文档介绍：Centrifugal Pumps: Basic Concepts of Operation, Maintenance, and
Troubleshooting (Part- II, Understanding Cavitation)
Introduction
In Part I of the article, two basic requirements for trouble free operation
and longer service life of centrifugal pumps are mentioned in brief.
1. PREVENT CAVITATION
Cavitation of the pump should not occur throughout its operating capacity
range.
2. MINIMIZE LOW FLOW OPERATION
Continuous operation of centrifugal pumps at low flows . reduced
capacities, leads to a number of unfavorable conditions. These include
reduced motor efficiency, excessive radial thrusts, excessive temperature
rise in the pumping fluid, internal re-circulation, etc. A certain minimum
continuous flow (MCF) should be maintained during the pump operation.
Operating a pump under the condition of cavitation for even a short period of time an
have damaging consequences for both the equipment and the process. Operating a
pump at low flow conditions for an extended duration may also have damaging
consequences for the equipment.
The condition of cavitation is essentially an indication of an abnormality in the pump
suction system, whereas the condition of low flow indicates an abnormality in the
entire pumping system or process. The two conditions are also interlinked such that a
low flow situation can also induce cavitation.
The concept of cavitation is explored in detail under following topics:
1. Meaning of the term ‘cavitation’ in the context of centrifugal pumps.
2. Important definitions: Static pressure, Dynamic pressure, Total pressure, Static
pressure head, Velocity Head, Vapor pressure.
3. Mechanism of cavitation.
4. General symptoms of cavitation and its effects on pump performance and pump
parts.
5. Types of cavitation:
a. Vaporous cavitation
i. Classic cavitation
ii. Internal re-circulation cavitation
b. Gaseous cavitation
i. Air ingestion induced cavit