IM 2020 June 20 | Page 56

MINING PUMPS diaphragm pumps in the process circuit to handle the underflow from the thickener at this operation. This stream had a solid content of 58-72% (by weight), along with an abrasive material both difficult to handle and pump, it said. ABEL said: “Due to these properties, the equipment used for transferring these materials acquires a high level of wear, unexpected downtime, unscheduled maintenance, etc. These are costs that the mining industry cannot accept.” Originally, two centrifugal pumps were installed in an unconventional way to perform the required task at the operation. ABEL explained: “Centrifugal pumps are designed for specific conditions which generally never occur given that the operating flow and the solid content of the materials being transferred vary during operation due to pressure fluctuations in other phases of the process. “In such circumstances, this type of technology sees its performance dramatically reduced, which directly impacts the pumps’ output, causes product recirculation and frequent downtime of the related production line.” The ABEL HM hydraulic diaphragm pumps now installed use piston-diaphragm pump technology and, therefore, can be operated for one year under the described conditions without requiring any preventive or corrective maintenance, according to ABEL. Among the benefits of ABEL HM pumps are: n A performance range of up to 100 m³/h and 10 MPa; n The ability to transfer media with a solid content up to 75%; n Extra-large suction valves for a high degree of volumetric efficiency; n Equipped with a pre-formed diaphragm to improve pumping efficiency, durability and availability of the equipment; n Offer constant operating flow, independent from the discharge pressure, which is mainly influenced by fluctuations of solid contents; and n The strokes per minute are low, ensuring low mechanic wear. Wear life and corrosion protection Increased impeller, casing and back liner wear life were just some of the reasons why Namawka Diamonds chose to install a FLSmidth KREBS millMAX™ pump at its Kao mine, in Lesotho. FLSmidth’s engagement at Kao started when the mine required a pump conversion in the field – a difficult and time-consuming task, according to the mining OEM. “It is also a high-stakes operation as a cyclone feed is critical to the overall process and ability to generate returns. A wrong decision can mean a lot of lost revenue,” FLSmidth said. It was the potential for cost efficiency that convinced the Kao diamond mine to implement the KREBS millMAX Pump, according to FLSmidth. After initial discussions, the first trial pump – a millMAX 8×6 centrifugal seal – was installed in a cyclone feed application. Initial results after seven months showed the millMAX was performing extremely well on the wear side, FLSmidth said. Brad Moralee, Head of Product Unit Pumps, Cyclones and Valves at FLSmidth, said: “It’s high pressure for us: you are typically given a window of opportunity during a shutdown to complete the change, after which the new pump must run as expected when the plant is re-started. “You need the combination of a great product but, more importantly, great technical understanding of the duty to be able to propose the correct solution. We understand what is at stake from the customer side.” The change produced impressive results in comparison with the previous solution from another supplier, according to FLSmidth, with the millMAX pump increasing the wear life by nine times across the impeller, casing and back liner. “This has seen Kao make significant cost saving on direct replacement costs, reduced downtime and saved labour expenditure,” the company said. While Kao mine operators were impressed with the benefits from the switch, a slight gland leakage was causing concern, according to FLSmidth. To resolve this, it suggested running a one-month trial with the slurryMAX, which had only just arrived on the South Africa market. “The slurryMAX trial was based purely on its sealing capabilities as Kao were confident of the hydraulic performance of the pump and had no concern about wear,” the company said. Kao’s confidence also came from the fact the slurryMAX design is based on the millMAX range, whose wear ring technology has created an efficient and long-lasting slurry pump, FLSmidth said. The main difference between the two is the millMAX is an all-metal pump without an outer casing and an inner wear liner (the casing itself is made from the high chrome wear material), while the slurryMAX is a split casing design that has a replaceable inner liner. The purpose of this design is that multiple material liner options are available to fit in the same outer casing. “The slurryMAX features an improved, more efficient impeller and an optional water drain plug for easier maintenance, allowing water that might have settled at the bottom of the pump to be drained quickly,” the company said. Leigh Rieder, FLSmidth Sales Engineer, concluded: “Kao is extremely happy with the hydraulics and lack of excessive wear of our pumps, which has meant that their cost of ownership is low. We have recently received an order from the customer for two more slurryMAX pumps and they have expressed interest in our slurryMAX 6×4 and slurryMAX 10×8 pumps.” As well as producing general drainage pumps, Tsurumi Manufacturing Co has put considerable effort into designing pumps for applications for difficult-to-handle materials, such as corrosive and high temperature liquids and seawater. In recent years, polluted water and runoff from mines and quarries have been cited as social problems in many countries to the point demand for pumps that can handle such liquids has increased year-on-year. According to Tsurumi, more than 40% of the runoff from mines is strongly acidic with a pH value of less than 4. To cater for this demand, Tsurumi recently launched its LH-14/LH-W-14 series corrosionresistant pumps that use 316 stainless steel. This type of molybdenum-bearing steel enables the pumps to handle corrosive acidic liquids and chemical-rich fluids with low pH values, according to the company. The use of highly corrosion-resistant materials goes beyond the pump casing, with all parts exposed to low pH fluids – including the impeller, motor frame, outer cover, strainer stand and flange – thoroughly protected from corrosion, according to the company. “These pumps deliver the durability needed in harsh fields where pumps made of aluminium, stainless steel and cast iron suffer damage in a matter of weeks, if not days,” it said. Cylindrical and slim, the pumps can be installed in a well casing for deep well dewatering, according to the company. The centre flange construction, meanwhile, assures a stable installation even if fixed by the discharge pipe. The pump incorporates seal pressure relief ports that prevent pressure from being applied on the shaft seal. Furthermore, to endure even extended operation at low water levels, these pumps feature a flow-through design that forcibly cools down the motor, Tsurumi said. The LH-14 series has a single impeller, with the LH-W-14 series having dual impellers. They are both available in a product line up that covers a discharge bore diameter of 80-200 mm, motor output of 11-110 kW, and heads of 51.8-184 m. These pumps, as well as Tsurumi's general drainage pumps, are equipped with an antiwicking cable, motor protector, SiC dual inside mechanical seals with silicon carbide faces, and oil lifter. The material used for the rubber parts, such as the mechanical seal, oil seal, O-ring and packing, uses fluorocarbon rubber to provide high resistance to heat and chemical exposure, meanwhile. “With these features, Tsurumi pumps are designed to provide high reliability and excellent durability, enabling continuous operations for long periods,” the company said. IM 52 International Mining | JUNE 2020