Dej dej uas txawv ntawm qhov tshiab mus rau me ntsis ntsev nrog cov tides tsim ib qho kev xaiv cov khoom sib tw rau lub tshav kub exchanger. Nws tsis huv txaus rau 316L los xaiv qhov muag tsis pom kev, tsis muaj kev txhoj puab txaus kom tau txais kev thov siab siab lossis titanium. Kev xaiv ntawm 316L thiab duplex yuav tsum tau ua los ntawm kev txheeb xyuas cov ntaub ntawv ntawm cov dej tsis zoo. To taub cov316L vs duplex stainless hlau brackish dejKev txiav txim siab yuav tsum tau soj ntsuam cov tshuaj chloride concentration, kub, dej ntws, thiab cov kev pheej hmoo ntawm stagnation thiab under-posit corrosion.
Cov kev hloov pauv tseem ceeb hauv Brackish Water Service
Cov dej hauv cov dej khib nyiab yog txhais los ntawm cov tshuaj chloride uas siab dua cov dej tshiab (feem ntau> 100 ppm) tab sis qis dua cov dej hiav txwv muaj zog (≈ 19,000 ppm). Chloride concentration tuaj yeem hloov pauv ntau nrog cov dej ntws, dej nag, thiab kev hloov pauv raws caij nyoog. Lub raj xa hluav taws xob hauv qhov kev pabcuam no tuaj yeem pom 200 ppm thaum lub caij ntub thiab 3,000 ppm thaum lub caij ntuj qhuav-tsav tidal surge. Qhov siab tshaj plaws chloride concentration, tsis yog qhov nruab nrab, dictates cov khoom haum.
Peb qhov hloov pauv ntxiv yog qhov tseem ceeb:
Hlau kub- Corrosion tus nqi thiab pitting kev pheej hmoo nce exponentially nrog kub. Lub raj phab ntsa kub yog feem ntau siab dua qhov kub ntawm cov kua dej vim yog cua sov hloov mus rau sab nraud ntawm lub exchanger.
Flow ceev- Cov dej ntws los tiv thaiv kev tsim ntawm cov ciam teb ruaj khov thiab tshem tawm cov khib nyiab. Tsawg tshaj tawm lossis lub sijhawm tsis txaus (piv txwv li, thaum lub sijhawm kaw) ua rau muaj kev cuam tshuam loj heev thiab kev tawm tsam tsis txaus.
Muaj cov deposits- Biofouling, silt, los yog nplai tsim crevices thiab cov cheeb tsam nyob ruaj khov nyob rau hauv qhov chaw uas cov tshuaj chloride tuaj yeem tsom mus deb tshaj qhov ntau. Txawm tias ib yam khoom uas tiv taus ntau pitting tuaj yeem ua tsis tau raws li qhov tso nyiaj.
Kev txwv ntawm 316L hauv dej Brackish
Hom 316L stainless hlau (UNS S31603) yog dav siv hauv cov dej tshiab thiab me me ntsev. Nws pitting kuj sib npaug tus lej (PREN=%Cr + 3.3×%Mo + 16×%N) yog kwv yees li 24–26, muab los ntawm 16–18% Cr, 2–3% Mo, thiab tsis tshua muaj nitrogen. Hauv cov dej huv, ntws ntawm qhov kub qis dua 30 degree, 316L raj tuaj yeem tiv taus cov tshuaj chloride txog li 1000 ppm yam tsis muaj pitting tseem ceeb. Qhov no suav nrog ntau qhov xwm txheej ntawm cov dej khov dej uas cov dej txias thiab zoo-oxygenated.
Txawm li cas los xij, thaum ib qho ntawm cov xwm txheej hauv qab no tshwm sim, 316L yuav ua rau muaj kev pheej hmoo ntxiv:
Qhov kub thiab txias tshaj 30-35 degrees- Pitting tej zaum poob sharply. Ntawm 50 degree, qhov kev txwv chloride muaj kev nyab xeeb tuaj yeem poob rau 200-300 ppm.
