TAILINGS dams in this case , Wikipedia ( 2024 ) states that , “ the use of generally lower design factors is used because the costs associated with structural weight are high ( ie , an aircraft with an overall safety factor of 5 would probably be too heavy to get off the ground ). This low design factor is why aerospace parts and materials are subject to very stringent quality control and strict preventative maintenance schedules to help ensure reliability .”
Ulrich concludes : “ The exact origin for the nearly universal acceptance of the 1.5 safety factor for dams and tailings dams seems to have been lost to obscurity . More important than the adoption of a single and unique value , though , would be to combine the recommendations from the GISTM together with the advice from the 1970 USACOE document . I , personally , would also add recommendations to employ judgment , experience , assessment of uncertainty and consequences of failure while also employing ‘ stringent quality control and strict preventative maintenance schedules to help ensure reliability ’ when developing a site-specific factor of safety .”
Schwing Bioset piston pumps at Aripuanã
Chuck Wanstrom , Schwing Bioset Director New Business Development , has outlined a major project it conducted at the Aripuanã mine , owned by Nexa Resources , in the state of Mato Gasso , Brazil . Aripuanã is a polymetallic underground mine that went through upgrades in 2022 that extend its operating life an additional three years , to a projected 14 , with a nominal production target of 6,065 t / d .
Several mining methods are employed at the site including bench stoping , longitudinal retreat , and transverse stoping , as well as both cemented and paste backfill . As part of the backfilling operations , Nexa Resources enlisted the consulting engineering firm , Minefill Services , to issue a tender package to begin the procurement process for the paste pumps in 2019 .
After evaluation of the received offers , three Schwing Bioset model KSP 220 H ( HD ) XL piston pumps were selected to deliver up to 150 m 3 / h of cemented tailings at pressures up to 130 bar . The pumps are powered by 600 kW power units , each comprised of two 300 kW motors . The power pack systems also include a customised sound attenuation enclosure to limit sound levels while operating to no more than 85 dBA .
The dual motor configuration in the power pack provides redundancy as , in the event of an unexpected failure of a motor or hydraulic pump , the pump can continue to operate at half capacity with only half of the power unit functioning . This allows the site to either complete the pour or allow the pipeline to be cleared until repairs can be made .
The piston pumps are also equipped with Schwing Bioset ’ s proprietary Ideal Control Circuit ( ICC ) technology that is internal to the pump design . The ICC is a dampening system that mitigates undesirable pressure transients in the pipeline that , are at times , observed with piston pumps by alternately ramping pumping speed down at the completion of a pumping stroke and gradually ramping up speed at the beginning of each new pumping stroke . This ramp up / down feature controls the material velocity in the pipeline and prevents the abrupt changes in material momentum that may otherwise induce water-hammer in the pipeline .
Another feature of the selected pumps is the inclusion of the optional Paste Flow Measuring System ( PFS ). The PFS will measure to within +/ - 5 % the volume of paste that has been pumped . This provides useful operating data that can be trended over time to schedule maintenance activities by tracking the overall performance of the pump and trending wear rates of replaceable components . The PFS also allows verification of the volumes of paste pumped to each stope to ensure the cavity has been adequately filled .
Wanstrom says that these features , combined with Schwing Bioset ’ s reputation for highquality reliable equipment and aftermarket support , made the pump selection an easy
choice .
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APRIL 2024 | International Mining 63