Vibratory Screening

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Introduction

The content of this article will provide everything you need to know about vibratory screening.

You will learn:

• What is Vibratory Screening?
• How a Vibratory Screener Works
• Types of Vibratory Screening
• Uses for Vibratory Screening
• And much more …

Chapter 1: What is Vibratory Screening?

A vibratory screening is a process that separates bulk solid materials from solids and slurries using inertial vibration that causes various sizes of particles to pass through openings in a screen or move across the surface of the screen. The operation of a vibratory screener begins with vibrations that move the mass of materials on a horizontal, vertical, or circular plane that causes the material to move across a sieve or screen mesh. The segregation process is able to provide two or more separations as the separated material flows from one level or deck of the vibratory screener to the next level.

The purpose of vibratory screening is to sort 2D materials such as plastic film, paper, cardboard, fibers and 3D materials like containers, plastic bottles, cans, stone, and wood. Once the materials are sorted, they can be collected separately from the screen openings. Vibratory screeners are able to separate and classify materials based on their size and shape using the gyratory motion of the vibrating screen. For the process to be successful, materials have to move across the surface of the screen and through the mesh openings that are perfectly sized for the material.

Chapter 2: How Vibratory Screening Works

The separation process has been an industrial process for centuries and a vital function for the mining industry. The initial separation methods involved the use of square or rectangular devices that were moved back and forth across a screen. Although the method was successful, it wasn’t accurate enough. At the beginning of the Great Depression, it was discovered that gyratory motion screens provided greater efficiency and accuracy for the separation process.

Gyratory Motion

Gyratory motion helps improve the distribution of materials during the screening, sifting, and separation process. The use of gyratory motion makes it possible to more effectively use the surface of the screen. The power of gyratory motion moves the screen, which leads to longer stroke and lower frequency screening.

The popularity of gyratory motion during screening is due to how quickly the material spreads across the full breadth of the screen deck to achieve a consistent depth of material. The horizontal motion stratifies the material with smaller particles moving toward the bottom and larger materials remaining on top making the separation, screening, and sifting process more efficient.

Screen Body

The welded or bolted screen body is the main structure of a vibrating screen since it serves as the support base for the screen mesh. It is supported by coil springs that allow the vibrating screen to bounce freely. The gyrating and vibration motion requires counterweights, which are provided by the screen body for linear and circular vibrating screens.

Screens

The number of screens of a vibrating screener varies in accordance with its design. A vibrating screening machine can have two up to six screens or screen decks, which are made of wire mesh. Each screen is manufactured to have the correct hook system and opening size. The intensity and stress of the screening process requires that the screen be exceptionally durable and tough enough to handle the constant motion as well as the weight of the material being screened. Additionally, screens have to be flexible to help particles separate without creating blind spots, which is having material stuck in an opening of the screen.

A critical part of the screen is its weave, which comes in square mesh, ton cap, and ty rod. Each level of the screen deck varies in the size of the opening of the weave with the square mesh weave being the most common.

• Square Mesh – The openings of the weave of square mesh is in the shape of squares and is woven using an over under pattern. The variations in the process can include two over and one under or other types of weaves. Regardless of the pattern of the weave the openings are always squares.
• Ton Cap – Ton cap weaves are chosen for their enhanced stability and strength, which makes them capable of handling higher amounts of material that is heavier. Ton cap is an anagram for tonnage capacity screen, which is a sturdier and more durable mesh. Its wires are heavier and thicker with a square pattern.
• Ty Rod – Ty rod weave is designed to control blinding, which is when particles get stuck in the weave. The open area of the mesh is rectangular with a larger opening to prevent material getting stuck. Shoot wires are placed on each side of the openings in the weave.

Circular Screens

The various meshes for circular screens are much the same as those for linear vibratory separators. The one distinction for circular screens is their movement, which is rotational. They are made of various kinds of woven metals or punch screen plates. Circular screens have a structure that makes it possible to adjust the angle of the surface of the screen by adjusting the screen’s position and the height of its spring supports.

