Control and Adjustment | Rasert™
Typical RASERT Mounting
Tube Dia. 2
Heated Radiant Tube Length
26"
min.
Furnace Hot Face
Mounting Gasket (required)
Tube Diameter
RASERT™ Mounting Flange
Radiant Tube Mounting Flange
CONTROL and ADJUSTMENT The 4748 burner fuel/air ratio can be controlled with a simple cross-connected ratio regulator such as the North American 7216. For firing rate control the burner can use conventional on-ratio turndown, StepFire™ or pulse firing. Since most of the pressure drop through the burner is taken in the relatively cool orifices in the burner body before the full preheat temperature is reached, the ratio will not shift as much as it does in typical hot air burner systems. When setting up the burner for the first time the high fire ratio should be set so the exhaust gas is 6-8% O 2 . Once the process gets to its maximum temperature the fuel/air ratio can be reset to the final desired setting of 3-4% O 2 in the exhaust. The low fire ratio may need to be set at a higher O 2 level to avoid CO when the burner gœs to low fire. The graph below shows the decrease in O 2 recorded in the flue stack as the radiant tube heats up from a cold start to a 1650°F tube temperature.
Typical Flue gas O 2 vs. Average Tube temperature O 2 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 250 500 750 1000 1250 1500 1750 Average Radiant Tube Temperature °F
Bulletin 4748 Page 5
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