Cavitation In Pumps

Cavitation In Pumps:

Cavitation is transient unsteady phenomenon characterized by a growth of holes or cavities. Cavitation creates problem in operation of all three types of centrifugal pumps viz.radial,mixed and axial flow pumps,whenever high discharge,high rotational speed or low head is encountered. Pumps with low specific speed are more susceptible to cavitation as compared to high specific speed pumps.

Types of Cavitation:

Occurrence of cavitation in pump can occur at various places and ways. So, depending upon that cavitation phenomenon can be segregated as below.

1. Traveling Cavitation: As name suggests, this type of cavitation is not a steady one, it moves from place to place within pump.
2. Fixed Cavitation: This type of cavitation is fixed at a place and hardly changes its position.
3. Vortex Cavitation: Here vortex i.e. circular flow is generated and thereby occurrence of cavitation.
4. Vibratory Cavitation.

Effects of Cavitation:

We may think that cavitation is unwanted phenomenon and it have only harmful effects only but cavitation have both harmful as well as favorable effects on the pump.

Harmful Effects of Cavitation:

1. Cavitation affects the performance of various hydraulic machines like pumps, turbines etc. This reduces their overall efficiency.
2. Noise is generated which is unwanted everywhere but in some cases like submarines noise must not be generated as it may create the problem while hiding.
3. Drag force increases in cavitation parts.
4. Due to braking of bubbles shock waves are produced which generates vibrations. Vibrations are damn dangerous at very high speeds.
5. Material damage due to erosion.

Beneficial Effects of Cavitation:

1. Cavitation can be used for agitation and mixing.
2. A cavitation noise boomer can be used as sound source for an echo ranging survey of ocean bottom conditions.
3. Jet cavitation can be used very effectively for tunneling through rock.

Methods to Avoid Cavitation Damage:

1. Primary Design.
2. Air Injection.
3. Cathodic Protection.
4. Hydrogen Evolution.
5. Corrosion Inhibitors.

Seminar On Cavitation in Pumps:

Engineering students can take seminar topic as Cavitation in Pump. This topic must contain following points:

• Introduction.
• Definitions.
• Cavitation In Centrifugal Pumps.
• Effect Of Cavitation On The Performance Of A Centrifugal Pump.
• Factors Influencing Cavitation In Pumps.
• Detection Of Cavitation Inception In Pumps.
• Cavitation Occurring At Places Other Than The Eye.
• Methods To Tackle Cavitation Damage.
• Conclusion.

References:

[1] http://en.wikipedia.org/wiki/Cavitation

[2] http://www.powerqualityanddrives.com/pump_cavitation/