NPSH for metering pumps

[Lijantropo]

Good morning,

I am reading about the NPSH available for metering pumps. I found that the NPSH is static, and it takes into account the height of liquid in the tank, the pressure of the tank, the vapor pressure and specific gravity of fluid at working conditions).

On the other hand, I found a "second" NPSH avaliable which includes the head losses along the suction pipe.

NOTE: With the "first" NPSHa you should also to substract the head losses when you are choosing the pump. In this way, both definitions have same conceptual basis.

So my question is:
In my datasheet, should I use the fisrt one or the second one? (what is the most usual?)

 

[BigInch]

Include the head losses for frictional flow in the suction pipe. Also include acceleration head losses, if its a PD pump suceptible to such considerations.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MJCronin]

I woud use the first one......

 

[BigInch]

Why? No suction piping?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Lijantropo]

Thank you for your responses.

I included the head losses (frictional and acceleration) and put a footnote indicating this.

Regards,

Lij

 

[djack77494]

You must use the second one since what you're trying to determine is the head available at the suction of the pump. Acceleration losses and suction line frictional losses impact that result.