Editing Steam engine (section)

=== Boilers ===
[[File:Dampfkessel für eine Stationärdampfmaschine im Textilmuseum Bocholt.jpg|thumb|right|An industrial boiler used for a [[stationary steam engine]]]]
{{Main|Boiler (steam generator)}}

Boilers are [[pressure vessel]]s that contain water to be boiled, and features that [[heat exchanger|transfer the heat to the water]] as effectively as possible.

The two most common types are:
; [[Water-tube boiler]]: Water is passed through tubes surrounded by hot gas.
; [[Fire-tube boiler]]: Hot gas is passed through tubes immersed in water, the same water also circulates in a water jacket surrounding the firebox and, in high-output locomotive boilers, also passes through tubes in the firebox itself (thermic syphons and security circulators).

Fire-tube boilers were the main type used for early high-pressure steam (typical steam locomotive practice), but they were to a large extent displaced by more economical water tube boilers in the late 19th century for marine propulsion and large stationary applications.

Many boilers raise the temperature of the steam after it has left that part of the boiler where it is in contact with the water. Known as [[superheating]] it turns '[[wet steam]]' into '[[superheated steam]]'. It avoids the steam condensing in the engine cylinders, and gives a significantly higher [[Heat engine#Efficiency|efficiency]].{{sfn|Hills|1989|p=248}}{{sfn|Peabody|1893|p=384}}