Cavitation is a common occurrence, but is one of the least understood of all pumping problems. Here, Trinath Sahoo explains how acceleration head phenomena and net positive suction head available are related to cavitation. The net positive suction head (NPSH) is defined as the difference between suction pressure and vapour pressure measured at the pump suction nozzle when the pump is running. In a reciprocating pump NPSH is required to push the suction valve from its seat and to overcome the friction losses and acceleration head within the liquid end. The flow output from a reciprocating pump is unsteady and the pumped fluid is constantly accelerating and decelerating. A certain amount of energy, the acceleration head, is required to produce the acceleration.
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