Management Of Non-Condensables


In the world of steam heating system management, non-condensables are fluids that remain in a gaseous state all the way through normal temperature/pressure ranges. Primarily, we're concerned with three kinds of non-condensables:

  • The mixture of atmospheric gases generally known as AIR
  • oxygen
  • carbon dioxide

Non-condensables are introduced into the system in two ways.


First, non-condensables can enter the boiler through the make-up water. Non-condensables often exist as dissolved gases. To understand what a dissolved gas is, think of it this way - when you boil water on the stove, you see gas bubbles expand and rise to the surface long before the water actually boils. These are non-condensable gases. Impurities in the makeup water that are released during thermal breakdown can release non-condensables into a system.

Another way non-condensables can enter a system is in the form of air being pulled in from the atmosphere. Air can get in through leaks in equipment or piping. This happens most often when the system is shut down and the steam pressure falls below the atmospheric pressure.

Non-condensables can be introduced into a system through vacuum breakers. These devices prevent a vacuum from forming inside the steam space.