We have an RO plant that the high pressure pump was supposed to work at 12 bars at start-up regarding the projection software report, but it's working at 14 bars (both @21 C & same TDS & recovery) to get design recovery. Have you experienced such difference between real operation condition and software report before?
If the system is new, then maybe you should check the quality of the antiscale product you are using. Even the dosing of the antiscale material counts. It should be chosen accordingly with the feed water analysis.
Dear Ali. The conceivable reasons would be membrane fouling, piping joints blockage or non-original membranes. With assumption that the system is new and has been properly flushed before coming into service, the two other reasons remains.
My suggestion is checking system pressure drop after unloading all membranes. Then you would find out if any blockage is there.
Also checking individual membrane test in a dedicated pilot containing a single membrane PV and required indicators to see if there is any difference between actual test amounts and ones reported by the manufacturer.
There is the membrane design (RO projections) and the system design (permeate pressure, pressure loss in feeding lines, pressure loss in RO skid and etc).
Maximum pressure of selected pump is always higher than the design duty point. The pressure goes up as the membrane becomes old and resistance to filtration starts developing. If throughput decreases even at high pressure then membrane needs replacement.
if all parameters in the projection matching with the actual operation conditions except the feed water pressure at the membranes inlet (after all valves and fittings), then check the following:
- accuracy of the pressure gauge reading.
- high pressure pump suction pressure.
- consult the membrane manufacturer and/or RO manufacturer.
What kind of pump? Centrifugal or positive displacement? If centrifugal then the pressure and flow are linked. What is the differential pressure across the pressure vessels? Is the module array the same as is assumed in the projection? Are there additional elements or pressure vessels there may be extra pressure required. Is the TDS the same as assumed in the projection? Can you measure the flow into the system? How is the pressure controlled on the concentrate side of the elements? Can you measure the actual flow? Are you getting more than the design permeate flow due to the higher pressure? Many different possible problems to consider. Pump, control valve, element array, feed TDS. Does the pump have too many stages? Good luck.
Dear Pat, your questions answer: 1- Centrifugal pump; 2- three stages RO, first stage dp: 1.3 bar; 2nd stage dp: 0.8 bar; 3rd stage dp: 0.7 bar; 3-The module array is the same 4- There is no additional membrane or vessel, operation conditions are same as design. 5- At concentrate side we have globe valve to adjust the pressure 6- We don't get more than design flow (permeate) by higher pressure 7- Pump is horizontal, multi stages.
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