Reasons for low flow rate after maintenance of the circulating water pump
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Our company’s circulating water system is equipped with 2 single-stage, single-suction centrifugal pumps, with a flow rate of 400 m³/h and a head of 50 m; the motors associated with these pumps have a power rating of 75 kW. 1 set of frequency converter with 2 water pumps, 1 in use and 1 as backup; the frequency converter maintains a constant water supply frequency of 45 Hz. The two circulation pumps have been operating normally for 5 years; after the last maintenance, the current of one of the pumps decreased, and the outlet pressure at 110A was 0.24 Mpa ； The other pump is working properly, with a current of 140A and an outlet pressure of 0.3 Mpa. On-site process configuration of the water pump: circulation water tank, inlet butterfly valve DN300, circulation water pump, outlet pressure gauge, outlet check valve, outlet globe valve
When starting the faulty pump, the inlet and outlet valves of the other functional water pump are closed; there is no water at the outlet, thus eliminating the possibility of a problem with pump circulation
Two new impellers have been replaced, so the impellers should be fine now
Is the sleeve that fits with the impeller worn?
If the overcurrent components are not worn out, it is recommended to check the current value in the electrical room; in cases like this, it’s necessary to determine whether the gap of the impeller has increased.
This post was last edited by WSRYLONG on 2016-5-10 at 11:19: “Two new impellers have been installed; the impellers should be fine now.” 1. The impellers do not seem to be original factory parts. Please check whether the outlet width of the impeller is too narrow and whether its diameter is too small How has the diameter at the interface with the sealing ring changed compared to before, and has the clearance there increased? All three of these factors will cause a decrease in flow head. 2. I’m not sure what the purpose of adding frequency conversion is for you? It’s currently at 45 Hz; if it runs at 50 Hz, the traffic will be even higher. The frequency converter also consumes around 3% of the electricity. 3. The pump is currently operating in a zone where efficiency is low and energy consumption is high; it is recommended to replace it. If it operates continuously, the cost savings from reduced electricity bills can cover the initial investment within 3–4 months.
You don’t even explain what the maintenance work involves; that’s not acceptable
Whether cavitation occurs in the pump; if cavitation damages the flow channels, the pump’s flow rate will certainly not increase.
It is planned to replace the pump casing during the end-of-month shutdown for maintenance; a preliminary inspection during the last maintenance session showed no obvious wear on the casing
It is planned to replace the pump casing during the end-of-month shutdown for maintenance; a preliminary inspection during the last maintenance session showed no obvious wear on the casing