The water tube boilers ( where water to steam flow is within tubes and combustion of fuel is out side, in a furnace), are top supported units, suspended from a self supporting steel structure , arranged to provide total freedom of expansion for all parts of the boiler in down ward direction. All the parts meet the design codes, quality standards, material testing procedure and hydraulic test code laid by Indian Boiler Regulation ,ASME standards or code of practices of respective country.