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How to successfully set up vibrating screens

By |  July 13, 2022
Manufacturers can recommend whether a horizontal (pictured) or inclined screen is best for an aggregate operation. Photo: McLanahan Corp.

Manufacturers can recommend whether a horizontal (pictured) or inclined screen is best for an aggregate operation. Photo: McLanahan Corp.

Aggregate producers have plenty of variables to ponder as they plan operations, with sizing and selecting screening equipment undoubtedly part of their many decisions.

For vibratory screens, producers should pursue answers to a number of key questions before coming to final decisions. They can seek out manufacturers and dealers to help them come to the right solutions, giving some thought to the three questions presented in this article.

Starting off

1. How many decks do you need for a vibratory screen? Vibratory screens can be configured with one, two, three or four decks, with some fine-screening operations having as many as eight decks. 

Three decks are pretty common within aggregate operations, but the number of screen decks depends on the number of products a site needs to make. In a typical application where multiple products are being made, the top deck (or decks) of the screen makes the coarse cut, the middle deck (or decks) makes a middle cut and the bottom deck (or decks) makes the fine cut.

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

Media selection

2. What type of screen media is best for your 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 particles will have to pass through – and the more efficient the screen will be.

Still, more openings in a 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 and hybrid.

Woven wire

Wove wire cloth is the most consistent, versatile media product. It averages 50 to 70 percent open surface area in most configurations and provides 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.

Polyurethane

Polyurethane is better suited for wet or wash screens and dry applications with highly abrasive materials. It provides 30 to 40 percent less open area than wire cloth, but polyurethane offers extended wear life over wire media.

Rubber

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 fewer openings than wire cloth, therefore delivering less throughput. It can, however, last much longer than wire screens.

Hybrid

Hybrid media combines a 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 forces production to halt in order for a screen to be cleaned. Hybrid media provides more open area than polyurethane and lasts longer than woven wire. 

Depending on the application, production can increase 40 percent using hybrid screen media.

Screen selection

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

Vibrating screen selection is based on several factors, including maximum tons per hour, gradation of the feed material, type and weight of material, desired size of separation, any surface moisture on material and any special operation requirements, including physical characteristics of the feed or product requirements.

3. How do you size a vibratory screen for an aggregate operation? Vibratory screens come in a variety of sizes. They can range from 4 ft. to 12 ft. wide and 6 ft. to 32 ft. 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 two-and-a-half to three times the size of the width.

Every manufacturer has its own screen sizing formula. Screens are tailored to an operation based on a few key factors:

Basic capacity. How much material is going to pass through a certain opening?

Incline. How much of an incline, if any, is needed?

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 material passing through the screen openings will be higher, and the screen will be that much more efficient.

Slot. How large are the openings in the screen?

Condition. This 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 the climate wet or dry?

Shape. Round or cubical particles have a higher chance of passing through the screen openings than a flat, elongated particle that has to find the right position to fall through.

Weight. The density of the material matters.

Open area. The more open area on the screen, the better the chance particles will find an opportunity to pass through.

Information for this article courtesy of McLanahan Corp.


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