If the centrifugal mud pump starts cavitating after entering rock, what should you do?

• A. Increase pump pressure and speed.
• B. Ignore suction line issues.
• C. Stop pumping and withdraw the string.
• D. Reduce pump speed; check suction line; ensure mud levels; verify mud viscosity.

Answer: (D)

Cavitation in a centrifugal mud pump happens when the suction pressure isn’t enough to keep the mud in the liquid phase, so vapor pockets form and implode near the impeller. When rock enters the system, air and solids can disrupt the suction path and lower the available NPSH, making cavitation more likely. The best fix is to decrease the demand on the suction side and restore a solid, continuous mud column.

Lower the pump speed to reduce flow and the pressure drop at the suction. Check the suction line for leaks or air leaks that let air enter the system. Make sure the mud pit has a sufficient level so the pump is drawing liquid rather than air. Verify mud properties (viscosity and overall mud density) to ensure a stable mud column that maintains adequate hydrostatic head. These steps address the root hydraulic and material causes of cavitation rather than worsening the condition. Increasing pressure or speed would typically worsen cavitation, and simply stopping pumping is not the most effective immediate remedy when you can resolve the suction and mud conditions.