Cavitation is a destructive phenomenon in centrifugal pumps where vapor bubbles form and collapse, causing noise, vibration, and damage to impellers and casings. Below is a detailed breakdown of its causes, effects, and solutions.
Cavitation occurs when the pressure inside the pump drops below the vapor pressure of the liquid, forming vapor bubbles that implode violently.
| Cause | Explanation |
|---|---|
| Insufficient NPSHₐ (Net Positive Suction Head Available) | The system does not provide enough pressure at the pump inlet. |
| High Fluid Temperature | Increases vapor pressure, making cavitation more likely. |
| Excessive Pump Speed (RPM) | Increases suction pressure drop due to higher velocity. |
| Clogged Inlet/Strainer | Restricts flow, lowering inlet pressure. |
| Long/Diameter-Small Suction Pipe | Increases friction losses, reducing NPSHₐ. |
| Improper Pump Sizing | Oversized pumps run at low flow, increasing recirculation. |
| Air Leaks in Suction Line | Introduces gas bubbles that expand under low pressure. |
Noise: Hissing or cracking sounds (like gravel in the pump).
Vibration: Due to uneven bubble implosion.
Damage: Pitting on impeller blades and casing.
Reduced Efficiency: Bubbles disrupt smooth flow, lowering head & flow rate.
Seal & Bearing Failure: Excessive vibration shortens component life.
https://www.pumpsandsystems.com/sites/default/files/cavitation-damage-impeller.jpg
(Pitting caused by cavitation bubbles collapsing on the impeller)
Raise Liquid Level in the suction tank.
Reduce Suction Pipe Length or increase diameter (lower friction losses).
Use a Booster Pump to increase inlet pressure.
Cool the Liquid (if high temperature increases vapor pressure).
Use a Double-Suction Impeller (reduces inlet velocity).
Select a Low-NPSHᵣ Pump (e.g., with an inducer).
Reduce Pump Speed (RPM) if possible.
✔ Avoid Sharp Bends in suction piping.
✔ Install a Strainer (but ensure it doesn’t clog).
✔ Ensure Proper Pump Sizing (avoid running at very low flow).
✔ Use a Recirculation Bypass for low-flow conditions.
Acoustic Monitoring: High-frequency noise sensors.
Vibration Analysis: Sudden spikes in vibration spectra.
Performance Drop: Decreased head & efficiency.
Visual Inspection: Pitting on impeller after disassembly.
Problem:
NPSHₐ (Available) = 8 m
NPSHᵣ (Required, from pump curve) = 5 m
Is cavitation likely?
Solution:
NPSH Margin = NPSHₐ – NPSHᵣ = 3 m (safe, should be ≥1.5 m).
If NPSHₐ drops below 5 m, cavitation will occur.
✅ Cavitation occurs when NPSHₐ < NPSHᵣ.
✅ Prevent it by increasing NPSHₐ or reducing NPSHᵣ.
✅ Symptoms include noise, vibration, and impeller damage.
✅ Always maintain an NPSH margin of 1.5–3 m.
Need help troubleshooting a cavitating pump? Provide your system specs (flow rate, suction lift, fluid temp), and I’ll analyze it!
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