Regarding the outlet flow rate of the pump
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Our unit has a new pump with a rated flow rate of 240 t/h. It is currently under trial operation: an outlet valve opening of 18% already results in the outlet pressure required for normal operation, but opening it further causes overload, with the flow rate dropping to only 80 t/h. Could this be due to an issue with the selection of the pump motor? The vortex flowmeter is relatively accurate.
First, vortex flowmeters are not particularly reliable. Second, it is necessary to understand the relationship between pressure and head, as well as the concept of outlet pressure. The original poster could provide the density of the medium, the pump’s head, as well as the inlet and outlet pressures of the pump, so that everyone can conduct a detailed analysis.
The medium is water, the inlet pressure is at atmospheric pressure, the outlet pressure is 1.8 MPa, and the head is 177 meters. Thank you!
It’s very likely that the vortex flow meter is inaccurate.
I think it’s probably because the motor has too low a power rating; I’ve encountered similar problems before. Our refrigeration cycle pump is designed to handle 50 cubic feet per hour of flow rate; it operated normally when the valves were opened just a little, but it became overloaded once they were opened to one-third of that level. The manufacturer later determined that the motor power was insufficient, and the problem was resolved after replacing the motor.
I have encountered this problem as well; the issue lies in the fact that the pump’s head rating is set too high. If you want to use this pump, please contact the pump manufacturer to have the outer diameter of the impeller reduced.
First, determine whether the pump selection offers excessive head based on your process parameters, and then consider reducing the size of the impeller or replacing it with a motor of higher power
May I ask the original poster, is this pump used to transport oil or water? If it is intended for transporting oil, but testing is carried out using water, then this phenomenon is normal, as the density of water is higher than that of most oils, resulting in higher shaft power and outlet pressure.
“It’s a new pump with a rated flow rate of 240 t/h. During the trial run, an outlet pressure of 1.8 MPa was reached when the outlet valve was opened to 18% of its full position. I want to know whether the pressure gauge should be installed before or after the control valve; if it’s installed after the valve, and the pressure remains this high even after flow is restricted, then it means the diameter of the pump’s impeller is too large, and it needs to be re-machined