NPSHR for Recip Pump 1

[larryli2004]

I have some questions regarding NPSHR for Recip pump. I have a separator which will operate around 300 psig. I am pumping the condensate from the separator to 1500 psig via a recip pump. How about the NPSHR for the recip pump? I got the data from vendor and they are saying 12 ft is needed. I am just curious whether my 300 psig pressure at separator helps NPSH?

Thanks.

 

[25362]

Look for the definition of NPSH, and also pay a visit to

thread124-196619
thread407-107656
thread407-150618

 

[BigInch]

Convert the 300 psi supply tank pressure into head and add it to NPSHA.

http://virtualpipeline.spaces.msn.com

 

[JJPellin]

The main problem that is often missed with NPSH for a recip pump is the acceleration head which is heavily dependant on the length of the suction line.

Johnny Pellin

 

[BigInch]

Ya we just went through that a short time ago. 25362 caught that with his thread reference.

http://virtualpipeline.spaces.msn.com

 

[larryli2004]

Thanks all of you. We just double check with Vendor and they said 9 ft NPSH shall be OK. We did some simulation, when the separator operates around 300 psig, the vapor pressure is around 1000 kPa at 30 degree C. In this case, I am wondering whether the 300 psig can make some contribution to NPSH since it is 1000 kPa higher than vapor pressure.

 

[BigInch]

Convert the 300 psi supply tank pressure into head and add it to NPSHA and subtract the vapor pressure.

http://virtualpipeline.spaces.msn.com

 

[larryli2004]

We are also thinking to put a mass flow meter in between separator outlet and pump suction. This mass flow meter will creat some pressure loss also which is a big concern to us. Do somebody has similar experience for this? To me, if we have 1000 kpa extra (operating pressure-reid vapor pressure, then the pressure loss across the mass flow shouldn't be a problem.

 

[BigInch]

1000 kPa will take you a long way and will probably overcome accelaration losses too, but did you calculate acceleration loss? Its a good habit to get into checking it.

http://virtualpipeline.spaces.msn.com

 

[larryli2004]

I will do that to see what happen.