Fire-tube boilers are those device in which hot gases, which originates from the fire passes through one or more tubes within the boiler. They are important boilers that are available in both horizontal and vertical configurations. They are also some times referred as smoke-tube boiler.

How It Operates?
To produce hot combustion gases in the locomotive type boiler, fuel is burnt in a firebox. A long, narrow, cylindrical boiler tube attached to the cooling jacket of water surrounds the firebox. Steam is generated by heating the water which happens when the hot gases are directed along a series of fire tubes penetrating the boiler. Thus, the steam is generated rising to the steam dome, where it gets collected. This dome is the site of the regulator which controls the exit of steam. In order to dry & superheat the steam, the saturated steam is always pumped into the super heater through the larger flues at the back in the locomotive fire tube boiler boiler. Mechanical power is now produced with the help of the steam directed to the cylinders or a turbine.

The exhaust gases are normally used to heat the feed water for increasing boiler's efficiency. Nowadays, fans are used to generate draught by modern industrial boilers. Generally in steam locomotives, the exhaust steam is pumped through a blast pipe from the cylinders, thus supplying extra draught needed for providing partial vacuum.

Types of Fire-Tube Boiler:

• Cornish Boiler
• Lancashire Boiler
• Locomotive Boiler