screening 101

screening 101

Screening is the passing of material through definite and uniform apertures is the only true and accurate means of grading to a required particle size. Air separation and hydraulic classification depend upon gravity and particle shape, and result in the segregation and retention of material of higher specific gravity and lower surface area irrespective of size.

The use of Screens increases with the education and civilization of a people and with the improving and perfecting of an art. In our advanced civilization practically everything that we eat, wear and use has been in contact with, or dependent upon screens in some phase of its growth, development or processing. In this treatise, we are only concerned with the sorting, grading or sizing as accomplished with a mechanical screening device.

Some materials such as beach sands, clays, native chemicals, etc., occur in nature in a closely graded state resulting from a mechanical water sorting, precipitation or gravity deposition. They require only scalping or some form of treatment for removal of tramp coarse foreign elements. Others such as salt, sugar and various chemicals are crystallized or precipitated in their processing to fairly close limits of size. They require only such sorting or grading as is dictated by market preference and conditions of use.

In mechanical mixtures such as raw cement, finished fertilizers, stock feeds, etc., the ingredients are blended, ground and screened to a definite fineness. This maintains the intimate relationship by preventing segregation of a coarse constituent through automatic sorting. We have all noted how by piling an ungraded material the fines will segregate in the center of the pile and the coarse will automatically run to the outside and bottom. Metallic and non-metallic ores, stone and other aggregates, coal and coke, various furnace products, chemicals, cerealsetcetera, must be crushed, ground, disintegrated or pulverized before they can go on to further processing and ultimate use. In these fields screens are used for sorting into definite grades, top scalping for removal of coarse oversize and foreign material, bottom scalping for elimination of fines and dirt, and to return oversize to a crusher or grinder until it is reduced to a size finer than the opening of the screen. This latter practice is known as closed circuit crushing or grinding.

A nest of standard brass framed screens, with a definite ratio between openings, is used to sort a representative sample into the clean fractions retained on each screen. The tabulated resulting sieve analysis graphically shows the percentages of given sizes present in the sample. (Table I, p. 347). It indicates just what is available for recovery by screening through and over certain openings in a commercial production screening operation and also shows the reduction obtained by passage through crusher or grinding mill.

Another important factor in commercial screening that will be revealed by a sieve analysis is the percentage of near-mesh material present in the screen feed. If, for instance, it is observed that 40 percent of the sample had passed through the 8-mesh testing screen and was retained on 10- mesh and another 40 percent had passed through 10-mesh and was retained on 14-mesh, an efficient productionscreening operation at 10-mesh would require the maximum in screen area, particularly as to length. This preponderance of near-mesh, or go and no-go size of particle, obviously makes a difficult separation condition. In such cases unless the proper care is taken in the selection of the type of screening device and the specification of the wire cloth used on it, the openings may fill up and blind to a point where no separation is obtained.

In addition to the necessary sieve analysis, other factors must be known before a proper and intelligent recommendation can be made on any but the simplest of screening problems. Many cases require a laboratory test, simulating actual operating conditions, before the size and type of the screen can be determined and proper specification of screen cloth selected. The screen doctor must have the answer to the following questions before he can make proper diagnosis and prescribe treatment:

Capacity required in tons or gallons per hour? This should be expressed in both average and maximum, because peak loads, even of short duration, may result in spoiling of products previously graded or may upset subsequent steps in the operation, due to the drop in screening efficiency. Sufficient screen area should be provided to handle the maximum load.

Type of screening, wet or dry? How much water can be added? In the case of wet screening it is necessary to know if a definite density of the through screen product must be maintained and how much spray water can be added to rinse the oversize.

Percentage of moisture present in the feed? The maximum figure should be given here because different materials become unscreenable at varying degrees of moisture. To effect a separationat a given fineness it may be necessary to dry the material or add water and wash it through the screen.

Is material free-screening? An affirmative answer here obviates practically all other questions. Sticky? As clay, some food products, chemicals, etc. This determines if screening is practical and type of wire cloth recommended.

By closed circuit crushing or grinding it is meant that the product from a crusher or grinder is fed to a screen. The material that has been reduced to sufficient fineness passes through the openings and the oversize is returned to the breaker for further reduction. Escape from the circuit can only be through the screen so this product, the undersize, is equal in tonnage to the initial feed to the crusher or mill. The oversize returned for further work is known as the circulating load. It is a most important factor and can be extremely insidious. If the screen is inefficient and rejects finished material or if the crusher will not reduce the oversize fast enough, this load may build up, and rapidly, to a point beyond the capacity of the breaker, the screen or the conveying equipment, whicheverproves to be the neck of the bottle.

For greatest economy and efficiency, fines should be removed by means of a screen just as fast as they are created in each successive stage of crushing or grinding. Most every case must be handled on its own individual merits and proper balance worked out. In some cases a circulating load as high as 1,000 percent is considered economical. Picture how this would affect the requirement in screening capacity with eleven tons of material handled for every ton produced.

The percentage of circulating load can be readily determined from the sieve analyses of the screen feed, the oversize and the undersize (See Table 1). Samples should be taken simultaneously after circulating load has reached its peak. Conditions and analyses will be similar to those set forth in flowsheet at right. The formula can be expressed:

PercentCirculating Load=100 (B-C/A-C -1) A=Percent finer than required sizein the screen feed. B=Percent finer than required sizein the screen undersize. C=Percent finer than required sizein the screen oversize.

In the example, A equals 35.0,B equals 95.0, and C equals5.0. The value of 1 in the formula represents the initial feed to the circuit which is equivalentto the undersize, or product removed through the screen.

