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
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PUMPS & PIPING Pumps and Pipelines Keep Mines on the Move From dewatering their workings to handling tailings from the mill, mines rely on pumps and pipework to keep fluids flowing. By Simon Walker, European Editor Efficiency Optimization Can Pay Dividends KWH Pipe supplied 37 km of slurry and water pipeline to Boliden during the recent expansion at the Aitik copper mine in Sweden. The pipes' flexibility allows them to bend and absorb stress caused by ground movement. Mines can't function without pumps and pipework. Period. At the front end of an operation, dewatering is key to maintaining production, be it from underground or an open pit. By the time ore enters the processing plant, slurries need transporting. Even in the rare instance of gravity mills where the flowsheet runs sequentially downhill, there will be some need for recycling material, involving both pipework and pumping. Within the plant, reagents have to be handled, separated flows directed to the appropriate next treatment stage, and at the end of the whole proceedings, tailings deposited and reclaimed water recycled. Things get even more complicated once backfill plants are in use, with further demands on equipment that is capable of handling abrasive slurries over long periods without requiring excessive maintenance. 68 E&MJ; • APRIL 2013 Each of the components involved in handling fluids that can be corrosive as well as abrasive has specific requirements in terms of the materials used in their construction, while the aim is always to keep maintenance and repair costs to a minimum. Manufacturers today offer pumps, pipework and valves made of materials that are appropriate to the duty required, with heavy investment having gone into developing new metallurgy that can provide better service at lower overall cost. Lighterweight plastics are also playing an increasingly important role, especially in pipework, while the reliability of valves has improved over the years, giving more precise control over fluid flows of all types. E&MJ; asked a number of the leading international suppliers of fluids-handling equipment for an update on their current product offerings. Here are some of their responses. According the German manufacturer of pumps and valves, KSB, the economic efficiency of groundwater extraction—as is often needed in open-pit and opencast mining—hinges on the overall efficiency of the submersible borehole pump employed. Poor efficiency costs lots of energy, so investing in a new, more efficient pump can pay for itself in less than a year by slashing energy expenditure. KSB states that one-third of all submersible borehole pumps work inefficiently. Since the late 1980s, it has examined the efficiency of more than 2,700 well pumps, with the results from these studies showing that 37% of the pumps it examined had an overall efficiency of less than 40%. For the user, this translates into excessively high operating costs. KSB points out that—assuming that the original choice of pump was correct— poor efficiency is often the consequence of a change in the pump's duty point. The most frequent causes are a deterioration of the well inflow distance (the well's filtration properties have changed and the pores of the gravel filter pack or layer are plugged up); changes in the groundwater level, since this can rise or fall over time; reductions in the pipe diameter; and pump wear. If the pump is responsible for poor efficiency, the most likely cause is wear. This can usually be traced to the pump's casing wear rings, which can be gradually abraded by sand entrained in the fluid pumped. Incrustation in the pump, the piping or both is another potential cause for a loss of pump performance, this being the accumulation of iron oxide, calcium or manganese on the inside surfaces. Having the wrong duty point means a waste of energy. In a real example, a 30-kW submersible borehole pump was designed to deliver 150 m3/h at a discharge head of 53 m. Because of licensing constraints, the operator had to limit the www.e-mj.com