causes of cavitation in centrifugal pump

Cavitation in centrifugal pumps occurs when the local pressure within the pump drops below the vapor pressure of the liquid, causing the formation of vapor bubbles. These bubbles collapse violently when they reach higher-pressure regions, leading to damage, noise, and reduced pump performance.

Main Causes of Cavitation in Centrifugal Pumps:

1. Low Net Positive Suction Head Available (NPSHA)

• Insufficient NPSHA: If the available suction pressure (NPSHA) is lower than the pump's required NPSH (NPSHR), cavitation occurs.

• High suction lift: Excessive elevation between the liquid source and pump increases suction pressure drop.

• Low inlet pressure: If the supply tank is under low pressure or vacuum, the pump may not get enough liquid.

2. High Fluid Temperature

• Hot liquids have higher vapor pressure, making them more prone to vaporization at lower pressures.

3. Clogged or Restricted Suction Line

• Blockages (e.g., debris, closed valves, or undersized pipes) increase friction loss, reducing suction pressure.

4. Excessive Pump Speed (RPM)

• Running the pump at higher speeds than designed increases NPSH requirements, raising cavitation risk.

5. Improper Pump Installation

• Long suction lines with too many bends or fittings increase pressure drop.

• Suboptimal pipe sizing (too small diameter) restricts flow.

6. Air or Gas Entrainment

• Air leaks in the suction line or dissolved gases coming out of solution can promote bubble formation.

7. High Viscosity Liquids

• Thick fluids increase friction losses, reducing suction pressure.

8. Incorrect Impeller Design

• Poorly designed impellers can create localized low-pressure zones, triggering cavitation.

Effects of Cavitation:

• Noise: Sounds like rattling or cracking.

• Vibration: Unstable operation due to bubble collapse.

• Damage: Pitting on impeller, casing, and vanes.

• Reduced Efficiency: Drop in flow rate and pressure.

How to Prevent Cavitation?

• Ensure NPSHA > NPSHR (by raising suction pressure or lowering pump height).

• Reduce suction line restrictions (clean filters, open valves, use larger pipes).

• Cool the liquid if temperature is too high.

• Avoid excessive pump speed.

• Use an inducer or double-suction impeller for critical applications.

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