Boiler

the vessel in which steam is generated to be used for power or heating purposes. There are several characteristics of a well constructed boiler: (1) a large amount of surface must be exposed to the heat; (2) the material must be strong enough to resist enormous pressure; (3) the parts must not be likely to corrode and weaken; (4) the water must not be likely to leave any part of a heated surface bare; (5) the utilization of heat without waste. A discussion of the various forms of boilers is too technical for this place. In general, the first and fifth requisites are met by having the flames and heat pass through flues or tubes that lead through a cylinder containing water; or else the water is contained in tubes that are located in a firebox or heated chamber. Fire tube boilers are those in which the fire occupies the tubes; water tube boilers are those in which the water occupies the tubes. Boiler making is a branch of business quite distinct from engine building. Of 40,533 stationary boilers produced in the United States in the year of the last census, but 4,731 were water tube boilers. The total output of boilers for the year was worth about $26,000,000. Pennsylvania leads in the manufacture of steam boilers. See Steam Engine; Locomotive; Safety Valve; Watt