vertical fire tube type

horizontal fire tube type

horizontal water tube type

forced circulation type.

heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum

water is supplied in drum and through down-comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam

feed pump is employed to supplement natural circulation in water wall type furnace

water is converted into steam in one pass without any recirculation

prevent flat surfaces under pressure from tearing apart

take care of failure in shear

take care of failure in compression

provide support for boiler

one-fourth

half

one

two

mean diameter and thickness

inside diameter and thickness

outside diameter and thickness

outside diameter and inside diameter