How we can avoid the pumps cavitation ?

The dynamic process formation of bubbles inside the liquid, their growth and subsequent collapse is called cavitation. 

The pump always need to have a sufficient amount of suction head present to prevent vaporization at lowest pressure point in the pump. So NPSH is important.

NPSH (Net positive suction head) is the total head at suction flange of the pump less than the vapor pressure converted to fluid column height of the liquid.

Cavitation can be avoided by increasing the NPSHa (Net positive suction head) available greater than the NPSH required.

NPSH available= Pressure head in suction reservoir + Static suction head + velocity Head at pump suction flange - friction head in suction line - vapor pressure of liquid at that temperature.

So as you see in the equation to increase the NPSHa you will have to

1. Increase the height of the tank
2. Pressurize the tank
3. Increase flow of the liquid
4. Reduce friction by increasing the diameter of the pipe
5. Reduce temperature of liquid to decrease the vapor pressure

1:  use reducer in suction line

2: Suction strainer or strainer mesh large mesh size (if the liquid viscosity is increase or mesh size decrease the pump suction is insufficient .

3: If the pump packing or M.seal leak the pump take air this sites.(If the packing leak thight the paacking or change the M.seal) 

4: Pump cavitation due to turbulense.Install the vortexes Breaker in pump suction

We can avoid pumps cavitation  doing the following in your pumps:-

1. Lower the temperature.
2. Raise the liquid level in the suction vessel.
3. Change the pump.
4. Reduce motor RPM if possible.
5. Increase the diameter of the eye of the impeller.
6. Use an impeller inducer.
7. Use two lower capacity pumps in parallel.
8. Use a booster pump to feed the principal pump

1)By increasing diameter of suction pipe and increasing size of strainer if found

2) Decreasing static suction lift of pump

3) Decrease flow rate of fluid

increase NPSH available value by increasing the level of liquid.

also reduce the temperature if u can