Important Considerations To Get The Most Out Of This Important Part Of Materials Processing.
By Mark S. Kuhar
Screening is a key part of processing aggregates. When you are sorting material into different sizes to determine the specification of your material, and to ensure you generate a high-quality product, here are a few tips to get the most out of the screening part of your material flow, courtesy of Eagle Iron Works.
1. Determine the Best Speed for Your Application
Speed and stroke are critical factors in determining the overall efficiency of your screening process. The optimal combination of these variables depends heavily on the type of material being processed and the specific application.
Adjusting speed and stroke can significantly influence material movement across the screen deck, affecting throughput, stratification, and separation accuracy. Since materials can have significantly different qualities, it’s important to adjust these settings to achieve the best possible screening results.
However, any changes to your screen’s speed should be made with careful consideration. Increasing speed can enhance the screen’s carrying capacity, accelerate material flow, and improve overall screening efficiency.
But this also comes with trade-offs. Higher speeds generate more wear and stress on machine components, particularly on bearings, which can lead to shorter equipment life and increased maintenance costs. Finding a balance between performance and longevity is key to maintaining both efficiency and reliability in your operation.
2. Determine the Best Stroke Type for Your Application
Different stroke types play a major role in screening efficiency and performance. Each stroke type affects how material moves across the screen and how effectively fines and oversize material are separated.
For example, circle throw motion is commonly used on inclined screens. It relies on gravity and the incline of the screen to move material and requires low energy. Circle throw can be achieved with either a single or dual shaft, making it a practical choice for many standard screening applications.
Linear or straight-line stroke, often found on horizontal screens, uses dual counter-rotating shafts to produce a back-and-forth shuffling motion. While this stroke type is known for its accuracy and energy efficiency, it doesn’t lift material into the air like a circle throw does. As a result, there’s a higher chance of material plugging the screen openings.
Oval stroke, on the other hand, is the most advanced of the three. It is typically found on triple-shaft horizontal screens and combines the benefits of circular and linear motion. Its high-energy, multidirectional movement helps dislodge fines and significantly reduces plugging, making it the most efficient and accurate option for demanding screening applications.
3. Consider Your Feed Material
Not all material can be screened the same way as different types of materials separate better than others. For instance, crushed material that is jagged typically doesn’t separate as easily or accurately as cubical products, like sand or gravel. However, with the right setup and equipment, any material can be screened, even the more challenging types.
Another factor to consider is how moisture and stickiness in the material can affect screening. Sticky or damp fines may cling to the screen media, causing blinding which can block the screen openings. This can lead to reduced efficiency and potential downtime for cleaning or maintenance. To help avoid these issues, it’s important to consider the type of equipment used upstream in your operation and choose one that produces a more uniform material.
4. Maintain Proper Screen Media Selection and Condition
Choosing the right screen media for your application is critical to achieving efficient screening performance. Screen media that is too coarse may allow undersized material to pass through with oversized materials, while media that is too fine can reduce throughput and cause blinding.
Factors such as material abrasiveness, moisture content, desired gradation, and the wear life of the media should all be considered when selecting the proper screen surface. Options like wire cloth, polyurethane and rubber each have their strengths, depending on your site-specific conditions.
In addition to choosing the right media, regular inspection and maintenance are essential. Worn or damaged media can cause inconsistencies in sizing, reduce screening efficiency, and even equipment damage. Establishing a consistent maintenance schedule for screen media and promptly replacing worn panels will help keep your screen performing optimally.
5. Monitor and Control Moisture Content
Moisture levels in the feed material can greatly influence screening efficiency. High moisture content tends to cause particles to stick together, increasing the risk of blinding and clogging screen openings. This reduces throughput and affects particle separation accuracy. If your feed material has consistently high moisture levels, consider adding a dewatering step prior to screening.
Controlling moisture not only enhances efficiency but also prolongs equipment life. Wet material increases the weight load on the screen, which can lead to excess wear on bearings and screen media. By proactively managing moisture content, you’ll minimize downtime and maintain a more stable, productive screening operation.
Information for this article courtesy of Eagle Iron Works.