Vertical Smoke Tube Boiler: A vertical smoke tube boiler is more popular and commonly found on ships. In this boiler arrangement, the furnace is in the bottom part of the boiler and is attached to the shell by means of an ogee ring at the bottom.
The furnace is fitted with refractory, which contains the produced heat inside the furnace and also protects the ogee ring from overheating. The combustion chamber with tube stacks is located above the furnace, where the hot smoke is passed for heating the water drum. The top of the combustion chamber is supported by a gusset plate that transfers the stresses to the boiler shell.