can someone give me information about cavitation in pumps?how it happens?how to prevent it?i need it asap..?

Answer 1

Cavitation is the formation and collapse of bubbles of a fluid on the suction side of a pump. Bubbles are formed when the pressure on the suction side is so low that the fluid being pumped 'boils' because of the low pressure. The bubbles immediately collapse once the pressure increases resulting excessive wear on the pump impeller.
Prevention of cavitation depends on the characteristics of the suction flow. These would include pump speed, suction side flow restrictions (pipe diameter and flow characteristics) and working head (How high are you trying to lift the fluid). Typical solutions are to increase the inlet pipe diameter (reduce flow resistance), reduce the head by lowering the pump or slow down the pump speed (reduce the suction).

Answer 2

Cavitation occurs when part of the fluid being pumped evaporates as it enters the inlet of the pump impeller. Then the vapor collapses when the pressure is increased within the pump. It often sounds like you are pumping mean B-B's. This can cause damage to the pump impeller and it can seriously limit the capability of the pump to perform. This is a common pumping design and application consideration. This vaporization occurs when there is a high suction "lift", when the fluid is near to its saturation temperature, the pump design has high speed and /or high inlet velocity and combinations of the above. The problem most often occurs when pumping hot fluids and special purpose pumps having a low NPSH (Net Positive Suction Head) are employed in the process design. One example is the pumping of hot steam condensate from a receiver.
To prevent cavitation there must be enough extra positive static pressure at the inlet to compensate for the transfer of static pressure energy to velocity energy. This is the NPSHRequired by a particular pump which is shown in the capacity curves for the pump model. The NPSSHAvailable is calculated based on the kind of fluid , its pumping temperature, its saturation temperature, the amount of static pressiure at the inlet. The NPSHA needs to be higher than the NPSHR to prevent the absolute fluid vapor pressure in the inlet from being less than the absolute saturation pressure of the fluid. (Absolute pressure is the gage pressure plus atmospheric pressure.)

Some corrective measures are cooling the fluid (expensive), using a low NPSAH pump, raising the elevation of the receiver above the pump, removing restrictions and equivalent length from the inlet piping, adding pressure to the fluid in receiver using compressed gas or vapor from another source.

Vaporization is what prevents real pumps from lifting water from a well more than about 25 feet. That is why deep well water pump are designed to go down into the hole. Heavy duty industrial water punps are installed with as little suction lift as practical and usually have a double suction design for low NPSHR.
Industrial steam trap manufacturers such as Sarco Inc. , have engineering manuals describing the pumping of hot water (condensate). The principles apply to any fluid.

Answer 3

Cavitation is caused when there is not enough water going in the pump to support the output. You need to lower the output of water. What is the pump being used for? And when does the cavitation happen?

Answer 4

it simple terms, cavitation is the rapid collapse of tiny bubbles of air that formed as a result of certain conditions in the process fluid flowing through the valve, as a result of pressure drops for example. flashing and cavitation can destroy control valves with very destructive force. care must be taken to avoid flashing and cavitation inside the valve as much as possible.