Scotch Marine Boiler - Variants - Inglis

Inglis

The "Inglis" modification adds an extra combustion chamber where an additional single large flue returns from the rear to the front of the boiler. Flow through the multiple tubes is thus from front to back, and so the exhaust is at the rear. Multiple furnaces would share a single combustion chamber.

The major advantage of the Inglis is the extra heating area it adds, for a comparable shell volume, of perhaps 20%. Surprisingly this is not from the additional combustion chamber, but from lengthening the narrow firetubes. These can now run the full length of the boiler shell, rather than just the rather shorter distance from the inner combustion chamber to the front tubeplate. Despite this advantage, it is rarely used.