RO system installed with centrifugal multistage pumps fails in higher variations in TDS. Higher the TDS higher is the pressure required for the pump which can not be catered by centrifugal pumps. This is specially true when centrifugal pump with nearly flat curve is available. Reciprocating pumps give almost constant capacity with variations in pressure. So with respect to change in TDS the pump pressure changes automatically. RO needs the constant flow so that it does not fall to less then minimum flow required otherwise will foul.
The efficiency of reciprocating pumps which is say 80% are much higher compared to centrifugal pumps. This is very true for smaller flow pumps having capacities less then 20 m3/hr where the efficiencies of multi stage pumps are in the range of 40% to 60%.
The higher the pressure the more number of stages are required which results in higher maintance and chances of failure. Another important point is the higher the recovery higher the pressure required. Centrifugal pumps have limitations that the high pressure more then 25 bar is difficult to obtain where as for reciprocating pumps this pressures are small. Reciprocating pumps are available to even 1000 bar pressure where in Sea water RO the highest pressure required is 70 to 80 bar.
The pumps made by PressureJet has following important features making it world class product.