What term describes the phenomenon when a pump starts to draw air instead of liquid?

The term that describes the phenomenon when a pump starts to draw air instead of liquid is cavitation. This occurs when the pressure in the pump drops below the vapor pressure of the liquid, leading to the formation of vapor bubbles. When these bubbles move into areas of higher pressure, they collapse suddenly, creating shock waves that can cause damage to the pump components. Cavitation is particularly problematic as it can significantly reduce pump efficiency, increase wear, and ultimately lead to pump failure.

Understanding this concept is crucial for maintaining the reliability and performance of hydraulic systems. Proper pump selection, ensuring adequate suction conditions, and maintaining system pressure are key strategies to prevent cavitation from occurring in hydraulic applications.