Document zoGL7z5j082zXbK6zn2zYJewg

974 CHAPTER 43 1955 GjjlBJlLrrosion and Water Formed Deposits, Causes and Prevention 975 it- ii Table 4. Plant Water Supplied fob Examination Table 5. Data Typifying the Deleterious Gas Content of Different Atmospheres WATER SUPPLYSAMPLE-- 200 feet deep well--average water temperature 53 j?JK water is producing a brown stain in plumbing fixture-' --------------------------------------------------------------------- :---------------------------- ----------------------------------------- LiTHSS The sample was scraped from the surface of the shell ami 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--pll at time of collection was 7.4. I Air Flub Gaseb Name of Gas Rural Chemical Formula % by Vol ume Pressure psia Metro politan Bitum. Coal Fuel Oils % by Volume Partial Pres- % by sure Vol- ume psia Partial Partial Pres- %bv Pressure Vol- sure ume ------------- psia psia Natural Gas % by Vol- ume Partial Pressure -- psia ANALYSIS REQUIRED- MACROSCOPIC lv] BACTERIOLOGICAL |V| MICROSCOPIC ORGANIC CONTENT Oxygen.......... Carbon Dioxide.. Sulphur Dioxide. 21 3.143 21 3.143 0.03 0.004 0.06 0.009 None None 0.003 0.004 2 15 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 PROBLEM- MACROSCOPIC EXAMINATION-- 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. Heavy brown flocculant material settles rapidly in clear water. pH--7.3 Odor--woody, mouldy. r carbon dioxide. In rare instances, hydrogen sulphide, sulphur dioxide, or ammonia are present. In most steam condensing equipment,1'8 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, or even exceed for short periods, the amount entrained by the steam. MICROSCOPIC EXAMINATION-- Inorganic Material--small amount white crystals. Amorphous Material--small amount--brown. Iron Bacteria--profuse growth of crenothrix--(Photo usually included). 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 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 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 psia. The most common deleterious gases entrained bv steam are oxygen and Fig. 1. DIVIDE VALUES OBTAINED DIRECTLY FROM THE GRAPH BY NUMBERS FOLLOWING THE CHEMICAL SYMBOLS 40 SO 00 70 60 90 IOO HO 120 130 (40 (50 160 170 TEMPERATURE - FAHRENHEIT DEGREES Solubility of Gases at Partial Pressure of 1 Psi