Stagnation lossis low flow (<1 m/s)- Cov zaj duab xis passive tsis khaws cia, thiab pitting pib ntawm qhov chaw tsis muaj zog.
Chlorides siab tshaj 500 ppm ua ke nrog qhov kub thiab txias- Localized corrosion accelerates.
Muaj hydrogen sulfide los yog tsis tshua muaj oxygen- Txo cov xwm txheej tuaj yeem rhuav tshem cov yeeb yaj kiab passive.
Yog tias cov dej khib nyiab muaj qee zaus chloride spikes siab dua 1000 ppm lossis ua haujlwm ntawm qhov kub siab tshaj 30℃rau ncua sij hawm ntev, 316L cov raj yuav zoo li hauv ob peb xyoos. Kev nyuaj siab corrosion cracking (SCC) tsis tshua muaj nyob rau hauv cov pa oxygenated brackish dej tab sis tuaj yeem tshwm sim yog tias cov tshuaj chlorides tshaj 1000 ppm thiab cov hlau kub tshaj 60 degree.
Kev txwv kev ua haujlwm ntawm Duplex 2205 hauv dej Brackish
Duplex 2205 (UNS S32205) muaj PREN ntau dua lossis sib npaug ntawm 35, muab los ntawm 22% Cr, 3% Mo, thiab 0.15% N. Nws cov pitting kuj nyob rau hauv ib puag ncig chloride yog ntau dua 316L. Nyob rau hauv dej ntws, aerated tej yam kev mob ntawm kub txog li 50 degree, duplex yuav xyuam xim lis chloride theem ntawm ob peb txhiab ppm -zoo tshaj li ib txwm brackish maxima (feem ntau 3,000–5,000 ppm). Txawm nyob rau ntawm 60-80 degree, duplex resists pitting thiab SCC ntawm cov tshuaj chloride uas yuav rhuav tshem 316L hauv hnub.
Duplex kuj muaj ob qhov zoo ntawm cov qauv:
Siab zog(yield zog ≈ 450 MPa vs . 170 MPa rau 316L) tso cai rau cov phab ntsa nyias nyias, txo qhov hnyav thiab thermal kuj.
Zoo heev SCC kuj- Duplex yog qhov zoo tiv thaiv cov tshuaj chloride kev nyuaj siab corrosion tawg ntawm qhov kub thiab txias (txog 80-100 degree).
Tsuas yog kev ceeb toom rau duplex nyob rau hauv dej brackish yog under-posit corrosion. Yog tias cov av xuab zeb los yog biofilms sib sau rau ntawm lub raj, cov kab mob tuaj yeem txhim kho. Txawm li cas los xij, ntau dua chromium thiab molybdenum cov ntsiab lus ntawm duplex muab kev tiv thaiv ntau dua rau kev tawm tsam crevice dua 316L.
Kev Xaiv Logic: Ib Qhov Kev Sib Tham-by-Case
Qhov kev xaiv ntawm 316L thiab duplex yuav tsum yog raws li qhov phem tshaj qhov sib xyaw ua ke ntawm cov tshuaj chloride concentration thiab hlau kub, nrog rau cov kev cia siab ntawm kev khiav dej num thiab kaw zaus.
Favor 316L Thaum:
Qhov siab tshaj plaws chloride concentration tsis tu ncua hauv qab 500-1000 ppm.
Hlau kub tseem qis dua 30 degree.
Kev khiav ceev yog khaws cia siab tshaj 1.5 m / s, tsis muaj lub sij hawm ntev stagnation.
Cov dej tau zoo-oxygenated thiab tsis muaj cov av hnyav lossis biofouling.
Kev kho tshuaj (piv txwv li, intermittent chlorination lossis scale inhibitor) yog siv los tswj cov nyiaj tso cia.
Lub exchanger yog siv tau rau kev soj ntsuam thiab hloov nyob rau hauv ib tug 5-10 xyoo lub sij hawm.
