Suppliers and customers alike talk about improving their screening efficiency while maximising throughput, to offer cost reduction, but it is often the incidentals that are overlooked in the rush for efficiency.
Capping rubber is an essential component in screening efficiency. It should be replaced at each screen changeover or immediately if it shows signs of wear. Capping rubber protects the screen, whether wire, rubber or polyurethane, from the rubbing effects of the machine sub-frame and allows the screen to be tensioned evenly, keeping it taut and functioning at its peak. If the screen is loose in parts it cops a double impact: the vibration of normal screening plus the extra movement of the screen flopping up and down.
The length of the hooked screen (along the hooks) should be the same as the clamping bar to ensure even tension is applied across the screen. Each screen should have its own clamping bar; it shouldn?t be sharing a clamping bar across two or more screens. If a clamping bar is being shared across two screens, it risks loose or over-tensioned screens. If the two screens are different in the slightest, the clamping bar does not have the opportunity to apply the correct loads to each screen. Worn or badly fitted clamp bars will result in the screen hooks being worn away, resulting in premature screen change-out.
When joining multiple screencloths, 16mm aperture and/or 5mm wire diameter or finer, a minimum 25mm overlap is recommended. The overlap ensures the deck is sealed properly and prevents product contamination.
When specifying overlaps, it is essential to understand which is the ?width? and ?length? of the screen to ensure the overlap (and hooks) are applied to the correct dimensions.
Excessive vibration in the screen box also reduces efficiency. Screening is one situation where harder and faster isn?t necessarily better. If the screen set-up is incorrect, it causes a secondary vibration or movement in the screen, increasing the wear and tear on the screen itself and reducing its lifespan. The Locker Group stroke magnet can help you assess if your machine is operating within the manufacturer?s specifications and whether it is contributing to any screening problems. In addition, Locker Group?s Extractive Screening Solutions Team can help you read and make an assessment of what is happening.
Of course, the type of screen makes a big difference. ?Poly ripple screens offer increased throughput, given the nature of their design,? noted Des O?Brien, Locker Group?s extractive sales manager. The wires are independent, with no cross wires holding them firm, which allows them to vibrate uninhibited. This reduces wear (high spots) and the potential for pegging and blinding as the wires are able to move about freely.
Bright blue poly strips identify Locker Group poly ripple screens and hold the independent wires in place. The poly ripple screens are custom manufactured in Locker Group?s Rocklea (Brisbane) manufacturing plant, offering a 10-day turnaround, after approval of drawings and screen specifications.
?Our poly ripples have a better seal than the industry average,? said Des. ?We pour the poly sealing strips at the same time as the poly for the screen. This ensures that the overlap strip is truly flat, and provides an excellent seal between screens, and prevents product contamination.?
Locker Group manufactures poly ripple screens to order, considering the exact size of the screen deck. Screens are available in a variety of wire diameters (up to 6.5mm) and apertures (from 2.5mm to 31.5mm). Bred to meet the unforgiving conditions of Australian quarries, the poly ripples utilise the best high carbon, high manganese wire to maximise the life of the screen.
?You can expect up to three times the life, when compared to a conventional cross-tension wire screen,? Des forecast.
Poly ripple is not the only product alternative Locker Group has on offer. Depending on the quarry location and product screened, there are numerous options available. Climate can play a big role in the choice of screening media; the seasons can affect the condition of the product being screened and therefore impact on throughput. Often sites will specify one type of screen for summer when the material is warm and dry, and a ripple screen for the wet and sticky conditions of winter.
Locker Group can offer each site unbiased advice on screen selection, including:
? Woven wire screens (hooked or flat), with a very fast turnaround from three strategically located manufacturing facilities around the country.
? Rubber cross-tension screens, ensuring superior impact and abrasion resistance, noise reduction and increased flexibility to reduce pegging and blinding.
? Wire ripple and poly ripple screens, a combination of high open area and increased vibration to ensure these screens are ideal for almost any screening environment.
? Piano wire or harp wire screens, for high productivity.
? Wedge wire, a static robust screen, ideal for dewatering.
? Moulded rubber screens, for heavy duty applications incurring high impact and heavy load conditions.
? Polyurethane cross-tension and/or modular panels, for high wear and corrosion resistance.
? Full range of complementary accessories and fixing systems.
? Walkway and handrails for plant maintenance.?
Source: The Locker Group