Circular screens operate by movement of the screen mesh and the angle of the screen with the optimum angles being between 15° and 30°. Much like linear screen mesh, circular screen mesh must be highly durable and capable of enduring constant motion as well as the weight of the material being sieved or separated.

Vibration Mechanism

The vibration mechanism works using a counterbalance or shaft for balanced and monitored vibration, which are necessary to avoid damage to the machine. There are various types of vibration mechanisms used to create the vibratory motion. Linear screen separators have dual motors that provide linear motion. Hummer screen mechanisms are operated by solenoid action that is mounted on a stationary box.

Of the various types of mechanisms, inclined screens tend to be one of the more popular. Vibratory motion is circular and lifts the material using vibrations and angle of incline. The mechanism is widely used in the mining industry for separating different sized materials.

Drive Motor

For the separation, sifting, and screening process to function properly, it requires the use of a motor to power the vibrating screen, which is connected to the vibration mechanism to generate force for the vibratory motion. The motor is installed on the frame support in the center of the screen assembly of a circular vibratory separator on a base of springs to allow the unit to vibrate freely and produce a variable speed of vibrations.

Motors for vibratory screens, sifters, and separators are specially designed for the process in order to produce multiplane vibrations. Weight is distributed at the top and bottom ends of the motor shaft. The placement of the weights provides the appropriate force for the separation operation. The top weight of the motor is positioned near the center of the mass. Its motion causes the material to move across the screen causing horizontal throw and the rapid discharge of large material. The bottom weight is below the center of the mass and causes the screen to tilt and vibrate vertically on the tangential plane.

Other Components of a Vibratory Screen Sifter Separator

The screen body, screen mesh, vibration mechanism, and motor are the main components of a vibratory separator and are the main components of the machine. Other components support the main parts and provide stability to the constant motion of the mechanism.

• Suspension Springs – The suspension springs isolate the vibrating screen from surrounding structures and ensure smooth and efficient operation. They absorb the constant vibrations and allow the screening mechanism to move freely.
• Supporting Structure – As with any form of industrial equipment, vibratory screen sifters and separators require a heavy structure capable of carrying the load and weight of the machine. The beams and columns of the supporting structure provide stability and support for the screening mechanism and prevent excessive vibrations and wobbling.
• Clamps and Seals – In order for the screen to operate properly, it has to be secured to the screen body. Clamps are used to securely hold the screen in place while seals prevent leakage of material and minimize the amount of dust that is released.
• Isolation Springs and Bearings – As with all forms of heavy-duty equipment that have to provide substantial force, it is necessary to have components capable of absorbing the intense vibrations produced by the vibratory motion. Isolation springs are necessary for the absorption of the constant vibrations and allow for smooth operation of the mechanism. Bearings are a preventive measure designed to protect the integrity of the machine by reducing friction and wear.

The components listed above are a generalization of the components found in vibratory screeners. Each manufacturer has their versions of vibratory separator design able to meet the needs of a wide assortment of operations. The one obvious factor that is common to all vibratory separators are the different types of screens, which vary in accordance with the design of the vibratory mechanism. The key factor to keep in mind when studying vibratory separators is their unique function and their efficiency, which far exceeds any other method of separation.

Chapter 3: Types of Vibratory Screeners

The types of vibratory screeners include a long list of devices each of which is designed to efficiently complete the separation process. The many variations, which are constantly changing, is due to the types of materials that are sifted, screened, and separated with each type of material necessitating some form of special handling.

In material handling, separators are an important and crucial part of the process in regard to efficiency, effectiveness, and productivity. The general categories for vibratory separators are divided into linear and circular vibratory separators, which are differentiated by their shape, method of vibration, and types of materials they handle.

Regardless of their differences, circular and linear vibratory separators are capable of separating several different types of materials using multiple decks or screens in order to more precisely separate and organize materials. The use of multiple decks makes it possible for both types of vibratory separators to separate two, three, four, or more sets of materials at a very high level of efficiency. As with all types of industrial functions, the goal of the separation process is to condense multiple processes into a single complete unit.

