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72 E&MJ; • JUNE 2014 www.e-mj.com S C R E E N S Last month (May 2014, pp.66-71), E&MJ; looked at some of the major suppliers of screens and screen media, with specialties ranging from dewatering in coal washeries to aggregate production, scalping and trash capture in carbon-in-leach (CIP) plants. Operators clearly have a large number of choices, with some manufacturers offering packages of both the screen hardware and the media to go with it, while others spe- cialize in the development of media that can be fitted to other companies' screens. As a follow-up to that, E&MJ; asked a number of industry experts for their views on developments that have taken place in screen media over the past five to 10 years. The questions covered topics such as the materials now available for different appli- cations, the design of screen media, and problems that they commonly en- counter in connection with the incorrect use of media on screening plants. They were also asked for their advice on how screening costs can be reduced, as well as their predictions about screen-media devel- opments and usage trends in the future. A Question of Materials E&MJ; 's first question concerned develop- ments over the past five to 10 years in the materials used in screen media, and their durability. Derrick Corp.'s sales manager for North America, David Perkins, told E&MJ; that the company has continued its quest to produce the finest, long-lasting screen panels in the world. Derrick uses its own proprietary blends of urethane materials to achieve a panel that is robust, while maintaining the highest open area avail- able, he said, noting that in 2013, Derrick produced its finest urethane panel yet at 45 µm (325 mesh). According to Sandvik, over the past 10 years, it has developed a complete range of screening media, encompassing modular, reinforced and tensioned panels. In appli- cations with high abrasion, such as hard rock and metalliferous ores, it recommends the use of a high wear-resistant rubber, with the flexibility of the rubber being cho- sen based on the separation and applica- tion criteria. Separation at smaller sizes requires more flexible rubber, while heavy- duty applications (coarse materials and larger separations) require stiffer media. The quality of the rubber is key, with each product needing a high-performance rub- ber with outstanding mechanical proper- ties, the company said. Jeff Easton, a principal process engineer at WesTech Engineering, told E&MJ; that since the mid-2000s, the company has put significant effort into improving its special- ty screening products such as its media retention screens. Adsorption carbon as well as newer synthetic resins must be retained in a leach vessel by the inter-stage screen while at the same time allowing the miner- al slurry to pass through, he explained. "Wear on the screen media can be significant, impacting not only longevity but also consistency in the retention aper- ture over time as well," he said. "WesTech has combatted these challenges by utiliz- ing a high wear-characteristic alloy and steeper wire wedge angle, allowing its screens to not only resist wear, but also maintain an appropriate aperture range ensuring less loss of near-size value- loaded carbon or resin." Speaking for the Canadian company, Major Wire Industries, President and CEO Jean Leblond said that high-performance, self-cleaning screen media using polyurethane strips have been achieving increasing market awareness, replacing woven wire on the one hand and poly- urethane or rubber on the other. The com- pany's Flex-Mat 3 eliminates virtually any blinding and pegging, he said, and accel- erates stratification due to its independ- ently vibrating wires. "It lasts between three and seven times as long as woven Media Selection and Installation— The Fast Track to Screening Success The correct choice of media can be critical to the effectiveness of screening. Wire, rubber and polyurethane are all contenders, while suppliers have been focusing on making screen-panel maintenance simpler and quicker. By Simon Walker, European Editor Sandvik advises its customers that it is important to review the whole process when problems occur in screening operations. Understanding media choices and performance characteristics—and having the knowledge to con- duct a proper study to identify the actual problem—is key to finding an effective solution. EMJ_pg72-77_EMJ_pg72-77 6/3/14 3:06 PM Page 72