What Is Pump Cavitation?

1. Introduction – Importance of Cavitation in Pump Systems

Cavitation is one of the most critical causes of performance loss in pumps used for fluid transfer. In simple terms, cavitation occurs when the pressure inside the pump drops below the liquid’s vapor pressure, causing vapor bubbles to form and collapse violently in higher-pressure regions.

These collapses create microscopic shock waves that damage metal surfaces over time, leading to impeller erosion, noise, vibration, and efficiency loss.

At POMEKA, we technically analyze how to prevent cavitation risks in pumps from brands such as Grundfos, Wilo, Standart, Etna, and Sumak.

2. What Is Cavitation? Physical Definition

Cavitation occurs when the local pressure of a fluid falls below its vapor pressure. Under these conditions, the liquid transitions into vapor, forming bubbles.

As the fluid moves to higher-pressure zones within the pump, these bubbles suddenly collapse, generating micro-shock waves. These waves primarily damage impeller blade tips and suction areas.

3. Symptoms of Cavitation in Pumps

Common signs of cavitation include:

• Abnormal noise (like gravel or metal friction)
• Irregular vibration
• Reduced flow rate and head
• Overheating
• Impeller damage (pitting on blade surfaces)

If not detected early, cavitation can cause severe damage to pump casing and bearings.

4. Causes of Cavitation

Main causes include:

• Insufficient NPSH (Net Positive Suction Head)
• Incorrect pump selection
• Long or narrow suction piping
• High fluid temperature
• Low liquid level in suction tank

5. What Is NPSH and How Is It Calculated?

NPSH is critical for evaluating cavitation risk.

• NPSH Available (NPSHa): Available suction head in the system
• NPSH Required (NPSHr): Minimum requirement specified by manufacturer

Formula:

NPSH_available = (P_atm - P_v) / (ρg) + h_s - h_f

Where:

• P_atm: Atmospheric pressure
• P_v: Vapor pressure
• h_s: Suction height
• h_f: Friction losses

👉 To prevent cavitation:
NPSHa > NPSHr

6. Mathematical Analysis of Cavitation

Cavitation is explained by Bernoulli’s principle:

P1 + ½ρv1² + ρgh1 = P2 + ½ρv2² + ρgh2 + losses

If pressure drops too low, vapor bubbles form.

Controlling pressure drop and flow velocity is key to prevention.

7. Damages Caused by Cavitation

• Metal erosion
• Efficiency loss
• Noise (gravel sound)
• Vibration
• Bearing and shaft damage

8. How to Prevent Cavitation in Pumps

8.1 Design Stage

• Keep suction line short and wide
• Avoid unnecessary fittings
• Ensure proper slope

8.2 Selection Stage

• Ensure NPSHr is met
• Use high NPSH-tolerant pumps (Grundfos CR, Wilo Helix, etc.)

8.3 Operation Stage

• Control fluid temperature
• Keep valves fully open
• Avoid low flow operation

9. Cavitation Types by Pump Design

• Inducer cavitation
• Suction cavitation
• Partial cavitation

Higher risk in hot water and chemical systems.

10. Detection with Modern Systems

Smart systems from Grundfos and Wilo detect cavitation using sensors.

Example: Wilo-Stratos MAXO detects pressure fluctuations with high precision.

11. Supporting Equipment

• Air release valves
• Vibration dampers
• Pressure tanks
• Filters

12. Example Calculation

Given:

P_atm = 10.33 m
P_v = 0.056 m
h_s = -5 m
h_f = 1 m

NPSHa = 4.27 m

If NPSHr = 3.5 m → Safe operation
If lower → Cavitation risk

13. Visual Damage Description

• Honeycomb-like pitting
• Surface deformation
• Shaft vibration marks

14. Effect on Energy Efficiency

• Efficiency drops 10–20%
• Energy consumption increases
• Costs rise up to 15%

15. Brand-Based Solutions

• Grundfos → Low NPSH impeller design
• Wilo → Smart detection systems
• Standart → Stainless impeller resistance
• Etna & Sumak → Cost-effective solutions

16. Conclusion – POMEKA Engineering Approach

Cavitation is the silent enemy of pumps.

But with correct design, selection, and maintenance, it can be fully prevented.

At POMEKA:

• We perform NPSH analysis
• Provide pump selection consultancy
• Offer optimized system solutions

👉 Contact POMEKA engineers to prevent cavitation and increase efficiency.