Favor Duplex 2205 Thaum:
Chlorides tshaj 500 ppm txhua lub sijhawm, tshwj xeeb tshaj yog tias qhov kub siab tshaj 30 degree.
Cov dej kub siab tshaj 30℃rau ntau tshaj li ob peb teev hauv ib hnub.
Tus neeg pauv hloov pauv yuav muaj kev ntxhov siab thaum lub sijhawm kaw lossis hnub so.
Cov dej muaj cov av xuab zeb, cov khoom siv lom neeg, lossis cov txheej txheem sib kis uas tuaj yeem tsim cov deposits.
Lub neej ua haujlwm ntev dua (15-25 xyoos) yuav tsum tsis muaj kev hloov raj.
Qhov hnyav los yog qhov chaw txwv, thiab lub zog siab dua ntawm duplex tuaj yeem txo cov raj phab ntsa tuab thiab sib pauv loj.
Yog tias cov dej qab ntsev me ntsis, thiab cov txheej txheem sov so, duplex pib zoo nkauj heev. Ib txoj cai yooj yim ntawm tus ntiv tes xoo: rau cov dej khib nyiab nrog chlorides> 500 ppm thiab kub> 30 degree, duplex yog qhov kev xaiv zoo dua.
Lub luag haujlwm ntawm Kev Kho Tshuaj thiab Kev Tshaj Tawm
Txawm tias muaj cov khoom siv alloy, kev ua haujlwm tuaj yeem hloov kho kom ntev cov khoom siv. Rau 316L hauv marginal brackish kev pabcuam, cov kev ntsuas hauv qab no pab:
Ua kom ceev ceev ntawm 2-3 m / s- Qhov no tiv thaiv sedimentation thiab ua kom cov yeeb yaj kiab tsis huv.
Siv cov tshuaj chlorination qis tsis tu ncua (0.1–0.3 ppm dawb residual)- Ib qho me me ntawm oxidising biocide yeej pab tswj cov zaj duab xis passive los ntawm kev ua kom muaj peev xwm oxidizing. Txawm li cas los xij, over-chlorination tuaj yeem ua rau pitting.
Tsis txhob ncua sijhawm kaw- Yog hais tias lub exchanger yuav tsum nyob twj ywm, nws yuav tsum tau drained, yaug nrog dej tshiab, thiab qhuav. Tsis tas li ntawd, qhov qis-flow recirculation tuaj yeem ua kom cov dej txav mus.
Nruab sab-kwj pom kev- Tshem tawm cov khib nyiab tshem tawm txo qhov kev pheej hmoo ntawm kev tso nyiaj qis qis.
Rau duplex nyob rau hauv nruab nrab aggressive brackish dej, cov kev ceev faj tsis tshua tseem ceeb tab sis tseem muaj txiaj ntsig. Duplex tuaj yeem ua rau lub qhov rais dav dav, tab sis kev coj ua zoo tshaj nws lub neej.
Kev txiav txim siab txog nqi lub neej
Tus nqi pib dua ntawm duplex (feem ntau yog 1.3-1.5 × ntawm 316L rau cov khoom siv raw khoom) yuav tsum tau ntsuas qhov kev ntseeg tau ntev. Kev txheeb xyuas tus nqi ntawm lub neej yuav tsum muaj xws li:
Cia siab tias lub neej- 316L tuaj yeem xav tau kev hloov pauv tom qab 5-10 xyoo hauv kev pabcuam ciam teb brackish; duplex yuav kav 20-25 xyoo.
Cov nqi qis- Hloov cov raj lossis tag nrho cov khoom sib pauv yuav tsum muaj kev cog qoob loo, uas tuaj yeem kim heev hauv cov txheej txheem txuas ntxiv.
