Maintenance Products

Are your cross-tensioned screens operating at their peak?

For any cross-tensioned screen deck to operate at peak efficiency and return maximum screen cloth wear life, your screen cloths must be installed and tensioned correctly. Poor cloth tension can result in wire breakage, accelerated wear, pegging, blinding, premature cloth failure and inefficient screening performance.

Think for a moment about the conditions of the average screen cloth. With around 1000 vibrations a minute, 10 or so hours a day for days, weeks, months on end, along with the impact from thousands of tonnes of abrasive material, it is easy to see how even the slightest movement from a loose cloth can cause significant problems. Woven mesh wires will rub, wear and fatigue, significantly reducing wear life. Synthetics or self-cleaning wire screens can peg, blind over, flap and flog out, resulting in premature cloth failure and inefficient screening if not tight enough.

Incorrect screen cloth tension can severely hamper screening efficiency. Picture in your mind a jig saw cutting through a piece of timber. If the timber is not firmly secured, it will just move up and down along with the jig saw blade. A similar action occurs with an under-tensioned screen cloth. The screen cloth can move up and down in unison with the material with less than ideal material stratification or screening taking place.

When installed correctly, the individual wires in the self-cleaning style wire screens vibrate independently at different frequencies, preventing material from accumulating between wires. The vibrating wires also aid stratification, enhancing screening efficiency. If not sufficiently tight, the wires can?t vibrate, allowing near size material to peg in the apertures or damp fines to cling to the wires, eventually blinding them over.

Loose rubber and polyurethane screens will flick the material into the air, giving little chance for stratification or screening to occur.

It can?t be stressed enough how important the right screen crown (camber) can be to a screen?s performance. A poor screen crown is common and often evident by the presence of J-bolts to secure screen cloths to support rails or failed screens in the bone yard.

For optimum screen cloth tensioning, the screen box must have a good, even crown across the entire screen box. Without a good crown, it is impossible to apply enough tension on the screen cloths to hold them firmly down on the support bars, and the wider the screen, the more critical it is.

Equally important is the use of the correct profile side clamping bars. To save money, many producers get the local steel fabricator to make their side clamping bars. If the profile isn?t right, it can pull the screen cloth side hook up off the support bar instead of down on to the side support rail which could lead to hook breakage and screen cloth failure.

Nepean Rubber has been conducting Major Wire?s screening plant audits. The audit aims to identify where and how the screening operation can produce more material for less cost. Nepean reviews screen box and screen media condition, screen cloth installations and screening accessories. The screening plant is inspected from top to bottom, inside and out, from material load to final product.

The problems can be many and varied but the majority of screen cloth failures, pegging, blinding or screening efficiency problems detected are related to the screen crown and, more specifically, support bar capping rubber.

Capping rubber is available in numerous shapes and profiles. It is common to see two or three different profiled capping rubbers used simultaneously supporting a screen cloth with height differences of up to 10mm. Under such conditions, it is impossible to achieve good screen cloth tension and screening problems are almost guaranteed.

To prevent use of odd capping, Nepean Rubber supplies its capping in different colours: an orange 15mm profile, a green 20mm profile (for use on self-cleaning wire or synthetic screen media) and a blue 25mm profile for screens that require extra crown.


Nepean Rubber offers seminars for aggregate producers about the screening issues and problems most have or will experience and how to avoid or fix them.

Developed by Major Wire, the operator-oriented Screen Maintenance Simplified Seminar identifies the common problems operators have with their screening plants, eg screen breakage, blinding/pegging/clogging, out-of-spec product and premature screen media failure.

The seminar identifies how these problems, left unfixed, seriously increase downtime, reduce production capacity, product quality and profitability of the entire operation.

Both of Nepean?s Screening Plant Audits and Screen Maintenance Seminars are a free service offered to its customers.

Source: Nepean Rubber

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