NPSHa for the pump
NPSHa for the pump
(OP)
How do I calculate NPSHa for the pump where suction of the pump is discharge of other pump? Pump 'A' is pumping liquid at 90F with discharge pressure 220 Psig. Pump 'B' has suction pressure of 220 psig, which is discharge of Pump 'A'. Pump 'A' has suction from the storage tank, and storage tank pressure is 190 psig @80F.
What value should I consider for Vapor pressure? What will NPSHa?
thanks,
gosooners
What value should I consider for Vapor pressure? What will NPSHa?
thanks,
gosooners





RE: NPSHa for the pump
I don't understand, is the inlet temperature of Pump A 80F or 90F? Or are you saying that there is a 10F temperature rise across Pump A?
Use the vapor pressure of fluid at 80F for calculating NPSHa of Pump A. Use the vapor pressure at 90F for calculating NPSHa of Pump B.
The total NPSHa calculation also depends on elevation changes, pipe system friction losses and fluid velocity. We don't know any of those with the information you have included.
For Pump B NPSHa, start out with P1=220 PSIG. Subtract friction losses, vapor pressure at 90F, velocity head, add or subtract elevation losses (whatever is the case).
Obviously, use the appropriate procedure when converting from head to PSI if necessary. Also, and again obviously, consider PSIA v PSIG.
RE: NPSHa for the pump
I am trying to calculate NPSHa for Pump B. Inlet temperature of Pump A is 80 F. And discharge of 'A' is appx. 90 F. both pumps 'A' and 'B' are closest and there is negligible elevation change between these two pumps. How do I get vapor pressure at suction of pump B at 90F. From simulation True vapor pressure is at 100 F is 240 psia, which is higher than suction pressure of pump which is 220 psig. This is the confusing part.
thanks,
gosooners
RE: NPSHa for the pump
Pump A must be run at a higher speed-head, or its suction pressure upped sufficiently, or changed out completely so that the discharge pressure is higher than the vapor pressure at pump A's discharge temperature + the NPSH Required of the second pump B.
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RE: NPSHa for the pump
80 F --> 0.507 psia
90 F --> 0.699 psia
100 F --> 0.950 psia
I2I
RE: NPSHa for the pump
I2I
RE: NPSHa for the pump
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RE: NPSHa for the pump
RE: NPSHa for the pump
RE: NPSHa for the pump
For anybody needing LPG mixture tables, how to pump LPGs, etc. check Corken Pumps. Their website has a lot of info on this,
http://www.corken.com/publications/training.html
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RE: NPSHa for the pump
I2I
RE: NPSHa for the pump
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RE: NPSHa for the pump
RE: NPSHa for the pump
Patricia Lougheed
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RE: NPSHa for the pump
RE: NPSHa for the pump
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: NPSHa for the pump
Brilliant - best one for a long while.
RE: NPSHa for the pump
You need your simulator to tell you what the mixture's vapor pressure is at 90F. Telling us what it is at 100F is of little value. (I do note however, that the vp at 100F is 240psia = 225.3psig. Since you have available 220psig at the discharge of Pump A, and assuming little delta in getting to the suction of Pump B, you are probably OK with NPSHa. But, do the math.)
RE: NPSHa for the pump
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain