CONDENSED MlLK AND MlEK PdWDER 



47 



The Jacket* forms' "the bottom of the" pan. ' The inside wall is 

 copper, the outside cast 'iron. It is' concave and in the case of a 

 six-foot pan about two and one-half feet 'deep. It is equipped with 

 two steam inlets and : brie 'outlet. The outlets for the Coils are also 

 brought through the jacket. Ill the,, center of the bottom there is 

 an opening, two to three inches in diameter, for the 'discharge^ of the 

 condensed milk and fitted with two valves and a nipple between, to 

 facilitate the sampling of the condensed milk. 



.-■■i.'TiiE' Body' or YapoK Beet 

 represents- the main part of the 

 pan. It is cylindrical, of vary- 

 ing height and is equipped with 

 copper coils which have their 

 outlets through the jacket. Their 

 upper ends connect, through the 

 body of the pan, with the main 

 steam line. Most pans are 

 equipped with two to three coils 

 located at different elevations. 

 Since steam should be turned 

 into the coils only when they 

 are covered with the milk, it is 

 desirable to have several short 

 independent coils rather than but 

 one large one. This will give a 

 larger range of the quantity of 

 milk that can be condensed and 

 increases the speed of evapora- 

 tion. The coils vary in diameter from about three to five 

 inches. The upper and outer coils are the larger ones. The 

 diameter and length of the coils necessarily vary with and 

 are limited by the capacity of the pan. The greater the total 

 heating surface, consistent with easy access to all parts of the jacket 

 and coils, the better. Other things being equal, the more square feet 

 of heating surface, the less steam pressure, by the gauge, is required 

 to furnish the necessary heat for maximum evaporation. This is 

 important because high steam pressure in the jacket and coils, means 

 exposure of the milk to high temperature, which is undesirable. The 

 heating surface should be sufficient to make possible the complete 



Fig. 10. Vacuum pan 



