Cavitation refers to the formation and subsequent collapse of vapor bubbles in a liquid due to a decrease in pressure. It occurs when the pressure in a liquid drops below its vapor pressure, causing the liquid to vaporize and form bubbles. These bubbles then collapse when they move to a region of higher pressure, resulting in a rapid release of energy. Cavitation can cause damage to pump components, reduce pump efficiency, and generate noise.

The net positive suction head (NPSH) for a pump is a measure of the pressure available at the pump’s inlet to prevent cavitation. It is the difference between the total suction head and the vapor pressure of the liquid being pumped. The total suction head includes the static head (the vertical distance between the liquid level and the pump centerline), the velocity head (the kinetic energy of the liquid entering the pump), and the pressure head (the pressure at the pump inlet). The NPSH must be greater than the required NPSH (NPSHr) specified by the pump manufacturer to avoid cavitation. If the NPSH is too low, cavitation can occur, leading to reduced pump performance and potential damage.