Short Answer:

The effects of cavitation on pumps and turbines are mostly harmful. When vapor bubbles form and collapse inside these machines, they produce strong shock waves that damage the metal surfaces, especially on blades, impellers, or runners. This damage appears as pitting, cracks, and erosion over time.

Cavitation also causes vibrations, noise, and energy loss, which reduces the efficiency and lifespan of the equipment. If not prevented or controlled, continuous cavitation can lead to mechanical failure and costly maintenance or replacement in hydraulic systems.

Detailed Explanation:

Effects of Cavitation on Pumps and Turbines

Cavitation is a dangerous phenomenon in hydraulic machines like pumps and turbines. It occurs when the pressure in a fluid drops below its vapor pressure, forming vapor bubbles that later collapse violently as pressure recovers. This collapse produces micro-jets and shock waves that affect nearby surfaces. These effects are more serious in pumps and turbines because of their high-speed rotating parts and continuous fluid contact.

Understanding the effects of cavitation is important for engineers to protect the system, maintain efficiency, and ensure long service life of equipment.

Common Effects of Cavitation

Surface Damage (Erosion and Pitting)

When vapor bubbles collapse near metal surfaces:

They release high-energy shock waves.
This leads to pitting, which are small dents or holes in the metal.
Over time, this becomes erosion, removing material from impellers, blades, or casings.

The metal becomes weakened and rough, reducing performance and risking part failure.

Noise and Vibration

Cavitation produces a distinct rattling or hammering noise, often compared to gravel or marbles inside the machine.
It also creates vibrations that can:

Loosen mechanical fittings.
Damage bearings and seals.
Create discomfort in surrounding structures.

These vibrations can spread to pipelines or foundations if not managed properly.

Efficiency Loss

Cavitation reduces the hydraulic efficiency of pumps and turbines:

Some energy is wasted in forming and collapsing bubbles.
Flow becomes disturbed and uneven, lowering output pressure or torque.
Machines require more power to maintain the same flow rate.

This means higher operational costs for less performance.

Mechanical Stress and Fatigue

Continuous vibrations and impacts cause fatigue failure:

Cracks form in metal parts due to repeated stress.
Bearings, shafts, and blades can break over time.
The structural integrity of the machine is compromised.

If left unaddressed, it may lead to unexpected breakdowns.

Maintenance and Cost Impact

Cavitation leads to:

Frequent repairs and increased downtime.
More replacement parts due to wear and damage.
Higher maintenance budgets and potential system redesigns.

Preventing cavitation is more cost-effective than fixing the damage it causes.

Specific to Pumps

Cavitation occurs mostly at the impeller eye or suction side.
It causes uneven flow and head loss.
Pump seals and bearings may fail due to vibration.

Specific to Turbines

Happens at runner blades or draft tube.
Affects power output and causes noise in hydropower stations.
May damage surrounding concrete structures if not controlled.

Conclusion:

Cavitation has severe effects on pumps and turbines, including surface erosion, noise, vibration, and reduced efficiency. If ignored, it can lead to mechanical failure, high maintenance costs, and operational losses. Engineers must identify cavitation signs early and apply preventive measures like proper design, pressure control, and flow management to protect hydraulic equipment and ensure reliable performance.