section_path: Components and accessories of steam engines/Boilers
section_name: Boilers
paragraph_text: Boilers
  
  Boilers are pressure vessels that contain water to be boiled, and features that transfer the heat to the water as effectively as possible.
  
  The two most common types are:
  
  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 efficiency.