Percent Efficiency=100(100 F-D/AF) A=Percent finer than required size in the screen feed. D=Percent coarser than required size in the screen feed. F =Percent coarser than required size in the screen oversize.

There are different schools of thought on this subject and other formulae. Some operators are satisfied to simply use the percentage coarser than the screen opening in the overscreen product as the efficiency figure. This would be F in the above formula and 95 percent instead of 90.22 percent.

Dependent on the nature of the material and type of operation, screening may be accomplished through bars, perforated plate or woven wire screen. The bar screen is used for scalping extremely coarse material where definite sizing is of secondary importance and abrasion is severe. Perforated plate offers a smooth surface upon which heavy oversize will slide very easily, often too easily for good screening. Under some conditions it blinds less readily than woven wire screen. Objections to it are the fact that the openings wear gradually larger and larger, and the percentage of blank area is so high.

For most purposes woven wire screen, or wire cloth, is the best medium. With it the maximum in open area can be obtained. Various weights, metals and alloys, and shapes of openings are available to satisfy conditions of heavy load, abrasion, corrosion, screenability and capacity. Mesh in wire cloth is the number of openings per lineal inch and means nothing unless accompanied by the decimal designation of the wire diameter or the actual opening of the screen. It is best to specify the required screen opening as this can then be obtained in several meshes, dependentupon the weight of wire that is used. Obviously, for a given opening, the greater the mesh count and the finer the wire diameter, the higher will be the percentage of open area in the fabric.

Much as we might like to do so, we cannot have our cake and eat it, too. Therefore, the selection of a screen specification is usually a compromise. Dependent upon conditions, screen life is constantly being sacrificed for screenability and vice versa. For instance, a heavy and abrasive material suggests an extra heavy wire to secure maximum life. It is found, however, that the low percentage of open area restricts capacity and that the large wire diameter promotes blinding and lowers efficiency. A compromise is, therefore, made by easing off on the weight of the wire. Conversely, another material may, for instance, be damp and sticky, dictating the use of an extremely fine diameter of wire to minimize the surface upon which it may build up. Such a screen specification may last only a few hours and capacity and efficiency must be sacrificed in the interest of longer screen life.

Rectangular and elongated screen openings assist greatly in increasing capacity and eliminating blinding. The opening in a square mesh screen is shaped similar to a funnel and particles can be wedged into it to bear on all four sides. The rectangular opening limits this contact to three sides and thus minimizes the possibility of wedge blinding. When this slot is further elongated to many times the opening width, a springing of the long wires is possible and permanent blinding is eliminated. Naturally, these long openings can not be used for true sizing of anything but cubical or granular materials. Where flakes and slivers are present and cannot be tolerated in the screen under-size, square mesh cloth must be used at the sacrifice of capacity.

For abrasion resistance, high- carbon spring steel wire is available. Stainless steel and the non- ferrous alloys give a selection where rust and corrosion are a factor. The difference between success and failure of a screening operation may rest with the selection of the proper screen clothspecifications and this subject requires considerable thought and study, plus experience.

Reviewing the foregoing, it is readily understandable that a fixed table of screen capacities would be misleading and dangerous. There are so many variables that two neighbouring plants, working on the same deposit, may have entirely different screening conditions, due, for instance, to a difference in crushing practice. Larger tonnages can be handled on scalping operations, and in some cases with closed circuit crushing, than on close grading into specific fractions. On some materials a scalping deck over the sizing screen increases capacity by breaking and distributing the load and opening- up the mat of material. Washing increases capacity materially over so-called dry screening.

From the grizzly and trommel we have seen the development of screening devices through the shaking, knocking and bumping stages to the high speed vibrating screen of today. This development ran the range of eccentric head motions; knockers; cams; air, cam and electric vibrators; unbalanced shafts and eccentric flywheels; grasshopper motions, etc., up to the present positive-drive, high-speed, circle-throw, eccentric- shaft screen.

In this type the throw and speed must be properly specified and coordinated to secure the best screening action. Bearings should not be under shock and design should not be complicated with compensators and adjustments to eat power and tempt experimentation. The loading of the bearings should be so minimized that the equipment manufacturer evidences his confidence in his design by extending a generous guarantee.

In closing, it is recommended that the screen user select a proved and simple machine that will give uniform, continuous, care-free operation. Your supplier should qualify to consult with you on installation, operation, and selection of proper screen cloth specifications. Do not overlook this important service feature.

tips for designing an efficient crushing and screening operation - quarry

tips for designing an efficient crushing and screening operation - quarry

There are several considerations in designing an efficient crushing and screening plant. The first is the raw materials to be crushed. The quarry shot material should be analysed for maximum feed size, gradation, chemical composition, amount of clay, hardness and variations within the deposit or ledges. A list of product sizes needs to be determined as well as the percentage of each product in the total production.

The quarry?s yearly production and operating hours need to be determined. An experienced crushing and screening expert with a computer flow simulation program to optimise the output and efficiency should check the entire system. FEEDER AND HOPPER DESIGN{{image2-a:r-w:200}}One of the first steps in the process is to select the equipment to load the primary hopper. The truck size and number of trucks or loaders needs to be determined to evaluate the hopper capacity. Typically, the minimum hopper live load capacity is about 1.5 times the size of the unit dumping in the hopper. Rock box hoppers are typically used in dump truck operations. Sloped side hoppers might be considered for sticky materials.

