Home/Fired Heater
VP
Data & Configuration ▾

Fired Heater Efficiency - Performance & Losses

API 560 · ASME PTC 4

Natural-gas-fired process heater · L3/L4 furnace

No data loaded

Upload a CSV or click Load demo data in the sidebar.

Batch summary
No batch processed.
Processed rows (most recent 50)
TimestampQ Abs (kW)Q Fired (kW)n Directn IndirectDeltaEA%O2%Stack (C)Bridge (C)Status
No rows processed.

Formulas

Heat absorbed: Q_abs = m_proc * Cp * (T_out - T_in) / 3600 [kW]

Fired duty (LHV basis): Qfired = Vfuel * LHV * 1000/3600 [kW]

Direct efficiency (ASME PTC 4 §5.12): ηdirect = 100 * Qabs / Qfired [%]

Excess air (ASME PTC 4 Appendix A): EA = 100 * O2 / (20.95 − O2) [%]

Indirect efficiency (loss method): ηindirect = 100 − Ldry − Lmoisture − Lradiation − Lunaccounted

Dry flue-gas loss: Ldry = mfg,dry * Cp,fg * (Tstack − Tambient) / LHVkg [% of fuel]

Moisture loss: Lmoist = mH₂O * (Latent + Cp,H₂O * (Tstack − Tfuel)) / LHVkg [% of fuel]

Alert Tiers

Stack temperature follows API 560 §5.4 guidance: advisory at 400 C, alarm at 450 C, trip at 500 C. Bridgewall follows tube metallurgy limits: advisory at 830 C, alarm at 870 C, trip at 900 C. Excess air advisory at 25%, alarm at 40%. Stack O2 below 2% triggers CO formation alarm.

Scope

Reference-grade PoC. Not a control system, not SIS. Indirect method uses sensible-only H2O loss on LHV basis. Efficiency values are not clamped to 0-100%. A negative or >100% value is a data-quality signal.

See engineering manual for complete tag list, assumptions, and standards references.

Engineering Manual - Fired Heater

1. Purpose & Scope

Thermal efficiency monitoring dashboard for a natural-gas-fired process heater. Computes both direct (input/output) and indirect (loss) method efficiencies per ASME PTC 4. Reports consistency gap between methods as a data-quality check. Tracks combustion, recovery, and tube temperatures per API 560.

2. Key Standards

API 560 - Fired Heaters for General Refinery Service. §5.4 covers stack temperature limits and efficiency guidance.

ASME PTC 4 - Fired Steam Generators. §5.12 direct efficiency, §5.14.4 loss method, Appendix A excess air from O2.

3. Input Tags (13 variables)

Process inlet/outlet temps (C), process flow (kg/hr), process Cp (kJ/kg/K), fuel flow (Nm3/hr), fuel LHV (MJ/Nm3), stack O2 (%), stack temp (C), bridgewall temp (C), ambient temp (C), fuel temp (C).

4. Output KPIs

Direct efficiency, indirect efficiency, efficiency delta, heat absorbed, fired duty, excess air %, stack O2, stack and bridgewall temps, loss breakdown (dry, moisture, radiation, unaccounted).

5. Alert Thresholds

Stack T: advisory 400, alarm 450, trip 500 C. Bridgewall: advisory 830, alarm 870, trip 900 C. Excess air: advisory 25, alarm 40%. O2 low: alarm < 2%. Efficiency: advisory < 82, alarm < 78%.

6. Fuel Properties (defaults)

Stoichiometric air: 17.2 kg/kg. H2O from combustion: 2.25 kg/kg. Fuel MW: 17.5 kg/kmol (methane-dominated gas). Flue-gas Cp: 1.08 kJ/kg/K. H2O Cp: 2.0 kJ/kg/K. Radiation loss: 2.0%. Unaccounted loss: 0.5%.

7. Assumptions

Perfect combustion with no CO. Flue gas modeled as ideal gas with constant Cp. Sensible-only H2O loss on LHV basis (latent heat of vaporization already excluded by LHV definition). No heat of formation corrections. Direct efficiency is Qabsorbed / Qfired. Indirect method is loss-based with %LHV reporting.

Keyboard Shortcuts

Navigation

Go to Home
GH
Go to Dashboards
GD
Go to Settings
GS
Go to Alerts
GA

Actions

Show shortcuts
?
Close modal
Esc