PUMPS AND PIPELINES
GEHO pump and autoclave feed applications
The transition to a low carbon economy and mass electrification is driving demand for nickel and lithium , Erik Vlot , Weir Minerals , Global Product Manager GEHO ® PD Pumps , says . These metals are essential not only for electric vehicles , but also the batteries and power packs that allow wind and solar farms to store energy .
Both nickel and lithium are recovered using high-pressure autoclave technology , which pose a number of challenges from a pumping perspective . Notably , it requires pumping high pressure , high temperature and often corrosive slurry . Weir Minerals employs its GEHO heat barrier technology – originally developed in the 1970s in gold autoclave applications – in these arduous duties .
Understanding the pump dynamics in this application is complex , but , as an OEM with a proven track record of designing and constructing GEHO heat barrier pumps that have performed reliably for decades , Weir Minerals is best placed to size these pumps accordingly , according to Vlot . If this isn ’ t done correctly , it can lead to overload on the pump and , ultimately , pump failure .
Combatting wear
The slurry enters the pump through the suction valve and flows out via the discharge valve . Both valves come into direct contact with the hot , erosive and corrosive slurry , so it ’ s important that these valves are highly wear resistant . In more general applications , the valves have a valve ring that can seal off to guard against coarse particles . But , in high temperature autoclave feed applications , the valve and the seat have only metal-tometal contact and are more susceptible to coarse particle wear caused by ‘ wash out ’, which is localised wear due to slurry jetting between the seat and valve .
Therefore , when pumping a coarsely ground slurry , it is not uncommon to see premature valve failures caused by ‘ wash out ’ before the end of the valve ’ s normal wear life is reached , Vlot says . Combatting these challenges is twofold and encompasses both engineering , as well as servicing aspects . In terms of the technology , GEHO heat barrier pumps have a unique valve design with special material selection that results in superior valve life in these arduous duties , he added .
From a servicing perspective , in addition to replicator valves failing prematurely , these pumps aren ’ t backed by a full-service offering on many occasions , according to Vlot . Weir Minerals , in contrast , has a global footprint with servicing and support capabilities , which includes having consumables on-hand , in all major mining regions .
Limiting diaphragm temperature
“ GEHO heat barrier pumps have a unique combination of separator , cooler and diaphragm section whereby hot slurry is cooled and any contact with the pump ’ s moving parts is eliminated ,” he said .
“ The separator section prevents the hot slurry from directly exchanging heat with the slurry in the cooling section , thereby minimising the amount of cooling capacity required . In large pumps , this is achieved with a freefloating separator disc that follows the piston and diaphragm movement . The heat exchanger , in the cooling section , then cools down the slurry and prevents hot slurry from coming into contact with the diaphragm .”
The diaphragm separates the slurry from the pump ’ s moving parts , ensuring these can be maintained at predictive intervals of 8,000 hours , which is usually once per year , according to Weir Minerals .
Lithium and gold autoclave applications
For lithium and gold autoclave feed , two-cylinder , double-acting piston diaphragm pumps are usually used , Vlot says . They are equipped with a horizontal and vertical heat barrier section , with a cooler installed in the vertical section . This design allows for thermal expansion of the piping . Due to the limited flows for these applications , these pumps are smaller and no separators have to be used . Static mixers are sometimes used to avoid a hot inner core of slurry accessing the diaphragms , which has been a proven solution that has been applied for decades , according to Vlot . GEHO pump design ensures diaphragm temperatures are kept significantly below 100 ° C to ensure pump availability . Similarly , this has been fieldproven in dozens of pumps operating for decades , he says .
Reliability in nickel autoclave operations
In nickel autoclave applications , piston diaphragm pumps must handle larger volumes and pressures , translating to higher dynamic loads . These larger pumps introduce more flow and pressure pulsations , which present further challenges . To cope with these loads , GEHO heat barrier pumps have a single piece casted power end and forged steel crankshaft .
“ These have been field-proven for decades , which speaks to their reliability ,” Vlot says . “ Earlier designs included a welded frame and casted crank shaft , but , due to the higher probability of manufacturing problems and pump failures , Weir upgraded its design and , thus , increased pump reliability decades ago .”
Furthermore , the GEHO TZPM heat barrier pumps feature a slidemounted frame , which enables the full pump to slide backwards a few millimetres when it expands . This prevents pump piping from bending and eliminates undue stress and the formation of cracks , according to Vlot . It maintains the integrity of the pump without using expansion seals that are subject to premature failure . Suction and discharge air vessels are also installed to compensate for the flow and pressure pulsations generated by the pump , ensuring vibrations of the pump and connected piping are minimised .
Trans-Pacific Partnership ( CPTPP )’, it has become even more important that we , as a UK manufacturer , offer mines around the world a premium quality and fast pump solution using the Cornell pump that we represent . To do this we need to use engines that the mines already have on site and , with no engines from certain traditional manufacturers being stocked in the UK , we had to think outside of the box .”
After working extensively with large Cummins engines , DXB assessed it would be able to offer over 90 % of its mining pump offering with Cummins engines built in the UK and able to be used in regions with high sulphur content and differing emissions laws .
Ruffles concluded : “ We are delighted to work with a premium quality manufacturer with a huge history in mining , like Cummins . The fact that their manufacturing plant is based in the UK means that well over 65 % of the components are UK-sourced and enable us to be sold in the new free trade region covered by the CPTPP that the UK Government is about to sign , meaning for those mining companies operating in countries like Indonesia , Peru and Canada , they can purchase Cummins-powered Cornell pumpsets tariff-free from DXB Pump with short deliveries .”
DXB Pump & Power is looking to improve the delivery times of pumps by addressing the engine issue that has affected suppliers across the globe
44 International Mining | JUNE 2023