Mance: Quarry Industry of Southern Indiana 101 



Fixed charges are those costs which are independent of the 

 output of power of the plant. In other words, they go on whether 

 the plant is in operation or not. The cost per kilowatt hour due 

 to fixed charges, of course, decreases wdth an increase of output, 

 but the total charge does not vary. The rate of interest varies 

 with different conditions, but for all calculations the rate will be 

 placed at 5 per cent, since this represents a fair average. 



Depreciation is the loss in value of a piece of apparatus with 

 increase in age. The methods of determining depreciation are 

 almost as numerous as the number of operators trying to determine 

 it. The main object of setting aside this fund or charging it 

 against power cost is to have available a sufficient sum of money 

 to replace the machinery when it wears out or becomes obsolete. 

 Power machinery decreases in value from its cost price to scrap 

 value during its useful life, and if the price of new machinerj^ is 

 to be available at the end of that time, it must be charged against 

 the power and set aside during the time the machine is in opera- 

 tion. The figure for depreciation used in the following calcula- 

 tion is 8 per cent. Of course, the rate will vary with the normal 

 life of the apparatus, that is, the time it should run and give 

 good service if properly cared for. The data of the following 

 table on the average life (in years) of power-plant and stone- 

 working machinery were collected from various articles on de- 

 preciation and from the observations of mill and quarry operators 

 in the stone district: 



Buildings 25 



Stacks, brick 40 



Stacks, guyed sheet-iron 12 



Boilers, water tube 25 



Boilers, fire -tube 18 



Pumps 15 



Piping ' 18 



Engines, high-speed 15 



Engines, low speed 20 



Heaters, open , .20 



Heaters, closed 15 



Belts 5 



Generators, du'ect current IS 



Generators, alternating current ... 20 



Motors, direct current 18 



Motors, alternating current 20 



Diamond saws 6 



General stone machinery 20 



The figures given above are only relative and are based on data 

 given by men who have not made a practice of collecting such 

 data. They would therefore be subject to considerable varia- 

 tion. 



While no definite rule can be applied covering charges for taxes 

 and insurance, they have been lumped at 2 per cent on the in- 

 vestment. 



Under the head of labor must be charged all wages paid to 

 firemen and engineers and for any extra coal handhng, etc. 



