Meanwhile, the BIVITEC® banana design has a unique curved deck that’s paired with innovative flip-flow technology. It’s engineered to maximize efficiency, improve stratification, and handle the toughest materials with ease.

Understanding Standard Vibrating Screens

These screens have a relatively simple design: a flat, horizontal deck vibrates at high speeds to separate materials based on size. As material flows across the deck – smaller particles fall through the openings, while larger particles continue to the discharge end.

These screens have a compact design and offer a controlled material flow, operating on a principle of precision conveyance. Their most common and effective application is as a finishing screen in aggregate and mining operations. After material has been crushed and washed, the horizontal screen provides the high accuracy needed to create precise final product specifications for concrete, asphalt, and other high-value applications.

However, standard vibrating screens may struggle with blinding and plugging as well as stratification efficiency, as the flat deck doesn’t always encourage material to spread evenly or separate quickly.

Compare inclined versus horizontal screens.

The BIVITEC Screen’s Banana Design

Unlike flat horizontal screens, the banana design features a steeper angle at the feed end that gradually lessens toward the discharge. This geometry allows material to move more efficiently across the deck while maintaining a consistent bed-depth from start to finish.

By keeping the bed-depth even, the Banana BIVITEC® maximizes tonnage capacity without sacrificing accuracy. Combined with the dual-vibratory, flip-flow system and flexible polyurethane screen mats of the BIVITEC® screen — engineered to eliminate blinding and clogging — the banana design offers greater efficiency, reduced downtime, and higher throughput compared to standard screens. 

The BIVITEC® is the definitive solution for applications defined by difficult, variable, and high-moisture feed materials.

• Recycling (C&D, MSW, ASR): The BIVITEC® is uniquely capable of screening materials that would instantly paralyze a horizontal screen, such as removing high-moisture fines from construction and demolition (C&D) waste, classifying auto shredder residue (ASR) and its associated fluff, and handling sticky incinerator ash.
• Compost and organics: The BIVITEC® is the ideal technology for screening compost, wood waste, peat moss, and other organic materials that are inherently fibrous, leafy, and tend to mat together on a screen deck. The high-G acceleration actively breaks up these clumps, ensuring a consistent and high-quality final product.  
• Difficult minerals and aggregates: In the aggregate and mining sectors, the BIVITEC® excels where the raw feed is contaminated with high percentages of silt, mud, and clay. It is a leading solution for producing manufactured sand and agricultural lime, where fine particles and moisture are inherent to the process.  
• High-moisture materials: The BIVITEC® is the definitive solution for any application where high or variable moisture content is a persistent challenge. Its flip-flow action eliminates the need for expensive and energy-intensive solutions, like heated decks or less effective ball decks, providing reliable performance in all weather conditions.

Ready to see how the BIVITEC® screen’s banana design can improve your operation? Request a quote today or contact our team with any questions — we’re here to help you find the right solution.

The post What Makes the Banana BIVITEC® Different from a Standard Vibrating Screen? appeared first on AEI Screens.

Understanding the fundamentals of industrial screening is essential for optimizing performance, reducing downtime, and achieving long-term success in any material-handling operation.

What is Industrial Screening?

Industrial screening is the process of separating materials into different size fractions or categories based on specific physical characteristics, such as size, shape, or other properties. Its main purpose is to ensure that only materials meeting certain specifications proceed through production or are prepared for sale, while oversized or undersized materials are filtered out for further processing or disposal.

The basic principle behind screening involves passing bulk materials over or through a screening surface — such as mesh, perforated plates, or vibrating screens — so that particles smaller than the openings fall through, while larger particles are retained. In some cases, screening also helps classify materials based on shape or density, depending on the equipment used.

