Cream Separation 



1873 



crease is known as overrun. In the computation shown in Figure 81 

 allowance was made for an overrun of one-sixth of the original amount of 

 milk-fat. 



According to the statements given, if the price of butter were 30 

 cents a pound there would be an annual loss of $9.60 on each cow by the 

 use of the water-dilution method, and $2.25 on each cow by the use of 

 the deep-setting method. These losses are computed on the basis of the 

 amount of milk-fat lost through the use of these methods as compared 

 with the amount lost if a modem centrifugal separator were used. 



SEPARATION BY CENTRIFUGAL FORCE 



Centrifugal force acts in direct proportion to the weight of matter. The 

 specific gravity of skimmed milk is greater than that of cream ; therefore 





.-- -its 



Fig. 81. — A comparison of the amount of butter lost in the skimmed milk from one 

 cow producing 5 ,000 pounds of milk in one year, hy the use of different methods of 

 cream separation. Reading from left to right: zoater -dilution method, JJ pounds; 

 shallow-pan method, 22 pounds; deep-setting method, 5.5 pounds; centrifugal 

 method, i pound 



the skimmed milk is forced from the center of a separator bowl with a 

 greater velocity, and the cream is crowded, or concentrated, toward the 

 center of the bowl. 



The purpose of the bowl devices in separators 



There is a device in all separator bowls which guides or feeds the whole 



milk into the region of the greatest centrifugal force. With one exception, 



all centrifugal separators with which the author is .familiar have internal 



bowl parts, such as disks, cones, blades, and the like. The purpose of these 



parts is to form pathways for the skimmed milk and cream to pass each 

 118 



