MechChem Africa talks to JD Singleton, process director for Weir Minerals Africa, about the company’s five core Integrated Solutions offerings for: pit and underground mine dewatering; crushing and screening plants; mill circuits; mineral beneficiation plants; and tailings management.
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The Weir Group PLC has been advancing the efficiency of pumps, valves, hydrocyclones, mill lining, crushers, screens and a host of interrelated equipment for nearly 150 years. “And our curiosity and determination to find efficient solutions remains as strong as ever,” says JD Singleton of Weir Minerals Africa.
“Increasingly, we provide customers with total solutions that optimise their entire process, removing any bottlenecks and holistically maximising wear life and recovery efficiencies, while minimising downtime and ownership costs,” he says.
From a minerals’ perspective, Singleton says the company’s Integrated Solutions offering can be categorised into five key areas: pit and underground mine dewatering; crushing and screening; the mill circuit; mineral beneficiation; and the management of tailings. “This general categorisation matches what we experience on customers’ mines, where there are separate plant engineers and section managers for the mine, its crushing plant and the mill circuit while a single manager is often responsible for the beneficiation and tailings plants or the back end of the circuit.”
Pit and underground mine dewatering
Dewatering, he says, is usually an essential first step before mining can begin. “While Weir Minerals has a whole spectrum of dewatering pumps, from clear water to high solids and slurry application across open-pit and underground projects, we find that engineered dewatering systems that include pumps, pipes, valves, controls and access platform or walkway solutions are always more effective than simply installing pumps.
“We design solutions using our Multiflo® or Warman® DWU pumps, which assist with high lift and high-volume dewatering. All solutions are application specific and designed to deal with multiple requirements: high volumes, heads, densities and accessibility. We may need walkways to get onto a pontoon in a pit, for example, and we are currently dealing with a client on an open cast coal mine that needs to anchor its pontoons against the sidewalls with suspended cables to ensure the system remains secure and in line with the fluctuating water levels.
“We manufacture pontoons that use Warman® DWU high-lift pumps that can deal with light slurries (specific gravities or SGs of up to 1.05), for example, into pressure heads of up to 130 m using a single stage centrifugal impeller. We also have our extensive Multiflo® MF range for higher head, higher volume applications.
“When pontoon access is impractical, diesel powered Multiflo dewatering systems with suitable priming additions can be mounted onto trailers and situated alongside the pit – and all of these solutions incorporate Isogate® valves and Linatex® hoses, combining best-in-class components to meet the applications’ exact requirements and wear characteristics,” he tells MechChem Africa.
Crushing and screening
Crushing and screening is the first processing stage for mineral ores once they have been extracted from the pit or lifted to the surface. “Our integrated crushing and screening solutions are centred around our Trio® and Enduron® brands, which can accommodate ore volumes from 40 to 1 500 t/hour. Solutions typically include the primary and secondary crushers, the interlinking feeders, the screens and all the conveyors required to move the materials to and from each crushing stage,” Singleton says.
“We have just won an order from an iron ore mine for the supply of primary feeders and crushers, and secondary crushers – including an Enduron® high pressure grinding roll crusher (HPGR) with HPGR product screens, which offers best-in-class wear life.
“Every sub-system used in this solution is from Weir Minerals and comes with our own process guarantees, so the client is dealing with us as single product supplier for everything needed to deliver suitably sized ore to the downstream processing circuit,” he adds.
As well as being the OEM for all the crushing and screening plant equipment, Weir Minerals process engineers such solutions. “We included a washing section to remove clay material from the ore prior to sending it to the Enduron HPGR. This involved using our Warman slurry pumps and Enduron dewatering screens and highlights our ability to bring together our wet and dry circuit expertise to create highly optimised plant solutions,” Singleton says.
Holistic mill circuit systems
The third category of Integrated Solutions is holistic mill circuit systems. “Before a mineral can be refined into its pure form, it has to be finely milled so the valuable mineral can be liberated from its ore. This has long been our bread and butter expertise,” he continues.