Industrial screening is widely used across various sectors and handles a broad range of materials. Common examples include:

• Compost and soil in waste management
• Minerals and ores in mining
• Refuse-derived fuel (RDF) in energy production
• Wood and gravel in construction

Different Types of Industrial Screening Equipment

Vibrating Screens

These screens use a vibrating motor or mechanism to move material across a screening surface, encouraging smaller particles to fall through openings while larger ones move along the surface. They can be configured in single or multiple layers to handle different sizes in one pass. Typical use cases include:

• Aggregates and mining (sorting gravel, crushed stone, ores)
• Recycling (separating plastics, metals)
• Food processing (sorting grains, powders)

Trommel Screens

Trommels consist of a rotating cylindrical drum with perforated sides. As material enters the drum, it tumbles and rolls, allowing smaller particles to fall through the holes while larger pieces exit the other end. Typical use cases include:

• Compost and soil screening
• Municipal solid waste processing
• Refuse-derived fuel (RDF) preparation
• Sand and gravel separation

Disc Screens

Disc screens use a series of rotating discs mounted on parallel shafts. The spaces between the discs allow undersized material to fall through while larger or elongated pieces are carried forward. The rotating motion also helps break up clumps of material. Typical use cases include:

• Waste wood and biomass screening
• Recycling (especially bulky materials)
• Pulp and paper industry (removing contaminants)

Flip-Flow/High-Frequency Screens

High-frequency or flip-flow screens have flexible screening mats that are tensioned and loosened in a rapid, wave-like motion. This aggressive movement helps prevent material from clogging the screen and enhances the separation of fine or difficult-to-screen materials. Typical use cases include:

• Wet or sticky materials (e.g., clay, compost)
• Fine particle separation (e.g., sand, silica)
• Mining (separating fine ores)

Key Components of Screening Equipment

Screen Media

This is the surface where material separation actually occurs. The choice of media determines the screen’s effectiveness, durability, and suitability for different materials.

• Wire mesh: This is a common choice for dry, granular materials, like sand or gravel. The mesh offers good precision and is available in a wide range of aperture sizes, but it can wear out faster with abrasive materials.
• Polyurethane panels: Known for high durability and flexibility, these are ideal for wet, sticky, or abrasive materials and are widely used in industries, like recycling and mining. Polyurethane resists clogging and extends wear life.
• Perforated plate: Made from steel or other metals, this is a rigid option suited to coarse materials and heavy-duty applications. It withstands impact well and is often used when strength and longevity are key.

Drive Systems

Powers the movement of the screen to enable material separation. The type of drive affects the screening efficiency and material flow.

• Vibratory motors: These create linear or circular vibrations and are widely used for many screening applications. They’re simple and effective for dry materials.
• Exciter mechanisms: They offer more powerful and customizable motion and are often found in large, heavy-duty screens.
• Rotary/drum drives: They’re used in trommel or rotary screens where the screening is done by rotating the drum. These drives are suitable for bulky or mixed-material streams.
• Flip-flow drives: Specialized systems, like the BIVITEC®, use flexible mats and high-frequency vibration to tackle wet, difficult-to-screen materials.

Feed and Discharge Arrangements

Ensures smooth entry of material onto the screen and efficient exit of separated fractions.

• Feed hoppers/chutes: Even, controlled feeding is critical for maximizing screen performance. A well-designed feed arrangement prevents overloading and promotes even distribution across the screen.
• Discharge chutes/outlets: Separate oversize and undersize material streams efficiently. The discharge system should prevent blockages and spillage and direct materials to their next processing step.
• Bypass or oversize routes: Some systems include bypass options to allow certain materials to skip the screen or be reprocessed if needed.

Benefits of Effective Industrial Screening

• Enhanced product quality: Screening ensures that only in-spec material moves forward in production. This reduces contamination and improves the consistency and quality of the final product.
• Improved process efficiency: Efficient screening removes unwanted fines or oversize material early in the process, reducing unnecessary wear on downstream equipment (like crushers or conveyors). This streamlines operations and helps maintain optimal material flow, saving both time and energy.
• Maximized resource recovery: Precise screening boosts recovery rates by ensuring valuable materials are properly separated from waste streams. This enhances profitability and supports sustainability goals.
• Lower maintenance and downtime: Well-designed screening systems with appropriate screen media reduce blinding, clogging, and excessive wear, which means less frequent maintenance and fewer unexpected stoppages.
• Flexibility and scalability: Modern systems can be adjusted or upgraded with different screen media or modular components, making it easier to handle changes in material streams or production demands. This flexibility helps future-proof your investment.
• Compliance with industry standards: For industries with strict regulatory requirements, effective screening helps ensure compliance by delivering consistently clean and well-classified material outputs.

