Fire tube boiler is the type boiler which is classified based on tube type. The combustion occurs and flow through inside tube and boiler water is distributed outside tubes. When fire tube boiler is running, there are possibilities of failure occur. Failure should be prevented to avoid damage in boiler itself and environment. Failure can be caused by water level in boiler exceed minimum low water level. This condition may be caused by operator who careless to maintain fire tube boiler keep in normal operating water level (NOWL). In modern boiler, fire tube boiler is designed automatic. If water level reaches minimum low level, fire tube boiler will sound alarm and automatically shut down.
Another cause of failure in fire tube boiler is the boiler age is very old. Material of boiler is fatigue so cause material strength can not resist the pressure. This condition will make pressure part such as tubes and header explodes. Furthermore other reasons for failure are may be safety valve does not work if the pressure exceeds maximum allowable working pressure. Safety valve does not open to vent steam so the pressure will be accumulated and lead to failure.
Too much scale in boiler water so heat is not transferred perfectly. This condition is similar with too much slag or smoky on inside tube or flue gas way. Heat transfer does not perform as expected condition. When metal temperature increases up to 600 F, the metal will be shrinkage and possibility of failure will be highly occur.