Problem of inability to pump fluid
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Recently, the pumps in the plant were modified by increasing the length of their inlets. Calculations showed that there was no issue with the net positive suction head, but the pumps had difficulty reaching full flow rates, especially at low temperatures. Checks revealed that neither the inlet filter nor the outlet check valve was clogged. Please help analyze the cause and suggest how to address this problem
The inlet pressure drop increases; try to minimize the use of pipe fittings such as elbows that cause a significant increase in resistance at the inlet； Or temporarily remove the inlet filter element and give it a try ； Or increase the inlet pressure.
Has the pump body been disassembled and reassembled? 1. The import resistance has increased. 2. The impeller clearance needs to be adjusted
Increasing the length of the inlet pipeline increases the pipeline losses, which in turn raises the required head. The pump in question might have had just enough head when it was operating originally; after the piping was changed, the pump’s head did not increase, which is why it couldn’t deliver the required flow rate. It is recommended to increase the impeller diameter to solve this issue.
I think there’s also an issue with the net positive suction head.
Does the density change when the temperature is low?
If that doesn’t work, switch to a larger-diameter pipeline
What is the medium being transported, and are there any issues with viscosity?
Check whether it is a problem with the operation, such as whether the pump has been filled with liquid before starting it.
Is it the fact that the density of the medium changes with temperature, which results in an insufficient amount being delivered?