Common Challenges

• Screen blinding and clogging: Fine, sticky, or moist materials can block screen apertures, reducing efficiency and causing throughput delays.
• Wear and tear on screen media: Abrasive materials (like minerals, sand, or glass) can quickly wear down wire mesh or other screen surfaces, leading to frequent replacements and potential downtime.
• Material flow issues: Uneven feeding, surges in material volume, or inconsistent particle sizes can lead to inefficient separation and overloading of screens, which stresses both the screen media and the mechanical components.
• Handling mixed material streams: Recycling and RDF facilities often deal with mixed or unpredictable materials. This variability can compromise screening accuracy and make it hard to maintain performance without frequent adjustments.
• High energy consumption: Some screening systems — especially high-capacity or high-frequency designs — can be energy-intensive, increasing operational costs if not optimized.
• Maintenance and access difficulties: In tight or older facilities, accessing screens for maintenance or changeouts can be physically difficult, increasing labor time and the likelihood of prolonged downtime.

AEI’s Industrial Screening Solutions

The BIVITEC is particularly beneficial in industries where wet, sticky, or tricky materials pose a challenge — like recycling, composting, waste-to-energy (RDF), and mining — offering a more reliable, low-maintenance, and long-lasting screening solution. Its standout feature is its dual-vibratory, flip-flow action, which uses flexible polyurethane mats that move dynamically. This keeps sticky, damp, or fine materials constantly agitated, virtually eliminating blinding and clogging.

The Freedom Disc Screen is best suited for high-volume, mixed-material applications, like construction and demolition (C&D) waste, mulch and biomass screening, and single-stream recycling — where its anti-wrapping technology, durability, and precision help overcome common screening headaches. With heavy-duty, abrasion-resistant materials used for the discs and shafts, the Freedom Disc Screen is built for longevity.

If you have any questions about our equipment, please don’t hesitate to reach out to us.

The post Industrial Screening 101: Understanding the Basics and Benefits appeared first on AEI Screens.

In this article, we’ll explore how BIVITEC screens can help you meet the challenges of industrial compost production.

What Makes Commercial Compost Screening Difficult?

Compost screening presents unique challenges that push traditional screening equipment to its limits. Feedstock is often wet, sticky, and fibrous, which can quickly blind conventional screen media and reduce throughput. Seasonal variability adds another layer of complexity — materials may be heavier and wetter after rain or snowmelt, then dry and inconsistent during warmer months, making it difficult to maintain consistent screening performance.

Contaminants (such as plastics, wood fragments, and oversized organic material) further complicate the process, increasing the risk of clogging, damage, and downtime. As a result, many composting operations experience high wear rates and frequent maintenance when using traditional screens, leading to lost production time, higher operating costs, and inconsistent end-product quality.

Throughput in Industrial Composting

In large-scale composting operations, throughput is an important factor that directly impacts productivity. 

BIVITEC screens are engineered with a focus on optimizing throughput, featuring a large screening surface area and multiple sizes of screen openings. These design elements contribute to the efficient handling of high volumes of composting materials, ensuring a continuous, streamlined process.

Uninterrupted Operations

BIVITEC screens are designed for durability and longevity, utilizing rugged materials and components that withstand the rigors of industrial environments. This results in minimized downtime and maintenance requirements, providing operators with the confidence of a reliable compost screening solution.

Elevating Compost Quality

Contaminants in compost piles (like plastic, glass, and metal) can negatively impact the quality of the compost, lower its value, and hinder its intended use.

BIVITEC screens excel in providing precise screening, removing contaminants, and achieving a consistent particle size distribution. The result is a higher-quality compost that meets industry standards and is suitable for various applications, from agriculture to landscaping.

Read about how the Bivitic has helped companies and municipalities improve composting operations.

Handling High-Moisture Materials

One common challenge in composting is dealing with excessive moisture that can lead to anaerobic conditions, unpleasant odors, and difficulties in turning the compost.

For composting operations looking for durable machines built to handle wet materials, AEI Screens is one manufacturer worth considering. BIVITEC screens are adept at handling materials with varying moisture content. Their design accommodates the nuances of high-moisture composting, contributing to the overall efficiency of the compost production process.

