Description
A steam boiler is an enclosed vessel that holds water and is heated by an external source that converts the water to steam. All steam boilers contain tubes that separate the water from the heat source. Steam boilers are described in this publication. Boilers are classified by two criteria: 1) operating pressure (i.e., the amount of internal pressure generated by the steam that is produced); and 2) the operational design (i.e., whether the water [water tube boiler] or the heat source [fire tube boiler]) passes through the inside of the tubes of the boiler vessel.