Boilers Maintenance


Boilers Maintenance

Importance of Boiler Feed Water Chemical Treatment

  1. Boilers are operated at High Steam Pressure, High Steam Temperature and High Steam Capacity
  2. So Boilers require Very Pure Water as Feed Water
  3. Even Pure Water will contain some Dissolved Salts (Hardness Salts)

(i) Some Dissolved Salts come out of Water/Solution on Boiling

These Salts adhere to the Heating Surfaces as a Scale

Scales reduce Heat Transfer, cause local overheating and failure of Tubes

(ii) Some Dissolved Salts remain in Water/Solution

These Salts produce Acids

Acids will attack the metal of the Boiler

Dissolved Oxygen and Carbon-di-oxide in Boiler Feed Water causes  corrosion of Boiler and Feed system

  1. Sometimes Feed Water / Boiler Water may be contaminated by suspended matter, an excess salts or oil

This causes Foaming

Foaming Leads to Priming

Priming is the carryover of Water with the Steam

If the Steam contains Water – Steam Turbine may get damaged

Boiler Feed Water Chemical Treatment

It is done to prevent boiler / boiler parts from getting affected by scale & corrosion causing salts and dissolved gases

It is achieved as follows:

  1. By keeping the hardness salts in a suspension in the solution/water to prevent scale formation
  2. By stopping any suspended salts from sticking to the heat transfer surfaces
  3. By eliminating dissolved gases and providing some degree of alkalinity which will prevent corrosion


Chemicals used/added for Auxiliary Boilers (Low Pressure Boilers) – Calcium hydroxide, Sodium carbonate, Sodium hydroxide


Chemicals used/added for Main Boilers (High Pressure Boilers) – Trisodium phosphate, Disodium phosphate, Sodium metaphospate