In the past, the most popular burner for general fired heater applications was the standard combination oil-gas burner illustrated in Figure 500-1. This cylindrical burner throws a round brush-shaped flame.
Gas is introduced through the outer cylindrical burner refractory tile by four to eight gas tips that come off a ring gas header at the rear of the burner. Oil is introduced centrally through its own internal cylindrical burner tile. Air comes through the adjustable cylindrical burner air register and past the burner tips at both locations as shown. Older burners may have separate air registers for oil and gas.
Now that oil firing is less common, the oil gun receiver is usually capped. Aging combination burners are candidates for replacement with gas burners.