Combustion should be performed completely to enhance efficiency of steam boiler. Operator need to check all of apparatus of combustion. One of them is air as one of source for combustion process. Combustion need excess air to supply air beyond required air to perform combustion completely. Excess air can be distributed through the burner or stoker and through wall furnace tubes. When maintenance or start up new steam boiler is performed, air leakage test must be done.
There are some ways to check air leakage. One of the ways is by burn small fuel such as wooden or fireplace butane lighter in area of potential leakage. If there is leakage, the fire will come out of the furnace. Another way is to give pressure with bomb which contain smoke, if there is leakage smoke will appear in the outside of furnace. Potential leakage can occur at seal area although furnace was welded.
Generally, air leakage test should be performed when there are signals as follow; flue gas exhausts temperature at stack decrease, volume of flue gas increase and O2 level increase. Furthermore, air leakage can affect to reduce function of O2 analyzer because infiltrated air disturbs O2 analyzer to read O2 content in flue gas.