Herreshoff steam generator in a Peruvian torpedo boat of 1879

A monotube steam generator is a type of steam generator consisting of a single tube, usually in a multi-layer spiral, that forms a once-through steam generator (OTSG). The first of these was the Herreshoff steam generator of 1873.[1]


For the sake of efficiency, it is desirable to minimise the steam content of the generator. Heat can then be transferred efficiently into liquid water, rather than into low-density steam. Monotube steam generators may either boil gradually along their length, usually pumped circulation systems,[2] but where this boiling does not disrupt the circulation. Otherwise they can use the Benson supercritical system, where the pressure is sufficient to prevent boiling (within the heated volume) altogether.[3]


White steam car steam generator

Examples of Monotube steam generators include:

Flash boilers

Main article: Flash boiler

A flash boiler is a particular type of low-water-content monotube boiler. Modern use is confined to model steam boats but, historically, flash boilers were used in Gardner-Serpollet steam cars.

See also


  1. ^ Light Steam Power. XXIV (3): 157–159. July–September 1975. ((cite journal)): Missing or empty |title= (help)
  2. ^ Newest on Process Equipments (2012-11-25). "Boilers circulation systems: natural circulation and forced circulation". Enggcyclopedia. Retrieved 2012-12-02.
  3. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2010-09-23. Retrieved 2008-10-08.((cite web)): CS1 maint: archived copy as title (link)
  4. ^ "Clayton Thermal Products UK - Steam Generators Principle of Operation". Archived from the original on 2012-02-09. Retrieved 2012-12-09.
  5. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2013-11-11. Retrieved 2012-12-09.((cite web)): CS1 maint: archived copy as title (link)