Inputs
Example data table
| Scenario | Flow basis | Source flows | Safety | Estimated total load |
|---|---|---|---|---|
| Example A | Mass flow | 1200, 800, 350 kg/h | 1.10 | 2585 kg/h |
| Example B | Standard volume | 3000, 1800 Nm³/h | 1.15 | ≈ 2390 kg/h |
| Example C | Actual volume | 900 m³/h @ 300 kPa, 40°C | 1.05 | Depends on MW and Z |
Formula used
- Total mass flow: Σṁi × SF
- Mass from molar flow: ṁ = ṅ × MW
- Standard volume to molar flow: ṅ = QN / 22.414
- Actual volume to molar flow: ṅ = (P × Q) / (Z × R × T)
- Volumetric flow at tip: Q̇ = (ṅ × Z × R × T) / P
- Tip diameter from velocity limit: D = √(4Q̇ / (πVmax))
- Heat release: HR(MW) = (ṁ/3600) × LHV
How to use this calculator
- Select a flow basis that matches your available data.
- Enter molecular weight and a suitable safety factor.
- If using actual volume, enter relieving P, T, and Z.
- Add each contributing source and its flow value.
- Set tip conditions and an allowable velocity limit.
- Press Estimate flare load to view results above.
- Download CSV or PDF for quick documentation.
Article
Flare load inputs and scenario framing
A flare load estimate begins with clear scenario boundaries. Identify credible relief cases, list contributing devices, and define whether flows are steady, simultaneous, or time limited. Capture the basis for each contributor and any isolation assumptions. This calculator sums multiple sources, then applies a safety factor to represent uncertainty and engineering margin. Screening factors often range from 1.05 to 1.25, depending on data quality and design phase.
Unit handling and basis selection
Data arrives in different forms: mass flow, standard volume, or actual volume. Mass flow converts to molar flow using molecular weight, where kmol/h equals kg/h divided by MW. Standard volume uses a reference molar volume of 22.414 m³ per kmol at 0°C and 101.325 kPa. Actual volume uses pressure, temperature, and compressibility, with ṅ = P·Q /(Z·R·T). Choosing the correct basis avoids unit drift and preserves auditability.
Tip sizing and velocity constraints
After total molar flow is estimated, the tool converts to volumetric flow at flare tip conditions. Tip pressure, temperature, and Z influence volumetric rate, so align them with your operating philosophy. A velocity limit then provides a screening diameter using area equals flow divided by velocity, and diameter equals √(4A/π). If the diameter seems extreme, revisit conditions, molecular weight, and the limiting scenario set.
Heat release screening and documentation
Combustion energy is estimated from mass flow and lower heating value, yielding a heat release rate in megawatts. For example, 2,500 kg/h with 45 MJ/kg is about 31 MW. This helps compare scenarios, support discussions, and build documentation packs. It is not a radiation study, but it highlights cases that deserve detailed modeling. Record inputs, assumptions, and selected limits to keep recalculations consistent.
Interpreting results for design decisions
Use the total load, heat release, and duration mass to communicate design intent. Duration converts flow to released mass, supporting blowdown inventory checks. Cross check with flare header hydraulics, backpressure allowances, and operational constraints such as depressuring. When multiple cases exist, document the governing case and the rationale. Exported CSV and PDF outputs support traceability for reviews and change control.
FAQs
What does the safety factor change?
It multiplies the summed load to reflect uncertainty and conservatism. Use a factor aligned with your data quality, project phase, and internal design practices.
Which flow basis should I choose?
Use mass flow when available. Use standard volumetric flow for normalized reporting. Use actual volumetric flow when your data is at relieving conditions and you can provide pressure, temperature, and compressibility.
Why does tip pressure and temperature matter?
They set the gas density at the flare tip, which controls volumetric flow. Higher temperature or lower pressure increases volumetric flow and can increase the diameter required for the same velocity limit.
Is the heat release value a radiation calculation?
No. It is a screening estimate based on mass flow and lower heating value. Radiation, noise, and stability checks require dedicated methods, geometry, and environmental assumptions.
How is the tip diameter estimated?
The calculator converts total molar flow to volumetric flow at tip conditions, then uses area equals flow divided by allowable velocity. Diameter is derived from circular area, giving a quick sizing check.
Can I export results for reviews?
Yes. After calculation, use the CSV button for spreadsheets or the PDF button for a formatted report. Both include the summary metrics and the source breakdown for traceability.