NPSH for HP/IP combine pumps

[MrProjectEng]

Hello,

For combine pump like Feedwater pumps(HP/IP), NPSH value for HP and IP refers to different values. For instance when NPSH for HP is 7,9 , IP is 8,9. Suction point is the identical for HP and IP.

What is the reason?

Thanks

 

[LittleInch]

Different pumps?
More flow?

what do the figures refer to?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DubMac]

physics

 

[stgrme]

For a combined HP/IP pump like a Feedwater Pump, the pump may be considered like two pumps in series. Therefore, the suction for each section (IP and HP) will be at different locations. For the IP section, the suction is at the inlet to the pump; for the HP section, the suction is at the IP take-off point. Also note that the flow through the IP section will be the greater than the flow through the HP section due to the IP take-off.

Best of luck!

 

[JohnGP]

Could you post a sketch of the setup? Also, are you referring to NPSHr or NPSHa for the pumps?

 

[MrProjectEng]

I mean NSPHa for IP and HP