5 replies to this topic

[Processeng1]

Hi,

 

I have following doubts about the Centrifugal Pump performance curve;

 1. Pump Efficiency -- at some place i have seen efficiency curve is parabolic down ward  on H-Q curve and at some place efficiency curve is parabolic upward.

 

2. NPSH- at some places NPSH is vertical on H-Q curve and at some place it is gradually rising upward with the flow rate

Can somebody please explain it? I have also attached the performance curve.

 

Attached Files

•  pump curve.docx   1.24MB   44 downloads

[Bobby Strain]

The cure you show is normal. But I don't think you know how to read it. Look for some basic information on centrifugal pump curve and how to read it. Are you a student?

 

Bobby

[Processeng1]

Yes sir , actually i am confused with efficiency curve in curve with RPM 1750 efficiency is upward parabola and in curve with 3550 RPM efficiency is downward parabola - why efficiency has been shown in two ways? please see pg 2 of the attached file.

 

 

Thanks & Regards

Processeng1

[Bobby Strain]

That's how the pump behaves. You don't need to understand the behavior. You only need to know how to read the curves.

 

Bobby

[Technical Bard]

I believe the efficiency curve is actually a series of ellipses, but we only plot the part that is in the zone, so it looks like a parabola.  Sometimes you are in the bottom half and sometimes in the top.  

[Aditya Karve]

Dear Member,

 

With all my understanding I can tell you few things.

 

Pump Performance curve is the combination of the Two Curves 1) Pump Curve 2) System Curve 3) Performance Curve.

 

1) Pump Curve is always be seen as downward curve because head (differential pressure) decreases as increase in flow. (Rated/Design condition)

2) System Curve is always be seen as upward curve because head of the system (piping system) always increases with the flow due to the increase in the flow.(Rated/Design condition)

3) Efficiency Curve: The efficiency curve typically has a maximum within the allowable operating range. This maximum is also known as the Best Efficiency Point (BEP). The normal operation should be preferably done close this best efficiency point for minimum power requirements.

 

Kindly tell whether I am wrong or right??