The flow rate of the metering pump fluctuates greatly, extremely!!!
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It’s a metering pump of the hydraulic diaphragm type; there is no blockage at the inlet and outlet, the check balls are in good condition, the temperature of the material remains stable, the pipelines are in order, and the oil pipes and other equipment are functioning properly. Yet the flow rate fluctuates greatly – neither manual control nor frequency conversion can stabilize it. What should I do, dear colleagues???
Try installing a metering pump pulse buffer!!
Add a sac-type buffer tank or pulse buffer on each side for import and export, OK
We have encountered such problems as well. I think it’s possible that there is an issue with your flow meter, or there could be a problem with the oil in the diaphragm chamber of the metering pump. Whenever there are fluctuations in flow rate, this is the first thing that comes to mind; it’s quite common for low oil levels in the diaphragm chamber to cause fluctuations in the flow rate at the pump outlet. You should also consider whether the pump’s stroke might be stuck – that’s another possibility.
Just add a damper and a backpressure valve. . .
A buffer tank and a backpressure valve can be added at the outlet
Now the flow rate is under normal and stable control!!! There is indeed a pressure-reducing valve; during the piping installation, the mechanical staff forgot to include a buffer tank. We didn’t want to stop production in order to make modifications, as the system operates with just one pump – stopping that pump means stopping production altogether. With no other option left, we took the risk of damaging the pump by closing the manual valve behind the flow meter for ten minutes; as a result, the flow rate increased by 6 times. Once the manual valve was opened, everything returned to normal, the frequency converter adjusted itself, and the flow rate stabilized! Could someone please explain this from a theoretical perspective???
Reply to 7# Lege: If that’s the case, then there is non-condensable gas in your pump, which is causing the pump to not deliver a proper flow rate. By closing the outlet valve and creating pressure, and then opening it again, you can improve the pump’s flow rate; the gas will be expelled once that’s done. . .
So next time we install the pump, we definitely can’t cut corners; multiple pressure stabilization and buffering tanks are still necessary. They help to stabilize both pressure and flow rate, as well as to remove air from the system. Thank you all!
Add a buffer (with an inflation pressure of 30-50% of the operating pressure) and a backpressure valve (set to the operating pressure range). I have another question for everyone: regarding the steps for starting a variable-frequency diaphragm pump, could anyone share that information? Also, is the coordination between the pump’s stroke and the frequency converter the same as in the case of variable-frequency centrifugal pumps? Does one start the motor at 40% frequency first and then adjust the pump’s stroke?