make it transportable, the boiler and its auxiliary equipment (fuel oil heating, pumping units, fans etc.), turbines, and condensers were mounted on wagons to be transported by rail. White-Forster The White-Forster type is similar to the Yarrow, but with tubes that are gradually curved. This makes their entry into the drums perpendicular, thus simpler to make a reliable seal. Thornycroft Designed by the shipbuilder John I. Thornycroft & Company, the Thornycroft type features a single steam drum with two sets of watertubes either side of the furnace. These tubes, especially the central set, have sharp curves. Apart from obvious difficulties in cleaning them, this may also give rise to bending forces as the tubes warm up, tending to pull them loose from the tubeplate and creating a leak. There are two furnaces, venting into a common exhaust, giving the boiler a wide base tapering profile. Forced circulation boiler In a forced circulation boiler, a pump is added to speed up the flow of water through the tubes. Other types O-type boiler A-type boiler Flex-tube boiler M-type control superheater See also Three-drum boiler Clarkson thimble tube boiler Corner tube boiler Internally rifled boiler tubes (also known as serve tubes) References External links Boilers