ENGINEMAN 1 & CFigure 3-11.—A cooling water system.A gradual increase in the freshwatertemperature is usually an indication of EX-CESSIVE SCALE on a cooler element. As scaleformation increases, there is a gradual increasein the pressure difference between the inlet andoutlet of the heat exchanger. Scale depositsgenerally form faster on the saltwater side thanon the freshwater side, because of the greateramount of dissolved salt present in the water.Complete prevention of scale formation is notpossible, but steps can be taken to reduce its for-mation by using proper cleaning methods and pro-cedures. Seawater discharge temperature shouldbe maintained below a specified limit (130°F),because the rate of scale formation is increasedas the temperature increases. The water used inclosed cooling systems must be as pure aspossible. Distilled water is recommended for afreshwater cooling system, but since distilled wateris not absolutely pure, additional steps must betaken to control acidity and alkalinity. The treat-ment used to control these factors will not removescales already formed, but it will prevent furtherprecipitation of scale-forming slats. You will finddetails for water treatment in closed water systemsin chapter 233, NAVSHIPS Technical Manual,and in most engine instruction manuals.Not only the hard deposits chemicallyprecipitated from the circulating water, but alsosuch items as marine life, grease, and debris ofvarious types may CLOG OR RESTRICTCOOLER ELEMENTS. The principal causes of3-12121.11
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