During relay pumping, which threshold triggers cavitation warning?

During relay pumping, which threshold triggers cavitation warning?

• A. Intake pressure below 140 kPa
• B. Discharge pressure above 700 kPa
• C. Pump speed above 1500 RPM
• D. Tank pressure below atmospheric

Answer: (D)

Cavitation on a pump happens when the suction side experiences too low absolute pressure, causing water to vaporize and form bubbles that can damage the impeller and reduce flow. In relay pumping, maintaining adequate pressure at the pump’s inlet is crucial to keep water a liquid. When the tank pressure drops below atmospheric, the pump inlet pressure can fall into a vacuum range. That negative or near-zero absolute pressure makes cavitation likely, so a cavitation warning is triggered. The other conditions don’t directly indicate a suction-side vacuum: intake pressure still above vapor pressure, high discharge pressure doesn’t by itself cause cavitation on the inlet, and RPM alone doesn’t define the suction pressure threshold for cavitation.

Cavitation on a pump happens when the suction side experiences too low absolute pressure, causing water to vaporize and form bubbles that can damage the impeller and reduce flow. In relay pumping, maintaining adequate pressure at the pump’s inlet is crucial to keep water a liquid.

When the tank pressure drops below atmospheric, the pump inlet pressure can fall into a vacuum range. That negative or near-zero absolute pressure makes cavitation likely, so a cavitation warning is triggered. The other conditions don’t directly indicate a suction-side vacuum: intake pressure still above vapor pressure, high discharge pressure doesn’t by itself cause cavitation on the inlet, and RPM alone doesn’t define the suction pressure threshold for cavitation.