ENGINEMAN 1 & Cof the desuperheating temperature in the steamside.The steam supply to the saltwater heater flowsfrom the auxiliary exhaust line, through theregulating valve (1-5 psig) and then through anorifice which provides, within limits, a uniformflow of steam. It then flows past the desuperheaternozzle, which reduces the steam temperature inthe shell of the heater. Steam pressure is indicatedby a pressure gage on the operating panel.The outlet for noncondensables is mounted onthe top of the shell and flanged to the suctionchamber of the first ejector of the two-stage airejector system. The two air ejectors produce thevacuum in the precooler which causes the flowof steam and noncondensables from theevaporator.A thermometer is mounted on the feedwaterinlet of the cooler.The entering steam is directed along the lengthof the tubes by impingement baffles. Steam con-denses on the tubes and falls to a condensate wellat the bottom of the heater shell. (A drainregulator of the float type controls the level ofthe condensate in the well. A salinity cell, set toenergize at 0.10 epm, controls a shutoff valvelocated in the ship’s piping between the drainpump and the regulating valve.) Thedesuperheater atomizes the heater condensate inthe low pressure steam side of the heater.Cooling water from the air ejector precoolerflows into the AFTER-CONDENSER, which isthe fifth of the heat exchangers mounted on theevaporator. The after-condenser completes thecondensation of any air ejector steam not con-densed in the precooler and cools noncondensablegases before venting them to the atmosphere. Theafter-condenser enables the unit to operatewithout emission of steam from the evaporator.Cooling water enters and leaves the after-condenser through an inlet pipe in the front andan 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 evaporatorstage flash chamber. Since the amount of heatfrom the steam is constant, the feedwater flowthrough the heater must be adjusted according tothe inlet temperature so that the feedwater flowis controlled by a valve on the outlet side of theheater.Air ejector steam and noncondensable gasesenter the shell side through an inlet in the frontof the unit. Noncondensable gases are ventedthrough a valve on the rear of the unit. A seriesof vertical baffles direct the steam around thetubes on which it condenses. Condensate is re-moved through bottom outlets on both ends ofthe condenser.The air ejector PRECOOLER is a gas orliquid heat exchanger which cools noncon-densables and condenses steam drawn from thefirst three evaporator stages and the saltwaterheater by a two-stage, vacuum-producing airejector.A salinity cell set to operate at 0.10 epm con-trols a shutoff valve below the condenser.The precooler receives its coolant from thefeedwater pumped into the distilling unit. Theflow of coolant is through the heat transfer tubes,where it makes six passes, entering and leavingat the front end of the cooler.Three high-pressure steam-operated vacuum-producing AIR EJECTORS are mounted on theprecooler side of the evaporator unit. The ejec-tor system consists of a single-stage (booster) airejector and a two-stage air ejector arrangementin which the steam outlet from one air ejector isflanged to the suction side of the other.Steam and noncondensables are drawn intothe 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 forefficient heat transfer.The single-stage ejector uses ship’s steam todraw vapor and noncondensables fromevaporator stages four and five. Gases are drawnfrom the evaporator through a vapor duct in eachdistillate collection trough so that a minimum ofsteam is withdrawn. Pipes from stages four andfive lead to a bronze tee flanged to the ejector.Condensate collects on the tubes and drops tothe bottom of the shell. A salinity cell operatesa shutoff valve in the precooler condensate lineto dump to the bilge or drain tank when the salin-ity is greater than 0.65 epm.The single-stage ejector steam and entrainedgases leave the ejector outlet tubing, flow througha check valve, and reenter the evaporator shellthrough the top of stage three, from which theyare piped into the bottom of the stage three con-denser section.7-30
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