All Topics
Feedwater Systems
Water supply to the boiler including pumps, injectors, treatment, and deaerators.
Feedwater Supply
The feedwater system supplies treated water to the boiler to replace water that has been converted to steam or lost through blowdown.
- Feedwater = steam output + blowdown losses
- Must be properly treated before entering the boiler
- Temperature: preheating feedwater improves efficiency and reduces thermal shock
- Common sources: city water, condensate return, or deaerator
Feedwater Pumps
Feedwater pumps push water into the boiler against steam pressure.
- Must develop pressure greater than boiler operating pressure
- Centrifugal pumps are most common in modern installations
- Positive displacement pumps provide consistent flow regardless of pressure
- A standby pump should always be available as backup
- Check valve prevents backflow from the boiler
Deaerator
A deaerator removes dissolved gases (oxygen and CO₂) from feedwater by heating it with steam.
- Dissolved O₂ causes pitting corrosion
- Dissolved CO₂ forms carbonic acid — causes corrosion in condensate lines
- Heats feedwater to near boiling point using steam
- Mechanical deaeration is more effective than chemical treatment alone
- Located between the condensate return and the boiler feed pump
Even with a deaerator, chemical oxygen scavengers (sodium sulfite) are typically used as backup.
Feedwater Check Valve & Stop Valve
These valves control water flow into the boiler and prevent backflow.
- Check valve: allows flow in one direction only — prevents boiler water from flowing back
- Stop valve (globe or gate): allows the operator to isolate the feedwater line
- Both are required on every feedwater connection to the boiler