Yuav ua li cas lub Crevice Geometry (Gasket Material thiab Clamp Torque) cuam tshuam rau lub sij hawm pib ntawm Crevice Corrosion ntawm Titanium Cua Kub Tubes hauv Cov Dej Ntsig Evaporation?

Cov dej ntsev evaporation rau kev tsim cov tshuaj sodium chloride, potassium chloride thiab lwm cov ntsev los ntawm cov brine yog ua haujlwm ntawm qhov kub ntawm 40-}60℃thiab chloride concentrations los ntawm saturation (li 26% NaCl) rau supersaturation nrog nag lossis daus ntawm ntsev. Titanium cua sov raj yog siv los tswj cov evaporation kub thiab tiv thaiv crystallization ntawm tshav kub hloov chaw. Qhov tseem ceeb tsis ua hauj lwm hom, txawm li cas los xij, yog crevice corrosion ntawm lub raj - rau-tubesheet pob qij txha, hauv qab gaskets, thiab hauv qab clamps. Tsis zoo li ntau cov teeb meem titanium corrosion uas yog ib qho kev ua haujlwm feem ntau ntawm alloy chemistry los yog phab ntsa tuab, lub sij hawm crevice corrosion pib nyob rau hauv ntsev evaporation kev pab cuam cuam tshuam los ntawm cov neeg kho tshuab tsim tsis xws li crevice geometry (qhov dav dav thiab qhov tob) thiab cov khoom siv gasket thiab clamp torque. Daim ntawv no ntsuas cov txiaj ntsig ntawm cov kev hloov pauv no rau lub sijhawm rau qhov pib crevice thiab muab cov tswv yim tsim qauv rau kev txuas lub neej ntawm lub rhaub dej hauv cov dej ntsev.

Mechanism ntawm crevice corrosion nyob rau hauv saturated chloride brine.
Saturated los yog ze saturated sodium chloride brine ntawm 50℃yog nruj heev vim chloride concentration (kwv yees 5.4 M Cl-) thiab siab ionic zog nyob rau hauv cov tshuaj ntau. Tab sis titanium yog passive nyob rau hauv tej brine, raws li tsis muaj pH qis txuam nrog cov ntsiab lus chloride siab. Cov xwm txheej tseem ceeb rau crevice corrosion yog oxygen tshaib plab hauv crevice. Lub anodic dissolution ntawm titanium tsim Ti4+ uas hydrolyzes rau daim H+. Yog li ntawd, pH hauv qhov crevice txo mus rau 2-3 thaum oxygen depleted. Rau saturated chloride brine, qhov txo qis hauv pH ua rau muaj qhov xwm txheej uas titanium tsis tuaj yeem rov ua dua thiab crevice corrosion propagates sai.

Lub sij hawm pib, piv txwv li, lub sij hawm ua ntej qhov kev tawm tsam tsis sib haum xeeb pib, muaj feem xyuam rau cov pa oxygen depletion thiab tus nqi ntawm pH poob qis dua qhov pib rov ua dua. Ob leeg yog tswj los ntawm geometry ntawm lub crevice, permeability ntawm cov khoom gasket rau oxygen thiab kev sib cuag siab ntawm gasket thiab titanium nto.

Cov teebmeem ntawm Crevice Gap Width
Ntawm qhov tsis muaj geometric, qhov tseem ceeb tshaj plaws yog qhov dav ntawm qhov sib txawv ntawm lub titanium raj thiab qhov sib txawv ntawm qhov chaw (tube ntawv, gasket lossis clamp). Rau ib qho kev sib txawv dav tus nqi ntawm diffusion ntawm oxygen mus rau hauv lub crevice yog proportional rau lub voos xwmfab ntawm qhov sib txawv (Fick txoj cai rau ib tug nqaim channel). Cov khoob khoob loj tso cai rau cov pa oxygen ntxiv, uas ua rau qeeb qeeb thiab ncua sij hawm pib. me me qhov khoob ua rau muaj oxygen ntau dua.

