Watertube Boiler
In watertube boilers the hot combustion gases are circulated around the outside of a large number of water-filled tubes. In older designs the tubes are either straight or bent into simple shapes, while in modern designs they often have complex and diverse bends. Because the pressure is contained inside the water tubes, watertube boilers can be used in high-pressure applications. Like the firetube design, watertube boilers can have a number of burners and can burn almost any type of liquid, solid or gaseous fuel. The design of the boiler can vary significantly depending on what fuel it is intended to burn.