ENGINEMAN 1 & Cauxiliary equipment. Some of the more importantmaintenance problems will be discussed in thefollowing paragraphs.AIR LEAKAGE.—Since all parts of thedistilling plant are designed to operate under avacuum except the circulating, feed, andfreshwater lines, extreme care must be taken toprevent leakage of air which might seriouslyinterfere with the proper operation of the plant.The brine overboard and distillate pumps taketheir suction from points of relatively highvacuum. Air leakage in the piping to these pumpsis particularly objectionable and must beeliminated. A small amount of air entering theselines, even though it is insufficient to affect thedistilling plant vacuum, may cause the pump tolose suction. Leaks in the lines to the pump suc-tion gages must never be overlooked.An 8 to 10 psig, low pressure hydrostatic testshould be applied to the entire system in accord-ance with the PMS, and at any other time whenthere is an indication that air leakage may exist.The saltwater circulating pump can be used toapply the pressure.PUMPS.—Proper operation of all pumps isessential for the successful operation of the dis-tilling plant. The effect of air leakage into the suc-tion line of the pumps has been discussed in thepreceding paragraph. Proper operation of thewater-sealed gland lines and proper mainte-nance of the glands themselves are necessary fordependable operation of the pumps. General in-formation on the operation and maintenance ofpumps is found in Engineman 3 & 2, NAVED-TRA 10541 (current edition). However, for detailsof any specific pump, consult the manufacturer’stechnical manual.SALTWATER LEAKAGE.—Saltwater todistillate or saltwater to condensate leaks at anyof the various tube bundles will be immediatelyindicated by an alarm bell and a red light whichshows at which cell a conductivity increase hasoccurred. These cells are located downstreamfrom each tube bundle. Tube leaks usually resultfrom damaged or corroded tubes or from im-proper expansion of tubes into the tube sheets.Faulty tubes may be sealed with plastic tubeplugs or may be removed and replaced in accord-ance with standard Navy procedures, as given inchapter 9581 of Naval Ships’ Technical Manual.Cleaning Heat ExchangersThe tubes of the distillate cooler, the air ejec-tor condenser, and the stage condensers operatewith comparatively cool saltwater inside them andseldom require cleaning. The seawater in thesaltwater heater, on the other hand, is at a highertemperature and its tubes will occasionally requirecleaning to remove the hard scale on the insideof the tubes. A special tool is furnished for thispurpose; this cleaning tool is shown in figure 7-6.Figure 7-6.—Tool for removing scale inside tubes.7-32
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