Cavitation

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Cavitation
A phenomenon which occurs within a moving
liquid when the static pressure at some location
falls to or below the vapor pressure of the
liquid.
To prevent cavitation NPSHA gt NPSHR
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Industrial Applications Cavitation
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Cavitation
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Industrial Applications
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Cavitation can occur at the inlet of the impeller
if the suction pressure falls below the liquid
vapor pressure.
Quadna Engineering Innovative Solutions for
Industrial Applications Cavitation - Impeller
Field Service
Expert Field Installation Including
Start-up and Commissioning
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Large vapor volumes can cause reduction in head
generation, or loss of prime.

• Bubbles collapsing create intense pressures and
• (10,000 psi) shock waves.
• Intense pressures near metal
• surfaces exceed material
• strength and fatigue metals.
• Creates pitted surfaces.

Large vapor volumes can cause surging and
unstable flows.
Quadna Engineering Innovative Solutions for
Industrial Applications Cavitation - Impeller
Field Service
Expert Field Installation Including
Start-up and Commissioning
Quadna Field Installation
5
Cavitation
Cavitation is caused by liquid changing into
a vapor and then back into a liquid. The
Formation of partial vacuums in a flowing
liquid as a result of the separation its parts.
When These collapse, pitting or other damage is
Caused on metal surface in contact.
Cavitation is NOT AIR in the PUMP!

• There are two forms of cavitation
• Suction Cavitation, which occurs at the eye of
  the impeller, (also referred to as
• true cavitation.
• Discharge Cavitation, which occurs at the tip
  of the impeller, (also referred to as
• recirculation cavitation).

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What Damage Does Discharge Cavitation Cause?

• Break Shafts
• Shortens Bearing Life
• Destroys Impellers and Volutes
• Ruins Mechanical Seals

Total Dynamic Head Too HIGH
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What Damage Does Suction Cavitation Cause?

• Shortens Bearing Life
• (Increased radial thrust loads)
• Destroys Impellers
• Destroys Wear Plates
• Ruins Mechanical Seals
• (Vibration thrust loads)

Total Dynamic Suction Lift Too HIGH Discharge
Head Too LOW
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Chemical Attack
Abrasive Wear
Suction Cavitation
Discharge Cavitation
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Shaft Breakage Problems

• Radial Fatigue Break
• Total Dynamic Head Too High
• Air (Hydraulic Imbalance)
• Mechanical Imbalance

• Torsional Break (Twisting Break)
• Pump Lock-UP
• Reverse Rotation (Open Check Valve)
• Short Cycling

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