(2) Double or triple pipe coolers in which brine and ammonia are circulated in annular spaces between pipes. (3) Shell type coolers in which the brine is passed through tubes within a shell similar to an ordinary flue boiler. For a close brine system, which is the term applied to a system where brine is circulated through pipes and not exposed to the atmosphere so as to absorb moisture, the shell type cooler is a convenient and economical means of chilling brine. It is so readily applicable to the use of a balanced system, thereby lessening the power requirement for pumping. Double pipe coolers can be used in the same method, but are not quite so favorably considered owing to the aggregate quantity of joints. Either the shell type cooler or the double pipe cooler can be safely used with an open system. The open type brine system is any system used wherein the cooling effect is produced by bringing the cold brine in direct contact with the air to be chilled, as in the spray system, the “Gardner” sheet system, or an open pan system. =Brine Methods--Recommendation.=--Where it would seem best for other reasons to use a brine system, and the plant would justify the expenditure, it would appear well to use a double brine system--open brine in the hog chill rooms, and a closed system on the freezers, beef chill rooms, storage rooms. =Types of Brine Coolers.=--Open tanks with submerged coils are used on some plants. The investment is greater, but the risk is slightly less than in the use of closed type brine coolers, commonly called shell and tube type. Unless the engineering force of the plant is fully qualified and alert, there is danger of diluted brine and freezing the solution in shell type coolers, which is likely to split the tubes, causing leaks and the possibility of brine finding its way to the ammonia compressors, rendering them liable to damage of a serious nature. Whereas, with the open type tank and submerged coils, weakened brine might cause ice to form on the expansion pipes and render them inert, but no comparable damage could arise. However, we advocate an alert engineering force and the closed system. [Illustration: FIG. 17.--DIAGRAM SHOWING BALANCED BRINE SYSTEM.] =Balanced Brine System.=--The balanced brine system as referred to in the preceding, is indicated by diagram and has the advantage of keeping the pipes full at all times, also of reducing the power requirement to the actual friction through the pipes in the shell type cooler, and a slight increase for passing through the coils. In practice twenty to twenty-five pounds friction represents the total head to pump against in a building nine stories high. The two types of the balanced brine system are as follows: