3 replies to this topic

[Kakka]

Hello everyone,

I'm currently analyzing a centrifugal pump operating in recycle mode, where the flow is being recirculated back to the pump inlet instead of being sent to the system. I've observed the following behaviors, and I’m seeking your insights or experience with similar situations:

1. Constant Power Consumption:
   The pump seems to be consuming  constant power, even though the flow rate fluctuates significantly. I understand that the pump has to overcome internal and external resistances (friction, system head losses, etc.), but could there be other factors at play that contribute to this power draw despite the flow being minimal or fluctuating?

2. Fluctuating Flow Readings:
   The flow rate fluctuates even though the system should theoretically be stable in recycle mode. 

Has anyone experienced similar issues with centrifugal pumps running in recycle mode? If so, could you provide any explanations or suggestions on the following:

• Why would the power consumption remain stable while the flow readings fluctuate?
• What are the potential causes of fluctuating flow in this type of setup, and how can we stabilize or better control the flow readings?
• Are there any recommended troubleshooting steps or design adjustments to improve efficiency and flow consistency in recycle mode?
• What is the purpose of recycle mode? Is it to operate the pump within the preferred operating region or allowable?

If you could help me with any of my questions it is really appreciable..

Thanks in advance
Nidhin

[krishnasagar.atluri]

power consumption stable --> Have you checked the performance curve? whether the performance curve is flat instead of steep curve? if the curve is flat, there will be minimal change in head even when the flow rate fluctuates.  

purpose of recirculation --> to ensure that operating flow is above mcsf and mtsf. 

in recycle mode, check whether the level of fluid inside the suction tank is fluctuating. this might be one reason as the system resistance might be cutting at various points on the performance curve.

[katmar]

You have said that the flowrate is fluctuating but you have not specified whether it is the recycle flow or the flow to the system that is fluctuating.  If the system is well designed then the sum of these two flows would remain constant and that would also explain the constant power consumption.

[Kakka]

@krishnasagar.atluri
Thank you for your response. The head curve is in good condition and matches the OEM performance curve. However, the power curve appears as a straight horizontal line because the motor power remains constant.

@Katmar
Thank you for your response. I understand your point.

 

I have been informed that the power measuring instrument might have some error, which could result in showing a constant power reading despite fluctuations in the flow rate. This seems like a possible reason for the issue.