Document RpKGjYQxe6kXo9QJb8j3Vyr5B

3 Woorf l",coo"" handling con,ton||, rwdroted - , llhn Ifom concnuotcd milt Ihoi o., 1,1, b,,hlnd Recirculating - Water Systems Lcngaller Soturollon Index lets you predict whether *i J9^*ur C00lln0 *o" ho* cry corrosive or scaling tendencies Prlnclpol elements of o typical open reci'Cukitlng system ore shown obove Need Expert Treatment Supervision . /-complexity, and the:room for the score ^vVfTtreatmsnt methods now common. .^jjiiieslly, however, you can reduce a4 /..vision to a tale rate by control of For industry'* needs, cooling-water supplies hove had to come dissolved solids alone. But ac^^iusliy you need a thorough knowledge from much-uged streams, falling-water tables. Then, when re r; ief'TWJr circultling-waier analysis end 'f^lUjbebarior in the recirculating system. circulated again ond again, it's prone to scale, foster algae, become corrosive. Here's some practical help on the problem .^Ptjlectirig any metal (rara corrosion by ^^wsterdepends on conditioning the sup- correct lu corrosive charucteris- Scale formation And corrosion rep* resent the two chief problems In cool ing-water operations. Scale, by itself, comet readily under control with proper water treatment. But its presence com* plicales the corrosion problem. And with today's heavy use o( cooling-pur pose water, emphasis U on corrosion control in these low-temperature piping systems. The old oncMhrough cooling system, still prevalent in small plants, just pushes the water through Its cooling ' 1H*!6* ?f cresting end maintaining a phyai* _!`V--fatu-.Kt'dtia*m-. lbe-.t.w...e..e...n .thle----a--n---o--d1i,c. and c_a..luh* fly SHEPPARD T POWCU, Chemical f^iWer |.;I.V^c,ptrt of metal surface and water. L;'Xfy?ProNttlvs Coaling. H,,uow, uduo yrou *gvo ^is protection? Oneway duties and the/i dumps it to waste. It's e system that bos the twin merits of low equipment cost and only the slightest scale and corrosion headaches. But so much water ii needed lor the job it does that operating costs become prohibitive. As a direct result, water recirculating systems, like the one in Fig. 7, serve most of industry's wants. The open system of water recircula tion. Fig. 7, employs spray ponds or coaling towen to release the heat picked up by the circulating water. These prays or cooling towers sacrifice a pshjjj .WJV?vT,ut r' a protective coating using of the water by evaporation to the atmf^ 4 or inorganic materials, or both. phere to effect the cooling action. Mi rou may lay down a deposit as a doing this, though, they make an ac^*?fW)i lutPJoduct of cathodic or anodic corrosion problem ol corrosion by 0) buUdict,j[| .^rJujcsctibns, or as a precipitate from the up the concentrations of the scale-fo*-; ' f:4Wi?n 4rca*- In any case, the de- ing solids in the water left behind (1)... '^'*iPflW;Hould he nonporoui ond continu- introducing the corrosive agents of 0*1*3!; '.^'.^TUi.if'it is io give complete protection. gen end carbon dioxide. Add to t^\fl lre,lm6m can guard against the possibility that micro-orgatduw5 .j^,e*Jtoiion provided some slept, like may be present in the water to influefl"fj} pf^facrstiwi, are taken to remove any the choice of corrective water ireaimeot^ [><** that form. For intance, a thin, and .yu begin m appreciate the hperviou, adherent deposit of calriu;- carbonate scale can l>e laid down by regulating and adjusting pH, alkalinity and calcium tons. This scale is a good general Inhibitor against corrosion. It covers both anodic and cathodic areas. There are a few natural waters, such as those of the Great Lakes, that meet the requirements lor laying down a proper calcium carbonate scale. Most waters need treatment to bring about the desired state of equilibrium for the ealcium carbonote in solution. Fortu nately, Professor W P l^angelicr1 pio neered in developing the idea of a colculated saturation Index as a means of predicting the corrosive or scaling effeet of a natural water. His iden has been so 6<lrtnc&) that in ute i widely uccepted. Because most natural water carries dissolved calejum and magnesium in the form of bicarbonate and noncatbo^ note hardness (chlorides and sulfates mainly) thara is a tendency for that water when heated or made more alka line to deposit a scale nr corrosively H.xnnlltf, W f, "Tb* Anal/ttc ("imlrol of AAnmite-CnotiarrotiVkintUrVtTV*Wrth Ait*, sat Wifi flMA). attack (he metal. But there are also sodium satis, dissolved carbon dioxide, oxygen and other gases In the water. Just which way the water goes--that is, to (ay down a protective scale or attack the metal--depends on how this dis solved material balances out. If the various forms of carbon dioxide (free C0S, bicarbonate and earbenate) are at equilibrium, they cause neither scale'nor corrosion. The surest way ol judging the state of the water, corrosive or not, and the steps thst will correct it, is to determine the solubility equilib rium relations of calcium carbonate. The Langelier Saturation Index chart. Fig. 5, (s a Convenient way of doing this. lanpoliar chart makes use of logarith mic expressions of calcium hardness, methyl orange alkalinity and a factor for temperature and total solids. (Tem perature accelerates corrosion or scaledeposit formation, whichever way the water lends to go.) ]{ you know (he value of calcium hardness, alkalinity and tola) solids, you pick off the chart the information to figure out the aoturalion pH (pNt) and the saturation Index. (Continued on pope 6ft). ENGINEERING AMO MANAGEMENT SECTION l powtfyj ENGINEERING AND MANAGEMENT SECTION