Linear Vibratory Screeners

A common use for linear vibratory screening is in the recycling industry for processing rubber products and metals. They are used for their ability to handle irregular shaped materials that require dynamic and aggressive handling. The heavy-duty construction of linear vibratory screeners enables them to handle high volumes of materials due to their large screen surfaces and their vibrational amplitude.

With a linear vibratory screen sifting separator, a linear motion vibrating screen is powered by vibrating motors. Material placed on the screen of the separator moves along the screen in a straight line. Its double exciters, which include housings, bearings, shafts, and mass, have an inclination angle for the surface of the screen. The excitation force and the gravity of the material causes the material to be thrown up and forward. As the material is separated, it is fed to hoppers, bags, or sent on for processing.

The out of balance motors of a linear vibratory separator are able to create vertical and forward motion. Various types of linear vibratory separators use single or multiple electromagnetic drives depending on the length of the tray with the number of decks determining the number of fractions that can be produced. The larger area of the screening for a linear vibratory separator makes it possible to have high throughput and enables it to handle higher volume.

Circular Vibratory Screening

Circular vibratory screening differs from linear vibratory screening in their appearance, which is round and not linear. They were introduced to improve the quality of the recovery, recycling, and separation processes. Circular vibratory separators are capable of sieving, classifying, de-dusting, and filtering a wide range of materials. The unique design of circular vibratory separators makes it possible to adjust the vibrating motion according to changes in the action of the material.

The maintenance and cleaning of circular vibratory screeners is very easy since the screens for the separator can be removed and replaced with little effort. The number of stages for circular vibratory screening varies according to the needs of the application with one to four stages available that provide two to five fractions. The diameters of the different types of circular screen sifting separators vary between 600 mm up to 1800 mm (24 in up to 71 in) for standard versions with custom designed types available.

Types of Circular Vibratory Screeners

Circular vibratory screeners are commonly referred to as fine screening machines. They are divided into circular vibrating screens, circular ultrasonic vibrating screens, circular direct discharge sifters, circular umbler screens, circular filter sieves, and circular high frequency vibrating screens.

Circular Vibratory Sifter or Vibro Sifter

Vibro sifters are used to sift or separate materials based on their size. They use gyratory motion for separating, scalping, and grading. As is common with most circular vibratory separators, vibro sifters vibrate around their center of gravity, which makes it possible for them to achieve vibrating motion across several planes. Weights at the top and bottom of the sifter’s motor generate the vibration motion.

The unique and simple operation of circular vibratory sifters are some of the many reasons for their popularity. The machines separate materials according to particle size. The number of decks of the vibrating sifter varies according to the materials being sifted. As the screen rotates, the material moves across the screen discharging larger particles. The bottom of the motor rotates and tilts the round screen and makes it vibrate vertically and tangentially.

The use of circular vibratory sifters is mainly confined to screening raw materials and the inspection of final products. The unique design of circular vibratory sifters makes it possible for them to remove agglomerates and various types of contaminants and can have as many as five fractions.

Circular Ultrasonic Vibrating Screen

A circular ultrasonic vibrating screen has an ultrasonic power supply, transducer, and resonance ring. The ultrasonic power supply generates a high frequency electric oscillation that is converted into high frequency sinusoidal form of waves by the transducer. The waves make the resonance ring send vibrations to the surface of the screen. The material on the screen experiences low frequency three dimensional vibrations.

The reason for the development of the circular ultrasonic vibrating screen was to improve the precision of the screening process. With ordinary vibratory screening, there are problems with material escape and precision, problems that circular ultrasonic vibrating screening resolves. The process of circular ultrasonic vibrating screening prevents material from blocking or blinding the screen. The precision of the process makes it possible to screen materials down to 20 micrometers (µm) with an increased screening accuracy of 80% and output increase of 2 to 5 times that of other methods.

Circular Direct Discharge Sifter

Circular direct discharge sifters are used to sieve powders and are known as flour sieves. The purpose of circular direct discharge sifters is to remove impurities from raw materials. They can have dual or single vibrating motors, which is determined by the amount and kind of material and the size of the screen. The dual motor design produces more force and a vortex motion on the surface of the screen while single motor designs vibrate up and down.

Unlike a vibro sifter, a circular direct discharge sifter works with powder materials such as flour, starch, milk powder, chilly powder, and additives. What distinguishes a circular direct discharge sifter from a vibro sifter is its size, which can be four times larger, a factor that is due to its open design to allow for higher output. Circular direct discharge sifters are used for screening coarse materials that cannot be completed using a fine screening process.

Circular High Frequency Vibrating Screen

Circular high frequency vibrating screen separators use a high frequency motor, two stage frequency vibration motors, a 50 Hz vibration frequency, and high motor speed. The high frequency breaks the viscosity causing glazed liquids to pass through the screen and impermeable impurities to be discharged. The intensity of the vibrations is two to three times more intense than ordinary vibrating screening. The design of circular high frequency vibrating screens is ideal for separating slurries with high viscosity.

A two-stage motor with a speed of 3000 rpm is used to create the excitation to destroy the tension of liquid molecules in a slurry material. As the frequency of the vibrations increases, the slurry gets smaller than the mesh of the screen and passes through to a lower layer. Impurities remain on the surface of the mesh screen and are screened out through an upper discharge port. The simpleness of the design of a circular high frequency vibrating screen makes it easy to main and switch screens.

A circular high frequency vibrating screen has a single layer screen box with two outlets with one for discharge and one for slag discharge. The purpose of circular high frequency vibrating screens is to screen high concentrations of ceramic glaze and paint and for filtration purposes.

Elliptical Motion Vibration Screening Machine

An elliptical motion vibration screening machine combines the advantages of linear motion and circular motion. The mechanical and elliptical motion of the screens can be varied using a control panel or manually. The high regard for elliptical vibrating screening machines is due to their exceptional screening ability and high capacity.

The components of an elliptical motion vibration screening machine include screen box, vibration exciter, and supporting springs. The excitation shafts are installed with a set of eccentric blocks with both shafts powered by gears that rotate in opposite directions with the same angle of speed. When the excitation shafts are activated, the screen box moves in an elliptical trajectory. The angle of the elliptical vibration is constantly changing causing particles to collide on the screen plane. As the collision frequency rises, the retention time of the particles on the screen increases.

Banana Vibrating Screen

Banana vibrating screening machines have a structure that is similar to linear vibrating screening machines and include a screen box that has the shape of a banana, screen mesh, vibration exciter, damping springs, and seat frame. The exciter is connected to the side plate of the screen box by a motor using a V belt or soft connection. Banana vibration screens are used for large to medium sized materials that have fine content and are capable of assisting with dehydration and desliming.

The surface of a banana vibrating screen forms a set of broken lines with each line having a different inclination angle. The screen has a banana shape with several segments on a linear vibrating screen. The feeding end is an inclined screen surface that descends in steps through the various angles until it reaches the discharge port. The sloping end allows for higher screening speed allowing more material to pass through the screen surface. Larger particles travel faster, which allows finer particles close to the screen surface to pass through gaps in the screen.

The wide use of banana vibrating screens is due to their high efficiency, large capacity, uniform screening, low noise level, and energy savings. They are widely used for their high yield screening due to their efficiency and exceptionally low noise level.

Additional reading:
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If you want to learn more, please visit our website Shitai.

The common types of vibratory screeners listed above are a sampling of some of the separators that are used by manufacturing for the separation process. In many cases, separation operations require a custom form of separation for material that does not fit the paradigm of traditional vibratory separation methods. From their initial use as a tool for mining, vibratory screeners have rapidly spread to several industries and found unique and critical use.

Leading Manufacturers and Suppliers

Chapter 4: Separation Processes

The many varieties of materials that are presented for the separation process require specific methods in order to be separated properly since one method of vibratory separation does not apply to all materials. Of the many methods used to separate materials for recycling, cleaning, or manufacturing, size separation is one of the most common and widely used. It is restricted to dry materials that can be easily inserted into the process.

Separation by Size

Separation by size is a grouping process that involves gathering like materials together according to their size. Vibration screen sifting separators can have up to five screens that can produce four to six fractions. Although particle classification is affected by shape and density, separating material size is commonly used. The material flows through a screen, stack of screens, or sieve. Material that passes through the screen or sieve is referred to as being under sized while material that remains on top is referred to as over sized.

Each of the screens used in the process are identified by a mesh number, which is a reference to the number of openings in the mesh. Higher mesh numbers refer to meshes with smaller openings for smaller sized particles. Regardless of the mesh number, all of the openings in the mesh are the same size. Meshes or screens are horizontal or at an angle, which is determined by the characteristics of the material being screened.

Scalping

Scalping is a screening method that is also a size separating method that is used in mining, recycling, waste management, and aggregate industries. Unlike size separation that separates particulate matter by size, scalping is designed to take large particles and break them down for separation. As the separator vibrates, materials break apart allowing small broken particles to settle into a lower level or deck of the separation process.

In order for the process to be successful, the scalping screens have to be exceptionally strong, durable, and sturdy to endure the constant motion and break up process. Stainless steel, carbon steel, and highly durable grades of aluminum are used to manufacture scalping vibratory machines.

Gravity Filtering

Gravity filtering, also known as gravity filtration, filter sieve, or filter sifter, is a method used to remove impurities from solutions by pulling liquids through a filter. It is a vibratory method that is used to separate solids from slurries or dewatering. Vibratory screeners used for this process have large outlet channels for rapid discharge of the separated liquid. They are designed to process 400 kg up to 1200 kg (882 lbs. up to 2646 lbs.) of slurry or powder material per hour.

Several of the types of circular vibratory screeners are used for the gravity filtration process. It is a very basic process and requires only one deck and one screen.

Chapter 5: How are Vibratory Screeners Used

Vibratory screeners are a tool that is used in any industry that is involved with powders, fluids, granular material, and chemicals. In many cases, they are a necessity for removing contaminants or organizing raw materials. Vibratory screeners have found wide use in the recycling industry as a means for collecting recyclable materials from general waste.

Food and Beverage Industry

The separation of materials is an essential need of the food and beverage industry. This is especially true in the preparation of ingredients. The wide use of vibratory screeners includes preparing ingredients for packaging, screening tea, straining juice, the production of flour for the correct consistency, and removing lumps from icing sugars.

Mining

Vibratory screening has been used for many years in the mining industry. They originally were operated manually by shaking a box with wire in the bottom. As technology has advanced and more sophisticated methods have been developed, modern vibratory separators are automated and used to remove dust from minerals. Vibratory sifters are cost effective, efficient, and labor-saving devices that assist in producing high quality minerals.

Recycling

Since the increased concern about the environment has become a predominant issue, vibratory screeners and separators have become an essential tool for separating simple waste material from recyclable materials. They are capable of taking huge piles of seemingly useless materials and removing metals, plastics, and other materials that can be recycled and remanufactured.

Pharmaceuticals

The mixing and blending of chemicals to produce medicines produces dust and moisture that has to be removed before a product can be prepared for mixing and packaging. Vibratory screeners and sifters are used to purify and clean medicines before they are ready for delivery.

Agriculture

The preparation for shipment of raw products for the agriculture industry involves the removal of dust and water and separating items that are the wrong size or quality. The separation process involves classifying and categorizing grains, beans, crops, and seeds and involves a long list of common raw vegetables, nuts, and condiments.

• Rice
• Legumes
• Peanut beans
• Kidney Beans
• Coffee Beans
• Corn
• Sunflower seeds
• Sesame seeds

• Canola
• Wheat
• Soybeans
• Oat
• Olives
• Barley
• Peppers
• Nuts

• Basil
• Cauliflower
• Ginseng
• Potato
• Onion
• Jalapenos
• Fertilizer
• Peas

• Garlic
• Cotton
• Rye
• Almond
• Alfalfa
• Sugar beets
• Sorghum
• Vegetables

The few industries listed above are a small sampling of the many industries that depend on vibratory screening as an essential part of their processes. With the rapid growth of technology and the ever growing need to improve the quality of products, vibratory screeners, separators, and sifters are being used in more and more applications.

