PRINCIPLES OF NAVAL ENGINEERING 



If the brine concentration is too high, there will 

 be an increase in the rate of scaling of the evap- 

 orator tube surfaces, and the quality of the dis- 

 tillate may be impaired. The density of the brine 

 overboard discharge should normally be main- 

 tained just under 1.5/32, and should never exceed 

 this figure. Since the average sea water contains 

 about 1 part of dissolved sea salts to 32 parts of 

 water (by weight), the brine density should be just 

 under 1 1/2 times that of the average sea water. 

 Brine density is measured with a special kind of 

 hydrometer 4 which is called a salinometer . 

 Salinometers as shown in figure 18-13 are cal- 

 ibrated in thirty- seconds, on four separate 

 scales which indicate the salinity of the brine at 

 four different temperatures (110° , 115° , 120°, 

 and 125° F), 



Special restrictions are placed upon the oper- 

 ation of distilling units when the ship is operat- 

 ing in contaminated waters. Because most dis- 

 tilling plants operate at low pressures (and 

 therefore low temperatures) the distillate is not 

 sterilized by the boiling process in the evapor- 

 ators and may contain dangerous micro-orga- 

 nisms or other matter harmful to health. All 

 water in harbors, rivers, inlets, bays, land- 

 locked waters, and the open sea within 10 miles of 

 the entrance to such waters must be considered 

 contaminated unless a specific determination to 

 the contrary is made. In other areas, contamina- 

 tion may be declared to exist by the fleet surgeon 

 or his representatives, as local conditions may 

 warrant. When the ship is operating in contami- 

 nated waters, the distilling units must be oper- 

 ated in strict accordance with special procedures 

 established by the Naval Ship Systems Command. 



4 Hydrometers are discussed in chapter 7 of this text. 



47.136X 



Figure 18-13. — Salinometer. 



470 



