In a steam system, condensate is a byproduct of heat transfer. It accumulates in the distribution system as a result of unavoidable radiation. It also forms in heating and process equipment due to the desired heat transfer from the steam to the heated substance. The hot condensate must be removed immediately after the vapor has condensed and released its valuable latent heat. Although the available heat in a pound of condensate is negligible compared to a pound of steam, condensate hot water should be returned to the boiler.
During equipment startup and boiler feedwater, the air is always present. Dissolved carbonates in feedwater may also emit carbon dioxide gas. The gases are pushed to the walls of the heat exchangers by the steam velocity, where they may obstruct heat transfer. These gases must be removed along with the condensate; otherwise, the condensate drainage problem is exacerbated.