HIGHER RPM's IN CENTRIFUGAL PUMPS 1

[cryopumps]

I am a cryogenic pump engineer. I recentley designed a pump in the 1250 specific speed pump at 3560 RPM (7960 FT at 1570 GPM, liquid is LNG). The diameter of the impeller that we used came out to about 13 inches and it was a 14 stage pump. My question is would it be usefull to speed up the motor to 7500 RPM which would bring the specific speed up to 2000, raise the efficiency and bring the diameter size down to 5 inches along with the stages to 10. I understand that cavitation might be a problem but suppose that an adequate amount of NPSH is present. Has this application been done? Higher RPM seem the way to go.

 

[25362]

Try:

http://www.barber-nichols.com/graphics/techpapers/highspeed.pdf

http://www.mcnallyinstitute.com/11-html/11-04.html

The second site ends with specific recommendations for high speed centrifugal pumps.

 

[cryopumps]

Thank you very much. Now I just need to figure out if it will be a smart decision to through a VFD in to save money. Seems that a VFD will be more expensive along with the fact that bearings must now changed and serviced more.

 

[BenThayer]

you might consider sundyne (sundstrand?) pumps

http://www.sundyne.com/

as they do some high speed high pressure pumping applications typically through a gearbox application.

used them for carbamate recycle in a urea plant. they turned ~11,500 rpm's as i recall and pumped out ~350 gpm and ~3500 psig and was pumping back to a reactor running ~3000 psig.

 

[electricpete]

<Soap-box alert>
High-speed pumps even 3600 rpm can be a major PITA to maintain over the long run. I realize it is a subject of some debate and many designers are quite comfortable specifying high-speed pumps. Speak to some people that operate, monitor, and maintain them before you decide.
<End of Soap-box alert>

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[CARF]

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