NPSH

[3cio]

Hello Guys,

Good day!

When we calculate for the NPSH with Strainer installed, is it correct to assumed that:

NPSH = Atm. pressure + Static Pressure - Vapor pressure - Pipe/Fittings/Valves pressure loss - Strainer pressure loss

The thing is, I am thinking that A pressure drop shall be considered for a strainer corresponding to its flow rather than equivalent length of pipe.

Let me hear your insights/.

Thanks in advance.

 

[TD2K]

Your equation is correct. The issue is what pressure drop do you use for the strainer? Do you use it as an equivalent length of piping per the vendor's charts which is when the strainer is clean? Or do you want to assume a fixed dP representing the pressure drop in a dirty state? If you are tight on NPSHR versus NPHSA, you are going to find out that you will have to monitor and be prepared to clean the strainer if the pressure drop increases to the point that cavitation starts to be a potential problem.

The recommended way to monitor the dP across that strainer is a dedicated dP gauge. Unless you can allow 10 psi pressure drop, I would not want to use two separate pressure gauges and subtract the downstream value from the upstream value.

 

[3cio]

Thanks TD2K.

I use the chart (flow vs. pressure drop vs. size) provided by the manufacturer.

Yes, this drop is base as when the strainer is clean..


Regards,