Scaling in Boilers

Evaporation of water causes the impurities and minerals in the water to concentrate.  Scale Formation in boilers when impurities precipitate from water.  Scaling also occurs when matter which is suspended settles down to the bottom.

Scaling forms usually on heat transfer surfaces.  Scaling affects the heat transfer and thus the overall efficiency of the boiler.  Severe scaling can cause blockages which can be very expensive to remove. 
Some of the contaminants which can form scales are calcium, magnesium, silica.  Calcium and Magnesium form their carbonate and sulphate salts.  These salts get deposited on the tubes and other internal surfaces of the boiler and other equipment. 

Scaling can be prevented by using good demineralized water as feed water.  Effective water treatment and maintaining good water chemistry can prevent scaling to a large extent.