Vibratory Screens cannot produce material; they can only size material that is already reduced to the product sizes. Vibratory Screens allow crushers to achieve maximum performance by sizing the material feed to the crusher and efficiently removing the finishing product from the circuit as it is produced.

Vibratory Screens can be subdivided into Inclined and Horizontal style screens. Today's screens come in widths from 4-12' wide and from 8-32' long. Screens are normally sized so that the length is 2.5 times the width. The width of a screen will determine the maximum carrying capacity of the screen deck, while the length of the screen will determine the overall efficiency of the deck.

McLanahan Vibratory Screens are engineered with ASTM A572 Grade 50 steel side plates. With a tensile strength of 65,300psi (65ksi), these side plates have a 45% higher yield strength than A-36 steel, which can withstand up to 36,000 psi (36ksi) of stress before it begins to drastically deform. A fully bolted construction reduces/eliminates cracking due to stress risers in the steel caused by welding. Worn components can be quickly replaced without cutting.

McLanahan Vibratory Screens are built with an integrated feed box and are able to withstand heavier loading and larger material in the feed end without worrying about bolts loosening or structural failure.

McLanahan Vibratory Screens feature robust side plate stiffening. Formed plates are bolted to side plates to form a rigid support grid along the length of the side sheet. Independent cross members can be pulled individually and relined in a clean work bay versus on a screen tower, and reduce the need for heavy and wear prone X-bracing. Cross members are on 4' centers to allow more clearance for personnel to access the decks. Replacement cross members come shorter in length and with machined/matched shims to allow for easy installation in areas with limited clearance.

Structural tubing gives the producer a variety of size options and allows you to replace only the worn tubes, not the complete deck frame. A sacrificial weld plate installed on top of the tubes allows stringers and bucker bars to be welded in without welding directly to the tube.

The performance of a screen is affected by four variables: eccentric throw, frequency (rpm), angle of adjustment and throw direction. By manipulating these variables, the operator can dial in the screen to match the application and material.

Eccentric ThrowEccentric throw is the radius of the screen box. Generally, the greater the throw, the more aggressive the screen action will be. Consequently, the smaller the throw, the less aggressive the screening action. Keeping this in mind, the operator can set up the operation with a heavy throw for heavier or larger materials, or a smaller throw to create a sifting action more suited for finer separations.

FrequencyThe frequency of the screen is measured in the number of revolutions per minute the screen makes. In conjunction with the eccentric throw, a lower frequency allows for a more aggressive screen action for larger material and cuts, while a higher frequency is used for smaller material and cuts.

Angle of AdjustmentThe angle of the screen plays a large factor in its overall performance as well. A flatter screen angle will provide a longer retention time of material on the deck and more probability that a particle will fall through the opening. As the angle is increased, the retention time is decreased.

ThrowIt may be advantageous to run the throw of the screen uphill. The goal is to increase the retention time on the screen, as well as change the orientation of the particles to the screen opening. The reverse action does not hurt the screen and is usually used in finer screening application, but be cautious not to increase the bed depth too much.

Stratification and SeparationTwo main operations have to occur for material to be screened: stratification and separation. Stratification is the process of larger sized material rising to the top of the bed, while smaller particles go to the bottom of the bed. Separation is the process by which particles introduced to the screen opening either fall through the opening or do not. Stratification must occur before separation can take place.

The separation probability is a function of the ratio between the size of the screen opening and the size of the particle. If the ratio is large in other words, the particle is much smaller than the opening there is a high probability the particle will fall through. If the ratio is small the particle is close in size to the opening then the probability is low that it will fall through.

Motion on a Vibratory Screen is produced with a combination of amplitude (stroke) and frequency (speed). The goal is to allow the particle to see as many openings as possible as it travels down the screen, but never see the same opening twice. Large screen openings for large cuts can be achieved with high amplitude and low speed. For small screen openings for finer cuts, the opposite is true: low amplitude and high speed.

Many producers have experienced a variety of problems that point to a screen deck that was improperly selected. It's wearing too fast. Its plugging (material getting stuck in the screen opening) or blinding (screen opening clogged by sticky material). The noise level is too high.

Many factors affect the overall efficiency of the screening process. Selecting the proper media for the application will be a big factor toward success. Wire cloth is the most widely used screen surface. Technological advances make it easier to consider other types of screen media.

The type of media chosen will depend on material abrasiveness, impact, material size, moisture content, cost-effectiveness and noise level. Wire cloth may be the lowest initial cost media, but the most cost-effective for anoperation will be the one that meets the specific application.

Rubber screens are a good choice for scalping decks in a dry, high-impact application. Rubber is very durable and can withstand the impact of the larger feed material hitting the deck. In a dry secondary application, a rubber screen can provide a long life, even in abrasive feed material.

tci manufacturing high frequency screens

tci manufacturing high frequency screens

TCI high frequency screens, commonly referred to as "PEP screens", come in a variety of sizes, frequency levels and configurations. Fine material is best separated with high speed and a small stroke. They are available in single or double deck configurations, and are equipped with either electric or hydraulic vibration. The ratchet-type screen tensioning makes for easy screen panel changes.

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