Boilers are closed vessels in which liquid is heated or vaporized by the direct application of heat. They are grouped into classes based on working pressure and temperature, type of fuel, shape and size, usage (heating or processing), and product (steam or water). Types of boilers are:
Cast-Iron Section Boiler - Assembly of individual hollow cast-iron sections connected with push nipples, external headers or internal seals.
Fire-Tube Boiler - Steel-shell boiler with straight tubes which are surrounded by water. Heat produced by the combusion of fuel passes through the tubes and is transferred to the water.
Packaged Boiler - Boiler which is shipped complete from the factory. It includes heating equipment, mechanical draft equipment, automatic controls and all necessary accessories.
Scotch Boiler - Fire-tube boiler consisting of a cylindrical shell and at least one cylindrical internal furnace. The cylindrical furnace is located in the bottom portion of the shell. A bank of tubes is attached to both end closures of the shell.
Steam Boiler - Enclosed vessel in which water is converted into steam.
Water-Tube Boiler - Boiler in which tubes contain water and steam. Heat is applied to the exterior surface of the tube and is then passed to the water/steam mixture inside the tube.
Typical use for a boiler would be to supply steam or hot water for institutional and commercial building heating applications and certain industrial applications.