Fired heaters burners, lighting

The lighting of fired heaters has the potential to create an explosion. Two issues are of particular concern. The first is that the firebox is filled with a flammable mixture of hydrocarbon gas and air (oxygen). If a burner is ignited, an explosion will occur. The second concern is that a furnace is operating normally, and then the fuel gas supply fails thus causing the burner flames to go out. If the fuel gas supply is then restored, an unbumed mixture of gas and air can enter the hot fire box and ignite. 

The entire 8-inch (20 cm) piping system was insulated and steam traced except for the heater tubes within the heater. Operations assumed the heat transfer fluid froze in the four heater tube passes. Each pass was a bare 4-inch (10 cm) diameter heater tube with 5 bends and the equivalent of 72 ft. (22 m) of straight pipe. The foreman and the operations team discussed the situation and decided to light and maintain a small fire on the burner to slowly thaw the material in the heater tubes. This method had been successful for a startup several weeks earlier. 

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