NPSHR and Positive Displacement

NPSHR

Whatever kind of pump it is, examine the manufacturer's literature, which should show the pump's NPSHR under various operating conditions (i.e., various points on its curve). You can't readily change this characteristic, but you can select the pump so that it will operate typically near the middle of the curve, which is normally the most favorable from the standpoint of NPSHR). Then verify that the suction geometry gives an NPSHA sufficiently greater than this. As the previous tutorial shows, this takes into account atmospheric pressure, fluid vapor pressure, elevation, and pipe friction.