What is a Water Tube Boiler?

schematic water tube boiler design

A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel burned in the furnace, creates hot gas which heats the water vapor generating tubes. In smaller boilers, extra generating tubes in the furnace apart, while larger utility boilers rely on water-filled tubes that form the walls of the furnace to produce steam.

The hot water then rises into the steam drum. Here, the saturated vapor withdrawn from the drum. In some services, the steam will go back to the furnace through the superheater to become hot. Superheated steam is defined as the steam that is heated above the boiling point at a certain pressure. Superheated steam is dry gas and is therefore used to drive turbines, because the water droplets can severely damage turbine blades.

Water tube boilers of different types of shell boiler in which water circulated in the tube, with heat sources around them. Referring back to the equation for hoop stress, it is easy to see that because the tube diameter is significantly smaller, much higher pressures can be tolerated for the same stress.

Cool water at the bottom back to the steam drums through the feed water drum'downcomer tubes' big-bore, in which pre-heats the feed water supply. (In 'large utility boiler', the feed supplied to the steam drum and down comers supply water to the bottom waterfalls). To improve the economics of boiler, the flue gas is also used to pre-heat the air blown into the furnace and hot water supply bait. Such as water tube boilers in thermal power station is also called a steam generating unit.