Fire (smoke) tube boiler has a cylindrical structure. Boiler body is filled with water and a smoke tube where combustion gas passes runs through the body. The heat of combustion gas heats water and generates steam.
Since it has large amount of water, usually medium amount of steam is supplied with low pressure. Therefore it can prevent pressure fluctuation or water level fluctuation even under fluctuating steam load.
Another characteristics are durability, easy maintenance, and easy operation.
Fire (smoke) tube boiler

Principle
