Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
Issue link: https://emj.epubxp.com/i/689616
SCREENS JUNE 2016 • E&MJ; 63 www.e-mj.com sections are steel-backed rubber pan- els that combine a proprietary blend of natural gum rubber with a high-strength/ low-alloy steel plate backing, making it ideal for tough, abrasive applications. According to Polydeck engineers, Arma- dex panels are created using a Binary Injection Molding (BIM) technology, which is a proprietary Polydeck manu- facturing method that produces 10 times the pressure normally used to produce compression-molded rubber. Poydeck said combining this process with premi- um natural gum rubber and HS/LA steel plate backing produces unprecedented strength, which results in longer wear life at lower costs per ton. Hoffman said, "We've got the best wash plant in the Klondike, hands down." His crew reported that over two seasons, they have put more than 800,000 yd 3 of abrasive, quartz-flled material over the rubber and polyurethane decks, at an av- erage of 250 yd 3 /h—running 24/7 from June through September each season. "The decks still look great and we've max- imized our uptime and saved big bucks on maintenance and labor. For example, if we had used standard AR Steel plate on our feed end (vs. the Armadex), we would have been changing that out once a week," said Turin. Big-picture Performance Mike Garrison, a Polydeck product sup- port specialist, has conducted hundreds of screen performance evaluations in the mining industry. He traveled twice to the Yukon to visit the 316 Mining site to complete an evaluation and offer solu- tions for greater effciency. "We offer the technical assistance that goes beyond looking at screen media and examines the entire screening circuit—to make the circuit more reliable, to increase their re- covery; and to minimize maintenance," said Garrison. Evaluations record a screen's orbits; motor speed; any harmful defections along the Z axis; material travel rates; and any movement of the support struc- ture. It also examines a screen's criti- cal frequencies to help determine the screen's optimal speed and stroke. Im- portantly, the fnal report includes any recommended adjustments to a screen's operating parameters and/or media to maximize its operating potential in its particular application. Within Garrison's detailed report, an example of one of the major issues uncovered during the evaluation is that the combination of the screen's dis- placement and acceleration was ex- cessive for the bottom-deck apertures (openings) and was likely contributing to ineffcient screening on the bottom deck. The level of acceleration was also causing body (Z) axis defections along the bottom deck. Consequently, adjust- ments were made resulting in an 11% reduction in the displacement (stroke) of the vibrating screen. "This adjust- ment boosted overall recovery and had an immediate effect upon overall eff- ciency," said Garrison. After fne-tuning the screen's operat- ing parameters, Turin reported that they saw a noticeable improvement in the bed depth and carryover on the bottom deck. "We have increased production to 280 yards per hour with very little car- ry over. Depending upon the quality of pay dirt that we run, our recovery rate is between 3/4- and 1-1/2-ounces for ev- ery hundred yards of material over the screen, which is a signifcant increase over last season," said Turin. While ini- tially skeptical of all the troubleshoot- ing, Turin said the results achieved after completing the recommended adjust- ments has him convinced of the value of conducting periodic screen perform- ance evaluations. Science and Synergy Optimum screening performance is less about trial and error, and more about un- derstanding the science of screening. The Hoffman/Turin crew acknowledged that its partnership with Polydeck has allowed them to "dial in" their requirements; and continually identify areas that will deliv- er the greatest return. Ultimately, it's all about less risk and greater recovery. This article was written on behalf of Polydeck Screen Corp. by Carol Wasson, an Indiana, USA-based freelance writer specializing in the aggregate and con- struction equipment sectors. Turin and Todd Hoffman (right), another cast member, say they are convinced the initial cost of installing polyurethane and rubber media panels and parts is signifcantly offset by reduced labor requirements and longer service life provided by the Polydeck products.