Influence on the performance of Pump Cavitation

In the four previous posts we have to know the influence of cavitation and cavitation classification based on the main cause.
This time we re-deepen this cavitation effect in more detail. Previously we have to know the effect of cavitation in general are as follows:

     Reduced capacity of the pump
     Reduced head (pressure)
     The formation of air bubbles in the area of ​​low pressure in the pump casing (volute)
     Noise when the pump is running.
     Damage to the impeller or pump casing (volute).

In this paper we will discuss why it all happened.
Cavitation is expressed with cavities or holes in the fluid we are pumping. These holes can also be described as bubbles, it is actually the formation of cavitation bubbles and the bubbles outbreak. Bubbles are formed when the liquid boils. Be careful to declare the same boiling water that is hot to the touch, as well as liquid oxygen will boil and nobody claimed it was hot.
Boiling of the liquid occurs when it is too hot or the pressure is too low. At sea level pressure of 1 bar (14.7 psia) water will boil at a temperature of 212oF (100oC). If the pressure drop of water will boil at a lower temperature. There is a table that states the boiling point of water at each different temperature. As an example can be seen in the following table:

Fahrenheit	Centigrade	Vapor pressure lb/in2 A	Vapor pressure (Bar) A
40	4.4	0.1217	0.00839
100	37.8	0.9492	0.06546
180	82.2	7.510	0.5179
212	100	14.696	1.0135
300	148.9	67.01	4.62

Pressure unit used here is not the absolute pressure gauge, this plural is used when we talk about the suction side of the pump to avoid the minus sign. So when calling the atmospheric pressure is zero, we say 1 atm is equal to 14.7 psia at sea level and on the metric system we used to wear 1 bar or 100 kPa.
We're back to the first paragraph to explain the result of cavitation, so we better know what actually happened.
Pump Reduced Capacity

     It happens because a lot of air bubbles takes place (space), and we could not pump fluid and air at the same place and time. Automatic liquid we need to be reduced.
     If it's a big bubble in the eye of the impeller, the pump will lose revenue and ultimately needed freming (extra fluid on the suction side to remove air).

Pressure (Head) sometimes reduced
The bubbles are not as liquid, it can be compressed (compressible). Well, the results of this compression is to replace the head, so that the actual pump head is reduced.
The formation of bubbles at low pressure because they can not form at high pressure.
We must always remember that if the velocity of a fluid increases, the fluid pressure is reduced. This means that high fluid velocity in the low pressure area definitely.
It will be a problem at any time if there is a limited fluid flow through pipes, volute or change direction suddenly. This situation is similar to the fluid flow on a small cross-section between the tip of the impeller with volute water cut.
Damaged parts Pump

     The bubble burst in its own right, this is called the opposite of exploding imploding. The bubble burst on all sides, but if he gets hit as part of a metal impeller or voluteia can not be broken from the side, the fluid entering from the opposite side at high speed followed by a shock wave that could damage the pump part. There is a unique shape that forms a circle as a result of this blow, which was hit with a metal such as a "ball peen hammer".
     The most damage occurs to form right angles to the metal, but experience shows that high-speed fluid seems to come from all angles.

The higher the capacity of the pump, it seems more likely cavitation occurs. Specific values ​​have a high speed pump impeller shape that allows it to operate at high capacity with low power and a small possibility of cavitation. It is usually found in the tubular casing, of the volute casing shaped as we often see.