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968 . CHAPTER 51" 1949 Guide Table'4. 'Plant Water Supply Examination WATER SUPPLY-- ,200 feet deep well--average water temperature 53 F-- water is producing a brown stain in plumbing fixtures. SAMPLE-- .The sample was scraped from the surface of the shell.and tube condenser of #2 Freon Compressor on the meat chilling room. The sterile sample bottle was `filled one-half with deposit and the balance with circulating water. No preservative was added--pH at time of col lection was 7.4. ANALYSIS REQUIRED-^MACROSCOPIC' ' b3 MICROSCOPIC Lfl BACTERIOLOGICAL bd ORGANIC CONTENT lyj PROBLEM-- ' A 25-ton Freon--12 Compressor has head pressure about 10 lb higher than during initial operation, without change in water temperature. Deposits have been observed on heat exchanger surfaces. It is desired to know the nature of these deposits and if they are the cause of this increased head pressure. MACROSCOPIC Heavy brown flocculent material settles rapidly in clear EXAMINATION-- . water.. pH--7.3 Odor--woody, mouldy. MICROSCOPIC EXAMINATION-- L Inorganic Material--small amount white crystals. Amorphous Material--small amount--brown. Iron Bacteria--profuse growth of crenothrix--(Photo usually included). CULTURAL EXAMI NATION-- TOTAL COUNT SabourXud's Agar 1. Aerobic gram positive spore-forming rod with mucoid sheaths. (Photo usually included). 2. Short gram negative coccibacilli (Photo usually included). 100,000 organism/cc. ORGANIC CONTENT (by WEIGHT, DRY BASIS)--60% DISCUSSION-- .The presence of common slime-forming organisms in the deposit. combined with high organic content indi- . cates that the deposit is.bacterial in origin. Heat transfer, reductions would be caused by such a deposit. These deposits, combined with crenothrix, can cause corrosion of both ferrous and. non-ferrous metals. . RECOM MENDATIONS- It is recommended that the water be treated at the suc tion side of the deep well pump with chlorine in quanti ties sufficient to maintain, a, free chlorine residual of 1.0 ppm at the discharge of the shell and tube cooler. ThiB treatment can be scheduled on an intermittent basis. results of such a test are1 commonly reported in the manner illustrated in Table 4. Condensates All condensates result from the chilling of water vapor. Such chilling may result'from natural causes, thus producing dews, sweats, rain, and snow, or from artificial causes, as in steam condensing equipment, pro ducing condensate or return water. In the heating and ventilating field, the biological characteristics of condensates are likely to be of concern only where the condensate is used Corrosion and Water Formed Deposits,. Causes and Prevention 969. as cooling water in recirculating systems. The deleterious gas contents of condensates, however, very often create.serious corrosion troubles.. The'data ih;Table 5 typify the chemical composition of the atmosphere in rural and inetrdplitan-areas, and of stack gases when various types of common fuels'are Used.: ;The curves in Fig. 1 disclose the solubility of the major deleterious gases present in such.atmospheres in otherwise pure water, when the partial pressure of the gas is one pound per square inch absolute. : . 1 The most common deleterious gases entrained by steam are oxygen and carbon dioxide. In rare instances, hydrogen sulphide, sulphur dioxide, or ammonia are present. , In most steam condensing equipment7-8, the non-condensable gases entrained with steam accumulate so that the amount present in the vapor space is several hundred times higher than in the incoming steam and, Table 6. Data Typifying the Deleterious Gas Content of Different Atmospheres Name of Gao - Air Chem ical Rural Metropolitan Bmml Coal Form- &ula %hy Volume . Partial Pressure psia Partial Partial Pressure psia V.%olubmye Pressure ' psia Flub Gases Fuel Oils Partial Pressure . psia Natural Gar Partial Pressure psia Oxygen-------- Oi Carbon Dioxide CO, Sulphur Dioxide SO, 21 0.03 None 3.143 0.004 None 21 0.06 0.003 3.143 0.009 0.004 ' 2 15 0.07 0.299 2.245 0.010 7 13 0.03 1.048 1.946 0.004 10 10 0X001 1.497 1.497 0.0015 the amount dissolved in, the condensate may therefore approach, or even exceed for short periods,, the amount entrained by the steam. CAUSES AND PREVENTION OF SCALES AND SLUDGES Scales may be formed oh surfaces of equipment in contact with water, and sludges in the body of the water, by the separation from the water of dissolved or suspended solids. According to the nature of a particular piece of equipment and the method of its operation such separation may be promoted by. one or more than one', of several factors: a. The cpncentration of solids may be increased by.the evaporation of water. b. The dissolved solids may. be rendered less soluble in the water by changes in temperature. '. ' c. Conditions may favor'.the decomposition of unstable compounds with the formation of less soluble compounds. . , Figs'. 2 and'3 show that the solubilities of both calcium carbonate and calcium sulphate decrease with'the rising temperature within a moderate range ,of temperatures. Surfaces transferring heat into water, such as condensers and coolers, are more-susceptible to scale and sludge formation than are the cold parts of the same system using the same water. . >: - .. The most common of the unstable soluble salts are the bicarbonates of calcium, magnesium,, and occasionally iron.", Under conditions favoring the removal of carbon dioxide, as when the water is strongly, aerated or when it is boiled, the bicarbonates are readily converted .to the relatively