This article discusses the cause of cavitation and how to avoid it through proper design and analysis.
Issue: 8/05
Editor's Note: "Back to Basics"
Figure 1. Vapor pressure of water versus its temperature.
What's Happening?
Vaporous cavitation occurs as water entering the eye of a circulator's impeller flashes into vapor. You could say that the water "boils"
Implosive Results
Cavitation begins when the water entering the eye of the impeller flashes into millions of tiny vapor pockets. The density of this vapor is about 1,500 less than that of liquid water. In other words, the water molecules take up about 1,500 times more space as vapor compared to liquid. This is comparable to a single kernel of popcorn expanding to the size of a baseball.