CONDITIONS AFFECTING EFFICIENCY OF SEPARATORS 165 



diameter of the bowl; that is, if the diameter of the bowl be 

 doubled, then at the same speed, the centrifugal force has been 

 doubled. The centrifugal force varies in quadratic proportion 

 to the speed of the machine; that is, if the speed of the separator 

 is doubled, the centrifugal force is increased four times. From 

 this it will be seen that speed is a great factor in determining the 

 centrifugal force generated. It is not a good plan to have the 

 diameter of the bowl too large, for the following reasons: A large 

 bowl is more likely to be thrown out of balance; it is harder to 

 keep on the bearings; and it is heavier and more unhandy to 

 handle. For these reasons it is better to lessen the diameter of 

 the bowl and increase the speed. This, of course, is true only to a 

 certain limit. 



Steadiness in Running. Smooth running of a separator is 

 one of the first essentials. If a machine runs roughly, there will 

 not be good separation, and it is dangerous to run it. The 

 bowl itself is likely to jump out, or burst. The causes for 

 unsteadiness in running are many. It may be due to a bent or 

 sprung spindle ; the machine not standing level ; changing covers 

 to bowls; using clamps which do not fit the bowl cover ; unclean, 

 worn-out bearings; condition of the bowl, and contrivances 

 inside the bowl; and dented and rusty bowls. Occasionally it 

 happens that a machine is run backwards. This is likely to 

 cause the cover of the bowl to run off. 



Thickness of Cream. The efficiency of skimming depends 

 to some extent upon the thickness of the cream skimmed. Most 

 separators, however, will skim within quite a wide range as to 

 thickness. The richness of cream usually skimmed by separators 

 ranges from 25 per cent to 50 per cent. Most separators, how- 

 ever, will do good skimming even if the cream contains as high 

 as 60 per cent fat. This, however, should be considered to be 

 about the maximum, in order to get the best results from a sep- 

 arator. 



Slush in Bowl. As has been mentioned before, there is 

 always a thick, slimy substance which adheres to the bowl-wall. 

 The composition of separator-slime is, according to Fleischmann, 

 as follows: 



