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Pump Curve Database

Created 8/31/2011 by Ray Hawksley
Updated 1/11/2012 by Ben Fowler
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Comments (7)
James White on 08/31/11 on 03:58 PM (Pacific Time)
These pump curves are great for determining the power usage of fixed speed pumps operating at various pressures and flows, but do you know where I can find the efficiency curves for pumps that vary their speed to maintain fixed pressures in response to variable flows? 
Ray Hawksley on 09/02/11 on 08:14 AM (Pacific Time)
I am glad that these pump curves will be useful to you for determining power usage of fixed speed pumps. Unfortunately I have not found a resource for pumps that vary their speed. Perhaps another user out there can share information with us all about such a resource if it exists.
James White on 09/19/11 on 04:29 PM (Pacific Time)
Here's a link I found that shows energy saving calculations for VFD's on irrigation pumpsI highly recommend reading this paper if you are considering installing VFD's on an irrigation pump.  It is from "USDA's National Resources Conservation Service (NRCS) Technical Note No. MT-14, dated January 2010".  The report does a good job of explaining various methods for controlling irrigation flows and pressures.  It also illustrates the difficulty of calculating energy savings for VFD's that are installed on pumps that have relatively high static head compared to the frictional head.  In other words, pumps that must pump water up a significant elevation gain may not be good candidates for VFD's.  It shows detailed calculations for various irrigation and VFD applications, and begins to, but does not doesn't fully incorporate efficiency curves for a pump operating at different speeds.  Most of the pump curves included on the database referenced above are for different sized pumps running at a single speed.  The pump manufacturers instead need to provide pump curves for a given pump running at different speeds.

I'm still looking for the "Holy Grail" that accurately calculates energy savings for VFD's that incorporates actual pump efficiency curves for a specific pump running at different speeds.  I will post it here when I find it.
James White on 10/10/11 on 01:55 PM (Pacific Time)
I could not find a calculator that adequately calculates the energy savings from installing a VFD on pumps that pump from a well so I created my own.  I will post it here on Conduit in the next day or so.

Well pumps are different than closed-loop pumps because the flow is zero until a minimum speed is reached to overcome the static pressure of the well.  Once that minimum speed has been reached, flow through the system resembles a closed-loop system, that is, the system pressure increases as the flow rate increases. 

There are three modes that a centrifugal pump can be operated:
1.) fixed speed that follows the pump curve (least efficient).
2.) control pump speed to maintain a constant pressure (more efficient).
3.) control pump speed based on the system curve (most efficient), which reduces discharge pressure of the pump as the flow rate decreases.  Note that following the system curve is the opposite of following the pump curve.   Constant speed systems follow the pump curve, which means that the discharge pressure goes up as the flows go down.  If the pump followed the system curve, the pressures would decrease as the flows decreased.  This could be done by placing the pressure sensor near the end of the piping system (rarely done) or by designing a smart controller that reduces the discharge pressure as the flow decreases.  To my knowledge, such a controller is not currently available for pumped well systems. 

A graph of these three operating modes can be seen herehttps://www.neea.org/emailcontent/PumpCurve.jpg
James White on 10/11/11 on 09:49 AM (Pacific Time)
Here is the link to the spreadsheet I put together to calculate the energy consumed by a centrifugal pump depending on whether it is operated at a constant speed, a constant pressure, or optimizes the discharge pressure depending on the flow rate.
https://conduitnw.org/_layouts/Conduit/FileHandler.ashx?RID=509
Ben Fowler on 10/11/11 on 11:09 AM (Pacific Time)
And if anyone wishes to see that spreadsheet file page (includes download link and descriptive summary of the file, it is here: https://conduitnw.org/Pages/File.aspx?rid=509

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