ELECTRIC AUXILIARIES ON MERCHANT SHIPS. 167 



The auxiliary exhaust steam is used to heat the feed water, and that which is in excess 

 of feed-water heater requirements is by-passed to the main condenser. 



Under full power, a fair operating average for this type of installation is as follows: 



Steam Consumption Per Hour: 



Pounds 



Main turbine, 2,500 horse-power 28,875 



Steam auxiliaries at sea 12,500 



Total steam consumption 41,375 



Steam Per Shaft Horse-power Hour_, All Purposes: 



41,375 



2,500 



= 16.5 pounds. 



Boiler Evaporation. — With water tube boilers, Howden draft system, feed water de- 

 livered to boilers at 220°, 210 pounds gauge pressure and 75° superheat, a conservative esti- 

 mate of the actual evaporation per pound of fuel oil is taken at 13.5 pounds. 



Fitel Consumption: 



Fuel per hour = ' — = 3,065 pounds = 9.6 bbls. 



Fuel per day, 73,560 pounds = 32.8 tons. 



Fuel in barrels per day 230 



Fuel Per Shaft Horse-power Hour: 



3,065 



2,500 

 Fuel in Barrels, Per Knot: 



1.23 poimds. 



96 

 Asstuning a speed of 10.5 knots, ' - = 0.915 barrel per knot. 



The economy to be gained through the application of electrically driven auxiliary ma- 

 chinery, in fuel consumption alone, may readily be seen from the following estimates: 



ELECTRIC AUXILIARIES. 



Superheat, 75° F. 



Heating Feed Water. — The proposed method would be to extract sufficient steam from 

 the turbine for feed-water heater requirements. 



Steam Consumption, Per Hour: Pounds. 



Main turbine, 2,500 horse-power 30,600 



Turbine generator 2,640 



Air ejector 1 ,000 



Total , 34,240 



Note: — 3,600 pounds per hour steam will be extracted from main turbine at about 10 

 pounds gauge to heat feed water. 



