52 Condensed Milk and Mh,k Powder 



pump, but goes direct into the sewer and the vacuum is sealed by the 

 barometric water column. So far as practical experience has shown, 

 there is no material difference in the efficiency between these two 

 types of condensers. The water column of the barometric condenser 



helps somewhat to maintain a 

 uniform vacuum. It necessi- 

 tates, however, the installing of 

 the pan inconveniently high and 

 requires somewhat more exten- 

 Fig. 16. The wet-vacuum spray condenser sive machinery, than is the case 



Courtesy of Arthur Harris & Co. w j th the wet-VaCUUHl Condenser. 



The chief difference between both of these systems and the sur- 

 face condenser is that, in the wet-vacuum and barometric condenser 

 the condensed vapors mix with the cooling water, while in the sur- 

 face condenser the condensed vapors are collected and carried off 

 separately and without mixing with the- cooling water. In the case 

 of condensing liquids, the vapors of which are of commercial value, 

 the surface condenser must be used. The surface condenser, how- 

 ever, is of relatively small capacity and the cooling water cannot be 

 utilized as economically as in the case of the other systems. Where 

 large quantities of vapors are to be handled and the vapors have no 

 commercial value, as is the case in condensing milk, the barometric 

 and wet-vacuum condensers are best suited ; their operation utilizes 

 the cooling water more economically. 



Care of the Condenser. — In the operation of the spray and 

 jet condenser, special attention should be paid to the condition of 

 the spray pipe. Especially, when the water used contains much 

 ' organic matter, as is the case with water from a creek, pond or lake, 

 there is a tendency of the spray pipe becoming filled and coated with 

 slimy organic matter, causing the perforations to clog. This ren- 

 ders the distribution of the spray irregular and the control of the 

 pan difficult. It causes great waste of water because much of the 

 water is discharged from the condenser and lost without coming 

 into direct contact with the vapors. The water is therefore not 

 utilized economically and the difference between the temperature of 

 the vapors and the discharge of the condenser is excessive. In or- 

 der to avoid this the condenser should be cleaned out thoroughly at 

 least once a week, or oftener, if necessary to keep the pores of the 