BIVITEC vs. Traditional Compost Screening Equipment

• Compared to trommel screens: BIVITEC systems are less prone to blinding and plugging when handling wet, sticky, or fibrous compost materials. Trommels rely on rotating drums and fixed openings, which can quickly clog and require frequent cleaning, increasing downtime and labor costs.
• Compared to conventional vibrating screens: BIVITEC’s flip-flow technology offers far superior performance with challenging organic material. Traditional vibratory screens struggle with moisture and variability, often requiring higher energy input and frequent maintenance to maintain throughput.

AEI’s BIVITEC Screen

AEI Screens manufactures the BIVITEC. This durable machine is designed to handle difficult material streams commonly found in commercial composting — including wet, sticky, and highly contaminated input — by continuously flexing the screen surface to prevent blinding and buildup.

Ready to enhance your commercial composting operations? Learn more about BIVITEC vibrating screens or contact us with any questions or specifications you need. We’ll even come to you to test the equipment in your operating conditions.

The post Breaking Down the Benefits: BIVITEC Screens for Commercial Composting appeared first on AEI Screens.

Electronic waste, often referred to as e-waste, refers to discarded electronic devices as well as components and materials associated with these devices. Because of the quick introduction of new electronics to the global market, many people discard electronic devices after only a few years of use. The most significant sources of e-waste include consumer products such as: 

• Computers
• Speakers
• Mobile phones
• Televisions
• Music players
• Keyboards and other computer peripherals 
• Home appliances

The U.S. is the world leader in producing electronic waste, followed closely by China. 

Electronic waste is an increasing segment of the larger waste stream, and safely processing this waste is essential to human health, the environment, and even the economy. However, processing e-waste effectively poses significant challenges for recyclers and materials recovery facilities (MRFs).

In this blog, we share projections for the future of e-waste, how it may impact the environment, and change the global economy.

E-Waste Growth Projections 

There are growing economic benefits of employing a circular economic model for e-waste. According to recent projections, more than 50 million tons of e-waste are discarded each year. Of this waste, only about 20% is recycled.

Every year, the amount of electronics that are discarded grows by 2.5 million tons. E-waste production is expected to grow exponentially in the coming years. By 2030, the e-waste industry is expected to grow to nearly 75 million tons, more than doubling the amount of waste currently produced annually. This growth will likely be attributed to more individuals purchasing products with shorter life cycles and fewer repair options for older electronics. 

The Health & Environmental Impacts of E-Waste

Electronic products can help improve living standards worldwide by providing information, communication, and educational opportunities. However, the growing global demand for electronics quickly outpaces the industry’s capacity to dispose of or recycle outdated products safely.

Electronic devices are typically not biodegradable and will not break down naturally or safely when discarded in landfills. Discarded e-waste often piles up in the environment, contaminating habitats and leaching chemicals that are harmful to people, animals, and plants. Further, when e-waste is exposed to extreme heat, harmful chemicals are released into the air. The release of pollutants and toxic chemicals is one of the biggest environmental challenges associated with electronic waste management. 

Screen e-waste more efficiently.

Challenges of E-Waste Screening

Recycling or otherwise breaking down electronic waste is a challenge for MRFs. There are several reasons why e-waste is difficult to process.

Product Complexity

The product complexity of many types of e-waste makes efficient material separation and sorting difficult.

Electronics are made up of multiple materials, including:

• Glass
• Various plastics
• Ferrous and non-ferrous materials

To process e-waste, recyclers must sort the smaller components electronics are composed of and avoid mixing different materials. There are multiple steps in this process, which can include:

1. Dismantling electronics to remove batteries and other hazardous waste. 
2. Shredding or crushing the remaining electronic components into smaller sizes.
3. Separating fine materials, like small plastic or glass pieces, from larger scrap metals.
4. Sorting the metals into various types, e.g. separating ferrous from non-ferrous.
5. Removing glass fines from plastics fines. 

Because electronics are increasingly complex, each of these stages is resource-intensive. Some stages, like dismantling, require human labor to complete. Other stages, like the separation of fines, are accomplished using material screening equipment.

Process Efficiency   

Another inherent problem with the e-waste separation process becomes obvious: efficiency. With the increased production of consumer electronics, e-waste generation continues to rise. As a result, MRFs must continually adapt to increased production demands.

Processing outputs must increase to match demand, and cost-efficient processes must be developed to decrease the cost of sorting e-waste. Sorting and screening solutions must be able to handle large volumes of waste and do so with minimal downtime.