? Apron feeders. These should be rugged and need to be designed to handle the impact and lump size of the raw feed from the quarry. Many manufacturers have cast manganese pans attached to a crawler tractor chain with sealed rollers. Impact rails are also necessary to ensure the lump size will not destroy the feeder pans. The modern apron feeder with tractor chain is known to provide very long life and is trouble-free. The apron feeder can be speed controlled to match the primary crusher capacity. Many times apron feeders are followed by a heavy duty scalping screen to separate products or to remove harmful materials. The scalping screen allows material that is already sized for the final products to bypass the primary crusher. ? Wobbler feeders. These are typically used for separation of clays in the feed. These machines are self-cleaning and handle sticky clay with a common separation at 89mm or less. These feeders have a high investment cost but are found to be extremely effective with sticky materials. It is recommended the feed size be controlled if the wobbler is used as the primary feeder. Dumping large rocks directly on a wobbler can result in damage to the feeder. As with any scalping device, the wobbler feeder is most efficient when the material bed depth over the feeder is fairly consistent. It is common for an apron feeder to be used as the primary feeder transferring material to the wobbler feeder for separation. The wobbler feeder is typically operated at a fixed speed but may be turned on and off as needed. ? Vibrating grizzly feeders. These are typically a small investment cost. These feeders perform a dual function of feeding/conveying and separating smaller material to bypass the primary crusher. The oversize materials are discharged off the feeder into the primary crusher. This machine has speed controls but cannot control the feed rate to the crusher as precisely as the apron feeder. Grizzly feeders are exceptional when processing free-flowing materials, due to their multifunction and price advantage over the apron feeder. The most prevalent G-force common to vibrating grizzly feeders is between four and five, which is sufficient to stratify the material bed and provide a feathering effect as the material passes over the grizzly section.

? Jaw crushers. These are used for extremely hard and abrasive materials. Reduction ratios are typically low at 6:1. However, jaw crushers are very durable, low maintenance and effective in nearly any type of friable material. Jaw crushers have a medium investment cost. Typically, 0.5hp (0.37kW) is required per tonne per hour of material produced. Jaw crushers are typically long-life machines. New technology has incorporated quicker adjustment time, tramp iron relief and automated product size setting.? Impact crushers. These are typically used for hard and medium abrasive stone. The primary impact crusher, also known as a primary breaker, has a reduction ratio of 20:1. Impact crushers are higher maintenance than jaws, although are still considered low-maintenance when accounting for the tonnage rate and overall productivity. Impact crushers are typically the lowest investment cost compared with other primary crushers with comparable feed size and capacity. ? ?Andreas-style? impact crushers use 0.75hp (0.56kW) per tonne per hour of material produced. While the Andreas-style primary impact crusher has become very popular worldwide due to many time-saving maintenance features, it remains less efficient than the traditional primary impactor or impact breaker. All Andreas-style crushers impact and grind the material past heavy aprons, with sizing controlled by speed and the apron proximity to the rotor.

In recent years, new impact crushers have been developed as ?true impact? crushers. This equipment combines the time-saving features of the Andreas-style impactor and the traditional primary impactor. These machines are designed to bounce material off heavy aprons, ricocheting material back into the rotating rotor, producing more crushed material with less horsepower. These ?true impact? machines use 0.5hp (0.37kW) per tonne per hour. They will produce a higher percentage of finished products than the Andreas-style machines. The impact crusher is one of the most versatile crushers and offers the advantages of high reduction ratio with lower horsepower per tonne. ? Hammermill (primary). Typically, hammermills are used for soft, non-abrasive and dry materials. Some non-clog models accommodate wet or sticky materials. Hammermills are used where higher reduction ratios are required. Normally they are used when a product must be reduced to a certain size for the next operation in the circuit. Hammermills are common in cement plants, where the top size of the primary crusher output must be a certain size for the next operation. Reduction ratios for this machine are typically 20:1. Hammermills are higher maintenance than the impact crusher due to the higher reduction ratios and the design of the machine. Hammermills will require approximately 2hp (1.49kW) per tonne per hour of material produced in a primary application. Hammermills are a larger investment than the impact crusher, although they are less than the jaw or gyratory.? Sizers. These machines are typically used for medium to soft non-abrasive material. Reduction ratios for this machine are approximately 5:1. They are typically lower maintenance than the impact crusher. Sizers have medium investment cost.? Gyratory crushers. These are used for hard and abrasive materials. Reduction ratios are typically 4:1 and maintenance is minimal. Gyratories have a high investment cost but are typically long-life machines. These machines use about 0.25hp (0.18kW) per tonne per hour of material produced.

In the primary crusher, consideration should be given to initial cost, reduction ratio, horsepower per tonne per hour, hardness, abrasiveness of the material, feed size input and product required. Power consumption per tonne produced has more recently become a very important factor in crusher selection.

Tightening the quarry shot pattern should mean less oversize material being fed to the primary crusher hopper. Not having to break or remove oversize rock in the primary hopper can dramatically improve efficiency in the system. Rock breaker hammers are definitely a necessity at many primary stations but at times can encourage the operators to put oversize rock in the hopper. SURGE CONSIDERATIONS{{image3-a:r-w:200}}In a stationary quarry set-up, there is typically a surge pile. The primary crusher is usually oversized for capacity and is operated at a lower efficiency than the rest of the plant. It is common for the primary sized material to be stockpiled in such a manner that it can be reclaimed from the bottom of the pile to feed the rest of the plant. This overcomes the fluctuations in the feed from the primary crusher. The surge pile is designed with a live capacity of two to three or more hours.Scalping, sizing considerationsA scalping screen is typically fed material after it has passed through the primary crusher. The machine separates oversize materials that need further crushing. Many times a specific product is pulled from the second or third deck of this screen. Scalping screens normally contain two or three decks. Scalping screens are often inclined-type screens and are not generally used for precise sizing. Oversize materials from this screen are usually conveyed to the secondary or tertiary crusher to be crushed further. Usually a sizing screen follows the secondary crusher.