Chapter 6: How to Choose a Vibratory Screener

The endless number of vibratory screening devices can make it difficult to choose the correct separator for a specific application. It is essential that the separator that is chosen meets the requirements of an application and the type of material to be separated. The right choice depends on several factors that can be discussed with a vibratory screener manufacturer who will provide guidance, literature, and advice regarding their equipment.

Vibration Frequency

Isolating the proper frequency of vibration for a vibratory separator is essential for a successful separation process. Too high frequencies or too low frequencies can be damaging or unproductive and inefficient. The frequency is connected to the force of the vibrations, which has to be in the correct range.

Types of Screen

There is a lengthy list of screen types that are used with vibratory separators that vary by porosity range, opening sizes, and percentage of open area. In order to assist in making the proper screen choice, manufacturers have engineers that assess the needs of a customer and provide a selection of screens that matches the application.

Location of Equipment

There are two factors that have to be examined when placing a vibratory screen sifting separator, which are level of noise and the foundation. A vibratory separator sets on springs that are constantly in motion during the operation of the machine. Where a vibratory separator is placed must be able to withstand the thrashing about of the machine. Additionally, most vibratory screeners produce a great deal of noise during processing. They should be located in areas away from uninvolved workers, and where the sounds of a vibratory separator do not reverberate off walls.

Type of Excitation

The direction and types of excitation need to be determined since vibratory separators can generate gyratory movement in multiple directions. Additionally, it is important to decide if the excitation is going to be horizontal, vertical, rotational, or a blend of the various types.

Frequency of Loads

Vibratory separators are heavy duty pieces of equipment that are designed to operate in a wide variety of conditions. Their capacity varies in accordance with their size and the types of materials to be separated. Mining operations require exceptionally durable and dynamic vibratory separators while food and beverage separators may not require such strength. In all cases, the constant motion and excitation places stress on a vibratory screen sifting separator. As the size of the loads increase, the amount of demands placed on them also increases. Determining the size of the loads and their frequency helps determine the necessary size of a vibratory separator as well as its load requirements.

Production Flow

All of the steps listed above may be moot if the chosen vibratory screen sifting separator does not fit into the flow of production. In many cases, vibratory separators provide necessary materials for further operations, an aspect of the process that has to operate quickly, smoothly, and without delay. Production engineers can provide efficiency data as a guide as to which vibratory screen sifting separator will best fit into a production process.

Conclusion

• A vibratory screen sifting separator separates bulk solid materials from solids and slurries using inertial vibration that causes various sizes of particles to pass through openings in a screen or move across the surface of the screen.
• The purpose of vibratory screening is to sort 2D materials such as plastic film, paper, cardboard, fibers and 3D materials like containers, plastic bottles, cans, stone, and wood. Once the materials are sorted, they can be collected separately from the screen openings.
• At the beginning of the Great Depression, it was discovered that gyratory motion screens provided greater efficiency and accuracy for the separation process.
• The types of vibratory screeners include a long list of devices each of which is designed to efficiently complete the separation process. The many variations, which are constantly changing, is due to the types of materials that are sifted, screened, and separated with each type of material necessitating some form of special handling.
• The multiple decks of linear and circular vibratory separators makes it possible for both types to separate two, three, four, or more sets of materials into fractions at a very high level of efficiency.

Leading Manufacturers and Suppliers

Basic concepts of vibrating screens: What they are, what they are for and how they work.

Basic concepts of vibrating screens: What they are, what they are for and how they work

What are vibrating screens and which are its main applications for use

Also called simply screens, a vibrating screen is formed by a vibrant chassis that supports in its interior one or several surfaces or elements of screening.

The screens serve to classify the different particles by size, starting from a bulk product in a continuous process. The inlet material (the raw product) advances from the part where the screen is fed to the opposite end in which the particles come out separately according to their size, shape or density. There are also vibrating screens that are loaded by the center and the product moves radially to the outputs that are on the periphery.