“We have been manufacturing mill circuit pumps, mill liners, hydrocyclones, hoses, valves and rubber liners for as long as I can remember and we are very good at it. We understand classification and value circuits, wear aspects of hydrocyclones and feed pumps, the wear inside the mill and the various lining options.”
For existing operations, for example, he says Weir Minerals has had significant success in applying computational fluid dynamics (CFD) to cyclone feed pump sump designs. “Excessive wear of hydrocyclone feed pumps can be caused by poor mixing in the sump. By optimising the flow and residence times in the sump, we have been able to double the life of the pump’s wear components and extend the life of the sump and interconnecting hoses. “In addition, more laminar feed to the pump results in better feed to the hydrocyclones, which results in improved plant recovery performance – an excellent outcome from a not so obvious intervention,” Singleton tells MechChem Africa.
On large mill pumps such as Warman® MCR®s, he says that Weir Minerals tries to match the changeout cycle times of the volute liners and throatbushes with the wear cycles of the mill. “When the mill has to shut down to replace the liners, the mill pump’s wear parts can be replaced at the same time. This avoids having to shut down the plant between mill shutdowns,” he explains.
“This is done by optimising the pump-liner materials and the hydraulic efficiency to extend the life of the wear components. Understanding the mineralogy of the slurry and its effect on the lining material is critical in this regard,” he adds.
This also applies to Weir Minerals’ Cavex® hydrocyclones. “Our entire range of Cavex hydrocyclones has laminar spiral inlets that minimise turbulence and result in increased efficiency and component life. Instead of using chrome carbide or ceramic liners, we can use replaceable rubber inserts over a mild steel casing, which not only improves the wear life in high silica content material, but customers are able to easily swap out the inserts onsite, minimising maintenance downtime,” he says.
For the grinding mills themselves, Singleton cites a success on a copper mill that involved using one of the company’s proprietary Linatex® rubbers to replace the commonly used steel liners for the inlet chute. “This has doubled the chute life, again avoiding having to add a shutdown to replace them. In addition, careful selection of the correct grade of Linatex rubber lining for the trommel screen on the outlet side has improved the overall wear life balance of the whole plant,” he tells MechChem Africa.
Once ore is milled, processing can begin to liberate high-value minerals. “We have done a lot of work on froth pumping: understanding the froth volume factors, froth generating factors and the sump geometry. We have found that froth is best discharged against the wall of the sump so that bubbles break down before reaching the suction inlet of the pump. To reduce turbulence, the resident time in the sump is also important. CFD analysis has proved very useful here, enabling us to optimise the flow through the hoses and valves and maximise froth pumping efficiency.
“We have froth pumping technology and expertise to make significant improvements in recovery efficiency for existing plants. These process plant optimisation solutions increase profitability through better recoveries, while also reducing costs: extending the life of pumps, valves and piping and reducing the number and duration of maintenance periods,” Singleton notes.
Tailings management
Weir Minerals’ tailings handling solutions have traditionally used various stages of Warman® AH and AHP high-pressure centrifugal pumps. From a systems perspective, however, the pipework must also be sized and lined correctly to suit the abrasive properties and density of the tailings slurry, and the number of pipe bends on the way to the deposition area, as well as in between the different pump stations, must be minimised.
Weir Minerals utilises its GEHO® range of positive displacement (piston) pumps for high specific gravity (SG of +60% solids) dewatered tailings that need to be transported against very high heads (above 300 m head or 30 bar up to 250 bar). “Using GEHO piston pumps enables dry-pumping of tailings, which minimises water and energy consumption. Again, these tailings circuits are built using careful combinations of pumps, valves, cyclones, hoses and pipelines. Many use our Cavex polyurethane-lined tailings hydrocyclones for dewatering the highly abrasive finely ground tailings,” he says.
“For us, this Integrated Solutions approach is underpinned by a holistic understanding of a client’s individual circuits and, because we understand our own equipment and have seen similar problems many times before, we can quickly generate tailored working solutions. This results in a quick return on investment for our clients,” Singleton concludes.
