Screening is one of the most important parts in aggregate production. It takes place before and/or after the crushing stage (or stages) and produces the specifications required of the final products.

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The purpose of screening is to separate a flow of aggregate particles into uniform sizes. This is accomplished by using Vibrating Screens.

What is a Vibrating Screen?

Vibrating Screens are machines used to separate aggregates by particle size by means of an exciting force applied to the machine. The vibration lifts the material, causing it to stratify, allowing the smaller material to move from the top of the depth of material to the bottom of the material, thus exposing them to the screening surface. 

Types of aggregate Vibrating Screens

There are two main types of aggregate vibrating screens for dry screening applications:

• Horizontal Screens
• Inclined Screens

The primary difference between Horizontal Screens and Inclined Screens is the Inclined Screen uses gravity to help with the flow and conveyance of the feed material.

However, both screens offer advantages for various applications. 

Inclined Screens

Inclined Screens are the most popular for aggregate applications. They are installed on an incline (anywhere from 5-45 degrees depending on the type of screen and the required cut) and employ the use of gravity to propel material down the screen. Since gravity helps to move the material, this type of screen requires low energy and low stroke. 

Horizontal Screens

Horizontal Screens are run flat at zero degrees but can be inclined or declined as much as 10 degrees in either direction. Because they don&#;t rely on gravity to move the material forward, Horizontal Screens require higher energy and a larger stroke.

These types of screens are ideal for low-profile applications where height requirements are limited, which makes them a great choice for portable plants. In stationary plants, they are often used as tertiary or finishing screens. Finer screening applications can greatly benefit from this type of screen. Read more about how McNamara Contracting, Inc. increased tonnage with a McLanahan Horizontal Screen.

Known for their efficiency and reliability, Horizontal Screens offer more accurate particle sizing. The high G-forces required to move the material ensure screen plugging is virtually eliminated, allowing for more continuous open area. The flat orientation of the Horizontal Screen allows material to be retained on the screen longer for higher efficiency. It also makes them a great choice for wet screening applications.

How to select the right aggregate screen

Because screening plays such an important role in producing the required specifications of a final product, it is imperative that the right screen is selected for the job.

Vibrating Screen selection is based on the following factors:

• The maximum tons per hour
• A gradation of the feed material
• The type and weight of material
• The desired size of separation
• Any surface moisture on the material
• Any special operation requirements, including physical characteristics of the feed or product requirements

Sizing Vibratory Screens

Vibratory Screens come in a variety of sizes. They can range from 4&#; to 12&#; wide and 6&#; to 32&#; long. The width of the screen determines the carrying capacity of the screen deck, while the length of the screen determines the overall efficiency of the screen. Typically, the length of the screen is 2.5 to 3 times the size of the width. 

Every manufacturer has its own screen sizing formula. Screens are tailored to an operation based on the following factors:

• Basic capacity &#; how much material is going to pass through a certain opening
• Incline &#; how much of an incline, if any
• Deck &#; not all of the length of the lower decks may be utilized, as material has already traveled down some length of the upper decks before reaching the lower ones
• Oversize &#; how much material should go over the deck
• Half size &#; how much material is half the size of the media opening With a high percentage of half size, the probability of the material passing through the screen openings will be higher, and the screen will be that much more efficient.
• Slot &#; how large the openings in the screen are
• Condition &#; applies to both the feed material and the atmosphere around the plant. Is the material wet and sticky? Does it have a high percentage of clay? What is the temperature outside? Is it a wet or dry climate?
• Shape &#; Round or cubical particles have a higher chance of passing through the screen openings than a flat, elongated particle that has to find just the right position to fall through
• Weight &#; the density of the material
• Open area &#; the more open area on the screen, the better the chance particles will find an opportunity to pass through

How many decks do I need for my Vibratory Screen?

Vibratory Screens can be configured with one, two, three or four decks. Some fine screening operations can even have as many as eight screening decks. Three decks are pretty common in the aggregate industry, but the number of screen decks depends on the number of products the site needs to make.

In a typical application where multiple products are being made, the top deck(s) of the screen makes the coarse cut, the middle deck(s) makes a middle cut and the bottom deck(s) make the fine cut.

