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UPDATE 2014-01-15: The attached .zip file now contains a Mathcad Prime 3.0 worksheet (.mcdx) and—for those of you who are still using earlier verisions of Mathcad—an Adobe Acrobat printout (.pdf) of the worksheet so can see how it is put together.
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Net Positive Suction Head (NPSH) is the measure of positive fluid pressure on the suction side of a pump. Unless the available NPSH (NPSH_a) exceeds—with appropriate safety factors—the required NPSH (NPSH_r), the pump will likely not operate properly, including increased vibration, not pumping, and/or cavitation. This worksheet calculates the NPSH conditions for a centrifugal pump.