Because of their unique design they provide operators a number of benefits. We’ll highlight additional details about flip flop screen design, usage, and benefits below.

Flip-Flow Screen Design & Working Principle

Vibrating flip-flow screens are increasingly employed in materials screening and preparation applications. This is due in large part to their high efficiency. In principle, a flip-flow screen is a subclass of other high frequency vibratory screens.

Flip-flow screens work through the combination of a double vibration principle and a flexible polyurethane-type screen media. The dual-vibratory forces work to apply linear acceleration to the materials traveling across the screen. Vibrations are simultaneously applied to the elastic screen, which rapidly stretches and relaxes. The stretching and relaxing of the screen transfers energy to the material, causing it to “jump” or “pop”. This secondary vibration, in turn, enhances the separation of materials.

How Are Flip-Flow Screens Used?

You can find this screening equipment used across a large number of industries. They’re most often used to screen difficult materials used in the manufacturing process for everything from sand, concrete, and compost. However, flip flop screens are also used in municipal solid waste processing.

Screening Difficult Materials

Materials like municipal solid waste, wood, and other organic biomass are notoriously difficult to screen. Other equipment, like trommels, tend to handle these materials poorly. This is because their drum, which spins and screens the materials passing through it, regularly becomes clogged with dense, higher moisture particles.

Flip flop screens vibrate at a high frequency which transfers constant energy into the material particles. This helps prevent the materials from clumping or sticking to the screen media. In addition, the media itself, a flexible polyurethane mat, makes for a poor surface for materials to adhere to.

Other Common Uses

Flip-flow screening equipment is used in other applications, as well. These machines can easily screen aggregate like coal or valuable minerals like gold ore. They’re also used to classify and dewater very fine materials like natural riverbed sand and manufactured sand.

Benefits of Flip-Flow Screens

Flip-flow screeners offer a number of benefits over other equipment. Their compact design is particularly advantageous in both reducing machine footprint and increasing operational efficiency. Because most models require fewer moving parts than alternative screening equipment, flip flop screens are much more modular.

High Screening Efficiency

In addition, both as a result of their polyurethane screen and streamlined design, they’re less prone to mechanical wear and tear, and are generally easier to maintain. This latter point is of importance when screening difficult materials.

Wet and sticky materials in particular, like consumer recyclables and biomass, can clog and blind conventional screen media. The elastic mesh media used in flip-flow screens is ideal for these materials. However, the media is as effective for other common materials from glass and scrap to fine-grained minerals and slag.

Improved Screen Media Durability

As an added advantage, the screening media itself is generally longer lasting. The elastic mesh is durable, less prone to blinding or binding, and is simple to replace. This helps to reduce downtimes and mitigate ongoing maintenance costs.

Lastly, the elastic mesh screen mats are self-cleaning, as the high acceleration forces directed to the mats keeps the screening surface clear of debris. Again, this offers an added benefit of less downtime during routine maintenance.

The BIVI-TEC® Flip-Flow Screening Solution

The BIVI-TEC® flip-flow screen was developed to screen even the most challenging materials. Its dual-vibratory screening process coupled with high-quality elastic mesh mats are capable of handling high-moisture materials.

Manufactured by AEI, the BIVI-TEC® rugged construction requires less maintenance, reduces downtime, and uses less energy than alternative screening equipment. Whether you need a long-lasting machine for screening aggregate or a plant able to efficiently separate C&D waste – the BIVI-TEC® can deliver. Looking for a flip-flow screen for sale? Contact our sales team to learn more and request a quote today!

The post What Are Flip-Flow Screens? appeared first on AEI Screens.

The post Benefits of Upgrading Your Screening Equipment Over Repairing Your Current System appeared first on AEI Screens.

The post Manufactured Sand: A Two-Pronged Approach – the BIVITEC® appeared first on AEI Screens.

The post Manufactured Sand: A Two-Pronged Approach – the Ortner® 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.

The post Mechanical Screening 101: Your Guide to Screening Equipment appeared first on AEI Screens.

The post Keep it Out of the Landfill: Composting with the BIVITEC® Screen appeared first on AEI Screens.

The post Ortner® Sand Classifier is a Very Diverse Machine appeared first on AEI Screens.

In 2013 AEI was challenged to screen high-silica gold ore at a green-field site located in a very wet, humid climate with plenty of clay. Other screen manufacturers had already turned this project down.  The customer had been told that dry screening was not an option; that this would have to be a wash screen application using thousands of gallons per minute of water. AEI was asked to present a solution that would prove the others wrong.

In the spring of 2014 the plant began operation with two KRL/DD(B) 2400×8 BIVITEC® screens (8’ x 27’). A jaw crusher feeds the primary BIVITEC® which separates the gold ore at 3/8”. The over-size is sent to a cone crusher which feeds a second BIVITEC®, also separating at 3/8”.  Finally, the over-size is recirculated through a finishing cone crusher and returned to the secondary BIVITEC®.

The system is handling 250-300 tons per hour of raw gold ore at moisture levels >10% with no blinding or carryover problems. AEI hopes to help this customer increase production with an identical second plant in the near future.

Learn more about the BIVITEC® and its capabilities for your plant.

The post Screening Gold Ore with BIVITEC® appeared first on AEI Screens.