Industry News

Modular screen media set to make waves

Quarries, sand pits and other aggregates suppliers are facing mounting pressures to produce the very highest quality of aggregates, while commercial pressures incentivise them to increase operational efficiencies. In response to these customer-driven requirements, Sandvik Construction has developed a new, modular screening media for use on screens with longitudinal profiles.

This radical development enables aggregate producers to enhance production capacity while simultaneously delivering the highest levels of screening accuracy.

It is easy to install, with no requirement for any screen modification, ensuring downtime is minimised, providing aggregate producers with high production capacity, accurately sized material and increased operational efficiency.

The new design of the WR screening media provides users with an open production area greater than is found in traditional modular media. This is achieved through the use of cross-mounted flexible screen panels that generate a revolutionary wave-like cascade effect in the material bed to improve stratification and allow undersize material to find a more rapid path to the screening surface.

OPTIMISED ACCURACY

The key to the WR system is the optimisation of screening accuracy. To achieve this accuracy, the Sandvik modular screening media utilises a fibre-reinforced rubber screen membrane, which enables the use of thinner panels, with closer aperture spacing, thus maximising the open screening area. Other efficiencies are derived through the elevation of the screen panels from the longitudinal support bars and the screen panels may be fully perforated from side liner to side liner. This absence of blind fields in the directional flow of material ensures maximum material separation and minimises the amount of undersized particles ?carried over? to the end product.

?There are no blind areas, or joints, in the length of the screen to which undersize particles can move without being screened out,? Elna Hov?n, Sandvik Construction?s screening media product manager, explained. ?This larger screen area improves accuracy and increases capacity.?

{{image2-a:r-w:250}}An additional benefit is that the screen cloths are mounted crosswise across the screen instead of along it, with the flexible modules creating an efficient cascade effect when the rock material is transported forwards. The ?billowing? movement hastens stratification, ensuring any undersize particles are more rapidly screened out. The radical design of the WR screening media, with its integral anti-blinding system, facilitates the accurate screening of even the most difficult to screen materials at exceptional capacities.

The benefits of the WR system were clearly seen at an Austrian aggregate plant last year, when Sandvik installed WR9000 screening media. In this application, the media was designed to enhance screening of a wet product at 8mm. After the successful installation, the managers of the plant noticed an exceptionally low level of blinding, with the large open area of the WR9000 providing a noticeable increase of throughput on the screen deck. During the fine tuning, the screen responded in a very precise manner to the necessary adjustment of apertures, achieving the correct screen curve and delivering a highly accurately screened end product for the plant.

MINIMISING DOWNTIME

Use of the WR screening media ensures operational downtime is minimised and service intervals extended, due principally to the long lasting rubber and polyurethane materials that are used to make the screen panels. Additionally, the WR screen panels possess a built-in cross beam protection lip which, together with support bar rubber capping, protects the adapter system against wear.

Replacing the screen panels, when the need arises, is easily accomplished, as the wedge locking them into place may be quickly removed and reinstalled. This keeps change over time to a minimum, while the absence of steel reinforcement makes the WR system light, reducing stress on the screen and bearings and the subsequent risk of unplanned production stops.

FOCUS ON QUALITY

The requirement for a productive screening media that delivers exceptional material quality was at the core of Nym?lle Stenindustrier AS? requirement for a new screening solution. The company?s facility at R?dekro, located near Aabenr? in Jutland, Denmark, produces about 250,000 tonnes of material each year, of which 110,000 tonnes is washed sand, with the remainder being aggregate. These materials are used for concrete structures, asphalt, road building, drains and other associated purposes.

Additionally, as one of Denmark?s largest suppliers of gravel, the company ? which started operation in 1909 and now operates 30 facilities in Fyn, Jutland and Sj?lland ? has a combined annual production of seven million to eight million tonnes of sand and aggregate. The company also possesses its own laboratory facility and can analyse and check the materials produced, ensuring customers receive high quality end products. This intense focus on quality has made the company highly receptive to solutions that can improve screening production and operational efficiency; these goals guided the decision to install the WR screening media.

