hot water heaters. Shore water is usually hardwater which contains high concentrations ofdissolved solids and silica. Although it can haveeither high or low pH, in a boiler, shore waterusually causes high pH. High concentrations ofdissolved solids lead to boiler water carryover withthe steam. Silica may be deposited on the boilerwatersides and in the steam system as it vaporizes.Water hardness leads to excessive usage ofboiler water treatment chemicals which causes cor-rosion, scale, and sludge buildup. Excessively highpH causes caustic embrittlement and subsequenterosion of boiler metal parts.Firetube and watertube auxiliary boilers arenatural circulation boilers. The water treatmentfor natural circulation auxiliary boilers is main-tained in the same manner as the propulsion boilerwater. Section 21 of Naval Ships’ TechnicalManual, chapter 220, volume 2, describes thiswater treatment. The control parameters for aux-iliary boiler water are alkalinity, phosphate, andchloride. In auxiliary boilers, the alkalinity of theauxiliary boiler water is measured instead of thepH because its higher alkalinity level can be moreeasily measured by the alkalinity test than by thepH meter test. The alkalinity range is equivalentto a pH range of 11.0 to 11.3. The auxiliary boilerlimits are given in table 7-1.The same treatment chemicals, trisodiumphosphate dodecahydrate (TSP) and disodiumphosphate anhydrous (DSP), are used for aux-iliary boiler water treatment except that a higherlevel must be maintained due to the loweroperating pressures. The TSP provides alkalin-ity and phosphate. The DSP provides additionalTable 7-1.—Auxiliary Boiler Water Limits For Firetube andNatural Circulation Water Tube Auxiliary BoilersAlkalinity:1.0 - 2.0 epm (1.0 - 2.0 meq/L)Phosphate:200 - 400 ppm (200 - 400 mg/L)Chloride:10.0 epm (10.0 meq/L) maximumChapter 7—AUXILIARY MACHINERYphosphate without significantly affecting thealkalinity.Initial TreatmentThe boiler is initially half-filled with feedwaterto partially dilute the treatment chemicals whichmust be added. The treatment chemicals are thenadded to bring the boiler water conditions to nearthe upper limits. The necessary amounts of treat-ment chemicals are weighed, dissolved in feed-water, and injected into the boiler.WARNING: TSP solutions are corrosive andcause burns to skin, eyes, and body tissues.Affected personnel should flush skin with coldwater. If TSP or its solutions enter the eyes, flushwith cold water and obtain immediate medicalattention.TSP is added to bring the alkalinity to 2.0equivalents per million (epm) (2.0 meq/L) and toprovide some of the needed phosphate. DSP isadded to bring the phosphate to 300 parts permillion (ppm) (300 mg/L) and not to the upperlimit of 400 ppm (400 mg/L). In order to deter-mine the amount of chemicals needed, the volumeof water requiring chemical treatment must beknown. This information is sometimes availablein the instruction manual for the boiler. If theweight of water at normal steaming level whilesteaming is given, divide the weight in pounds by8.33 to determine volume in gallons. If the boilerweight data gives only the dry weight and the wetweight of the boiler, determine the boiler waterchemical treatment volume as follows:1. Subtract the boiler dry weight from theboiler wet weight to obtain a weight of cold waterin the boiler.2. Divide the weight of cold boiler water inpounds by 9.30 for boilers operating at 125pounds per square inch (psi) or 8.87 for boilersoperating at 35 psi to obtain the boiler watervolume, in gallons, for chemical treatment. Thisvolume times the initial chemical treatment fac-tors (ounces per gallon) given in table 7-2 deter-mines the ounces of TSP and DSP required. Enterthe volume to the nearest gallon and the calculateddosage to the nearest one-half ounce in theappropriate columns.7-9
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