Centrifugal pump is designed as a hydraulic machine to move liquids. Caviation or entrained gas causes problems in pump performance. Pump cavitation is caused by vaporization of the liquid in pump suction due to several reasons. Experiments claim that a volume of only one per-cent air will cause a loss of head and efficiency. Pump cavitation can severely damage the pump impeller blades and frequent dry running of pumps can damage other pump parts. These damages are described in the following paragraphs.
Pump damage caused by cavitation
Damage to pump mechanical seal
Mechanical seal are very important in any pumps as they prevent any foreign materials from entering into the pump casing and the pumped liquid to escape to the environment so any damage that may occur to the mechanical seal will increase operating cost and consumption of natural resources. Cavitation can badly affect the performance of the mechanical seal as it will cause damage to the seal faces and if the cavitation phenomena continues the seal may run dry without continues cooling or lubrication.
Damage to pump shaft alignment
Shaft miss-alignment can occur after pump operation due to many reasons but the most important one is the vibration that may be caused due to cavitation and expansion of pump shaft due to heat generated in the pump due to cavitation.
Damage to Bearings
The bearing life will decrease significantly due to the vibration which will be transmitted from the pump casing to the bearing housing, the vibrations cause the balls and rollers to jam into the raceways causing the very small bents the races will appear like a corduroy cloth
Pump Impeller damage
When pressure in the eye of the impeller falls below the vapor pressure of the fluid, then cavitation can begin and gas bubbles are formed the bubbles can collapse as they pass from low- to high-pressure zones in the pump. When vapor bubbles collapse inside the pump the liquid strikes the metal parts at the speed of sound. The noise we hear from outside the pump when we say that cavitation sounds like pumping marbles and rocks.