Each screen deck is covered with screen media containing the openings for the particles to pass through. Screen media comes in many different forms, and the type of screen media plays an important role in screening efficiency. 

What type of screen media is best for my Vibratory Screen?

Screen media is all about open area, or the number of openings in the screen. The more openings in the screen, the more opportunities the particles will have to pass through and the more efficient the screen will be.

However, more openings in the screen can decrease the wear life of the media. The correct screen media for an application will balance both wear life and efficiency.

Common types of screen media for aggregate applications include:

• Woven wire
• Polyurethane
• Rubber
• Hybrid

Wove wire cloth is the most consistent, versatile performing media product. It averages 50-70% open surface area in most configurations and provides the most flexibility for operations that need to make frequent media changeouts due to varying product specifications. Overall screening efficiency is good with this type of media.

Wire media

Polyurethane is better suited for wet/wash screens and dry applications with highly abrasive materials. It provides 30-40% less open area than wire cloth; however, polyurethane offers extended wear life over wire media.

Polyurethane media

Rubber media is used for heavier, coarser materials that can damage standard wire screens. It is most often used for dry applications or abrasive materials. Rubber media has less openings than wire cloth, and therefore less throughput; however, they last much longer than wire screens.

Rubber media

Hybrid media combines wire screen with reinforced rubber or urethane strips to fit screen supports. It is highly popular in dry screening applications with high moisture materials and a high proportion of fines. This type of media works to eliminate blinding and pegging, which ends the need to stop production to clean the screen. It provides more open area than  polyurethane and lasts  longer than woven wire. Depending on the application, production can increase 40% using hybrid screen media.

When sizing and selecting a Vibrating Screen for an aggregate operation, be sure to provide the manufacturer with as much accurate detail about the feed material and the application as possible. From there, they can recommend what type of screen (Inclined or Horizontal) is best for the site, as well as the number of decks required and the type of screen media that will provide the best wear life and efficiency. 

6 Types Vibrating Screen And How To Choose The Best One

-07-08 16:40:36

In sand and gravel aggregate production line, screening is an essential stage, and the purpose of screening is mainly to separate materials with different properties. Therefore, the selection of vibrating screens has an important impact on the particle size distribution of the final product. In the following part, we mainly introduce 6 types of different vibrating screen and how to choose suitable vibrating screen.

6 types of vibrating screens

According to their structure and motion characteristics, vibrating screens are divided into the following 6 types, and different vibrating screens have their own advantages and applicability:

&#; Circular vibrating screen

&#; Resonance screen

&#; Linear vibrating screen

&#; Fixed sieve

&#; Roller screen

&#; Constant thickness screen

Among them, circular vibrating screen and linear vibrating screen are the most commonly used screening equipment in mining production.

Circular vibrating screen

Circular vibrating screen uses the centrifugal force generated by the rotation of the eccentric block in the vibrator to force the screen box, vibrator, and other parts to move in a continuous or approximately circular motion.

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It has the characteristics of reliable structure, high screening efficiency, strong excitation force, durability, convenient maintenance, and safety use, widely used in mining, building materials, transportation, energy, chemical and other industries.

Linear vibrating screen

Linear vibrating screen uses vibrating motor to excite the force, causing the material to be thrown up on the screen and move forward in a straight line.

Linear vibrating screen has reasonable vibration parameters, smooth movement, low energy consumption, high yield, and high screening and dehydration efficiency.

Besides, it has fully enclosed structure, no dust overflow, automatic discharge, more suitable for assembly line operations.

Resonance screen

Resonance screen is a vibrating screen that the vibration frequency is consistent with the natural vibration frequency of the screen surface (including loaded materials).

It can effectively utilize the natural frequency of the equipment and operate in a state close to co vibration, thus consuming very little power.

But, the structure of resonance screen is relatively complex, difficult to adjust, and has a high failure rate. There are many issues with structural strength.

Fixed screen

The working part of the fixed screen is fixed and stationary, and the screening process of materials relies on the sliding of the material along the working surface under its own weight.

Fixed screen has the advantages of simple structure, convenient manufacturing, less power consumption, and the ability to directly unload ore onto the screen surface, saving costs.

