Depending on your specific aggregate processing application, screening equipment may fit in different points of your material handling operation. Screens size and separate your material after crushing, but they may be integrated just after the primary crusher—as in most crushed stone plants—or screening may occur just before stockpiling or material transport (as in the construction industry and others).
The bottom line is, you need screens. But choosing the right ones—especially if you’re new to the rock, sand, gravel, or mineral processing industry—can be complicated. Fortunately, here at Kemper Equipment, we’ve got decades of screening experience ready to help you set up an efficient circuit that will enhance your operation’s overall performance.
Today’s post gives just a little background on what screening actually is, as well as important points you’ll need to think about as you prepare to purchase or lease new, high-tech screen machinery.
Screening: An Art and a Science
Pit & Quarry University’s excellent lesson on screening discusses how separating and sizing material is a little bit artful while also being a scientific process. The lesson notes, “the art of screening lies in the meticulous fine-tuning, tweaking, and synchronizing of screen setups within a near-limitless number of applications. Its science is stratification.”
Stratification is a big word for the separation of large and small particles. Screening machines achieve this through vibration or agitation of the material, though that vibrating movement may be mechanically different (more on that below) depending on your particular needs. No matter what, stratification is the reason screening works.
Main Types of Screen Machines to Consider
Interestingly, there are only two main types of screen equipment: incline and horizontal configurations. And, industry veterans will tell you that incline screens are almost always the more efficient choice.
However, you need to have a solid understanding of your operating parameters and overall production goals to make the call on which screens will work best. Additionally, there are several options related to how your screens will actually run that you’ll need to choose between. You’ll need to evaluate your requirements for feed tonnage, screening area, and efficiency to guide your choice.
Make the wrong equipment selection in screening, and you’ll be introducing the biggest bottleneck in your entire process flow. (Feeling overwhelmed? Let Kemper help you find the best retrofit or new system solution.)
Incline vs. Horizontal Screens
It’s true that incline screens are typically your best bet, no matter where they fit in your circuit. Why? Well, because they harness the power of gravity to reduce power consumption. As a result, the incline configuration has better capacity abilities when operating at similar speeds versus horizontal screens.
Of course, if you’re limited at your quarry or mine site by vertical clearance challenges that would prevent the incline from being constructed at the proper angle—often about 20 degrees on the top deck—you will have to choose a horizontal screen. Also, horizontal screens are commonly used in portable plants, or if you’re feeding from a dredge in water-intensive operations.
Motion Differences
There are three main ways that screens can move to achieve necessary stratification.
Horizontal screens will typically vibrate with either linear motion or an elliptical motion. Both movement patterns are effective, but the linear—or straight-line—motion produces high G-forces that P&Q University asserts, “can both dislodge material and convey it forward across the screen.”
Inclined screen machines can also vibrate in linear or elliptical patterns, as well as in a circular motion, which tends to be preferred in continuous feed setups where screening of large material must be accomplished.
Other Considerations in Screening Operations
In addition to considering whether you will use incline or horizontal screens and how they should vibrate to provide your desired output, setting up a screening operation will require you to look at a few more decision points.
Dust Suppression
As we covered in our previous blog post about dust suppression basics, screening is one of the most significant dust producers in most operations. Your screening equipment will need to incorporate screen dust covers that physically block dust from escaping the machinery—a dry suppression tactic. You may also want to consider wet dust suppression techniques depending on the material you’re working with, especially if you’re subject to the OSHA’s new silica standard. Kemper Equipment stocks screen parts, including spray nozzles and dust covers to suppress dust in your operation.
Feeders
Per Pit & Quarry University, “depending on the process stage, the material to be screened is fed to the screen from an intermittent-feed loading device like a wheel loader or from a continuous-feed device like a hopper or a conveyor.” In other words, you need to understand whether your operation’s production goals require the use of continuous or intermittent feeding tactics.
Need Help Finding the Right Screens for Your Operation?
Whether it’s stationary or portable equipment, and whether you’re looking to buy or lease, Kemper Equipment is your best resource for expert advice on efficient screening operations.
Already set up and looking for screen parts or screen media? We can help you there, too. Shop QuarryParts.com for fast delivery on select parts in stock, or simply get in touch with us for friendly and knowledgeable service for your screen equipment and much more in the realm of material handling solutions.