Thinner phab ntsa rau duplex- Vim tias duplex muaj kev ntxhov siab ntau dua, cov phab ntsa ntawm lub raj tuaj yeem yog 0.7-0.9 hli es tsis txhob 1.0-1.2 hli rau 316L, txo qhov hnyav thiab qee zaum tso lub plhaub me me.
Kev tshuaj xyuas thiab kev saib xyuas- Duplex yuav tsum tsis tshua muaj kev tshuaj xyuas thiab tu.
Hauv ntau qhov xwm txheej, duplex muaj tus nqi qis dua ntawm cov tswv cuab hauv 20 xyoo, txawm tias tus nqi pib pib siab dua.
Kev txiav txim siab tshwj xeeb: Cov xwm txheej ruaj khov thaum lub sijhawm kaw
Ib qho ntawm cov kev ua tsis tau zoo tshaj plaws hauv cov khoom siv hluav taws xob hauv dej tsis zoo tshwm sim tsis yog thaum lub sijhawm ua haujlwm, tab sis thaum kaw. Thaum cov dej tso tseg tsis tu ncua thiab sov, cov tshuaj chlorides concentrated nyob rau hauv cov deposits, thiab cov pa oxygen poob qis . 316L yog qhov cuam tshuam rau crevice corrosion nyob rau hauv cov xwm txheej zoo li no. Duplex, nrog nws cov PREN siab dua, yog kev zam txim ntau dua. Yog tias cov nroj tsuag yuav muaj kev cuam tshuam ntau zaus lossis ncua sij hawm kaw (xws li, kev ua haujlwm raws caij nyoog, cov txheej txheem batch), duplex tau pom zoo txawm tias qhov kev ua haujlwm ib txwm muaj chlorides tsawg.
Kev txiav txim siab Matrix
| Qhov xwm txheej | 316L | TIAB SA 2205 |
|---|---|---|
| Chlorides<300 ppm, T<30°C, good flow | Pom zoo | Tshaj qhia |
| Chlorides 300-500 ppm, T<30°C, good flow | Txais tau nrog tshuaj kho mob | Kev xaiv nyab xeeb rau lub neej ntev |
| Chlorides 500-1000 ppm, T<30°C, good flow | Marginal - kev pheej hmoo ntawm pitting tom qab xyoo | Pom zoo |
| Chlorides >500 ppm, T>30 degree, txhua qhov ntws | Tsis pom zoo | Pom zoo |
| Txhua yam tshuaj chlorides, lub sijhawm tsis khov | Tsis pom zoo | Pom zoo |
| Chlorides >1000 ppm, qhov kub thiab txias | Ua tsis tau | Pom zoo (txog ~ 5000 ppm) |
Xaus
Qhov kev xaiv ntawm 316L thiab duplex rau dej brackish yog qhov kev txiav txim siab engineering uas them rov qab rau kev ntseeg tau ntau xyoo. Kev xaiv cov khoom siv yuav tsum yog raws li qhov xwm txheej phem tshaj plaws, tsis yog qhov qub.316L vs duplex stainless hlau brackish dejKev txiav txim siab pob khawm ntawm cov tshuaj chloride concentration, kub, thiab ntws tswj. Yog tias cov tshuaj chlorides tshaj li ntawm 500 ppm thiab kub siab tshaj 30 degree, duplex 2205 yog qhov xav tau kom tsis txhob pitting thiab crevice corrosion. 316L tuaj yeem txaus nrog kev tsim qauv tsim, tshuaj kho mob, thiab tsuas yog qee zaus brackish spikes -tab sis tsuas yog thaum dej txias thiab ntws. Rau cov nroj tsuag uas muaj nuj nqis rau lub neej ua haujlwm ntev thiab xav kom zam kev kaw tsis tau npaj tseg, duplex muab cov txiaj ntsig zoo, kev daws teeb meem. Kev xaiv cov khoom siv yog hais txog kev ua tau zoo ntawm cov npoo ntawm lub hnab ntawv ua haujlwm, thiab hauv cov dej khov, cov npoo feem ntau xav tau duplex.
