Large fluctuations in the flow rate of centrifugal pumps – what harm do they cause to the pump?
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This post was last edited by 02042304 on 2012-2-23 01:05. The designed rated flow rate is 70 T/H, while the minimum flow rate of the pump is 20 T/H. This pump is a product transfer pump, and its outlet flow rate is affected by the liquid level in the suction tank. In order to maintain a stable liquid level in the tank during operation, the outlet flow rate often fluctuates between 30–60 T/H. What harm might this cause to the pump itself?
It is recommended to establish an automatic flow control system between your pump and the liquid level, using variable frequency speed control to regulate the flow rate； Frequent and large fluctuations in flow rate, as well as operation outside the designed conditions, can affect the service life of the pump, particularly that of the rotor and bearings ； There will be no problems when operating under the designed conditions ；
If this flow variation is not very drastic (for example, dozens of tons changing within just a few dozen seconds), it generally has little impact on centrifugal pumps.
Based on the parameters provided by the poster, I personally think it has little impact on the pump, but the best approach is to install an automatic adjustment device.
Each specific issue should be addressed individually. What was said on the second floor makes some sense, as pump design is generally based on the rated operating conditions; it is recommended to operate the pump within a certain flow rate range, otherwise its efficiency will decline and it is prone to vibration and other problems. However, these may not be the most important factors – changes in axial force are rather crucial, especially in pumps that operate under high pressure and with high flow rates.
I agree with what was said above. Excessive fluctuations in pump flow rate can lead to larger variations in the axial force acting on the pump. If these fluctuations occur frequently, they will result in large-scale, short-period variations in the axial force, which inevitably causes damage to the bearings. When the bearings are unable to counteract this axial force, it leads to increased axial movement and greater vibration. Prolonged operation under such conditions causes wear on the impeller and seal rings, further exacerbating the pump’s vibration and increasing its electrical current consumption while reducing its efficiency
I’m not sure what the revised investment budget is. I suggest installing a return flow mechanism after the pump, so as to maintain the pump’s flow rate constant; the level can then be controlled using a return flow control valve and an outlet control valve, thereby keeping the pump load unchanged. As for what kind of control to use, that needs to be handled by the colleagues in the instrumentation and control department; I’m not familiar with that.
I have a small question: is it true that the greater the outlet flow rate of a centrifugal pump, the greater the axial force on the pump? Please help answer this. Thank you!
As long as the pump does not experience cavitation, there will be no impact. The pump itself has a flow rate range. Pay close attention to the motor current.