Understanding HPSHA & HPSHR
Understanding HPSHA & HPSHR
(OP)
Im having a little bit of a problem understanding how these effect my design of the pumping system.
The pump im looking at has a NPSHR of 10' at 40GPM and rises to 20' 150GPM.
What does this mean. Is this the limit that I can place the pump at above the source before I get the fluid boiling under a vacuum?
My application (as part as my other post about turning a non-priming in to an auto-priming pump. ) is that I need to pump out of a sump that is 10 - 15' below where I will be mounting the pump. I also will be pumping out of a pond with the same pump that is only 3' below where the pump is mounted.
How does the NPSHR effect my application. I tried to watch some videos and read some articles on the subject but I am still at a loss to understand really what its telling me.
Here is the spec sheet of the pump I will be using. (the pump Im using will be Curve B.
http://www.wegotpumps.com/pdfs/87-88.pdf
Thank you for your help.
The pump im looking at has a NPSHR of 10' at 40GPM and rises to 20' 150GPM.
What does this mean. Is this the limit that I can place the pump at above the source before I get the fluid boiling under a vacuum?
My application (as part as my other post about turning a non-priming in to an auto-priming pump. ) is that I need to pump out of a sump that is 10 - 15' below where I will be mounting the pump. I also will be pumping out of a pond with the same pump that is only 3' below where the pump is mounted.
How does the NPSHR effect my application. I tried to watch some videos and read some articles on the subject but I am still at a loss to understand really what its telling me.
Here is the spec sheet of the pump I will be using. (the pump Im using will be Curve B.
http://www.wegotpumps.com/pdfs/87-88.pdf
Thank you for your help.





RE: Understanding HPSHA & HPSHR
There has been much discussion around NPSHR and NPSHA in this forum and on the internet - have a search - see
http://en.wikipedia.org/wiki/NPSH for a bit of an explanation, but there is heaps out there.
Cheers,
John
RE: Understanding HPSHA & HPSHR
If the sump is 10-15' below pump's inlet the pump will cavitate if the NPSHR is not significantly higher than that or the pump will not work at all.
NPSHA is not just the geodetic height between fluid level and pump's inlet but the geodetic height is a very important part of it. Suction line diameter, length, no. of elbows and valves, fluid velocity, atmospheric pressure and vapor pressure of the fluid affect NPSHA, too. Assuming you could neglect all this, then the atmospheric pressure (in ft) minus suction lift would indicate NPSHA.
RE: Understanding HPSHA & HPSHR
RE: Understanding HPSHA & HPSHR
"The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward X-CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Understanding HPSHA & HPSHR
The published curve on http://www.wegotpumps.com/pdfs/87-88.pdf is just a generic curve for brochure use, what you need is a pump curve for that particular pump from the manufacturer on which you will have to over-lay a system curve for combined inlet and discharge losses. this will show you where the pump will operate under actual conditions and will show if NPSHr exceeds or is less than NPSHa.
There are no short cuts in getting a real answer and wishful thinking never solved an NPSH problem.