Fire Tube Boiler
A fire-tube boiler is a type of boiler in which hot gases pass from a fire through one or (many) more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam.
Water Tube Boiler
A high-pressure water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which boils water in the steam-generating tubes.
Electric Steam Boiler
An electric steam boiler is a type of boiler where the steam is generated using electricity, rather than through the combustion of a fuel source.