What's the difference between surging and cavitation?

Cavitation: This is a change in the absolute pressure of a liquid, below the steam pressure. Vapor bubbles form when fluid moves towards a higher pressure zone. The bubbles collapse and their implosion can cause stings in the impeller. Surging: Occurs when an air in a dynamic computer, low enough to immediately change the flow direction. If the Velocidadisminuye, the suction flow is also low, being able to reach a point where this pressure is less than the existing one, generating a momentary investment of the sense of flow.

Surging happens due to insufficient suction water flow , but cavitation happens when air pockets formed inside the pump resulting vapor formation and heat accumullation 

When a pump cavitates you are dealing with air pockets in the system, when a pump serges there is a suction shortage, or the delivery overcomes the suction.

  surging is caused due to black out due to that vacuum gets created and hammering of water occurs in the pipe line and cavitation is cussed due to temperature difference in the pipe line where water becomes vapor and after condensing a small pocket of vacuum gets created and that causes the water splash on itself and gets divided in to micro jets which will hammer inside of the pumps and pipelines damaging interior of the water system.

The surging phenomenon occurs when the suction flow of the pump is less than the permissible flow , cavitation phenomenon occurs when the pressure of the liquid is less than the steam pressure.

pipe up to the valve with the fluid to be pumped, taking out all the air, before starting the pump. If air is present, it develops a very low pressure head (almost 800 times lower if we compare air and water) which is not enough for the suction of the fluid disrupting the function of the pump. Cavitaion, on the other hand, is the forming of bubbles in the suction pipe when the -ve pressure developed at the eye of the impeller is lower than the saturation pressure of the fluid to be pumped causing it to boil, and the bursting of those bubbles in the vanes where the pressure is higher. Cavitation causes noise, vibration and damages the components of the pump.The basic difference is the defintions of the two processes. For further comparison , we can say that,

• primng is done before the motor is started (for submerged pumps, it's not needed as the inside of the pump is always filled with liquid). On the other hand, to prevent cavitation, measures are taken while manufacturing. The shape of the impeller should be such that, while running, the pump pressure will never go below or equal the saturation pressure of the liquid