Seeking help regarding the issue of low current operation in shielded pumps
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I would like to ask: Centrifugal pumps are prone to cavitation when operating at low flow rates, which can cause damage to the pump. Since the flow meter is inaccurate, the flow rate can only be determined by the current. What percentage of the rated current is the lowest allowable current when the shielded pump is in operation?
This post was last edited by Xiu Pump’s Xiaoxixi on 2021-1-16 09:15. What is the opening degree of the pump outlet valve? Is frequency conversion used when the motor starts? How is the flow rate controlled? The normal flow rate must not be lower than 70% of the rated flow rate, and the rotational speed must not be lower than 70% of the rated rotational speed
The manual valve at the pump outlet is fully open, and it is controlled by the control valve located behind it; for a pipe diameter of DN150, the opening degree is 20%. The abnormal reading on the flow meter cannot be addressed for the time being. So it is determined by electric current. I just want to ask by how much this current should be above the rated current.
You can’t rely on experience for this question; it depends on the compatibility between the pump and the motor you choose. Check the performance test results sheet of the pump, look at the rated point, the minimum flow rate point, and other values related to the operating current during tests – from these values, it is possible to determine the current required under the actual flow conditions of the medium being used (sometimes the manufacturer will also calculate this value using a curve). Based on this current value, it is then possible to determine the safe flow rate desired.