In the summer of 2011, the Nym?lle Stenindustrier R?dekro facility identified a requirement to replace the screening media in one of its primary screens ? a Svedala VFS 48/21, which also operates as a washing screen.

?We wanted to reduce the proportion of undersize particles further and were open to try a new solution,? explained Jens Rasmussen, the site?s production manager. ?Once the Sandvik WR modular screening media had been installed, the improvement was considerable and, additionally, the production capacity of the screen increased.?

In fact, the company has reported a 17 per cent increase in productivity since installation.

NO MODICATIONS REQUIRED

To replace existing screening media, the WR system requires no modifications to the screen body or sub-frame, ensuring user-friendliness and efficiency. Helping to ensure this, the WR adapter system is installed easily by replacing the existing ?nock-in bar?, with the screen panel lips being simply inserted in the crosswise-mounted profiles and locked in place with a wedge.

{{image3-a:l-w:250}}No bolting or special tools are needed and dismantling the screen panels, once they are worn out, is equally simple, by just pulling out the wedge and removing them. Furthermore, the WR system adapter creates transverse tracks into which the screen cloths are placed and locked with a rubber wedge.

?The screen cloths were easy to replace,? Rasmussen said, ?and we were pleased that the screen did not have to be rebuilt. In addition, this modular system fits all machine types.?

Rasmussen explained that the replacement of R?dekro?s screen system was easy, with neither the frame nor the screen needing to be rebuilt; the existing polyurethane screens were quickly removed and a new adapter system installed. Further enhancing the system?s flexibility and ease of installation, the WR media is made of rubber ? which is fibre-reinforced and produced through a unique manufacturing process ? or different grades of polyurethane, as is the case at R?dekro.

Rubber is primarily used as the medium for fine to medium coarse screening in dry applications, while polyurethane is primarily used for wet screening. This means that whatever the material used in the make-up of the screen panels, they can be delivered to site already cut to length to fit the required screen width.

COST-EFFECTIVE INVESTMENT

After the change to the WR modular screening media, Rasmussen noted considerable improvements in the operation at the site. The proportion of undersize particles, which had been 23 per cent, had now reduced to only nine per cent and Rasmussen was also delighted to note an improved capacity of 350 tonnes per hour ? a 17 per cent improvement on the 300 tph the old screen modules had been capable of delivering. Rasmussen said the combination of the large, open screening area and cascade effect was enormously efficient.

?It provides greater capacity through the screen and we get sharper [material] separation. We are now able to deliver an even higher quality to our customers: Sandvik Construction?s new system is proving to be a highly cost-effective investment.?

As with all Sandvik screening media, productivity and efficiency are only part of the ethos behind the design. Minimising environmental damage and ensuring operator safety are equally important concerns and, to that end, the WR system consists primarily of parts   that do not contain any steel.

This makes the product lightweight and safe to handle and, as highlighted by the Danish example, the installation and replacement of screen panels is safe, easy and requires no special tools. Furthermore, all parts in the system are environmentally friendly and fully recyclable, with the use of rubber and polyurethane screen panels producing the additional benefit of being currently the best way to reduce noise in the screen area, thereby minimising sound pollution.

The new WR system can potentially increase aggregate producers? profitability by allowing high quality aggregates to be produced at high production rates, while simultaneously delivering operational efficiencies. WR has been developed to fit most screens that are currently equipped with modular media on longitudinal profiles and is made of rubber or different grades of polyurethane, allowing the screen panels to be delivered cut to length to fit any screen width on the market. Being highly productive, accurate, tough wearing, easily replaced
and environmentally focused, Sandvik anticipates the WR screening media will become a key tool in the aggregate producer?s armoury.

Source: Sandvik Construction

This article first appeared in the March 2013 issue of Quarry Management (UK) and is reprinted with kind permission.

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