BOILER FEED WATER
The setup used to produce steam in industries is known as ‘Boiler’.  Water is fed to the boiler and heated to produce steam.  The water fed into the boiler is known as “Boiler feed water”.
S.No
Requirements for boiler water
If not, it will cause
1
Free from hardness causing salts
Sludge and scale
2
Free from oil and greases
Foaming
3
Free from dissolved salts, suspended impurities
Caustic embrittlement
4
Free from dissolved gases, suspended salts
Boiler corrosion

1.Sludge and scale:
If the water contains hardness causing salts like MgSO4, MgCl2 ,CaSO4 , Ca (HCO3)2
On evaporation, the salts are precipitated to produce scale and sludge.

No
Sludge
Scale
1
Loose, slim , non-adherent precipitate
Hard, thick , adherent precipitate
2
Due to  salts like MgSO4 , MgCl2
Due to  salts like CaSO4 , Ca(HCO3)2
3
Due to poor conductance, they decrease the boiler efficiency to lesser extent and causing chocking in the pipelines.
Due to  poor conductance, they decrease  the boiler efficiency to maximum extent, cause reduced fuel economy , improper boiling, boiler explosion etc.,
4
It can be prevented by periodical replacement of concentrated hard water by fresh water. This process is known as “blow down” method.
It can be prevented by special methods like
i)                    external treatment of ion exchange ,
ii)                  Internal carbonate, phosphate, Calgon conditioning
iii)                Mechanical hard scrubbing methods.

Diagram: