Document V3O4JEpZywrQNNp3mg7e8GQk4

CHAPTER 43'. 1953 Guide !fir J . '39C0 }.:c3 4 gs =s6 Si. 13 BS (2-s ; S' ~ . a~ 3 &<3 8 -S3 H .Eg J*oj a'a .223o=^O. H0=E2 "Sjs H50S-r_0t, ' TT i,.i i 11 iir,,,i..,.`.,i..".T...'.i.......' I'NTItl w ;.. w e : wn-- no nwmqoo oa omoe oooo on coowoo o oo oo oo oo -- - wniq oo I& wo. 1 8 "3 6 s5 fc> s a a. 22 8 g 8. =3 |.s|j H Kg'goSgus< - 3' OH t |3?5 Z< 'a a `3 'H fc" O <! 8 m ^T 9" a > Hi <3~ i ..SO ! *3 a < Ba'-j 22 O I < 3 i 2 l i J" oowj- O O . 9 O I..III.Milt..,t J , *3 r. o-- w- tov *im> rqon nononoOo wo OOO h o. n- - 2w 2 to 2w f. O <M____ l"ITn 11 lMlll,Mi- ' | 11 M '111'I'I'111,"||1,1_l | ' | <| 2 = 8 8 S 8 2 8 | 88 88 8. J j i 111) 11 ' i S*! 8* i r i ( r, I | IT I I |'l II J pVI I J I o &S 2 3 1" 3JS.1 ill' 'S'.* O S .2 PS " 1 . Pb ":2S. -Ss3f 3 Ko SJ-8J- o O2 s* a 5 9 Heu *< ij os O a I T3 gs 36 II O *O3 *8 8 J5 *3 n 6 <o g we aQo a8 .21 CJP eO si ll- 'Corrosion and Water Formed Deposits,' Causes and Prevention 937 While chlorine is the most generally used chemical,-the use of others may. occasionally prove to be more practicable. Choice of the chemical is conditioned largely by the design and operation of the system. Open Recirculating Systems In spray ponds and cooling towers of the open type, light-loving algae growths are likely to cause blocking of the distribution piping and troughs. These organisms are most" troublesome in areas accessible to sunlight. Algae slimes are usually stringy in character. In open recirculating systems, continuous use of small quantities of chlorine is generally most satisfactory. In once-through systems, where large quantities of water are used, intermittent treatment a few times.each day - will usually result in satisfactory slime removal and chemical economies. .. : Neither the phenols nor copper sulphate may be used for the removal of slime already formed;. For this purpose, chlorine gas is used. After being cleaned, the other chemicals may be used to prevent the reestablish- Table 6. Common Chemicals Used fob Slime Control Chemical Tbade Name Phybical State* Chlorine Hypochlorites Chlorinated Phenols Sodium-- Potassium Permanganate Copper Sulphate Chlorine Calcium Hypochlorites Sodium Hypochlorites Chlorophenylphenate Tetrachlorophenate Pentachlorophenate Permanganate of Potash Blue Vitriol Gas Crystalline Briquettes Briquettes Briquettes Crystalline . Crystalline * As Shipped. ment of slime in the system. The removal of green algae from a cooling tower should never be used as an indication that the true slime-forming organisms on heat exchanger surfaces have been removed.. The more resistant slime formers, which so materially reduce heat transfer efficiency, will often be unaffected by treatment which completely eliminates algae. Closed Once-Through Systems In equipment where light is excluded, slime formations are due to fungi. Usually, they predominate on the heat exchange surfaces. Bacteria form thick, soft slime. Yeast and molds form tough rubbery slimes, Chlorine and hypochlorite solutions, fed intermittently, are used to prevent such slimes. UNDER-WATER CORROSION When deleterious substances are present in water, the corrosivity of the solution is increased in proportion to the amount of deleterious substances present, the temperature, and usually the rate of flow of the solutiomover the metal surfaces. There are other relevant factors, but their influence in general is subordinate to those mentioned. Dissolved oxygen, acid