RE: Parallel Pump Suctions

From: <ed>
Date: Thu Apr 14 2005 - 13:17:00 EDT

Your Calculated NPSH is what's "available". The "NPSH required" always comes from the manufacturer
and was based on some test run by the specific pump.

Also you do not combine the calculated NPSH of both pumps. The NPSH resulting from your formula
will be the "available" for each pump. If the pumping arrangement is symmetrical the NPSHa will
be the same for both pumps, otherwise you have to make separate calculations.

In calculating for the suction friction loss, you have to take into account if one pump is on standby
or (2) pumps running simultaneously.

-----Original Message-----
From: dornnalex [mailto:adornn@kgsgroup.com] Sent: Tuesday, April 12, 2005 4:27 PM
To: <a href="/group/PipingDesign/post?postID=wDzEvSuS1bPB732-UeQmcf0m0QY5WqoSywK8jrA_qUoRuDbqzwK0AuKnhTutv0nS-dMo1gv0-IhGqnDzQd93eDGqvD8Bs8M">PipingDesign@yahoogroups.com</a> Subject: [PipingDesign] Parallel Pump Suctions

How do you calculate the NPSH available when 2 pump are drawing from the same suction line. I imagine I add the total flow of both pumps to calculate the friction losses in the suction line. The absolute pressure, vapour pressure and the static height remain the same. NPSH avail = Habs - Hvpa +/- Hst - Hfs

Will this mean that the total "NPSH required" is just the sum of the NPSH of each pump?

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Yahoo! Groups Links Received on Thu Apr 14 13:17:00 2005