Net Positive Suction Head Available (NPSHA)

Definition - What does Net Positive Suction Head Available (NPSHA) mean?

Net positive suction head available (NPSHA) refers to all the types of energy present in different levels on the suction portion in a pumping system. In short, it is the absolute pressure within the pump’s suction port.

This is the overall function of the system that should be calculated in order to prevent the formation of holes or the process of cavitation in pump systems.

Corrosionpedia explains Net Positive Suction Head Available (NPSHA)

Net positive suction head available is especially significant within turbines and centrifugal pumps. These are parts involved in hydraulic systems that are most prone to the formation of holes. If there is cavitation, the pumping power of the impeller vanes drastically elevates, potentially putting a stop to the flow of water.

Prolonged exposure could lead to impeller damage. The holes typically occur when the pump inlet pressure drops below the liquid’s vapor pressure. The bubbles from the vapor form within the pump inlet and travel to the pump discharge where they collapse. The cavitations are characterized by loud noise within the pump, capacity loss and pitting damage to the different areas of the material.

The NPSHA should be enough to deliver according to the requirements while the net positive suction head required (NPSHR) should be obtained from the pump manufacturer.

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