72 SWEETENED CONDENSED MILK CONDENSING 



milk, fitted with a valve. In the case of pans that have no 

 special "striking" or sampling cup, this discharge is equipped 

 with two valves and a short nipple between valves, to make 

 possible the sampling of the condensed milk while the pan is in 

 operation. 



The Body or Vapor Belt represents the main part of the 

 pan. It is cylindrical, of varying height and is equipped with 

 copper coils w r hich have their outlets either through the jacket 

 or the walls of the body. Their upper ends connect, through 

 t'he body of the pan, with the main steam line. Most pans are 

 equipped with two to three or more 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 con- 

 densed and increases the speed of evaporation. The coils vary 

 in diameter from about three to six 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 shorter each individual coil, and the greater the number of 

 independent coil sections and the greater the total heating sur- 

 face, consistent with maximum rapidity of circulation of the 

 milk and with easy access to all parts of the jacket and coijs, 

 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 un- 

 desirable. . The heating surface should be sufficient to make, 

 possible the complete condensation of the steam in the jacket 

 and coils. If the heating surface is inadequate, more steam has 

 to be turned into the jacket and coils, in order to secure the 

 necessary heat for rapid evaporation, than will condense; free 

 steam will blow through and out of the coils, resulting in un- 

 economic and wasteful use of fuel, and jeopardizing the quality 

 of the product. The presence of numerous but short coils also 

 increases the intensity of heat-transmission, as practically all 

 of the steam is condensed in the uppermost convolution of each coil. 

 There is a considerable variation in the area of the heating sur- 



