CHAPTER 6
VELOCIS SOLUTIONS @2018
7
Figure 7.5: Main parts of radial centrifugal pump
Since centrifugal pumps are designed to pump liquid, any entrained gas and vapor bubbles can
damage to internals of pump. Gas near the impeller of pump can cause cavitation or vapor lock.
Vapor bubbles can form in the low-pressure area around impeller and damage it within exploding.
Cavitation can be noticed with fluctuation of pressure in the discharge line of pump and noisy
operation. It reduces efficiency of pump and capacity.
When too much entrained gas enters through pump suction, vapor lock happens. The gas
separates from liquid and fill the space around impeller, hence no liquid can enter to impeller eye.
If pump is vapor locked, the pressure gauges of suction and discharge lines read the same value.
Vapor lock generally occurs as a consequence of low liquid level in an upstream vessel.
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