Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/420189
AGGREGATES MANAGER December 2014 18 dewatering screens are used; however, a modular panel design is used almost exclusively. 'Pin and Sleeve' design was once the only game in town, but the development of rail type aach- ment systems has gained favor over the last decade. It should be noted there are also unique media systems available, includ- ing some with side-tension aachments. With modular panels, the most important thing to guard against is metal-on-urethane interfaces where the metal almost always loses. Fine silica is the most aggressive and gets in ev- erywhere. is is where metal components cast into urethane and urethane-to-urethane connections come into their own. With rated capacities now almost double what they used to be, the media also needs to be much heavier in construction. Typical screen apertures range from 0.3 mm to 2 mm depending on the application; there is much conjecture about this subject, and a lot depends on the downstream process for the throughs. You can guarantee that some material will pass through the screen at the aperture size, most oen requiring recirculation either back to a source or through a separator. Deck-dividers can be used to segregate size fractions down the length of a single screen, with three fractions being the practi- cal maximum. Other accessories to assist with the unique pro- cess or other material can be incorporated by the manufacturer. W hile rubber buffers, or springs, generally isolate the screen from the structure (shear mounts are the most effective for this, but typically lack the large carrying capacity), it is abso- lutely critical that support structures are adequately designed for the very high dynamic loads. It is recommended that sup- port columns always be immediately under the screen mounts, transferring forces into the substrate. Catastrophic screen fail- ure can result due to inadequate or incorrectly aligned support. e most common aggregates applications are: 1. Dewatering concrete/mason/industrial sand products or any granular mineral (these screens do not do well with long fibrous material); 2. Fines recovery (100 x 400 mesh), which when combined with cyclones can turn a sloppy mess into a conveyable and very stackable secondary product; 3. Dewatering downstream of existing dewatering devices, such as screws or bucket-wheels; 4. Dewatering downstream of sand tanks, hydrosizers, etc.; and 5. Washing and rinsing sand or even coarser aggregates. Each manufacturer places its own limits on feed dilution, and care must be taken with batch or variable solids feed processes such as lignite removal plants, classifying tanks, With the moisture reductions achieved through the use of a dewatering screen, material can be conveyed cleanly and safely.