page_title: Three-drum boiler
section_title: Normand boiler
hierarchical_section_title: Three-drum boiler / Types / Normand boiler
caption_attribution_description: Normand boiler
context_page_description: Three-drum boilers are a class of water-tube boiler used to generate steam, typically to power ships. They are compact and of high evaporative power, factors that encourage this use. Other boiler designs may be more efficient, although bulkier, and so the three-drum pattern was rare as a land-based stationary boiler.
  The fundamental characteristic of the "three-drum" design is the arrangement of a steam drum above two water drums, in a triangular layout. Water tubes fill in the two sides of this triangle between the drums, and the furnace is in the centre. The whole assembly is then enclosed in a casing, leading to the exhaust flue.
  Firing can be by either coal or oil. Many coal-fired boilers used multiple firedoors and teams of stokers, often from both ends.
context_section_description: The Normand boiler was developed by the French Normand shipyard of Le Havre. It was used by the navies of several nations, notably those of France, Russia, Britain and United States. In 1896, the Royal Navy had them installed in twenty-six boats, more than any other water-tube design.
  Initial design of the Normand boiler was as a development of the Du Temple, with the sharp corners of the tubes replaced by a smooth radiused bend, but still retaining the S shape.
  The design of the Normand gave a particularly large heating area (tube surface area) in relation to the grate area. The cost of this was a dense nest of tubes, where each of the numerous rows of tubes was bent into a different and complex shape. Tube ends entered the cylindrical drums perpendicularly, for good sealing. The space needed for all these tubes filled the entire lower half of the steam drum, requiring both a large drum and a separate steam dome from which to collect dry steam. The external boiler casing entered the flue uptake at one end, usually enclosing this dome. The ends of the drums extended outside the casing as hemispherical domes. Cold downcomers outside the casing linked these drums, providing a path for the return circulation of cold water.
  A further development was the Normand-Sigaudy, where two Normand boilers were coupled back-to-back, for use in large ships. This effectively gave a double-ended Normand (as was later common with the Yarrow) that could be fired from both ends.
caption: Normand boiler
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