Calculator Inputs
Example Data Table
Use this example to verify your setup and expected output scale.
| Case | Pressure | Flow | Vent % | Rule Steam | O₂ In | O₂ Target | Steam/Air | Design Steam |
|---|---|---|---|---|---|---|---|---|
| Example | 200 kPa(abs) | 30,000 kg/h | 0.20% | 60.0 kg/h | 5,000 ppb | 7 ppb | 3.0 | 60.0 kg/h |
Formula Used
1) Rule method (screening):
Vent steam (kg/h) = Feedwater flow (kg/h) × Vent% / 100
2) Gas-load method (oxygen-based lower bound):
O₂ removed (kg/h) = Flow × (O₂_in − O₂_target) × 10⁻⁹
Air (kg/h) = (O₂ removed / 0.232) × Air-leak factor
Vent steam (kg/h) = Air (kg/h) × Steam-to-air ratio
3) Recommended design steam:
Design vent steam = max(Rule steam, Gas-load steam) (when enabled)
Saturation temperature is estimated from pressure using an Antoine correlation. Vent volumetric rates use ideal-gas approximations for quick screening only.
How to Use This Calculator
- Enter the deaerator operating pressure and feedwater flow rate.
- Start with a vent percentage in the screening range (0.1–0.3%).
- Add oxygen inlet and target values if you want a gas-load check.
- Set an air-leak factor and steam-to-air ratio based on standards.
- Keep “Use maximum” checked to avoid under-venting.
- Click Calculate to display results above the form.
- Use Download CSV or Download PDF for reporting.
Technical Article
1) Why Venting Matters in Deaeration
A deaerator removes dissolved gases—primarily oxygen and carbon dioxide—by heating and stripping. The vent continuously releases non‑condensables and a small amount of steam to maintain low oxygen at the outlet. Under‑venting can allow oxygen carryover that accelerates corrosion in feedwater lines, economizers, and boilers. Over‑venting increases steam losses and makeup demand, which raises operating cost.
2) Rule Method for Fast Project Screening
During early design and construction planning, a common starting point is vent steam at about 0.1%–0.3% of feedwater flow. For example, at 30,000 kg/h feedwater, 0.20% gives 60 kg/h vent steam. This calculator applies that percentage directly and reports both the mass rate and the percentage for quick comparison between cases.
3) Gas-Load Check Using Oxygen Removal
Where inlet and target oxygen data are available, the tool estimates a minimum air load from the oxygen removed. If inlet oxygen is 5,000 ppb and the target is 7 ppb, the removed oxygen fraction is 4,993 ppb. At 30,000 kg/h, that equals roughly 0.150 kg/h oxygen removed. Assuming air is 23.2% oxygen by mass and applying an air‑leak factor (e.g., 1.2), the estimated air rate becomes about 0.776 kg/h.
4) Selecting Steam-to-Air Ratio and Margins
Steam-to-air ratios of 2–5 kg/kg are often used to ensure effective stripping. With 0.776 kg/h air and a ratio of 3.0, the gas-load method implies about 2.33 kg/h vent steam. In many projects, the rule method will still govern, but gas-load results help confirm that chosen venting is not unrealistically low.
5) Reporting, Auditing, and Construction Handover
Construction teams benefit from traceable calculations for commissioning packages. This page stores the last run in the session and exports CSV for spreadsheets and a concise PDF report for submittals. Use the “Use maximum” option when you want a conservative design steam value that avoids under‑venting across uncertain operating conditions.
FAQs
A common screening range is 0.1%–0.3% of feedwater flow. Start near 0.2% and adjust using plant standards, commissioning results, and observed oxygen performance.
The rule method is fast for early estimates. The oxygen-based gas-load check provides a data-driven sanity check and can highlight when the rule value may be too low.
No. It is a lower-bound estimate tied to oxygen removal only. Actual non‑condensables can be higher due to nitrogen, carbon dioxide, vacuum in‑leakage, and transient operating conditions.
It adds margin for unknowns like gasket leakage, vacuum effects, and measurement uncertainty. Values around 1.1–2.0 are often used depending on project conservatism.
Many designs use 2–5 kg steam per kg air for stripping. Use your specifications when available, and increase the ratio if oxygen targets are difficult to achieve during commissioning.
Volumetric flow is estimated using ideal-gas behavior at an approximate saturation temperature. It is suitable for quick comparisons, but final vent piping and valve sizing should use validated steam-table properties.
Use it for preliminary sizing and documentation. For final approval, confirm operating envelope, vendor recommendations, and site performance data, then validate with detailed thermodynamic calculations.