How boilers are classified?

A high pressure steam boiler is boiler in which steam is generated at pressure exceeding 15 psig and operates hot water boiler above 160 psig or 250o F. Application this type usually is used for utility plants, big industrial plants and process application. A high pressure steam boiler can be named as Power Boiler, in which design and construction rule following to rules of ASME Boiler and Pressure Vessel Code Section I - Power Boiler.