SCREENING CHALLENGES & SOLUTIONS
Wear of Screening Surfaces
Wear is a naturally occurring process in all aggregate producing plants. Wear begins the moment that aggregate comes into contact with any and all processes in aggregate producing facilities. Abrasion or friction of the aggregate coming into contact with steel or other synthetic surfaces manifests the wearing situation, and this wear occurs on all surfaces "where the steel meets stone." Loader buckets, crushers, bins, chutes, conveyor belts, transfer points and screen media are most subject to rapid wear caused by the aggregate. These are the primary high-wear areas involved in aggregate production. Specifically, however, we would like to address screen wear.
Remove the "Fine Material" First
Removing the "fine material" before crushing, screening and/or washing, dramatically reduces wear of all major processing components downstream. Removing the fines first not only reduces downstream wear but also increases processing capacity. The removed fines can then be processed in a secondary or tertiary circuit where further crushing, screening and/or washing can be performed more effectively. Fine removal will also increase production and wear-life of all components involved in primary crushing and screening operations.
Install a "Rock on Rock Feed Box"
This is especially beneficial when scalping screens are utilized in the primary circuit. Larger aggregate impacts other aggregate material instead of causing localized and, quite often, severe wear of the feed box and screen media. Additionally, the material discharge from the feed box onto the feed screen panel should not exceed >8 inches. This will effectively increase the wear-life of the screen media by "laying" material onto the screen surface versus "throwing" it on.
Put Hoyt Guard Rods on Duty
For scalping decks where this severe wear occurs, Hoyt recommends the use of "guard rods" to effectively transfer the larger aggregate down the screen deck. The guard rods are positioned on the feed panel, under the impact area and parallel to the material flow. Guard rods essentially act as an impact pad in addition to offering increased screening area and no loss of open area. (See photo.)
Hoyt guard rods
Hoyt's "Smoothtop Construction Prevents Destruction"
Many other aggregate screen cloth manufacturers utilize a "Hi-Lo" or an "Arch Type" crimp construction on larger opening sizes. This "under/over" crimp positions the rapidly wearing "knuckles", or crimps, on the wearing surface of the screen cloth. High points on this screen surface, being the first to wear away, are exposed to the aggregate flow. Once these high points, knuckles or intersections of the screen cloth wear, the cloth must be replaced, which occurs frequently in many situations. Hoyt's smoothtop construction utilizes no high points, which, of course, rapidly wear away. The smoothtop screens are manufactured with "deeply pressed crimps" in a downward direction only, thereby positioning all the high wear points, or knuckles, on the underside of the screen cloth. This smoothtop construction places 70% more wearing surface where it is needed — on top. Almost the entire diameter of the wire is then available to combat premature wear. Many aggregate producers have enjoyed much longer wear-life with Hoyt's smoothtop construction, and two to three times longer wear-life is not uncommon. (See below.)
Notice the thinly worn wires
Hoyt Rises to the Occasion with Hi-Rise™
This newly developed technology in screen cloth manufacturing utilizes compressed and expanded oblong wires that are positioned vertically. Hi-Rise™ offers two distinct advantages over traditional round wire screen cloth: increasing both the effective open area and wear-life. By compressing round wire into the oblong shape, Hi-Rise™ reduces the wire diameter width while increasing the height dimension. Both longer wear-life and increased open area are thus realized. Aggregate producers have achieved drastic increases in production by using Hoyt Hi-Rise™ screen cloth panels. (See photo below for open area comparison.)
Please consult Hoyt Wire Cloth or its affiliates before ordering the Hi-Rise™ Screen.