Steam boilers

Gunboat fire tube marine steam boiler

The so-called "gunboat boiler" was provided with tubes in the extension of the furnace.
A cylindrical boiler, of relatively small diameter and extended length, provided with a furnaces in a fire-tube leading to a bank of flue-tubes through the water drum to the smoke-box at the boilers backside.

The gunboat boilers were, as the name indicates, used in small navy ships such as gunboats, escort vessels and corvettes where the width and the height were limited. Besides, the limited height of the boiler made it possible to have it installed entirely below the sea water line and hence protected from direct hits.

The gunboat boilers also existed with two furnaces.