Which of the following is associated with low internal pressure or excessively high flow rates that are structurally detrimental to centrifugal pumps?

• A. Water hammer
• B. Cavitation
• C. Air lock
• D. Priming

Answer: (B)

Cavitation occurs when the pressure inside the pump falls below the liquid’s vapor pressure, which can happen with low suction pressure or excessively high flow. In those conditions, vapor bubbles form in the liquid. As these bubbles move into higher-pressure areas, they collapse violently, sending shock waves that erode impeller surfaces and impair performance. That destructive effect is why cavitation is linked to structural damage in centrifugal pumps. Water hammer involves pressure surges from sudden valve changes in piping, not the pump’s internal low-pressure/vaporization issue. Air lock is trapped air blocking flow, and priming is the process of filling the pump with liquid; neither causes the same internal cavitation-related damage. To prevent cavitation, maintain adequate net positive suction head and avoid operating conditions that push the suction pressure below the liquid’s vapor pressure.