The sizing screen separates the material, with the top deck returning on a conveyor to the secondary crusher for another pass. The rest of the decks on the sizing screen are blended onto conveyors for stockpiling. In cases where a tertiary crusher is used, the secondary crushed material may be conveyed to the tertiary crusher and possibly to an additional screen or screens. All reputable screen manufacturers offer formulas for capacity but a knowledgeable specialist should also be consulted due to variables regarding the material characteristics.

? Cone crushers. These are suited for crushing hard abrasive materials. They are compression crushers. Cone crushers are a high initial investment and low maintenance. Reduction ratios are typically up to 6:1. It should be noted that the cone crusher is limited to a certain top size material being fed to it. Cone crushers use about 1hp (0.75kW) per tonne per hour making a 1? (25mm) product. Typically, the cone will have about 15 to 20 per cent oversized product recirculated back to be re-crushed to size.? Roll crushers. These can be used to crush hard and abrasive materials. They are also compression crushers. Roll crushers are medium to high initial investment and are average maintenance. Reduction ratios are up to 3:1. This machine requires 1.25hp (0.93kW) per tonne per hour of material crushed making a 1? product. The product from the roll crusher has almost no oversize. The triple roll crusher is the same as previously stated except it has a reduction ratio up to 5:1. Roll crushers typically have lower tonnages than their counterparts. Roll crushers are most noted for their low production of fines and controlled output gradation. ? Horizontal shaft impactors. These are typically used with soft or medium abrasive materials. This type of impact will crush abrasive materials, although the wear cost may be prohibitive based on the metallurgy of the wear parts selected. Horizontal shaft impacts have a reduction ratio of up to 12:1 in a secondary application. They are low cost machines with a minimum investment value and are capable of high tonnages. Typically, the horizontal shaft impactor will have about 15 per cent of the product that will need to be re-screened, then oversize material recirculated back to be re-crushed. Impact crushers require about 1hpper tonne of material crushed making a 1? product. ? Vertical shaft impactors. These are typically used in medium abrasive materials. These machines are usually installed as a tertiary (third crusher in the system). They are very good at fine crushing down to 1/8? (or 3.17mm) and providing a cubical product.? Hammermills. These are primarily used in soft and non-abrasive applications. They are usually installed to make finer graded finished products. They require high horsepower per tonne per hour produced. Hammermills require about 2hp (1.49kW) per tonne of material crushed making a 1? product. They have a low investment cost and are small in size. Hammermills have sizing grates through which the material must pass, yielding little oversize. The finer the desired product, the more horsepower is required.

COMPREHENSIVE ANALYSISThere are many considerations in designing an efficient crushing and screening system. Doing a complete analysis of the equipment should include considerations for improving efficiency, minimising the number of pieces of equipment, analysing power consumption based on the volume of material produced, maintenance schedules, labour hours required to maintain equipment, capital costs and personnel requirements.

woven vibrating screen mesh for quarry, crusher screen

woven vibrating screen mesh for quarry, crusher screen

Woven vibrating screen mesh is also called quarry screen mesh, crusher screen mesh. It is made of spring steel wire (high carbon steel wire, medium carbon steel wire, manganese steel wire) and stainless steel wire.

With so many features, the woven vibrating screen mesh is used on vibrating machines in screening and sizing all kinds of sand, gravel, coal, stone, rock and other materials in mining, quarry, aggregate production industries.

Woven vibrating screen mesh can be used as screen deck in quarry screen and crusher screen to separate and sort stone, sand, gravel, coal, rock and other materials. It is widely used in the large scale stone processing, asphalt mixing plants, coal, metallurgy, chemical and other industries.

ambica crushtech pvt. ltd

ambica crushtech pvt. ltd

We are Ambica CrushTech, spreading wings from Vadodara (Gujarat) towards all around the globe. We are glad to introduce ourselves as the leaders in crushing, screening & material handling industry since last couple of decades. We understand, design, manufacture, supply & export various sizes of feeders, crushers, screens and material handling systems along with pre & post sales services. We have dedicated technical team for all the products and services we extend; along with individual experts & skilled personnel carefully handpicked based on their experience & specialization for specific tasks. Our immense knowledge of latest metallurgical techniques ensures optimal utilization all equipment and resources, which enables us in providing reliability & long service life for products with excellent functionality.

AMBICA CRUSHTECH is immensely grateful to its director MR. URMIT HIRUBHAI PATEL, for leading the company from roads of growth towards the zenith of success; enabling Ambica CrushTech to become synonymous with consistency & quality. This prestigious level of the company is merely a result of continuous efforts and dedication of the Director. He has engraved the priceless values he imbibed through over 20 years of his industry experience. Our excellence in metallurgy is a consequence of experience in foundry of about 4 years. His qualities of gentle behaviour, sound technical knowledge, passion for work and prioritizing customers have been priceless assets for the companys existence and growth. He not only follows quality as his personal ethics but has also empowered one and all with and around him follow as well. Our reputed clients & sustained relationships of over one decade is our most valuable among all of our achievements the soulful synopsis of our MDs visionary thinking.

vibrating screen - eastman rock crusher

vibrating screen - eastman rock crusher

Vibrating screen is the most popular screening equipment widely used in the crushing and screening plant. It does circular trajectory, so also known as the circular vibratory screen.rectangular single-, double-, and multi-layer, high-efficiency new screening equipment.Screen Layer1-4 layer.Applicationsmining, quarrying and so on industries to screen ore, sand, gravel effectively.Screen materialssteel, ethoxyline resin.

