Low pressure in a hydraulic pump's suction line causes which malfunction?

• A. Cavitation
• B. Overheating
• C. Clogging
• D. Leaks

Answer: (A)

Low suction pressure in a hydraulic pump allows the pressure at the suction side to fall below the fluid’s vapor pressure. When this happens, vapor bubbles form in the liquid. As the fluid moves into the pump where pressure rises, those bubbles collapse violently, creating shock waves, microjets, and surface erosion on impeller and housing. This cavitation disrupts smooth flow, reduces pumping efficiency, causes noise and vibration, and can shorten pump life.

Overheating isn’t caused directly by low suction pressure; it comes from excess heat in the system due to friction, high viscosity, or poor cooling. Clogging results from contaminants blocking passages, not from suction pressure alone. Leaks stem from damaged seals or joints rather than the suction pressure condition. To prevent cavitation, ensure there’s enough suction head, keep the fluid clean and within spec, minimize suction line restrictions and air leaks, and verify that Net Positive Suction Head available (NPSH_A) exceeds the pump’s NPSH required.