However, with the increasing popularity of modern, larger width 6’ x 8’ single-crown screen boxes, maintaining good tension on the rubber screen cloths can be a real problem. The long span from hook to hook and high G-forces of the screen box can cause the cloths to flap and cut through on the support bars, resulting in premature failure. In attempts to prevent flapping, the cloths can easily be over-tensioned, pulling the rubber out of the hooks, destroying the cloth.
Fortunately, there are a number of options at hand to solve this problem.
The use of higher profile capping rubbers can be a quick fix, increasing the crown radius and creating more downward pressure of the cloth on the support bars. On the downside, more material can flow to the outer sections of the screen. Bed depth increases, screening efficiency may be reduced and accelerated wear can occur down the edges of the screen cloth and side clamping bars.
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One very simple method to ensure good tension of the rubber cloth is to incorporate a centre hold-down bar into the design of the cloth. Attachment is usually via commercially available J-bolts. It costs no more to design the cloth to accommodate a hold-down bar or J-bolts, so it makes good sense to ask for this feature to be included when ordering new cloths.
For heavy-duty screening applications handling large material with high wear rates, Nepean Rubber’s steel cable-reinforced cloths are a more practical alternative and are suitable for use on any cross-tensioned or end-tensioned screen box.
Multiple stainless steel cables are moulded into the rubber screen, ensuring maximum tension force is applied to the hooks without risk of damage or failure. For added security, include a hold-down bar or J-bolts along the centre stringer bar on single-crown screens.
BENEFITS OF CABLE SCREENS
The selection of many different rubber compounds, such as natural or synthetic, hard or soft rubbers, depends on site-specific operating conditions. A special slip additive can be blended into the rubber where build-up of damp fines causes blockages. Conventional rubber cloths are manufactured using the same 60 Duro rubber compound for fine abrasive screening and heavy impact scalping of large rock.
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Cable-reinforced screens have the apertures moulded with a relieving taper and are not limited by the same design parameters as conventional punched screens, where the rubber thickness must be smaller than the aperture. Otherwise the apertures take an “hour glass” shape and pegging of the apertures is almost guaranteed. Therefore it is possible to build a much more robust, long-lasting screen for the most arduous applications.
Cable screens can be custom designed and moulded with a multitude of aperture types such as slot, teardrop, round or square for self-cleaning, long wear life or maximum screening efficiency. Other features such as rider bars or diverter ribs to control material flow can also be included.
Source: Nepean Rubber