According to motion theory, screening machines can divide into linear, circular, horizontal, eccentric shaft vibratory screens and inclined screen.The vibratory screening machine is to utilize reciprocating vibration of the vibration generator produced. The processing of the screen separates the different size material by a single- or triple-deck screen. That is, according to the size of particles to separate. The underlayer is a small material, and the upper layer is coarse particle material. In the end, the coarse and fine particles are separated and the screening process is completed.

The single deck, double deck, and multilayer vibrating screen is the basis of the numbers of the layers. Because of the different screening materials, we also call it gravel screen, sand screen machine, aggregate screening, wet vibratory screens.

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

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

screening/sizing | mclanahan

screening/sizing | mclanahan

Sizing is the general separation of products according to their size. The simplest form of sizing is screening, the purpose of which is to separate minerals or other materials into specific particle sizes to create various final products.

When selecting equipment to screen a product, considerations should be given to material being screened, including shape and size; screen media openings; amount of material already to size; presence of harmful materials; need for water; and more. McLanahan offers a variety of screening solutions for both wet and dry applications to fit the needs of producers in many industries. Learn more about McLanahans screening solutions on the individual product pages.

McLanahan Vibratory Screens separate material through the vibration of screen decks covered in screen media of various sized openings. As the screen decks vibrate, the smaller material falls through the openings, while the larger material remains on the top of the screen deck.

McLanahan offers Feeders that provide screening/sizing capabilities in addition to controlling the flow of material to various pieces of equipment. These feeders can scalp out fines and remove material that is already to size to minimize wear on the crusher.

Screening equipment plays a large and important role in a processing plant. It can greatly affect your plants capacity, as well as the quality of your products. Screening equipment can be stationary or portable, designed for quick setup and teardown and for easy transport from site to site.

Screening equipment is commonly used to size and separate material throughout the production process. Screens used ahead of a primary crusher can remove fine material, like abrasive stone or sand, which can cause wear and tear on the crushers liners. They can also keep material that is already to size from entering the crusher feed, which reduces unnecessary power consumption and wear on the machine.

After the primary crushing stage, screens with multiple decks can separate material into various categories for further crushing in the secondary and tertiary stages. They can also decrease the load the crushers and other processing equipment have to handle by removing undersized and oversized material from the feed ahead of the next reduction stage.

Screens can also be used in other stages of the processing plant to produce a final, saleable product, as well as to dewater washed material to less than 14 percent moisture for easy conveying and/or stockpiling.

To size and separate material, screening equipment employs a vibrating or tumbling action that causes the feed material to divide by size. The screen media removable, easily replaceable panels attached to the deck frame through which undersized particles pass makes the separation by allowing smaller particles to pass through its openings. Larger particles rise to the top of the material bed due to the vibrating or tumbling action of the screen, while smaller particles filter out through the openings in the screen media, creating two or more fractions.

Each application is unique in its screening needs, though every application relies on its screen media for successful material separation. Popular screening media includes woven wire cloth, urethane, rubber or a combination of urethane and wire cloth or urethane and rubber. Each type of screen media offers producers different options when it comes to capacity and efficiency, and efficiency is key to creating a quick return on investment.

Besides sizing and separating material, screening equipment can also spilt a feed stream for separate processing, remove refuse material, reduce fines generation, and minimize crusher size. Screening equipment that is used effectively can make your processing plant more efficient.

crushing and screening | agg-net

crushing and screening | agg-net

Several considerations need to be taken into account in designing an efficient crushing and screening plant, the first being the raw materials to be crushed. The quarry shot material should be analyzed for maximum feed size, gradation, chemical composition, amount of clay, hardness and variations within the deposit or benches. A list of product sizes needs to be determined as well as the percentage of each product in the total production. The quarrys annual production and operating hours also need to be determined. The entire system should be checked by an experienced crushing and screening expert with a computer flow simulation program to optimize the output and efficiency.

One of the first steps in the process is to select the equipment to load the primary hopper. The truck size and number of trucks or loaders needs to be determined to evaluate the hopper capacity. Typically, the minimum hopper live load capacity is approximately 1.5 times the size of the unit dumping into the hopper. Rock box hoppers are typically used in truck dump operations, while hoppers with sloping sides might be considered for sticky materials.

Apron feeder Apron feeders should be rugged and designed to handle the impact and lump size of the raw feed from the quarry. Many manufacturers use cast manganese pans attached to crawler tractor chain with sealed rollers. Impact rails are also necessary to ensure the lump size does not destroy the feeder pans. The modern apron feeder with tractor chain is known to provide very long life and is trouble-free. The apron feeder can be speed controlled to match the primary crusher capacity. Apron feeders are often followed by a heavy-duty scalping screen to separate products or to remove deleterious materials. The scalping screen allows material that is already sized for the final products to bypass the primary crusher.

Wobbler feeder Wobbler feeders are typically used for the separation of clays in the feed. These machines are self-cleaning and handle sticky clay with a typical separation at 31/2in or less. These feeders represent a high investment cost but are extremely effective with sticky materials. It is recommended that the feed size is controlled if the wobbler is to be used as the primary feeder. Dumping large rocks directly on a wobbler-type feeder can result in damage to the unit. As with any scalping device, the wobbler-type feeder is most efficient when the material bed depth over the feeder is reasonably consistent. It is common for an apron feeder to be used as the primary feeder transferring material to the wobbler feeder for separation. The wobbler feeder is typically operated at a fixed speed, but can be turned on and off as needed.

Vibrating grizzly feeder Grizzly feeders typically represent a small investment cost. These feeders perform the dual function of feeding/conveying as well as separating smaller material to bypass the primary crusher. The oversize materials are discharged from the feeder into the primary crusher. This machine has a range of speeds but cannot control the feed rate to the crusher as precisely as an apron feeder. However, grizzly feeders are exceptional when processing free-flowing materials, owing to their multi-function capability and price advantage over the apron feeder. Typically, grizzly feeders offer a G-force ranging between four and five, which is sufficient to stratify the material bed and provide a feathering affect as the material passes over the grizzly section.

