Coal Age

OCT-NOV 2017

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34 October/November 2017 conveyors Moving More For Less The industry is asking for conveyors with higher capacities, lower energy costs and safer, more reliable components, along with less environmental impact. Here's how system suppliers are meeting those requests. by russell a. carter, contributing editor Conveyor systems offer mine operators a seemingly simple solution to a perpetu- al problem — getting bulk material from Point A to Point B in the quickest, low- est-cost and most reliable way possible. And at the most basic level, a sufficient number of frames, pulleys, idlers and mo- tors, and a roll of conveyor belting can be arranged to transport just about any type of mined material almost anywhere. But, as the saying goes, "the devil is in the de- tails." Simplicity and engineering elegance are not necessarily one and the same, and the frequent need to assign critical pro- duction flow to a single conveyor system can elevate the risk of high downtime costs to a level that makes faulty design, component failures or unplanned mainte- nance unacceptable. The bulk conveying market is moving in the direction of larger, faster, longer and often more specialized conveyor systems that deliver high performance while re- maining energy efficient, and in some cas- es, causing less impact on the local envi- ronment. A rundown of conveyor-related project news illustrates the trend. Drives, Couplings Focus on Flexibility The capital costs of these systems are sig- nificant budget items by themselves, and CEMA (Conveyor Equipment Manufac- turers Association), the U.S.-based trade association for conveyor equipment sup- pliers, estimates that annual maintenance costs for a belt conveyor typically total about 5% of the purchase cost of the belt, and 2% of the cost of the structure and equipment. An unplanned shutdown of a main conveyor link at a large mine can quickly rack up additional lost-production costs, in addition to repair expenses, in the million-dollar range. To help custom- ers avoid problems, suppliers maintain a steady stream of product and service im- provements, along with technical guide- lines, to keep conveyors running reliably and efficiently. For example, the mechanism used to transmit power to large conveyors has a direct impact on system simplicity and reliability. Bosch Rexroth pointed out that its direct drives provide superior torque control from standstill, enabling trou- ble-free starting with a loaded conveyor. The drives' precise pressure limitation prevents overloading or straining of the conveyor structure. The motor is installed directly on the pulley shaft without a gear- box, foundation or fluid coupling, which makes for a simple drive solution that installs easily and saves valuable space around the pulley. Some of the main operational features of direct drives include torque control that protects the belt from overloads; soft starts and stops to keep belt stress to a mini- mum; the convenience of low speeds for belt inspection; and high-starting torque that can be maintained for an unlimited period of time. Bosch Rexroth noted that because the design of hydraulic direct drives is modular, it allows an optimal solution to be sized and tailored for any conveyor, small or large, from a few kilo- watts up to megawatts of installed power — and the original solution can be adjust- ed in the future if necessary. Hydraulic di- rect drives are easy to upgrade or adapt as needs change and develop over time. Last year, Voith unveiled its TurboBelt 500 TPXL fluid coupling — the first model in the new TPXL family, which combines the advantages of hydrodynamic drive Voith's new compact TurboBelt 500 TPXL drive needs only half the volume of conventional drives to provide equal power to the conveyor.

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