CENTRIFUGAI, SEPARATION 89 



portionate amount of skim milk and cream delivered, as caused 

 by a change in the position of the skim milk or cream screw, 

 does not affect the capacity of the separator. The richness of 

 the cream delivered, therefore, has no material effect on the 

 capacity of the separator. 



The capacity of the separator is naturally directly affected 

 by the rate of inflow. When the rate of inflow drops below 

 the designated capacity, less milk flows through the separator 

 and more time is required to separate a given amount of milk. 

 When the rate of inflow is increased beyond the designated 

 capacity, more milk flows through the separator than its capa- 

 city calls for and less time is required to separate a given am- 

 ount of milk. This latter fact is possible only because the 

 skim milk and cream outlets are not filled to full capacity when 

 the separator is operated under normal conditions. Hunziker 1 

 shows that the same volume of milk that under normal inflow 

 required 7 minutes for separation, required 11 minutes in the 

 case of a reduced inflow and 6 minutes in the case of an; in- 

 creased inflow. The reduced inflow did not affect the skim- 

 ming efficiency, while the excessive inflow caused a greater loss 

 of fat in the skim milk. 



The speed of the separator exerts a powerful influence on 

 the capacity of the machine. The speed generates the centrifugal 

 force which expels the skim milk and cream through their 

 respective outlets with great force. The greater the speed and, 

 therefore, the greater the centrifugal force, the more rapid the 

 exit of skim milk and cream and the greater the capacity of 

 the separator. Hunziker 1 shows that, when at normal speed, it 

 required 5 minutes to separate a given volume of milk, the same 

 volume required 9.6 minutes at a speed reduced 25 turns of the 

 crank below normal and it required only 3.3 minutes at a speed 

 increased 15 turns of the crank above normal. The decreased 

 speed lowered the skimming efficiency while the excessive 

 speed very slightly increased it. 



The state of cleanliness of the separator may affect the 

 capacity of the machine to a considerable extent and, in the 

 case of extremely bad condition, may clog the machine entirely. 



1 Hunziker. Why Cream Tests Vary. Purdue Bulletin No. 150. 1911. 



