Deaeration of Boiler Feedwater

Pour yourself a tall glass of cold water. Place it in front of you and read on.

The water you have just poured for yourself is much like the feedwater you may be sending directly into your boiler. 

It contains among other things, dissolved gases such as oxygen and carbon dioxide that can be particularly destructive to feed lines, condensers and to your boiler.

The oxygen in this raw feedwater is released within the boiler as a result of heat and rises in the form of bubbles. These bubbles attach themselves to the boiler tubes, water legs and the sides of the boiler drum shell at the water line.

The oxygen along with the carbon dioxide attacks the iron and set up chemical musical chairs in which the steel in your system will always lose. This destructive game will continue until either all the oxygen is entirely removed from the water or the steel or iron is dissolved.

A deaerator will prevent the game from ever starting. This piece of equipment removes corrosive gases from boiler feedwater and preheats the water prior to entrance into the boiler.

Now take a good look at that glass of water you poured earlier. Those little bubbles that have formed on the inside of the glass are just what we have been describing. Imagine the inside of your boiler system with high temperatures and high pressures.

If you don't have a deaerator, maybe it is time to consider one.

Dissolved Gases In Water

CORROSION is defined as the destruction of a metal by chemical or electromechanical reaction with its environment. The metal is eaten away in much the same manner as fender rusts on a car. Corrosion dramatically increases maintenance costs and can cause unnecessary safety risks. It will occur when levels of oxygen or carbon dioxide are high, where pH values are low, where contact occurs between dissimilar metals and in damp environment or corrosive atmospheres.

Corrosion is an electrochemical process in which electricity flows through a solution of ions between areas of metal. Deterioration occurs when the current leaves the negatively charged metal or anode and travels through the solution to the positively charged metal or cathode, completing an electrical circuit in much the same manner as a battery cell. The anode and the cathode can be different metals or areas of the same metal. Corrosion occurs when there is a difference in the electrical potential between them.