88 CENTRIFUGAL SEPARATION 



The Capacity of the Cream Separator. By the capacity of 

 the cream separator is understood the amount of milk the ma- 

 chine will skim per hour. Every cream separator is rated at a 

 definite capacity; that is, it is built to separate a certain spe- 

 cified amount of milk in a given length of time. The farm separa- 

 tors range in capacity from about 150 to 1,200 pounds of milk per 

 hour. For dairies with five to six cows a 350 to 400 pound capacity 

 machine is recommended. The capacity of factory machines 

 ranges from about 1,200 to 10,000 pounds of milk per hour. 



The capacity of the separator must have a definite relation 

 to the centrifugal force, ff the machine is to do efficient skim- 

 ming. An increase in the capacity, of any given separator, 

 hastens the passage of the milk through the bowl and shortens 

 the time during which it is subjected to the centrifugal force. 

 The maximum capacity of a separator should, therefore, not ex- 

 ceed the amount of milk which can be efficiently skimmed in an 

 hour. Greater capacity, without also increasing the centrifugal 

 force, overtaxes the separating ability of the machine and causes 

 excessive loss of fat. 



Theoretically, the size of the skim milk and cream outlets 

 of the bowl obviously influence the capacity of the separator, for 

 the larger these outlets, the more milk the separator is capable 

 of taking in. If the bowl were not in motion and the discharge 

 of skim milk and cream were depending only on the mechanical 

 overflowing of these parts, this hypothesis would be correct. In 

 this case these parts would be completely filled. 



But when the bowl is in motion such is not the case, the 

 increased rapidity of the discharge due to the centrifugal force 

 generated in the revolving bowl, greatly augments the capacity 

 of the discharge parts, so that the skim milk and cream outlets are 

 not completely filled and do at no time discharge skim milk and 

 cream in accordance with their full capacity. This fact has been 

 conclusively demonstrated by Eckles & Wayman, 1 who found 

 that, under normal conditions, the skim milk tube does not run 

 much over one half of its actual capacity. 



For this reason it is obvious, also, that a change in the pro- 



1 Eckles & Wayman. Factors Affecting the Per Cent of Fat in Cream 

 from Farm Separators. Missouri Bull. No. 94, 1911. 



