ENGINEMAN  1  &  C of the desuperheating temperature in the steam side. The steam supply to the saltwater heater flows from  the  auxiliary  exhaust  line,  through  the regulating valve (1-5 psig) and then through an orifice which provides, within limits, a uniform flow of steam. It then flows past the desuperheater nozzle, which reduces the steam temperature in the shell of the heater. Steam pressure is indicated by a pressure gage on the operating panel. The outlet for noncondensables is mounted on the top of the shell and flanged to the suction chamber of the first ejector of the two-stage air ejector  system.  The  two  air  ejectors  produce  the vacuum in the precooler which causes the flow of  steam  and  noncondensables  from  the evaporator. A thermometer is mounted on the feedwater inlet of the cooler. The entering steam is directed along the length of the tubes by impingement baffles. Steam con- denses on the tubes and falls to a condensate well at   the   bottom   of   the   heater   shell.   (A   drain regulator of the float type controls the level of the condensate in the well. A salinity cell, set to energize at 0.10 epm, controls a shutoff valve located in the ship’s piping between the drain pump   and   the   regulating   valve.)   The desuperheater  atomizes  the  heater  condensate  in the low pressure steam side of the heater. Cooling water from the air ejector precooler flows into the AFTER-CONDENSER, which is the fifth of the heat exchangers mounted on the evaporator.  The  after-condenser  completes  the condensation of any air ejector steam not con- densed in the precooler and cools noncondensable gases before venting them to the atmosphere. The after-condenser  enables  the  unit  to  operate without emission of steam from the evaporator. Cooling  water  enters  and  leaves  the  after- condenser through an inlet pipe in the front and an outlet pipe in the rear of the condenser. The function of the saltwater heater is to pro- vide feedwater to the inlet of the first evaporator stage flash chamber. Since the amount of heat from the steam is constant, the feedwater flow through the heater must be adjusted according to the inlet temperature so that the feedwater flow is controlled by a valve on the outlet side of the heater. Air ejector steam and noncondensable gases enter the shell side through an inlet in the front of  the  unit.  Noncondensable  gases  are  vented through a valve on the rear of the unit. A series of  vertical  baffles  direct  the  steam  around  the tubes on which it condenses. Condensate is re- moved through bottom outlets on both ends of the condenser. The  air  ejector  PRECOOLER  is  a  gas  or liquid   heat   exchanger   which   cools   noncon- densables and condenses steam drawn from the first  three  evaporator  stages  and  the  saltwater heater  by  a  two-stage,  vacuum-producing  air ejector. A salinity cell set to operate at 0.10 epm con- trols a shutoff valve below the condenser. The precooler receives its coolant from the feedwater pumped into the distilling unit. The flow of coolant is through the heat transfer tubes, where it makes six passes, entering and leaving at the front end of the cooler. Three  high-pressure  steam-operated  vacuum- producing AIR EJECTORS are mounted on the precooler side of the evaporator unit. The ejec- tor system consists of a single-stage (booster) air ejector and a two-stage air ejector arrangement in which the steam outlet from one air ejector is flanged to the suction side of the other. Steam and noncondensables are drawn into the cooler at the top near the rear of the cooler. Impingement baffles at the inlet and seven ver- tical baffles, through which the transfer tubes run, direct the flow of hot gases around the tubes for efficient heat transfer. The  single-stage  ejector  uses  ship’s  steam  to draw  vapor  and  noncondensables  from evaporator stages four and five. Gases are drawn from the evaporator through a vapor duct in each distillate  collection  trough  so  that  a  minimum  of steam is withdrawn. Pipes from stages four and five lead to a bronze tee flanged to the ejector. Condensate collects on the tubes and drops to the bottom of the shell. A salinity cell operates a shutoff valve in the precooler condensate line to dump to the bilge or drain tank when the salin- ity is greater than 0.65 epm. The  single-stage  ejector  steam  and  entrained gases leave the ejector outlet tubing, flow through a check valve, and reenter the evaporator shell through the top of stage three, from which they are piped into the bottom of the stage three con- denser  section. 7-30