Document 1Q6ZZeJexROdJR6xZxvyGBR6o

984 CHAPTER 43 1956 Guide Table 4. Plant Water Supplied for 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 No. 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 Ld BACTERIOLOGICAL |VJ MICROSCOPIC Lfl ORGANIC CONTENT IV] 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 EXAMINATION-- Heavy brown flocculant material settles rapidly in clear water. pH--7.3 Odor--woody, mouldy. MICROSCOPIC EXAMINATION-- 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 Sabouraud's Agar 1. Aerobic gram positive spore-forming rod with mu coid sheaths. (Photo usually included). 2. Short gram negative coccibacilli (Photo usually in cluded) . 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. This treatment can be scheduled on an intermittent basis. In the heating and ventilating field, the biological characteristics of condensates are likely to be of concern only where the condensate is used as cooling water in recirculating systems. The deleterious gas contents of condensates, however, very often create serious corrosion troubles. The data in Table 5 typify the chemical composition of the atmosphere in rural and metropolitan- areas, and of stack gases when various types of common fuels sire 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 psia. The most common deleterious gases entrained by steam are oxygen and Corrosion and Water Formed Deposits, Causes and Prevention 985 Table 5. Data Typipting the Deleterious Gas Content of Different Atmospheres Aik Flub Gases Name of Gas Chemical Rural Metro politan Bitum. Coal Fuel Oils Formula % by Vol ume Partial Pres sure psia % ume Partial Pres % by sure Vol ume psia Partial Pres % by sure Vol ume psia Partial Pres sure psia Natural Gas ' ume Partial Pres sure psia Oxygen................... Carbon Dioxide... Sulphur Dioxide.. O. COj SO, 21 3.143 21 3.143 . 2 0.03 0.004 0.06 0.009 15 None None 0.003 0.004 0.07 0.299 2.245 0.010 7 13 0.03 1.048 1.946 0.004 10 10 0.0001 1.497 1.497 0.0015 carbon dioxide. In rare instances, hydrogen sulphide, sulphur dioxide, or ammonia are present. In most steam condensing equipment,7 -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 the amount dissolved in the condensate may therefore approach, of even exceed for short periods, the amount entrained by the steam. CAUSES AND PREVENTION OF SCALES AND SLUDGES Scales may be formed on 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