=Ample Capacity.=--All of the above factors must be considered in the calculations for refrigerating requirements, and it is best to make allowances for a considerable factor of safety over and above the actual maximum, as well as for the economical operation of the plant. It never pays to crowd a plant to its limit or capacity. Guard against emergencies and possible abnormal demand for refrigeration by providing ample equipment. The plant should be constructed as far as possible in duplicate, not only as regards the machinery but also in the apparatus, as a safeguard against accidents and total cessation of refrigeration. With two machines and duplicate apparatus one-half the maximum refrigeration is always available, and the preservation of the product in storage is assured, even if it be found necessary to stop killing for a sufficient period to make the repairs on the broken machinery or apparatus, while with one machine only available, a breakdown might result in a very serious loss and considerable damage to the stored products. With regard to insulation, it may be said that the best is the most economical in the long run. There is no such thing as absolute insulation, some heat leakage must occur through the very best insulation, and the reduction of this heat leakage to the minimum should be the chief object or factor for consideration. First-class insulation costs more in original investment, but it creates a continuous saving and economy in refrigeration, resulting oftentimes in a less investment also in refrigerating, pumping and steam equipment. CHAPTER V. REFRIGERATION REQUIREMENTS. REFRIGERATION -- NECESSITIES -- ICE PLANTS -- NATURAL ICE -- CHILLING -- QUANTITY REFRIGERATION TO PROVIDE -- SPACE PER TON MACHINE -- MACHINERY PER HEAD -- ICE COMPUTATION -- COMPRESSOR CAPACITY -- SUMMARY COMPUTATIONS -- LOW TEMPERATURE BRINE SYSTEM. =Refrigeration.=--This word covers the “bugbear” and the “solace” of the packers. No other one thing is of so much importance. Since the abolishment of the use of chemicals, such as borax, boracic acid, etc., as a preventive or retardant in the propagation of bacilli during the curing process, the packer’s sole dependence is refrigeration. Consequently there has been considerable development and importance in its use. From the moment the animal is killed until the parts are disposed of, refrigeration is a necessity. The proportion of freezing space to be provided or hired at a commercial storage house is growing daily. In many plants the total volume of freezer space approaches or exceeds, that given over for moderate temperature storage purposes. =Necessities.=--In the order of progress the first necessity for refrigeration is the use of ice for chilling water for fats and meats. Practically every packing house is now equipped with a small ice making plant both for its use, and with commercial possibilities of selling ice. =Ice Plants.=--Ice plants are of various kinds: