is 1)Cavitation the formation and then immediate implosion of cavities in a liquid that are the
consequence of forces acting upon the liquid. If the pressure of the system is reduced to such an
extent that it drops below the vapor pressure of the fluid, as a result, some part of the fluid will
vaporize forming bubbles or cavities.
APPEARANCE:
Cavitation normally appears in the form of rapid stream of bubbles which implode drastically as
they enter a high pressure region.
SOUND:
Low level cavitation in pumps may be inaudible, but higher levels generate distinctive sounds
that we can hear. Cavitation makes different sounds depending on the equipment and conditions.
Following are some of the descriptions of cavitation sounds:
Pumps
Crackling or sizzling
Hissing, rushing, swishing, or a static like sound similar to radio or television static.
Valves
High pitch squeal
High pitch singing
DIFFERENCE BETWEEN CAVITATION AND AIR RELEASE FROM WATER:
Water contains 2% - 3% soluble air. As water temperature rises and/or pressure in line
changes, the this soluble air is released from the water. These bubbles grow and rise to the top of the
pipe and accumulate at elbows and high points in the system. This phenomenon is much different
from cavitation in which bubbles are formed due to the vaporization of pumped fluid.
2) Cavitation is visible downstream of the throat despite the lowest pressure occurring inside the
throat as the vapor bubbles though formed at the throat section implode in the high pressure
region beyond the throat. What is visible to us is the imploding of the bubbles not their formation
which is why we witness that in the downstream section.
3) Cavitation in a hydraulic system may cause broad, high-frequency vibrations, excessive noise, material
damage, erosion and thermal degradation of the fluid. In addition, bubbles in the reservoir may be
concentrated at the gas-liquid interface as foam. It can adversely affect the productivity of the process
being carried out in the system as losses are greatly increased due to cavitation.
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