PASTE & TAILINGS 2021
The pulsation free concept is now available for the GEHO ® DHT swing tube pump , through the introduction of a third cylinder combined with energy recovery in the HPU
only be controlled if their respective positions and speeds are monitored continuously during the complete length of the stroke . This is achieved with a linear transducer system that is integrated in the hydraulic side of each cylinder . The timing of the piston speeds and the corresponding opening and closing of the valves is critical for the correct functioning of the system .
Pulsation-free paste pumping
Erik Vlot - Global Product Manager GEHO ® Pumps , Weir Minerals , outlines how GEHO ® DH pumps provide reliability and performance
Hydraulic driven piston pumps are typically two cylinder , single acting , positive displacement pumps , consisting of a pump unit and a hydraulic power unit ( HPU ). The HPU drives one or more hydraulic pistons that are connected to the slurry pistons . When a piston moves backwards ( suction stroke ), the cylinder space in front of the slurry piston is filled with slurry . When the piston moves in the opposite direction ( discharge stroke ), the slurry is discharged from the cylinder into the main slurry line .
GEHO ® DHC hydraulic valve-style pumps work on this principle and have been applied in many projects over the years . Through the development of a pulsation free system , these pumps produce a constant and smooth flow , reducing operation and maintenance costs . Now the pulsation free concept is also available for the GEHO ® DHT swing tube pump , through the introduction of a third cylinder combined with energy recovery in the HPU .
The GEHO ® DH series are capable of pumping high-density slurries , mine backfill , paste and sludges . The GEHO ® DHC has cone valves and is suitable for pumping paste with a limited maximum solids diameter , while the GEHO ® DHT uses a transfer tube and can work with larger particles .
As hydraulic driven pumps typically consist of two cylinders , the pump discharge flow fluctuates when switching from one cylinder to the other . Flow fluctuations cause pressure pulsations , which can create enormous forces on the pipeline and the pumping system more generally . If the pipeline ’ s design doesn ’ t account for these pulsations , parts of the system can get damaged . Sheared‐off pipeline supports are the most common and visible result of this ; however , inline equipment – such as control and isolation valves or measuring equipment – can also get damaged . This inevitably leads to unplanned interruptions because if a piece of equipment or instrumentation is damaged the entire pumping system has to be shut down to carry out the required repairs .
One common way to reduce pressure pulsations is to use pulsation dampers in the discharge pipeline . A pulsation dampener is a vessel that ’ s pre‐pressurised with gas – usually nitrogen – and has a rubber diaphragm that separates the gas from the slurry . For optimal performance , the dampener is placed in the discharge line close to the pump .
The gas is pre‐compressed to a certain value that is determined by the operating pressure of the system . Flow fluctuations will be compensated by the dampener and will therefore automatically reduce the pressure pulsation level . But dampeners only work in a specific operating range and for smaller flow variation volumes and , thus , are less suitable for hydraulic driven pumps .
The most effective way of dealing with pressure pulsations is to avoid generating them . This is done by creating a discharge flow that is continuous , despite the reciprocating motion of the pistons . With a two cylinder pump this can be achieved if both pistons are driven independently of each other , where the cylinder working in the suction stroke has completed its cycle and has pre-compressed the chamber , ready for discharge , before the cylinder working in discharge has reached its end position . In this way a pulsationfree takeover is ensured . The pistons are controlled by a programmable logic controller ( PLC ) that directs the respective piston speed profiles so that the total net discharge flow is smooth , resulting in a constant discharge pressure .
The speed profile of the individual pistons can
Utilising a third cylinder
Specially designed for slurries with large particle sizes , the GEHO ® DHT ’ s third cylinder compensates for the flow variation during the switch‐over of the transfer tube . Rather than having the cylinder discharging a fixed volume into the main pipeline over a predetermined time period , a unique working principle has been devised . During each discharge stroke of one of the main cylinders , an additional flow above the nominal slurry flow is delivered , which is then fed into the third cylinder . The hydraulic flow from this third cylinder is transferred back to HPU and hydraulic pumps that are mounted on the same motor shaft . The additional energy required to move the third cylinder is mostly fed back to the same motor shaft , increasing the pump efficiency .
During switch‐over , the third cylinder discharges into the main pipeline , allowing the pump to operate at nominal flow . The third cylinder starts to ramp up when the discharge cylinder is ramping down in order to generate a smooth take over from one cylinder to the other . This constant flow ensures pressure fluctuations in the pump discharge line will be reduced to a minimum .
The GEHO ® DH pumps can be Synertrex ® enabled ; Weir Minerals ’ advanced IoT platform harnesses the latest digital technology to transform productivity , foresee risk and enhance performance . Operators have access to detailed real-time insights into how their equipment is performing , while machine learning enables continuous improvements .
Specially designed for slurries with large particle sizes , the GEHO ® DHT ’ s third cylinder compensates for the flow variation during the switchover of the transfer tube
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P12 International Mining SUPPLEMENT | JULY 2021