Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGIf the brine concentration is too high, there willbe an increase in the rate of scaling of the evaporatortube surfaces, and the quality of the distillatemay be impaired. The density of the brineoverboard discharge should normally be maintainedjust under 1.5/32, and should never exceedthis figure. Since the average sea water containsabout 1 part of dissolved sea salts to 32 parts ofwater (by weight), the brine density should be justunder 1 1/2 times that of the average sea water.Brine density is measured with a special kind ofhydrometer 4 which is called a salinometer .Salinometers as shown in figure 18-13 are calibratedin thirty- seconds, on four separatescales which indicate the salinity of the brine atfour different temperatures (110° ,115° ,120°,and 125° F),Special restrictions are placed upon the operationof distilling units when the ship is operatingin contaminated waters. Because most distillingplants operate at low pressures (andtherefore low temperatures) the distillate is notsterilized by the boiling process in the evaporatorsand may contain dangerous micro-organismsor other matter harmful to health. Allwater in harbors, rivers, inlets, bays, landlockedwaters, and the open sea within 10 miles ofthe entrance to such waters must be consideredcontaminated unless a specific determination tothe contrary is made. In other areas, contaminationmay be declared to exist by the fleet surgeonor his representatives, as local conditions maywarrant. When the ship is operating in contaminatedwaters, the distilling units must be operatedin strict accordance with special proceduresestablished by the Naval Ship Systems Command.4 Hydrometers are discussed in chapter 7 of this text.Figure 18-13. — Salinometer.47.136X470