The Nyrand Grusgrav quarry in Svebölle, Denmark, plays a vital role for the NCC Roads Group, producing a 2-5mm aggregate for use in manufacturing asphalt and concrete. Production of this accurately sized material is in the region of 70,000 tonnes per annum, with the quarry operating to a five-day, 40-hour week.
Prior to screening, the aggregate goes through a traditional primary and secondary crushing process at a feed rate of 100 tonnes per hour. Initial screening removes the +10mm material which is recycled back into the crusher for further processing.
The main feed material is then sent to a static double-deck screening plant with a 5mm top deck and 2mm bottom deck. The final product is sent to a washing plant. A further screening plant is available to deal with any operational downtime and when extra capacity is required.
Although the plant has been able to satisfy demand, the screening process has not been without problems. The “blinding” nature of the wire mesh screen media resulted in material being “misplaced”, reducing the amount of saleable product and leading to an overrun of fines.
Blinding, however, was not the main problem; the wire mesh screens had to be replaced 10 times a year due to breakages etc, and the plant was losing a great deal of production. This resulted in operational downtime, as replacing the screen media was a time-intensive process and extremely costly. Many man hours were being used in this often dangerous undertaking.
After intensive discussions during a site survey in 2014, NCC and Sandvik Construction decided to replace the wire mesh on the bottom deck of the double-deck screen.
{{quote-A:R-W:300-Q:"Dam bars slow undersized material, enabling oversized material to pass more quickly, resulting in more accurate screening and a better end product."}}After collecting data from the process, and setting targets for production, Sandvik proposed a solution involving its WX7000 anti-blinding screen media. In addition to this technical solution, Sandvik proposed providing a technical supervisor and training for the operators at the site.
NCC accepted Sandvik’s solution and replaced its wire mesh with Sandvik’s WX7000 at the beginning of 2015. The anti-blinding screen media has been working effectively for more than a year without the need for manual cleaning or replacement.
The WX7000 solution is a tensioned, soft polyurethane screen media with dam bars and punched holes designed primarily for fine screening in difficult conditions. Its design solves blinding problems, providing superior screening efficiency.
When compared with traditional wire mesh, the wear life of WX7000 media is up to 10 times longer (or more in many applications), significantly lowering operating costs.
Dam bars slow undersized material, enabling oversized material to pass more quickly, resulting in more accurate screening and a better end product. Furthermore, the polyurethane tensioned, anti-blinding screen media needs minimal service maintenance which benefits operational safety and improves cost per tonne production.
A major difference, in comparison with other meshes or screen cloths, is that Sandvik’s WX7000 anti-blinding screen media keeps the apertures open in difficult conditions due to its flexibility, ensuring high end product quality during its long lifetime. This is accomplished because there are no blind areas, or joints, in the length of the screen to which undersized particles can move without being screened out.
A larger efficient screen area also improves accuracy and increases capacity, with the WX7000 screen cloths having an especially hard wearing polyurethane design. This ensures a long working life, and minimises the number of operational stoppages for screen cloth replacement (vitally, when a replacement has to be made, the process is fast and smooth).
The screen media has contributed to Svebölle becoming a more productive, cost-efficient and potentially safer workplace. The 2-5mm product is produced more efficiently, with fines in the final product reduced from six per cent to three per cent. This improved product quality has made NCC’s products more competitive, and ideal for concrete production, among other applications.
The hard wearing nature of the WX7000 polyurethane screens has resulted in safer handling and increased production capacity. This is due to the elimination of manual cleaning and screen media life being extended by more than 10 times that of the previous wire mesh. This more efficient operation has reduced the cost of production, providing NCC Svebölle’s management with greater peace of mind and confidence in Nyrand Grusgrav’s production capabilities.
Source: Sandvik Construction