It is widely used in mineral beneficiation plants, but with low productivity and screening efficiency, mainly used for pre-screening before coarse or medium crushing.

Roller screen

There are plates on the roller screen shaft, and fine materials pass through the gaps between the rollers or plates while large materials are moved towards one end by the roller belt and discharged from the other end.

The materials running at two different speeds begin to move axially when they meet at a certain position on the screen surface, achieving the goal of improving screening efficiency.

Constant thickness screen

The principle of constant thickness screen is an efficient screening technology developed on the basis of the theory of material group movement on the screen surface. The thickness of the material layer on the screen surface remains unchanged or increases during the screening process. The constant thickness screening method can greatly improve the processing capacity of the screening machine.

Zenith circular vibrating screen for you to choose

In sand and gravel aggregate production plant, circular vibrating screen is the most commonly used type. Zenith provides 3 different types of circular vibrating screens of you to choose, YK, YKN and S5X series. They have different production capacities to meet different requirements.

YK series vibrating screen

Max. Capacity: 700t/h

Max. Input Size: 400mm

Min. Power: 15Kw

YKN series vibrating screen

Max. Capacity: 850t/h

Max. Input Size: 400mm

Mesh Size: 6-150mm

Min. Power: 30Kw

S5X series vibrating screen

Max. Capacity: t/h

Max. Input Size: 300mm

Mesh Size: 2-150mm

Min. Power: 11Kw

The three types of circular vibrating screens all have high screening efficiency and Zenith has many customer sample lines in China and abroad.

How to choose suitable vibrating screen

The main factors to consider when selecting vibrating screen are:

The characteristics of materials: such as the content of the particle size proportion of the material under the screen, the content of particles that are difficult to screen, the content of water and clay in the material, the shape of the material, the specific gravity of the material, etc.;

The structure of the vibrating screening: mesh area, mesh layers, mesh size and shape, mesh area ratio, motion mode of the vibrating screen, amplitude and frequency, etc.;

Production process requirements: processing capacity, screening efficiency, screening method, inclination angle of the vibrating screen etc.

In addition to considering the above mentioned factors, the following basic principles should also be followed:

• (1) After determining the screening area, the width of the screen surface should be at least 2.5-3 times the size of the largest block material to prevent the vibrating screen from being blocked by large blocks of material.
• (2) To ensure that the vibrating screen is in good working conditions, the ratio of screen length to width should be selected within the range of 2-3.
• (3) Reasonable material and structure of the screen surface should be selected according to the working conditions.
• (4) Determination of screen mesh size.
  • For the linear vibrating screen used for fine grain screening, the size of the screen mesh is 2 ~ 2.2 times of the separation size, the maximum is not more than 3 times;
  • For circular vibrating screen used for medium size material screening, the size of the screen mesh is 1.2 times of the separation size;
  • For coarse material screening, the screen mesh size is 1.05 of the separation size;
  • For probability screens, the size of the screen mesh is generally 2 ~ 2.5 times of the actual separation size.

(5) Determine whether to use double or multi-layer screen

When the particle size range of the screened material is wide, using a double layer screen as a single layer screen can improve the processing capacity of the vibrating screen, while also protecting the lower layer mesh screen and extending the service life of the lower layer mesh screen.

The selection of the upper screen mesh size of the double-layer screen should generally be determined according to the characteristics of the feeding particle size.

(6) Determine the effective working area of the screen

The screening area calculated according to the production process requirements is the effective area of the vibrating screen, while the specification of the screen is the nominal area of the vibrating screen.

For vibrating screens for screening medium sized materials, the effective screening area should be 0.8-0.85 times the nominal area of the screen.

(7) For materials above 200mm, heavy-duty vibrating screens are often used;

For materials larger than 10mm, circular vibrating screens are often used;

Linear vibrating screens and high-frequency vibrating screens are commonly used for desilting, dewatering, and grading.

(8) When conditions permit, select seat screens for easy maintenance and repair. When it is necessary to use suspending vibrating screen, the lifting height should be minimized as much as possible to reduce the swing amplitude of the vibrating screen and facilitate production operations.

When selecting screening equipment, we should not only consider one reason, but also fully consider various factors to ensure the selection of equipment suitable for the working conditions.

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