Cavitation is a common and potentially damaging phenomenon that occurs in pumps and other hydraulic systems. It arises when the pressure of a liquid locally drops below its vapor pressure, causing vapor bubbles to form and subsequently implode. This process can cause significant damage to the pump and reduce its efficiency. On this content page, we take a closer look at what cavitation is, how it occurs, its consequences, and the ways it can be prevented or minimized.

Cavitation occurs when the pressure in a liquid at a certain point drops below the vapor pressure of that liquid, causing vapor bubbles to form. When these bubbles move to an area with higher pressure, they implode, generating powerful shock waves. These shock waves can damage the pump material and other components.

The process can be summarized in the following steps:

Formation of vapor bubbles
When the pressure in the liquid drops below the vapor pressure, vapor bubbles are formed.
Transport of vapor bubbles
These bubbles are carried by the flow to an area with higher pressure.
Implosion of vapor bubbles
In the higher-pressure area, the vapor bubbles implode, resulting in microjets and shock waves.

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Several factors can cause cavitation:

Low inlet pressure
If the pressure on the suction side of the pump is too low, the liquid may begin to boil, leading to the formation of vapor bubbles.
High fluid velocity
High velocities can cause a pressure drop according to Bernoulli’s Principle, which may trigger cavitation.
Increased temperature
A higher fluid temperature lowers the vapor pressure margin, making cavitation more likely to occur.
Pump design
Incorrect sizing or poor impeller design can create low-pressure zones that promote cavitation.

Cavitation can have serious effects on pumps and other hydraulic systems:

Physical damage
The implosion of vapor bubbles causes erosion and pitting on the surfaces of the impeller and other pump components, reducing equipment service life.
Reduced efficiency
The presence of vapor bubbles disrupts the flow, resulting in decreased pump performance and efficiency.
Vibration and noise
Cavitation causes vibrations and a characteristic rumbling noise, indicating abnormal operation.
Operational failures
Severe cavitation can lead to complete pump failure, resulting in costly repairs and downtime.

Several strategies can be applied to prevent or minimize cavitation:

1. Optimization of inlet conditions

Increase inlet pressure
Ensure sufficient pressure at the suction side of the pump to prevent the pressure from dropping below the vapor pressure. This can be achieved by increasing the liquid level in the suction reservoir or reducing the height difference between the liquid source and the pump.
Reduce velocity
Lowering the fluid velocity at the inlet helps minimize pressure drop.

2. Use of proper pump designs

Select the right impeller
Use cavitation-resistant impeller designs, such as double-suction impellers, to improve pressure distribution.
Correct sizing
Ensure the pump is correctly sized for the application, particularly with respect to flow rate and head.

3. Temperature management

Control fluid temperature
Keep the fluid temperature under control to reduce vapor pressure and prevent cavitation.

4. Regular maintenance and inspection

Inspection and maintenance
Perform regular maintenance to keep the pump in optimal condition and to identify early signs of wear or damage caused by cavitation.