The brine-coils can be placed on the walls, as shown in fig. 96, or on the ceiling, or both; whereas, if the flow and return pipes were both in the same corridor, pipes could, to give good results, only be placed on the ceiling. The flow of brine through each room can be regulated by the valves, and a whole coil can be shut out if necessary. The general system of the arrangement of brine piping is as follows:-The cold brine from the brine cooler enters the stand-pipe A at B. This stand-pipe runs right up to the roof of the building, and is fitted at the top with a dead-weight, blow-through valve, loaded to lift at, say, 12 lbs. per square inch. The overflow from the valve passes back into the brine-tank through a separate pipe. This valve is provided to guard against accident, should all the deliveries be shut off at any one time while the pumps were running; in ordinary work it is seldom or never in action. From the stand-pipe the flow to each floor passes off into the headers C, which run along the corridors; that for the ground floor rooms is encased in the floor as shown. The cold brine leaves the headers through the pipe D outside the cold room, passes through the wall, through the grid of pipes on the ceiling or wall, and back to the return header E placed in the corridor above. The wall and ceiling coils should be on separate circuits controlled by separate valves, so that they can be turned on or off, or regulated independently of the others. Where the pipes from the various circuits enter the return header, they are fitted with a thermometer, so that the temperature of the brine can be read at any time. The return header runs along the passage and discharges into the brine-tank as shown. Each header 1 Reproduced from Ice and Refrigeration, Chicago. is at this point provided with a thermometer, by means of which the engine-driver can see at a glance the temperature of the brine from the various floors. It will be observed that each floor is one main circuit, and that the various rooms form branch circuits from this. The return headers passing down to the brine-tank must have a perforated flange at the top of the vertical portion, or a small pipe running up above the level of the highest floor, in order to break the vacuum and prevent the brine siphoning out of the pipes. The lowest point of the system should be connected to the suction of the brine-pump through a small pipe, so that the brine-pipes can be pumped out at any time. As the resistance to the flow of brine through the lower coils is less than that through the upper, there is nothing to prevent the brine-pipes on the upper floors emptying through those on the lower when the pump is stopped. In the majority of plants this difficulty is overcome by fitting each main return pipe with a valve, and closing it, and the valve by the pump, when the latter is stopped. The flow of brine through the various rooms is rendered even by merely regulating the valves on the various floors. In some designs, however, the return pipes from each flow are taken to the level of the top floor and then returned to the brine-tank. The former system is that most commonly in use, and it saves power, as the brine does not all have to be pumped to the highest level. In other designs each separate circuit throughout the building returns to the brine-tank, where it is labelled and fitted with a thermometer and valve. The flow of brine through any circuit is controlled from this point more or less, being passed according to the reading of the thermometer. Before the brine-pump is stopped these valves are all shut off, and the brine is retained in the coils. This arrangement is very simple and effective, but, where a variety of temperatures have to be carried, is not so convenient as the system first described. In order to secure an even flow through the various pipes, the coils should all be of approximately the same length. Too large circuits should be avoided, and with 14-inch pipes 400 feet is about the maximum advisable. With 2-inch pipes this may be increased to 1000 feet. Practice, however, varies, and the circumstances of each case must determine the lengths of the various circuits. Under normal circumstances the brine will gain some 6 to 8° F. in temperature in traversing the coils. The best spacing for the pipes is in grids at not less than 9-inch centres. Where chilled beef is being hung the pipes are frequently nested between the rows of carcasses. Brine walls, somewhat similar in construction to those used in the cell and plate ice-making plants, are frequently used for this purpose. In cases where two or more floors are all kept at the same temperature and no insulation is used in the floors, the brine-pipes can be conveniently nested between the main timbers of the floor; in this case, as before, the brine enters at the lower level and flows away to the return header at the higher level. Brine-Tank and Brine-Pumps.-The brine-tanks containing the evaporating coils can be of the ordinary oblong pattern as in ice-making, but, in order to save room, it is most usual to make them more after the pattern of the submerged condenser, the brine surrounding the evaporating coils, which are contained in a vertical circularwrought-iron tank. |