Further, because the global market for electronics constantly shifts, equipment that can minimize recycling production costs is vital. 

Material Contamination

High product complexity and inefficient screening lead to an obvious e-waste issue: contamination. While the global generation of e-waste is on the rise, many of the world’s largest buyers of recyclable materials are tightening their regulations. 

Higher thresholds for material purity are being established, placing a heavier burden on MRFs to produce a cleaner product. This means less material mixing and more stringent processing. 

Solutions are needed that offer the capabilities of high volume processing coupled with an equally high degree of e-waste screening efficiency. Many traditional technologies are incapable of meeting these requirements. 

Related Article:

Three Ways MRFs can Reduce Material Contamination

Lack of Uniform Regulations

A critical hurdle in addressing the e-waste challenge lies in the absence of uniform international regulations. Varying policies and standards across different regions make it challenging for industries to establish standardized recycling practices. The lack of a cohesive global approach hampers the efficient management of e-waste, as different jurisdictions grapple with diverse compliance requirements.

Limited Infrastructure and Awareness

Despite the escalating volume of e-waste, the infrastructure for its proper recycling remains inadequate on a global scale. Many regions lack dedicated facilities equipped to handle the complexities of e-waste, leading to improper disposal methods, such as landfilling or incineration.

Additionally, there’s a lack of awareness among consumers regarding the importance of responsible e-waste disposal.

AEI’s E-waste Screening Solutions

Aggregates Equipment, Inc. is a leader in e-waste and scrap metals screening. We custom engineer screening equipment to meet the demands of today’s waste industry.

Our BIVITEC flip flow screen uses a dual vibratory principle to efficiently sort metallic or plastic fines. The BIVITEC’s polyurethane screen panels are durable and resistant to plugging and blinding. Meanwhile, AEI’s Freedom Disc Screen utilized HARDOX discs to efficiently size larger fines, without the downtime of trommels or other traditional screening equipment. 

Contact our sales team for more information about our e-waste screening equipment or request a quote to get started today!

FAQ

Why is E-Waste Recycling more Complicated than Other Types of Recycling?

Unlike materials like cardboard or plastic, electronic devices are made from a mix of metals, plastics, glass, and chemicals—often layered together. Efficient separation and safe handling require specialized equipment and processes.

How does E-Waste Harm the Environment?

Improperly disposed e-waste can leach toxic chemicals into soil and water, pollute air through burning, and release greenhouse gases. It can also harm ecosystems and contaminate local food and water supplies.

How can Screening Technology Improve E-Waste Recycling?

High-performance screening equipment can:

• Reduce clogs and downtime when separating sticky or fine particles
• Improve material purity by separating valuable metals from contaminants
• Increase throughput and efficiency in the recycling process

The post The Challenges of E-Waste Recycling appeared first on AEI Screens.

Trommels are one of the most commonly deployed screens for a number of jobs – from ores and minerals to aggregates, compost, and municipal solid waste. However, despite their wide usage, trommel screens have a number of disadvantages that can make them less than ideal.

What is a Trommel Screen?

Trommel screens (also known as drum screens or rotary screens) are cylindrical drum-like machines used for sorting and separating materials based on size. It consists of a cylindrical drum that rotates around its axis, and material is fed into one end of the drum. As the drum rotates, the material tumbles and rolls, allowing smaller particles to fall through the openings in the drum while larger particles are retained. Trommels are often used for:

• Compost screening
• Topsoil and mulch separation
• Construction and demolition waste sorting
• Recycling operations
• Mining (e.g., separating ore)

Diving into the drawbacks of trommel screens will help you make informed decisions for your specific application needs.

Low Efficiency

While trommels are frequently used to process materials, they do so inefficiently. Trommel screens are simple in design.

The advantage of this design is a relatively lower cost. In fact, basic, small trommels can be made at home with relative ease. However, for heavy duty industrial applications, that same simplicity results in an overall inefficient design.

When compared to other solutions, like vibrating screens, trommels simply cannot handle the same volume of materials. While rotating, only a portion of the screen is being utilized for sizing. Comparatively, the entire screen surface of other material screening solutions can effectively size materials. This not only places the trommel drum at a volumetric disadvantage to other screening equipment, but can also lead to additional material flow concerns.

