160 STEAM BOILERS 



more heating value, in the form of oil fuel, in a given space, 

 than can be done if coal is the fuel. Oil possesses the addi- 

 tional advantage that it does not deteriorate or lose its heating 

 value when stored for some time. Coal, on the other hand, 

 not only deteriorates but is liable to spontaneous combustion. 

 The cost of handling oil is less than that of handling coal, for 

 the reason that oil is run into the storage tanks by gravity, or 

 else is pumped into and out of storage. 



Saving of Labor and Equipment. When oil is employed for 

 fuel, instead of coal, there is no necessity for cleaning fires, and 

 consequently the boiler can be operated continuously at maxi- 

 mum capacity. There is a lower temperature in the boiler room, 

 because the fire-doors are kept shut. There is less wear and 

 tear on the pumps and other machinery that may be installed 

 in the boiler room, inasmuch as the absence of coal dust and 

 ashes enables the boiler room to be kept clean. The expense 

 of removing ashes is avoided, and there is a great saving in 

 labor, as fewer firemen and attendants are necessary. There 

 is no formation of clinker on the grates or side walls, and no 

 firing tools are used, so that the damage to furnace linings by 

 careless handling of tools is obviated. 



Disadvantages of Oil Fuel. One of the disadvantages of 

 oil as a boiler fuel is its low flash point; however, if oil having a 

 flash point of not less than 140 F. is used with care and judg- 

 ment by firemen of ordinary intelligence, there should be no 

 serious danger. The regulations as to the location of storage 

 tanks for oil fuel may be found irksome; for, in the case of a 

 plant situated in a thickly populated district in a city, it may 

 be wholly impossible to place the storage tanks at least 30 ft. 

 from the nearest building, and also underground. The tem- 

 perature of the fire obtained from oil fuel is greater than that 

 of a coal fire, and if the feedwater used contains much scale- 

 forming matter, the intense heat may cause more rapid deposit 

 of scale, and thus increase the cost of tube cleaning and repairs. 



UNIFORM STEAM PRESSURE 



Desirability of Uniform Pressure. The attendant should 

 -aim to carry the pressure in the boiler as uniform as possible. 

 The reason why a steady steam pressure and a steady water 