Jaw crusher Jaw crushers are used for extremely hard and abrasive materials, with reduction ratios typically as low as 6:1. However, jaw crushers are very durable, have low maintenance requirements, and are effective with almost any type of friable material. They represent a medium investment cost and, generally, half a horsepower is required per ton per hour of material produced. Jaw crushers are typically long-life machines. New technology has incorporated quicker adjustment times, tramp iron relief and automated product size setting.

Impact crusher Impact crushers are typically used for hard and moderately abrasive stone. The primary impact crusher, also known as a primary breaker, has a reduction ratio of 20:1. Impact crushers are higher maintenance than a jaw, although are still considered low maintenance with regard to their tonnage rate and overall productivity. Impact crushers typically represent the lowest investment cost compared with other primary crushers with comparable feed size and capacity.

Andreas-style impact crushers use three quarters of a horsepower per ton per hour of material produced. While this type of primary impact crusher has become very popular worldwide, due to many time-saving maintenance features, they remain less efficient than the traditional primary impactor or impact breaker. All Andreas-style crushers impact and grind the material past heavy aprons with sizing controlled by speed and the aprons proximity to the rotor.

In recent years, newer designs of impact crushers have been developed as true impact crushers. These units combine the time-saving features of Andreas-style impactors and the traditional primary impactor. They are designed to bounce material off heavy aprons, ricocheting it back into the rotor to produce more crushed material with less horsepower. These true impact machines use half a horsepower per ton per hour and produce a higher percentage of finished products than the Andreas-style machines. The impact crusher is one of the most versatile crusher types available and offers the advantages of high reduction ratio with lower horsepower per ton.

Hammermill (primary) Typically, hammermills are used for soft, non-abrasive and dry materials, although some non-clog models can accommodate wet or sticky materials. Hammermills are used where higher reduction ratios are required. Normally, they are used when a product needs to be reduced to a certain size for the next operation in the circuit (eg cement plants). Reduction ratios for this machine are typically 20:1. Hammermills are higher maintenance than the impact crushers owing to the higher reduction ratios and the design of the machine. Hammermills require approximately two horsepower per ton per hour of material produced in a primary application. They represent a larger investment than an impact crusher, although less than a jaw or gyratory.

Sizers These machines are typically used in medium-to-soft non-abrasive material. Reduction ratios for this machine are approximately 5:1. They are typically lower maintenance than impact crushers and represent a medium investment cost.

Gyratory crushers Gyratory crushers are used for hard and abrasive materials. Reduction ratios are typically 4:1 and maintenance is minimal. Gyratories represent a high investment cost but are typically long-life machines. They use approximately a quarter of a horsepower per ton per hour of material produced.

With primary crushers, consideration should be made regarding initial cost, reduction ratio, horsepower per ton per hour, hardness, abrasiveness of the material, feed size input and product required. More recently, power consumption per ton produced has become a very important factor in crusher selection.

Tightening the quarry shot pattern should result in less oversize material being fed to the primary crusher hopper. Not having to break or remove oversize rock in the primary hopper can significantly improve efficiency in the system. Rock breaker hammers are a necessity at many primary stations, but at times can encourage operators to put oversize rock in the hopper.

In a stationary quarry set-up, there is typically a surge pile. The primary crusher is usually oversized in terms of capacity and operated at a lower efficiency than the rest of the plant. It is common for the primary sized material to be stockpiled in such a manner that it can be reclaimed from the bottom of the pile to feed the rest of the plant, thereby overcoming fluctuations in the feed from the primary crusher. The surge pile usually is designed with a live capacity of 23h or more.

The scalping screen is typically fed with material after it has passed through the primary crusher, separating out oversize materials that need further crushing. Often, a specific product is pulled from the second or third deck of this screen. Scalping screens normally contain two or three decks, are often inclined, and are not generally used for precise sizing. Oversize materials from the scalping screen are usually conveyed to the secondary or tertiary crusher for further reduction.

Usually, the secondary crusher is followed by a sizing screen which separates the material, with the top deck material being returned, via conveyor, to the secondary crusher for another pass. The materials from the other decks on the sizing screen are sent, via conveyors, for stockpiling. In cases where a tertiary crusher is used, the secondary crushed material may be conveyed to the tertiary crusher and possibly to an additional screen or screens. All reputable screen manufacturers offer formulas for capacity, but a knowledgeable specialist should also be consulted owing to the variable material characteristics.

Cone crushers Cone crushers are a type of compression crusher suitable for crushing hard, abrasive materials. They represent a high initial investment but are low maintenance. Reduction ratios are typically up to 6:1. It is worth noting, however, that the cone crusher is limited to a certain top size of material feed. Cone crushers use approximately one horsepower per ton per hour making a 1in product. Typically, around 1520% of oversized product is recirculated for re-crushing to size.

Roll crushers Roll crushers are another form of compression crusher that can be used to crush hard and abrasive materials. They represent a medium-to-high initial investment and maintenance requirements are average. Reduction ratios are up to 3:1. This machine requires one-and-a-quarter horsepower per ton per hour of material crushed to make a 1in product. The product from the roll crusher has almost no oversize. The triple roll crusher is the same as above except that it has a reduction ratio of up to 5:1. Roll crushers typically have lower tonnages than their counterparts and are most noted for their low production of fines and controlled output gradation.