Looking for an efficient screening solution?

Energy Consumption

Trommel screens often have high energy requirements during operation, especially when dealing with large volumes of material. This not only contributes to increased operational costs, but also raises concerns about their environmental impact.

Screen Plugging

When screening multiple particle sizes or when material begins to back up, trommels also have the disadvantage of plugging. Plugging occurs when a larger feed material gets stuck in the screen aperture. This can lead to further plugging or back up of material traveling through the drum.

When a plug happens, it can halt production, in turn lending to additional maintenance. Wet materials, though commonly processed through trommel screens, can cause additional hindrances to the screen.

Screen Blinding

Much like plugging, when sorting wet materials, trommel screens are prone to blinding. As wet feed materials (such as compost or solid waste) pass through the rotating drum, they can begin to clump and stick to the screen. This can cause further materials to build-up, leading to less efficient sorting if not halting production.

Even when blinding does not require immediate attention, it still requires cleaning of the trommel and can lead to additional maintenance. Cleaning of the drum and replacing trunnion wheels and cleaning brushes can be costly.

Drum Damage

Plugging, blinding, or simply regular use can cause damage to the trommel’s drum. While some minor damage is to be expected and can be prevented through proper usage and care, larger damage can be costly. One of the biggest disadvantages of the trommel screen’s design is the inability to replace part of the drum when damage occurs.

In the event that damage is unable to be repaired, the entire drum must be replaced. This is both expensive and can halt further production.

Size and Space Constraints

The large physical footprint of trommel screens can be a hindrance, especially in facilities with limited operational space. Finding suitable areas for installation can be a logistical challenge.

AEI Solutions

Aggregates Equipment, Inc. manufactures screening solutions which overcome the disadvantages of trommel screens. The BIVITEC® Screen operates using a flip-flow principle and features a dual-vibratory process which prevents clogging and blinding.

The BIVITEC® is an ideal screening solution for applications commonly using trommel screens, including sorting C&D waste, roofing shingles, compost, and more. Learn about the benefits of vibratory screens or contact our sales team to request a BIVITEC® for your operation.

The post Disadvantages of Trommel Screens appeared first on AEI Screens.

Read on to learn more about mechanical screening and how material and operating characteristics impact screen efficiency.

View available screening equipment and systems for demanding applications from Aggregates Equipment, Inc. (AEI).

Why Do Materials Need to be Screened?

Processors screen materials for different reasons, often to:

1. Produce a product with a desired particle distribution or characteristics
2. Split a feed stream to separate processing lines
3. Remove fines
4. Remove finished product prior to an additional reduction step

Screening is often given a cursory glance in a process, but it can have a great effect on the capacity of a system and the quality of your products. Often the screen is one of the least expensive pieces of your system, while having an outsized impact on your profits.

Many applications utilize mechanical screening processes for the reasons mentioned above. Below are some of the most common screening applications.

Process control in aggregates and mining

Screens serve as a process control to protect process equipment, possibly a boiler for power generation, or to maintain the finished characteristics of a product such as asphalt or concrete.

Means to split feed stream in recycling and waste

Screening is often used as a means to split the feed stream between separate processing lines. Because of limitations in downstream sorting capacity, whether manual (picking stations) or mechanical (sensor sorters or magnetic separators), multiple processing lines are often required to handle the volume of the feed stream

Plant maintenance and cleanliness

Fine material can be removed from the process and treated separately, greatly reducing maintenance concerns throughout the plant. Fines collect in other machinery, creating health and explosion hazards and ferrous fines create problems in magnetic sortation processes.

Operating cost reduction and increased capacity

There is often a fraction of raw material that is already properly sized. In a size reduction process such as crushing, grinding, shredding or shearing, feeding finished product unnecessarily into a reducer creates avoidable wear and power consumption. Size reduction machines are often the most expensive wear related operating cost in a plant, as well as the largest consumers of power. Pre-screening the material or scalping reduces unnecessary operating costs and increases plant capacity.

If your operation needs efficiency screening, AEI offers industry leading materials screening solutions

What is mechanical screening, and how does it work?

