CHAPTER VIII. 

 THE BOILER. 



function of the boiler is to heat water 

 sufficiently to change it into steam, for use 

 in an engine, or for other purposes. The 

 supply of water for the boiler has been 

 treated under "The Feed Water" in Chap- 

 ter II, and the management of the fire with 

 various fuels under "Firing" in Chapter III. 

 Temperature of Water and Steam in a Boiler. Although 

 water boils in an open vessel at 212 degrees Fahrenheit, if 

 it be confined, a pressure will be developed, which will pre- 

 vent it from boiling until a higher temperature is reached. 

 A certain relation exists between the pressure and tempera- 

 ture of the steam in a boiler and for any given pressure there 

 is a corresponding temperature. Thus, for a pressure of 50 

 Ibs., the temperature is 267 degrees, for 100 Ibs. pressure the 

 the temperature is 337 degrees, and for 125 Ibs. pressure, 

 the temperature is 352 degrees. The temperature in the 

 firebox is, of course, many times greater. 



Boiler Fittings. The fittings necessary for the operation 

 of a boiler, are the feeder, (for supplying the water), glass 

 gage and gage cocks, (for indicating the water level), a 

 steam gage, (for indicating the pressure), a pop or safety 



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