FROM THE PRACTICAL VIEWPOINT 



second tank, while in the third tank the milk is 

 flowing in and is being heated. These operations 

 are repeated in rotation. 



Many tests have shown that if the water in the 

 heating coils is heated by injecting steam directly 

 into the heating coil, the temperature at the inlet 

 end is rarely above 165. It may occasionally 

 reach 175. Usually it is sufficiently low so that 

 the milk is not injured by superheating. It can be 

 readily seen that the temperature at the inlet end 

 of the coil is much greater than at the outlet end, 

 since the cold milk takes up the heat, therefore the 

 heating efficiency of the coil is not equally great 

 for its entire length. Some attempts have been 

 made to improve matters by placing a smaller per- 

 forated coil inside the larger pipe, so that the 

 water distributed through the coil would have the 

 same temperature in its entire length. 



An objection to the submerged coil is that it be- 

 comes necessary to have the bearings packed with 

 some sort of a stuffing-box. Stuffiing-boxes are 

 always a source of possible danger both on account 

 of the absorption of milk, which renders cleaning 

 difficult, and on account of the fact that the con- 

 stant attrition of the metal at the point of bearing 



73 



