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60 E&MJ; • JUNE 2014 www.e-mj.com C R U S H E R S Siemens noted that one particular area where its control sys- tems are proving invaluable is in torque sharing in HPGR plants. Since there are separate drives to each of the rollers, it is essential to have equal torque sharing—if this is not the case, one roller will end up doing more work than the other. Once this happens, there will be more wear on that particu- lar roller and throughout its drive components, so maintenance and wear-part replacement will increase. However, the other roller will probably still be serviceable then, and will only need maintenance later on, meaning that overall, downtime will be higher and the crusher will be out of action for longer. Siemens stated that as different sizes of material enter the HPGR rolls, fast torque-to-speed response is critical. Enabling the machine to compensate for load variations allows for more consistent quality, less strain on components, and lower ener- gy consumption. Speed compensation also adjusts for the reduction in the roller diameters resulting from wear on the roller faces. Siemens said that it uses a proprietary load-sharing technology to ensure that torque is shared accurately to with- in 1%—reducing wear on mechanical components and pre- venting system overloads. Continuous speed control also reduces process vibration by compensating for variability in the ore feed. Electrical Drives Bring Benefits Turning to conventional mining crushers, Siemens noted that the inclusion of an electrical drive at the crusher's front end provides benefits such as improved energy efficiency during operation as well as a reduction in the inrush current at start- up. Together with smoother control during startup, this in turn helps to reduce any negative impact of crusher operation on the stability of the power network, the company added. Other benefits include the optimization of the relationship between torque and speed control, which allows the machine better to compensate for variations in the ore characteristics. Accurate speed control also helps maintain consistency in the size of the crushed material, while the use of an effective elec- trical drive gives the operator improved capabilities to avoid or clear system jams. As well as this, crusher systems with multiple motors bene- fit significantly from drive control as mechanical wear caused by torque imbalance is reduced, Siemens said. There is also greater operational flexibility through the use of independent motor control, while maintenance requirements can also be simplified. Writing in the most recent edition of the company's cus- tomer magazine, Results , Metso's Pasi Airikka explained that automation decreases variations due to raw material quality changes, process and machine loads, and external circum- stances such as moisture contents and the weather. "Consequently, stabilized variations result in better production, quality and plant availability," he said. A product manager for Metso Automation, Airikka noted that while even the most intelligent process automation system for a crushing and screening process may not outperform the best operator at his best—in the long run, it will prove its worth. "Achieving maximum results requires integration of the process, machine, and automation expertise already in the plant engineering and design phase," he stated. COMPANY PROFILE-PAID ADVERTISEMENT The Hannay 2000 Series reel is ideal for hydraulic or gas welding applications and handles temperatures from +20¼F to +400¼F. Hannay Reels, the world's leading manufacturer of industrial hose and cable reels, offers a wide range of cus- tom design capabilities to produce a variety of heavy-duty models ideally suited to meet the unique needs of mining applications. 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