Firebox appearance

If the firebox appears bright and clear, then there is more than... 

If the firebox appears hazy and the flames are long, licking, yellow,... 

Nickel and its alloys form another important class of non-ferrous metals (Table 1.3). The superb creep resistance of the nickel-based superalloys is a key factor in designing the modern gas-turbine aero-engine. But nickel alloys even appear in a model steam engine. The flat plates in the firebox must be stayed together to resist the internal steam pressure (see Fig. 1.3). Some model-builders make these stays from pieces of monel rod because it is much stronger than copper, takes threads much better and is very corrosion resistant. 

Regardless of and in preference to oxygen analyzer results, we must consider the appearance of the firebox and flames when we assess whether more combustion air is needed ... 

The temperature of the inside of a firebox can also be estimated by its visual appearance. Table 20.1 provides a color/heat guide. 

If we operate with a positive pressure in the firebox, although the burners may appear to operate normally, the hot flue gases will leak outward. This damages the roof arch supports and the steel structure so as to shorten the life of the heater. 

Figures 7.71 and 7.72 are plots of NO, (NO -1- NO2) af locafions before and in fhe middle of the convection section at various depths. The data clearly show that NO, varied by a maximum of 11% over a disfance of 46 cm (18 in.). Nofice fhaf fhe NO appeared to be lower af a locafion before fhe convecfion section than at a location in the middle of fhe convection section, for all depfhs tested. If is unclear why this occurs because the total NO, (NO -f NO2) should be conserved between these two locations. Perhaps the recirculation pattern in the upper corner of fhe firebox creates this anomaly. At a probe depth of 61 cm (24 in.), the average NO, in the stack appears to be in the center of the data scatter for NO, collected af various locations in the convection section.

A gas-fired healer firebox will have a hazy appearance when short of air. A heater making a regular thumping sound is also likely to be air deficient. Sometimes an increase in fuel gas flow will result in a decrease in process-side temperature. This is a sign that the firebox does not have enough air. 

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