Horizontal-shaft impactors Horizontal-shaft impactors are typically used in soft or moderately abrasive materials. This type of impact will crush abrasive materials, although the wear cost may be prohibitive depending on the metallurgy of the wear parts selected. Horizontal-shaft impactors have a reduction ratio of up to 12:1 in secondary applications. They are low-cost machines with a minimum investment value and are capable of high tonnages. Typically, about 15% of the horizontal shaft impactor product will need to be re-screened, with oversize material being recirculated for re-crushing. Impact crushers require approximately one horsepower per ton of material crushed when making a 1in product.

Vertical-shaft impactors Vertical-shaft impactors are typically used in moderately abrasive materials. These machines are usually installed as a tertiary unit. They are very effective at fine crushing down to 1/8in size, and providing a cubical product.

Hammermills Hammermills are primarily used in soft and non-abrasive applications. They are usually installed to make finer- graded finished products and require high horsepower per ton per hour produced, typically around two horsepower per ton of material crushed to make a 1in product. They represent a low investment cost and are small in size. Hammermills have sizing grates through which the material must pass, yielding little oversize. The finer the desired product, the more horsepower required.

There are many considerations to be taken into account when designing an efficient crushing and screening system. Carrying out a complete analysis of the equipment should include considerations for improving efficiency, minimizing the number of pieces of equipment, analysing power consumption based on the volume of material produced, maintenance schedules, labour hours required to maintain equipment, capital costs, and personnel requirements.

crushing and screening equipment guide | wheeler machinery co

crushing and screening equipment guide | wheeler machinery co

Each year, over a billion tons of crushed stone is produced in the United States.Seventy-six percentof the crushed stone used in the U.S. is for construction material such as road construction or maintenance. Without crushing and screening equipment, none of this production would be possible and road, building, and bridge construction and maintenance would be forced to come to a halt. While there can be cases made for all pieces of construction equipment, perhaps the most compelling is for crushing equipment and screening equipment, which so often work together.

But the sole existence of these pieces of equipment is not enough. If you want to process materials in the most precise and efficient way, its essential to choose the right equipment for your process which is exactly what this crushing and screening equipment guide was designed to do. Weve gathered information on each of these pieces of equipment so you can learn more about their parts and how they work. By understanding more about the equipment and applying the background knowledge, you have about your material and your process, you will be able to choose the right crushing and screening equipment.

Together, crushing and screening equipment are a dynamic team they work together to turn big pieces of material into smaller pieces and then sort them into batches of similarly sized materials. While they make a great pair, these pieces of equipment dont necessarily have to be used together. In fact, in many cases, they work independently. Heres an overview of how each of them works.

There are different types of crushers. Some are meant to be built into full circuit material handling systems while mobile crushing equipment is smaller and portable. There is also heavy-duty crushing equipment that is meant to handle really large pieces of raw material jaw crushers are often used for this purpose. They are designed with a jaw composed of two plates that move up and down to apply pressure and break raw material into smaller pieces. Even if a heavy-duty crusher isnt necessary for the job, the overall crusher design is similar two heavy plates moving up and down to apply pressure just on a smaller scale.

The easiest way to think of the function of screening equipment is like a filter or sieve that separates similarly sized materials. The smaller particles pass through the screen, and the larger particles remain above the screen.

There are a variety of different types of screening equipment, as different materials have different characteristics and requirements for the result. Even within the construction industry, there are a variety of shapes and sizes needed for different jobs, whether its a new building or road maintenance. If you want to get the maximum amount of efficiency along with the correct particle size, there are several parts of screening equipment that vary to get the result you need. These variables include the screen material, size, slope, hole openings, number of decks and type of vibration motion.

Aggregate production statisticsshow that in 2017, approximately 1,400 companies produced 1.3 billion tons of crushed stone, down slightly from the previous year. Overall value was also down slightly at $15 billion, but per ton the value was up. The overwhelming majority of that crushed stone is used as construction materials. But the stone that comes directly from the quarry cant be usedimmediately it needs to go through stone crushing equipment and screening process before its ready.

While the exact quarrying process depends on the type of construction material thats being created, there is one part that remains the same crushing. The rock that is extracted from quarries is in large chunks, and so the first step in processing it is putting the rock that has been extracted from the ground through stone crushing equipment. This creates pieces of rock that are easier to process. Often this crusher leads the rock, by conveyor belt, to another crusher. Remember that different construction materials require different sizes of aggregate, so getting the rock into smaller and smaller pieces is key to the result. After a couple of rounds of crushing, the next step is to put the crushed stone through screening equipment to sort the various smaller sizes and shapes of aggregate, and to remove impurities. Now its ready to be transported to distribution centers or construction sites.

The exact size and shape of aggregate are essential for each different type of construction project where the material is used. The screening equipment cant work in the quarrying process without stone crushing equipment breaking it down into a smaller size. These two pieces of equipment are essential to the quarry and aggregate industry. Without stone crushing and screening equipment, we would be at a loss for materials that make up many of the roads, buildings, and bridges in our communities.

Not all crushing equipment is an ideal match for all raw materials and all material processing systems. Instead, choosing the right crushing equipment requires careful consideration of a few factors, including material hardness, desired output, mobility needs and part quality. Considering all of these factors in your decision will ensure that you get a piece of equipment that maximizes performance and efficiency.

It can be challenging to be sure youre choosing the right screening equipment. There are several components to screening equipment that need to be considered, including the screen media, angle and motion of the screen. Of course, the raw material youre working with also needs to be considered as the best fit for many of these factors will depend on your process. Here is some background information to get you started.

The raw material youre working with is going to have an impact on what kind of screening equipment you get for the job. The shape of the particles of material, weight and even the humidity of the material will affect the screening process and should be taken into consideration when youre choosing the right screening equipment for your process.

