Carry over in steam boiler: The phenomenon of carrying of water along with impurities by steam is called "carry over". This is mainly due to priming and foaming. Priming and foaming mainly occur together. They are objectionable together:
1. Dissolved salts or suspended solids in water carried by the wet steam to super heater and turbine, blades, where they get deposited as water deposited. This deposit decreases the efficiency of boiler.
2. Dissolved salts may enter the parts of other machinery, thereby decreasing their life.
3. The maintenance of the boiler pressure becomes difficult because of improper judgement of actual height.