Cavitation may occur in which parts of a flowing liquid system?

• A. Only in intake screens.
• B. In pumps, on impellers, or at restrictions in the flowing liquid.
• C. Only in discharge lines.
• D. Only in storage tanks.

Answer: (B)

Cavitation happens when local pressure in a flowing liquid drops below its vapor pressure, causing tiny bubbles to form and then violently collapse as pressure rises again. In practical systems, this pressure drop most often occurs where the liquid is being accelerated or forced through restrictions, such as inside a pump or on the impeller where suction pressure can fall, and at restricted sections of the piping (like partially closed valves, contractions, or other flow throttling). These areas raise velocity and lower static pressure, creating the conditions for cavitation. Intake screens or discharge lines are not the primary sites; they can contribute if they create a sharp enough pressure drop, but the common culprits are pumps, impellers, and restrictions in the flowing liquid. To prevent cavitation, ensure adequate suction head (NPSH) and avoid excessive flow, leaks, or restriction-causing blockages that push local pressures toward the liquid’s vapor pressure.