Mechanical screening is the probability of a particle of a given size passing through an opening of a given size. As the size of the particle approaches the size of the opening, the probability of passing that particle through the screen decreases. Conversely, as the particle size decreases and the screen opening increases, the probability of passing the particle increases. Each opening in a screen presents an additional chance for a given particle to pass through. The more openings a particle is presented with, the higher the probability of passing that particle.

In real-world screening, this is witnessed through the particle distribution of the fines product and the coarse product. 100% efficiency does not happen in practice. Screening efficiency is defined as the ratio of the material that should pass through a given opening and the material that actually passed through that opening. In practice, the product distributions will be shaped like a curve. Fine particles pass the quickest with the highest efficiency, while near size particles have reduced efficiency.

When feeding a given distribution of material to a screening machine, there are three main steps to screening performed on a single screen deck.

1. Bed stratification: The activation and agitation of the material through the screen motion or the movement of the material.
2. Crowded screening: This section the smaller particles are in contact with the screen media and begin to pass in volume.
3. Separated screening: In this section, the majority of the undersize material is already removed and the near size material has the opportunity to pass.

Material Characteristics of Screening Equipment

By increasing the screen length, you can increase screen efficiency by providing a longer time and probability for near size material to pass through the screen media.

Every application and material presents a unique challenge for a particular screen. Even the same material at a different location will not have exactly the same characteristics.

Particle Size Distribution

The particle distribution describes the sizes of the discrete particles in any feed stream. The percentage of material at each size will determine the capacity of a given machine. Key factors include the percentage passing the chosen sizing point; the more material required to pass through a screen, the larger the required screen area for the duty. The top-size of the material will also have a direct impact on the material’s screening.

Moisture

There are two types of moisture: surface and inherent. Inherent moisture is the moisture present inside of a material. Surface moisture is the moisture that is coating the exterior of a particle. Surface moisture has the greatest impact on the screening performance of a material.

Particle Shape

The particle shape in both the feed stream and the desired products affects the screen selection for the application, and understanding the type of particle is critical.

Density

Density of the material helps to describe the load and bulk the screening machine must convey. Conveying volume and maintaining effective bed depth are keys to handling low-density materials.

Operating Characteristics

When choosing a machine for a screening application, there are also important operating characteristics that must be considered. These may be present in an existing system or can be incorporated into the design of a system.

Feed Rate

Regular, consistent feed is critical to the proper operation of a screen. Irregular feed will result in the passage of oversize material when the screen load is running at its minimum, or result in carryover of fines when the load is at its maximum.

Bed Depth

The depth of the material on the screen affects the ability of the screen to stratify the material and allow the fines to pass through the deck; this is called bed depth.

Screen Openings

When choosing the opening of a screening surface, there is the nominal size of the screening mesh and the effective size of the mesh. Because of crowding of particles on the screening surface, there is a reduced probability of near size particles passing through the mesh. The nominal size of the mesh is the actual diameter of the opening on the deck. The effective size is the size of the product that the mesh produces. In a given application, the chosen nominal mesh size will produce an effective product size smaller than the nominal size.

The design of the openings on the screen surface helps to determine the efficiency of the machine, the capacity of the machine and the quality of the product. Open area on a screen, the ratio between the area of the holes and the screen surface, helps to determine the screen capacity. By decreasing the space between holes, webbing or wire diameter, the open area may be increased, increasing capacity.

Efficient screening is the quickest return on investment within your plant. Although outshined by processes that physically transform a material stream such as size reduction or color sortation, proper screening optimizes all these processing steps. Because the effect of screening is less observable, it is often overlooked. Do so at your own detriment.

To learn more about mechanical screening processes and equipment, contact AEI with specific questions about your processes or topics that you would like to investigate further. You can also email us at sales@AEIscreens.com or call (717)-656-2131.

Below is a list of references used in compilation of this blog and for additional reading on the topic:

Kelley, Errol and David J. Spottiswood, Mineral Processing Short Course, Colorado School of Mines, June 2012

Kelley and Spottiswood, Indroduction to Mineral Processing, Denver: John Wiley & Sons, 1989.

Vibrating Screen Manufactures Association, Vibrating Screen Handbook, Stamford, 1980.

Korte, DJ, Dry Screening Tests Conducted with BIVITEC® Screen, South Africa: Coal Tech, 2008.

Aggregates Equipment Inc, BIVITEC® Operations and Maintenance Manual, Leola, PA: 2012.

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