APPLICATION OF REFRIGERATION TO HANDLING OF MILK. 61 



creameries, and dairies, it is unnecessary to employ a regular attend- 

 ant, as some persons regularly employed in other work on the premises 

 can find time to start and stop the machine and to keep it oiled. 



The curve marked "Total cost per ton of refrigeration" has been 

 calculated from the estimated cost of the plant, repairs, depreciation, 

 and miscellaneous items, such as oil, waste, packing, etc. The in- 

 terest on the money invested is figured at 6 per cent and the repairs 

 and depreciation at 10 per cent. 



While the above curves representing the cost of producing refrig- 

 eration in the smaller-sized creameries are believed to represent 

 a fair average, it is 

 also believed that the 

 cost can be materially 

 lessened if more atten- 

 tion is paid to the 

 economic operation 

 of the compressor. 

 In a great many in- 

 stances the engine 

 drove long lines of 

 shafting that were not 

 in the best of condi- 

 tion and a number of 

 idle pulleys in addi- 

 tion to the refrigera- 

 ting machine. 



In many instances 

 where electricity is 

 available motors may 

 be installed at an ad- 

 vantage for operating 

 the refrigerating ma- 

 chine as well as other 

 apparatus. Motors of 

 comparatively slow- 

 speed type can be 

 readily connected by belt to the compressor. With the present price 

 of electric power the cost of operating small units with electricity 

 is slightly greater than when operated by steam power, provided 

 the steam plant is run at or about normal load. But when the 

 engine and boiler are operated at only a fraction of their capacity 

 they become very inefficient and the cost of power is greatly increased. 

 In view of the fact that with electricity the consumption of power 

 starts and stops with the opening and closing of the switch it is often 

 more economical to instaU electric motors for operating small refng- 



MONTHS 



Fig. 28.— Curves showing the relation between the milk supply and 

 the temperature of the air, averaged from the most important 

 dairying States, and the hours necessary to operate the com- 

 pressor based on the maximum amount of work being done in 

 eight hours. 



