Sweetened Condensed Milk — Condensing 73 



both of these systems and the surface condenser is that, in the wet- 

 vacuum and barometric condensers the condensed vapors mix with 

 the cooHng water, while in the surface condenser the condensed va- 

 pors 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, however, is of relatively small ca- 

 pacity 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 con- 

 densers are best suited; their operation utilizes the cooling water 

 most 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, or spray plate. Especially, when the water used con- 

 tains 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 renders 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 utiHzed economically and the difference between the temperature 

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

 order 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 

 spray pipe free from obstructions. It is advisable to install con- 

 densers equipped with a manhole on top or at the end, otherwise 

 access to the spray pipe is not sufficiently convenient to insure fre- 

 quent inspection and thorough cleaning by the average operator. 



The Expansion Tank, Catch-AU, or Milk Trap.— T his is a 



tank frequently installed between the dome of the pan and the con- 

 denser. Its purpose is to collect and reclaim any milk that may be 

 carried over from the pan and to prevent its escape and loss through 

 the condenser. 



