Feedwater systems and deaerators
The equipment that decides how long the boiler lasts. Most premature vessel failure is a feedwater problem wearing a boiler-shaped disguise.
| Sized on | Total feedwater flow: steam rate plus blowdown |
|---|---|
| Storage | Rated in minutes of feedwater at full firing rate |
| Deaeration | Heats to saturation and vents dissolved O₂ and CO₂ |
| Chemistry | Scavenger polishes what mechanical deaeration leaves |
| Pump NPSH | Governed largely by vessel height above the pump |
| Type | Pressurized or atmospheric |
| Around it | Receiver, transfer and feed pumps, makeup control, chemical injection |
| Blowdown | Separator and heat recovery where the plant justifies it |
Most premature vessel failure is a feedwater problem. Size this alongside the boiler, not after it.
The short version
Dissolved oxygen and carbon dioxide in feedwater attack the vessel and the condensate system continuously. A deaerator removes them mechanically, heating the water to saturation and venting the liberated gases, and a chemical scavenger then polishes what remains. The chemical alone is a treatment; the deaerator is the fix.
Around it sits the rest of the feedwater train: condensate receiver, transfer and feed pumps, makeup control, chemical injection, and blowdown separation. It is routinely specified last and is routinely the reason a plant underperforms.
What decides the selection
- Steam rate and makeup
- The deaerator is sized on total feedwater flow: steam rate plus blowdown. The makeup percentage sets how much heating and venting it has to do. A plant returning 80% of its condensate and one returning 20% need very different equipment at the same boiler horsepower.
- Storage
- Storage is rated in minutes of feedwater at full firing rate. It buys ride-through when makeup or condensate is interrupted, and it is the dimension most often trimmed to fit a room and later regretted.
- Pump NPSH
- Feedwater leaves a deaerator at saturation, so it flashes given the slightest excuse. Available NPSH, which is mostly the height of the vessel above the pump, is a hard constraint, not a preference.
- Pressurized or atmospheric
- A pressurized deaerator reaches lower oxygen levels; an atmospheric system suits lower-pressure plants and tighter rooms. The boiler pressure and the oxygen target decide it.
- Makeup water
- Softening, RO, or neither, based on an actual water analysis rather than an assumption about the municipality.
What to send us
Send what you have and we'll tell you what's missing. Knowing this up front is the difference between a quote this week and a quote after three rounds of questions.
Lockwood Products is signed for this category. Selections, pricing and submittals available now.
- Boiler rating
- Horsepower or steam rate for every boiler the system feeds, including future units if the room is being built for them.
- Condensate return
- Percentage returned and at what temperature.
- Water analysis
- A recent one for the makeup source. This is worth chasing rather than guessing.
- Room
- Available floor area and, critically, ceiling height above the pumps.
- Pressures
- Boiler operating pressure and required feed pump discharge pressure.
- Scope
- Whether this replaces an existing deaerator or is a new train.
The rest of the room
- Firetube Boilers The workhorse of the commercial boiler room: packaged, factory-assembled, and the default answer for most steam and hot water loads under a few hundred horsepower.
- Watertube Boilers Where the load is bigger, the pressure is higher, or the demand swings faster than a firetube can follow.
- Burners The burner decides the emissions, most of the efficiency, and nearly all of the reliability complaints.
- Combustion Controls Two different jobs that get discussed as one: keeping the boiler safe, and keeping it efficient.
- Auxiliary Equipment The equipment around the boiler that decides whether the boiler behaves: blowdown handling, condensate return, surge capacity, and water treatment.
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