CONDITIONS AFFECTING EFFICIENCY OF SEPARATORS 161 



Also, if the outlet for the skim-milk were near the circumference 

 of the bowl a great deal more power would be required to run 

 the machine. As the skim-milk passes through the tubes 

 towards the center it gives up its force. The nearer the skim- 

 milk outlet can be brought to the center of the bowl, the more 

 easily will the machine run. 



The size of the skim-milk outlet is usually such that it bears a 

 certain relation to the size of inlet, size of bowl, and speed of the 

 machine. Most skim-milk outlets are made so as to discharge 

 from .4 to about .9 or a little more, of the whole milk that enters 

 the bowl. The remainder is the cream, which is forced to the 

 center of the bowl and discharged through the cream outlet. 



CONDITIONS AFFECTING EFFICIENCY OF SEPARATORS 



i. Manner of Heating Milk. Owing to the fact that fat- 

 globules rapidly change their shape and properties when exposed 

 to heat and excessive agitation, it is essential that care 

 should be taken in heating milk previous to skimming. When 

 fat-globules are heated they become more liquid, and if stirred 

 very much the clusters of fat-globules break up more rapidly. 

 The individual globules, if stirred violently, will break or sub- 

 divide into several small ones. The higher the temperature 

 of the milk, the more fluid it becomes, and the easier the separa- 

 tion. If milk is stirred violently, the individual fat-globules 

 break up into smaller ones, which are separated from milk with 

 difficulty. The table 1 on p. 162 illustrates what effect the dif- 

 ferent degrees of agitation of milk have upon the efficiency of 

 separation. 



In the experiments the diameter of the agitator in the pas- 

 teurizer was 14 inches. The speed at the periphery, at 250 

 revolutions per minute, was 15 feet per second. 



It will be seen from the table (p. 162) that the higher the speed 

 of the agitator, the greater the difficulty in getting a complete 

 separation. Besides the speed of the agitator in the heating 

 apparatus, undoubtedly the shape of the pasteurizer is a factor 



1 Hoard's Dairyman, Fort Atkinson, Wis. 



