68 



D CONDENSED MILK CONDENSING 



THE DOME: rests on top of the body of the pan. It is equipped 

 with a manhole, manhole cover, thermometer, vacuum gauge, sight 

 glasses, lights and blow-down valve, or vacuum breaker. The 

 manhole measures about fourteen 

 to eighteen inches in diameter. It is 

 closed by a solid brass cover with 

 a well-fitting, ground surface flange. 

 The cover carries a five-inch eye- 

 glass or sight-glass through which 

 the operator watches the boiling 

 milk in the pan. The stem of the 

 thermometer is enclosed in a brass 

 casing and reaches to near the bot- 

 tom of .the pan. Some processors 

 prefer a short thermometer which Fig . 17 . vacuum gauge 



registers the temperature of the va- courtesy of Arthur Harris & Co. 

 pors instead of that of the milk. As both, the milk and the vapors are 

 subjected to the same pressure, their respective temperatures are the 

 same. The long-stem thermometer, the bulb of which 

 is submerged in the milk, however, is more sensitive 

 and registers changes in temperature more rapidly, 

 because the milk is a better conductor of heat than 

 the vapors. The vacuum gauge connects with the 

 interior of the pan, and indicates the number of 

 inches of vacuum. A mercury column may be used 

 in the place of the vacuum gauge. In the rear of 

 the dome there are two sight glasses. Through these 

 the interior of the pan is illuminated by means of 

 lamps, gas or electric lights. The "blow-down" 

 valve, or vacuum breaker, serves to admit air into 

 the pan in order to "break" the vacuum. This is 

 Fig. 18. necessary for readily drawing off the finished con- 



Thermometer densed milk. It is further needed to prevent the 



for vacuum pan 



Courtesy of contents of the vacuum pan from being drawn over 

 Arth & r c? arriS * nto tne conQl enser, whenever the milk rises above a 

 safe level. 



A further accessory of the dome may be an automatic milk 

 sampler. The sampler tube is carried through the wall of the dome 

 and extends to near the bottom inside of the pan. Where this tube 