For the correct advancement of the product it is necessary that the process is continuous, and it is due to the vibration if the screening surface is horizontal. Most of the screens have a certain inclination in such a way that the advance movement of the product is due to a combination between gravity and vibration.

Screening elements

The screening elements are flat or slightly curved surfaces having perforations of a certain size such that when a product is poured in bulk on the element it only passes those particles whose size is smaller than the size of the perforations.

The screening elements can be a metallic or nylon wire mesh, bars that pass material between them, metal sheet with circular, square or hexagonal perforations, more or less rigid sheets of rubber or polyurethane with perforations.

The type of element is chosen according to the application, nature of the product, size and shape of the particles, abrasivity, adhesion, humidity and temperature.

A screen can have several screening elements on top of each other forming different floors. In this case, the floor with the larger perforations is placed in the upper part and successively in lower floors the elements with smaller and smaller perforations are mounted. In this way each particle is trapped between the floor that has cut points (openings) greater than the particle and the floor that has smaller cut points.

Screening efficiency is much higher with vibrating screens

Traditionally there have been non-vibrating screens consisting of a fixed mesh with a lot of inclination. When introducing the vibration, the product shakes and the particles jump without sliding on the screening surface. Each jump is an attempt of the particle to pass through a hole and the probability of this happening is much greater if the machine vibrates. In other words, the effectiveness is much greater.

When a particle jumps and falls again it can do so in a hole or an area where there is no hole. If the screening element is a wire mesh, the particle can fall on the wire or on another particle and not squeeze through the hole it should. This is why no screen has an efficiency of 100% because it would require an infinite number of jumps so that all the smaller particles that the holes actually leak.

The concept of screening efficiency is clear: it is the percentage by weight of the particles that actually filter through the holes divided by the total that should be screened.

Production capacity of vibrating screens

The more quantity of product you intend to classify, the more surface you need for screening. The most immediate symptom that a screen has become too small is that it decreases its effectiveness because it simply does not fit so many particles through the holes.

On the other hand, the smaller the size to be classified, the more surface is needed since the smaller holes, the less quantity of product can pass through them.

Vibration frequency in vibrating screens

As a general rule for large classifications, low frequencies and large vibration amplitudes are preferable and for fine classifications high frequencies and small amplitudes. In other words, if the particle is large, a slow and wide movement is better in which the particle gives few jumps but large and if it is small it is better than many jumps but smaller. It is a question of the particle not passing several single jump holes.

As a general rule for large classifications, low frequencies and large vibration amplitudes are preferable and for fine classifications high frequencies and small amplitudes.

Importance of the correct feeding

In the screens, as in any sorting machine, it is necessary to take advantage of the entire width of the work surface from the beginning of it. If the product falls “piled” on the screening surface, the particles of the top of the pile will not touch the mesh or the screening element until the pile disappears by the vibration. By the time this happens, it will already have traveled half way of the surface. In other words, we waste surface with a very important loss of production and also the area where the pile is made will receive severe wear with the consequent extra maintenance expenses. It also increases, especially with products of low density, the risk of jams if the pile takes a lot of height. This makes no sense and it is not acceptable for correct screening.

That is why it is essential to pay attention to the implementation and design of the ducts that pour the product on the screen and use auxiliary means as vibrating distributors if necessary.

Good screens and bad screens

A good vibrating screen must be reliable, minimize wear and maintenance and have a strong vibration as any vibrating machine that boasts: the more it vibrates the better it goes, that is, it gives more production and efficiency.

On the other hand, most of the “bad” screens are not really bad but inappropriate to use: If the product is wet and sticky, it will stick to a metal screening element rather than a polyurethane screening element. If it is dry and fine, the screen should be dust-tight. If it is a matter of screening large and heavy particles, the screen should be very robust. If it is very robust and used with fine products, it will consume more than necessary in electricity and maintenance costs (but that shouldn’t pose as a problem because business energy suppliers can be compared at Utility Saving Expert).

The combinations are endless, and a good selection, suitable for use at first, will make the user does not have to remember this machine again in life, or at least until he needs to install another screen.

For more information, please visit Vibrating Screen Mesh Manufacturers.