Mance: Quarry Industry of Southern Indiayia 



95 



machinery. The generation and use of steam in engines as a 

 source of power has been understood for a long time, and many 

 of the best engineers have studied the development of the boiler 

 and engine until this type of power plant is now comparatively 

 near the highest point of development that can be hoped for. 

 And in its present high state of development, it stands con- 

 demned as most wasteful. The following figures as to the per- 

 centage of the heat of the coal that can be turned into mechanical 

 energy in the steam plant should be of interest in this connection. 

 These figures are taken from Gebhardt's Steam Power Plant 



Engineering (p. 4) : 



B.T.U. 



Heat value of 1 pound of coal 14 , 500 



Boiler and furnace losses, 50 per cent 7 , 250 



Heat of the steam 50 per cent 7,250 



Heat equivalent of one horse-power hour 2,545 



Heat used to develop one horse-power hour (50 pounds of steam per 

 horse-power hour, pressure 80 pounds gauge, feed water 62 degrees 



Fahrenheit) 57 , 500 



2.545 Percent 



Percentage of the heat in the steam realized as work — ^ 4.4 



57,500 



2 545 



Percentage of heat value of the coal realized as work — - — — ... 2.2 



The above is given as an average output for a small steam 

 plant. 



The dissipation of the heat of the coal in a large steam plant 

 has been figured as follows: 



B.T.U. 



Lost in ashes 135 



Lost in radiation from boiler 675 



Carried off in stack gases 2 , 970 



Carried otf in auxiliary exhaust 190 



Lost in radiation and leakage in main pipes 210 



Lost in radiation and leakage in small pipes 30 



Lost in radiation and leakage in engine pipes 280 



Rejected to condenser 7,737 



Total loss in one pound of coal 12,227 



Converted into power 1 , 273 



Coal value 13,500 



= 9.43 per cent. 



The above figures show what has been done toward developing 

 the steam engine into an economical power producer. It seems 



