Need help with pump flow rate and head issues?
Thread Content
This post was last edited by jiahongleiqw on 2019-10-23 at 19:38. With the same piping system, a pump from one manufacturer is able to meet the required flow rate and head pressure; however, when another manufacturer’s pump is used, the flow rate increases significantly while the head pressure drops greatly. It becomes necessary to close the pump outlet valve to half its opening in order to achieve the desired pressure, and at that point the flow rate is met, but the pressure required at the end of the pipeline cannot be ensured. What is the reason?
Can the density of the design be matched?
The parameters of the pumps may vary.
The pumps from the two manufacturers have the same rated flow rate and rated head.
The pump from another manufacturer has a much higher flow rate, but its head pressure is much lower. . . . The rated parameters of the two pumps are the same, but the slope of Q-H is different, with the new pump having a steeper slope. But when operating at the rated head, the flow rate must be the same; otherwise the manufacturer is cheating you. For the new pump, keep the outlet valve fully open and the small return line slightly open to see if that works
What causes the large q-H slope?
"The rated flow rate and rated head of the pump are the same” – this condition does not hold; although the two well-known brands indicate the same values, in reality they are different. The speed of the impeller, as well as its diameter, width, and shape, all play a role in this. Pumps produced by reputable manufacturers may come with a flow and head curve for the pump, but it’s hard to say whether this curve corresponds to the actual performance of the pump
There are allowable errors for the performance curves and actual pumps. However, the pumps used in our country are all copied, as are their performance curves; so it’s really hard to say… Only those standardized joint ventures conduct performance tests on each pump.
For comparison, the pump’s curve graph.