Choosing the Proper Vibratory Screener

Jan 03, 2018

A vibratory screener is a piece of equipment used to separate materials by particle size, remove small amounts of oversized materials from fine material, or remove excess liquid from finished products. Screeners are used in industries as diverse as food, pharmaceutical, chemical, coal, minerals, wood pelleting, asphalt, and many more. Using gravity and motion and along with mesh screens, these units perform the work of several people in a fraction of the time.

Manufacturers offer multiple vibratory screeners to handle separation and sizing of materials, or removal of unwanted materials from a batch. These durable and cost-effective units are usually custom built using a variety of screening media with screen openings ranging from 20 micron to 4 in., depending upon the product.

Linear vibration—achieved with two synchronized vibrator motors or a single pneumatic vibrator—helps these industrial-type screeners reach peak performance with minimal downtime. Screeners built with pneumatic or electrically-powered vibrators are available in single, double, or triple decks, again depending upon the size and composition of the material. Models with pneumatic vibrators can be used for handling hazardous or explosive materials. Hazardous rated electric vibrator motors are also available.

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Specifying the right vibratory screener involves making sure the manufacturer understands the production goals and is supplied with complete application data, which includes information such as material type, top particle size, particle shape, application type (wet or dry), and the method of material feed. Some of the more detailed information a manufacturer needs is the following:

Types of Vibratory ScreenersDifferent applications require a specific type of vibratory screener to ensure a seamless fit into an existing production process. There are formulas to help select the proper size of the vibratory screener and it's best to work with a manufacturer that understands the complete parameters of the application. The following are some of the more popular types for industrial and commercial applications:

Choose the Proper Screen MediaSelecting the proper screen media for a given application is the key to delivering screen-sizing accuracy and maximum throughput, which also impacts the performance of upstream and downstream equipment. In its most basic definition, screen media is a surface with openings on a vibrating screen deck that allows undersized particles to pass through and oversized particles to carry over.

Every application is a unique screening challenge, so the type of screen media selected is critical for success. Here are some different types of screen media and their advantages relative to the application:

Wear life for any type of media is largely determined by its mass: the diameter of the wire or the thickness of the plate or the urethane. The media must be heavy enough to handle a given top-size material and peak feed rate. Synthetic screens (rubber or urethane) will wear far longer—often more than 10 times longer—than wire cloth or perforated plate screens.

Reducing Plug Blinding during ScreeningThere are many obstacles that reduce efficient screening and one of those root causes is plug blinding. This occurs when material that is being screened contains particles with irregular shapes—similar to candy corn. The point falls into a screen opening and gets stuck or plugs the opening, preventing the fine material from passing through the screen.

Eventually, the screen section can lose its effectiveness as more particles plug into the screen openings. Because the material wedges into the screen opening, the vibration energy used to screen the material is not always sufficient to displace the stuck material, resulting in costly downtime to manually clean the screen deck.

The solution? Install a ball tray deck beneath the screen section. The ball tray has compartments with perforated plate at the bottom. Balls are placed in each compartment and freely bounce during screener operation. The balls strike the underside of the screen surface and randomly knock out the plugged material. The fine material then passes through the screen and the perforated plate at the bottom of the ball tray where it can be collected.

Electromechanical screeners are the ideal choice for making the balls more effective in reducing plug blinding because of their linear action and drive angle. Screeners which use an electric motor to rotate a shaft with counter weights on both ends producing a circle throw motion are also effective.

Jack Steinbuch is equipment sales engineer at Cleveland Vibrator Co., Cleveland, OH. For more information, call 800-221-3298, email [email protected] or visit www.clevelandvibrator.com.

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