Asme Ptc 4.1.pdf May 2026

The code requires you to measure the flue gas temperature after the last heat recovery device (economizer or air heater). However, if air infiltration occurs downstream, PTC 4.1 provides a complex correction to back-calculate the temperature at the air heater exit. Most engineers skip this; the best engineers follow Appendix F to the letter.

| Parameter | PTC 4.1 (old) | PTC 4-2013 (new) | |-----------|---------------|------------------| | Radiation loss curve | Empirical (Fig. 7) | Removed – requires measurement or CFD | | Fuel analysis | Ultimate (C, H, O, N, S) | Same + detailed ash | | Uncertainty method | ±% of reading | Full Monte Carlo / root-sum-square | | Computerization | None | Mandatory digital data logging | | Solid fuel testing | Extensive | Reduced (delegated to ISO) | Asme Ptc 4.1.pdf

| Loss Symbol | Description | Typical Range (%) | |-------------|-------------|--------------------| | ( L_1 ) | Dry flue gas loss (sensible heat leaving stack) | 4–8 | | ( L_2 ) | Loss due to moisture from burning hydrogen in fuel | 3–6 | | ( L_3 ) | Loss due to moisture in fuel (as fired) | 0.5–3 | | ( L_4 ) | Loss due to moisture in combustion air | 0.1–0.5 | | ( L_5 ) | Unburned carbon in fly ash & bottom ash (combustible in refuse) | 0.5–2 | | ( L_6 ) | Radiation & convection loss from boiler outer surfaces | 0.2–1.5 | | ( L_7 ) | Loss due to sensible heat in ash (bottom + fly) | 0.1–0.5 | | ( L_8 ) | Unmeasured losses (e.g., manufacturing tolerance, miscellaneous) | 0–0.5 | The code requires you to measure the flue

He scraped residue from the ash hopper. The PTC 4.1 warned that if the stoichiometry was off, the energy wasn't just lost—it was hiding. The Exit Gas Temp: | Parameter | PTC 4