Cavitation vs Flashing
Side by side comparison: how they work, where each fits, and which to choose.
Quick answer: In cavitation, vapour bubbles form and then collapse as pressure recovers; in flashing, outlet pressure stays below vapour pressure, so the vapour remains.
Cavitation vs Flashing: Comparison Table
| Aspect | Cavitation | Flashing |
|---|---|---|
| Outlet pressure | Above vapour pressure | Below vapour pressure |
| Bubbles | Collapse downstream | Stay as vapour |
| Damage look | Rough, cinder like pitting | Smooth, polished erosion |
| Noise | Gravel like | Lower, hissing |
| Prevention | Anti cavitation trims, staging, high FL | Cannot prevent; use hard trim, angle body |
| Flow | May choke when severe | Chokes |
Choose Cavitation when
- Cavitation: check σ and use staged trims
Choose Flashing when
- Flashing: size for choked flow and protect downstream pipe
Key Differences Explained
Both start at the vena contracta where pressure falls below the vapour pressure. What happens next depends only on whether the outlet pressure recovers above vapour pressure.
Changing the valve location to a higher pressure point can turn flashing into no vaporisation at all.
Related Glossary Terms
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Frequently Asked Questions
What is the difference between Cavitation and Flashing?
In cavitation, vapour bubbles form and then collapse as pressure recovers; in flashing, outlet pressure stays below vapour pressure, so the vapour remains.
Is cavitation worse than flashing?
Both damage trim; cavitation is more violent and noisy, flashing erodes over large areas.
How is cavitation predicted?
With the cavitation index σ compared with maker limits.
Does flashing affect sizing?
Yes, size with the choked pressure drop.
Learn more on the blog
Control valve passing causes
A practical guide on instrumentationblog.in that goes deeper into this topic with field examples.
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