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NPSH is one of the most important variables to be considered when it comes to pump selection and system design. Not having a complete understanding of this hydraulic principle can lead to pump failure and poor system performance. In this post, we’ll define NPSH, and layout the ways changes in your system, can affect NPSH and pump performance.
NPSH stands for Net Positive Suction Head. Simply stated, NPSH is the measurement of liquid pressure at the suction nozzle of the pump. There are a couple variations on this measurement to point out as well, NPSHR (required), and NPSHA (available).
NPSHR is related directly to the design of the pump, where NPSHA is a calculation of the head the system is able to deliver to the pump. As expected, if the amount of NPSHA is less the amount required, the suction system will not perform properly, resulting in cavitation and damage to the pump.
NPSH should be calculated any time a new system is being designed, or during revisions to existing systems. Not doing so puts your pumps at risk of cavitation, causing decreased flow and head, increased noise and vibrations, and permanent damage to the internals of the pump.