Water is sprayed or cascaded over trays in a steam atmosphere and heated to saturation, a few psi above atmospheric, so gases come out of solution and leave through a small continuous vent. A well-run deaerator gets oxygen down to a few parts per billion, and chemical scavengers finish the job. Smaller plants use an atmospheric feed tank instead, which removes less oxygen.
Deaerator vent should have a little plume, not a big cloud and not nothing, crack it back to about 18 inches of visible steam.
Check the DA pressure and the feedwater temperature together; if they don't match saturation, the vessel isn't deaerating.
Also heard as
- DA
- DA tank
- deaerating heater
Related terms
Feedwater
The water pumped into a steam boiler to replace the water boiled off, a blend of condensate and treated makeup.
Oxygen scavenger
A chemical fed to boiler feedwater that reacts with and removes the last traces of dissolved oxygen.
Oxygen pitting
Deep localized corrosion pits in boiler steel caused by dissolved oxygen in the water.
Makeup water
Fresh water added to a boiler system to replace water lost to leaks, blowdown, venting and unreturned condensate.