Making Waves
Less blinding and reduced downtime with new WR modular screening media from Sandvik Construction
The quarrying and aggregates industries face constantly demanding pressures to maximize the productivity and efficiency of their screening operations. As a result, there has been significant demand for the development of a new type of screening solution that is highly productive, efficient and accurate.
As an acknowledged market leader in the development of screen media, and with a long track record in producing new solutions to existing problems, Sandvik Construction have developed the WR screening media for use on screens with longitudinal profiles. This radical screening development possesses a purpose-developed anti-blinding system that allows the media to screen even the most difficult of materials very accurately and at high rates of production.
The basis for the new production technique found on the WR screening media is its pioneering design, which provides users with an open production area greater than that found in traditional modular media. This is achieved through the use of cross-mounted flexible screen panels which generate a revolutionary wave-like cascade effect in the material bed, thereby improving stratification and allowing undersize material to find a more rapid path to the screening surface.
Furthermore, the new media is easy to install, with no requirement for any screen modification, thereby ensuring that downtime is minimized.
Optimized accuracy and productivity
The key to the WR system is the optimization of screening accuracy; in order to achieve this accuracy, the Sandvik modular screening media utilizes a fibre-reinforced rubber screen membrane, which allows the use of thinner panels with closer aperture spacing, thus maximizing the open screening area. Other efficiencies are derived through the elevation of the screen panels from the longitudinal support bars, as well as the fact that 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 minimizes the amount of undersized particles ‘carried over’ to the end product.
Commenting on the benefits of the larger open area, which is extended across the entire width of the screen, Elna Hovén, product manager - screening media with Sandvik Construction, said: ‘There are no blind areas or joints in the length of the screen to which undersize particles can move without being screened out. This larger screen area improves accuracy and increases capacity.’
An additional benefit derived from the system 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 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, thus facilitates the accurate screening of even the most difficult to screen materials at exceptional capacities.
The benefits of the WR system were clearly demonstrated at an Austrian aggregate plant in 2012 when Sandvik installed WR9000 screening media. In this particular application the media was designed to enhance the 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 in throughput on the screen deck. During 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.
Minimizing operational downtime
Use of the WR screening media ensures that operational downtime is minimized; this is due, principally, to the long-lasting rubber and polyurethane materials used to make the screen panels, thereby extending the service intervals. 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 can be quickly removed and reinstalled. This keeps changeover time to a minimum, while the absence of steel reinforcement makes the WR system light, which reduces the stress on the screen and bearings, thereby further reducing in the risk of unplanned production stoppages.
Focus on quality
The requirement for a productive screening media that delivers exceptional material quality was at the core of Nymølle Stenindustrier AS’s requirement for a new screening solution. Their facility at Røde Kro, near Aabenrå in Jutland, Denmark, produces approximately 250,000 tonnes of material each year, of which 110,000 tonnes consist of washed sand, with the remainder being aggregate.
Additionally, as one of Denmark’s largest suppliers of gravel, the company – which commenced operations in 1909 and now operates 30 facilities in Fyn, Jutland and Själland – has a combined annual production of 7–8 million tonnes of sand and aggregate. The company also possesses its own laboratory facility and is able to analyze and check the materials produced, ensuring that customers receive high-quality end-products. This intense focus on quality has made the company highly receptive to any solutions that can improve screening production and operational efficiency, and it was this that was behind the decision to install the WR screening media.
During the summer of 2011, Nymølle Stenindustrier’s Røde Kro facility identified a requirement to replace the screening media on one of the primary screens – a Svedala VFS 48/21 – which also operates as a washing screen. Explaining the requirement to replace the existing screening media, the site’s production manager, Jens Rasmussen, said: ‘We wanted to reduce the proportion of undersize particles further, and were happy to try a new solution. Immediately after the Sandvik WR modular screening media had been installed the improvement was considerable and, additionally, the production capacity of the screen increased. In fact, a 17% increase in productivity has been reported since installation.’
Versatile with no modifications required
In order to replace existing screening media the WR system requires no modifications to the screen body or sub-frame, thereby ensuring user-friendliness and efficiency. Helping to ensure this, the WR adapter system is easily installed by replacing the existing ‘knock-in bar’, with the screen panel lips being simply inserted in the crosswise-mounted profiles and locked in place with a wedge. No bolting or special tools are needed, and dismantling the screen panels, once they are worn out, is equally simple by pulling out the wedges and removing them. Furthermore, the WR system adapter creates transverse tracks into which the screen cloths are placed and locked with a rubber wedge. Commenting on the fast and easy installation and replacement of the screen cloth, Jens Rasmussen said: ‘The screen cloths were easy to replace, and we were pleased that the screen did not have to be rebuilt. In addition, the modular system fits all machine types.’
As noted by Mr Rasmussen, replacing the screen system at Røde Kro proved to be 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 flexibility and ease of installation of the system, 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 Røde Kro. 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 in order to fit the required screen width.
Cost-effective investment
After the changeover to the WR modular screening media, Jens Rasmussen noted considerable improvements in the operation at the site. For example, the proportion of undersize particles, which had been 23%, was now reduced to just 9%, and capacity improved by 17% to 350 tonnes/h from the 300 tonnes/h the old screen modules had been capable of delivering. ‘The combination of the large, open screening area and cascade effect is 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,’ said Mr Rasmussen.
Environmental protection, health and safety
As with all Sandvik screening media, productivity and efficiency are only a part of the ethos behind the design. Minimizing environmental damage, while ensuring operator safety, are equally important concerns. To this end, the WR system consists primarily of parts that do not contain any steel. This makes it lightweight and easy to handle, and as has been highlighted by the Danish example, installation and replacement of the screen panels is safe, simple 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 reducing noise in the screening area, thereby minimizing sound pollution.
As this example from Denmark demonstrates, the new WR system is set to increase aggregate producers’ profitability by allowing high-quality aggregates to be produced at high production rates, while at the same time delivering increased operational efficiencies. It has been developed to fit most screens on the market that are currently equipped with modular media on longitudinal profiles, and is made of rubber or different grades of polyurethane that allow the screen panels to be delivered cut to length in order to fit any screen width. Being highly productive, accurate, hard wearing, easily replaced, and environmentally focused, Sandvik fully expect their WR screening media to become a key tool in an aggregate producer’s armoury.