[naren.iitr]

Centrifugal pumps are basically used to maintain flow or provide head for incompressible fluid (liquid) and if vapors are formed cavitation occurs which is undesirable. Centrifugal compressors does the same job for compressible fluid (gases) in similar way. I want to know what will happen if only gas enters a centrifugal pump. what  e mechanical design difference causes incompressible flow in centrifugal pump and compressible flow in compressor ?

[Montemayor]

Pumps are designed and manufactured to pump liquids.

Compressors are designed and manufactured to compress gases and vapors – which contributes a driving force and allows gas/vapor flow.

Pumps will never “pump” gas or vapor.  Compresors cannot compress liquids without suffering mechanical damage.

If vapors are formed in a pump, cavitation DOES NOT OCCUR.  You have an erroneous idea of what cavitation is and how it behaves.  Cavitation is a sequence of actions: a liquid is vaporized into bubbles these are subsequently “imploded” by a downstream increase (or recovery) in pressure.  Physical damage and noise are the result of these implosions.  What you are asking has nothing to do with cavitation in a pump.

Additionally, a centrifugal compressor is certainly not like a centrifugal pump.  They may look alike on the outside, but their design and mechanical actions are totally different.  A centrifugal pump does not employ a diffuser.  A centrifugal compressor depends on a diffuser.

You want to know “what will happen if only gas enters a centrifugal pump”?  Absolutely nothing --- as it should.