For example, the capacity youre able to screen will be partially determined by the weight of the material youre screening. Natural stone is mostly round and fairly even, making it easier to screen than crushed stone, which tends to be more angular and rough. Humidity is most influential when the screen hole sizes are 16 millimeters or smaller. Moist, doughy or thick slurry consistencies can be nearly impossible to screen while a dry or thin slurry consistency is ideal for screening.

The screen media is the rubber, polyurethane or wire cloth that has the openings for the particles to either pass through or over, depending on size. There are pros and cons of each of these screen media.

Rubber panels are known for being durable in high-impact situations and for reducing noise a great fit for large batches. The downside? Smaller rocks act like sandpaper, wearing away the rubber and thinning the panel out time. Urethane panels are best for sand and wet material when water is used to support the screening process. Its durable but doesnt make a great match for high-impact processes. Wire cloth panels are the most affordable up front, but abrasive materials can wear it down pretty quickly, meaning youre likely to have to replace it more frequently. This type of panel will also have a higher open area.

Is the screen at an angle? If so, to what degree? While having an angle to the screen can certainly help move the raw material along the screen, too much of an angle can be detrimental to the process. Unfortunately, there is no single measurement that works for everyone. It ultimately depends on the material youre working with, the screen media and the motion of the screen. As a rule of thumb, flat screens are frequently used in portable applications due to road height restrictions. They are efficient but will produce fewer tonnages than an inclined or angled screen. Inclined or angled screens use gravity to help move the process along. In addition to having a single screen at an angle, there are also multi-sloped screens. Multi-sloped screens have three sections to each deck each with its slope or angle. These screens are also known as banana screens.

Part of screening is the motion of the screen. The motion varies depending on the piece of screening equipment that you use, but can usually best be described as screen vibration. This vibration helps get the smaller particles through the screen and separated from the larger particles. There are several different vibration patterns available, but a few of the most common are vibrating freely, circular vibration, linear vibration, and elliptic vibration.

Weve mentioned that there can be more than one screen deck, but what exactly does that mean? Think of decks as tiers of screening on top of one another. When the raw material is dumped into the top deck, particles smaller than the hole size in the screen media will fall through to the second deck. At the second deck, the hole size in the screen media would likely be slightly smaller, capturing some of the particles, but again allowing particles smaller than the hole size in the screen media to fall through to a third deck and so on. At the end of the process, you have multiple decks with multiple particle sizes appropriate for whatever your output is.

Crushing and screening are both processes that require additional equipment. At Wheeler Crushing Systems, we have crushing and screening equipment, as well as the other pieces of equipment to complete your process. Bins and hoppers for storage solutions, feeders for optimal flow and a variety of conveyors to match your site and your material.

All of these pieces of equipment bins, hoppers, feeders, conveyors, crushers and screens are available to purchase new or used, or to rent. At Wheeler Crushing Systems, we understand that there are a variety of reasons crushing and screening equipment may be needed. You may be looking to invest in a brand new piece of equipment for a longer-term crushing and screening process. However, we also understand that budgets and jobs vary. Perhaps buying used is the way youve determined to meet your budget. Or, maybe youre only going to be crushing a screening for a limited amount of time, and so a piece of rental equipment makes sense.

Regardless of what piece of equipment you need, and whether youre interested in buying new, used or renting, at Wheeler, were here to help you complete your crushing and screening process with a piece of equipment that will maximize your output and efficiency.

Youll find everything necessary for your crushing and screening equipment, from rentals or financing to parts and service. We carry the leading manufacturers recognized for reliability, throughput and high product quality Metso, Anaconda, Edge Innovative, RD Olson and Masaba.Our crushing and screening equipment selectionincludes new, used and rental crushers and screens, of course, either track- or trailer-mounted, as well as conveyors, bins, hoppers, and feeders. If you arent sold on a particular model, we can show you the options and benefits of each in detail to help you choose the best crushing and screening equipment.

And it doesnt stop with a purchase. We support every piece of crushing and screening equipment we sell through superb parts availability and skilled service technicians. Our goal is to provide a piece of equipment that helps you increase profitability by providing a solution to your crushing and screening challenges. If youre near one of our ten locations throughout Utah, Nevada or Wyoming, get started by calling us at 801-974-0511, or reaching us through ourcontact form.

Skid Steer Loaders: 262 Multi Terrain Loaders: 277, 287, 297 Compact Wheel Loaders: 903, 906, 907 Telehandlers: TH514, TH1055, TH1255, TH642, TH943 Small Hydraulic Excavators: 311, 313, 314, 315, 316, 318 Mini Hydraulic Excavators: 308

Compact Track Loaders: 249 Skid Steer Loaders: 252 Multi Terrain Loaders: 247, 257 Mini Hydraulic Excavators: 300.9, 301.4, 301.7, 302.4, 302.7, 303, 303.5, 304, 305, 305.5, 307 Telehandlers: TH255, TH306, TH3510, TH357, TH406, TH407, TH408

Skid Steer Loaders: 262 Multi Terrain Loaders: 277, 287, 297 Compact Wheel Loaders: 903, 906, 907 Telehandlers: TH514, TH1055, TH1255, TH642, TH943 Small Hydraulic Excavators: 311, 313, 314, 315, 316, 318 Mini Hydraulic Excavators: 308

Compact Track Loaders: 249 Skid Steer Loaders: 252 Multi Terrain Loaders: 247, 257 Mini Hydraulic Excavators: 300.9, 301.4, 301.7, 302.4, 302.7, 303, 303.5, 304, 305, 305.5, 307 Telehandlers: TH255, TH306, TH3510, TH357, TH406, TH407, TH408

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