Kev tswj xyuas ntawm titanium Qib 2 cov qauv nrog cov khoom siv dag zog ntawm kev tswj qhov dav dav, nyob rau hauv saturated NaCl ntawm 50 degree, pH 7.0, tau qhia cov sijhawm pib hauv qab no (lub sijhawm pom kev tawm tsam hauv qab 10x magnification):

Ntawm qhov sib txawv ntawm 0.05 hli (zoo ib yam ntawm lub qhov dej -Torqued PTFE gasket tiv thaiv lub tshuab flange), oxygen depletion tshwm sim nyob rau hauv 24-48 teev thiab crevice nres pib hauv 50-100 teev. Ntawm qhov sib txawv dav 0.10 hli pib tshwm sim ntawm 200-300 teev. Ntawm qhov sib txawv ntawm 0.25 hli, pib txuas mus rau 500 txog 1000 h. Oxygen diffusion tso cai rau kev ua kom tsis muaj zog thiab yog li tsis muaj kev tawm tsam ntawm qhov sib txawv ntawm 0.50 hli tom qab 5,000 teev. Ntawm qhov sib txawv ntawm ntau tshaj 1.0 mm lub geometry tsis yog ib qho crevice tab sis ib qho qhib qhov sib txawv. Tsis muaj kev tawm tsam tshwm sim.

Hauv kev xyaum, qhov no txhais tau hais tias qhov nruj nruj heev (tsawg dua 0.1 hli) yog qhov txaus ntshai tshaj plaws. Cov neeg tsim qauv yuav tsum ua kom lub qhov khoob dav dua 0.5 hli (thick gaskets lossis standoffs) lossis tshem tawm qhov khoob (welded pob qij txha).

Cov teebmeem ntawm Crevice Depth
Qhov luaj li cas ntawm qhov crevice (qhov kev ncua deb ntawm qhov sib txawv nkag mus rau hauv lub gasket los yog mus rau hauv cov ntawv raj) txiav txim siab cov pa oxygen-depleted nto muaj rau anodic dissolution. Txoj kev pib yog nrawm dua rau qhov sib sib zog nqus vim tias lawv muaj cov pa oxygen loj dua - thaj chaw depleted thiab ntev diffusion txoj hauv kev rau qhov dav dav.

Rau qhov muab qhov dav dav ntawm 0.1 hli, lub sij hawm pib yog txo los ntawm 300 teev mus rau 100 teev raws li qhov tob tob ntawm 5 hli mus rau 20 hli. Ntawm 50 mm qhov tob, pib tshwm sim ntawm 40-50 teev. Tsis txhob fissure qhov tob tshaj 15 hli rau kev pabcuam ntsev evaporator. Tube-rau-tubesheet junctions yuav tsum tau tsim kom muaj qhov tob tob (tsawg dua 10 hli) los yog yuav tsum tau welded thoob plaws kom tshem tawm qhov crevice.

Permeability ntawm Gasket Material
Gasket cov ntaub ntawv sib txawv nyob rau hauv lawv permeability rau oxygen thiab nyob rau hauv lawv muaj peev xwm nqus brine, ob qho tib si uas cuam tshuam rau crevice chemistry. non- ntxeem tau, tsis yog -pas dej permeable (PTFE, PEEK, hlau) muab lub foob kaw ntom ntom thiab tsis txhob tso cov pa tawm ntawm lub gasket nws tus kheej, yog li ua kom cov pa oxygen depletion nyob rau hauv qhov crevice. Cov roj hmab muag muag, EPDM, silicone (porous, permeable gaskets): Qee cov pa oxygen tuaj yeem cuam tshuam los ntawm lub cev gasket los hloov qhov crevice thiab retard pib.

Cov ntaub ntawv sib txawv gasket raug kuaj (qhov sib txawv 0.1 hli, qhov tob 10 hli, saturated NaCl ntawm 50 degree) thiab cov txiaj ntsig yog:

PTFE gasket (impermeable) - pib ntawm 200-300 teev. EPDM roj hmab (moderate permeability): pib ntawm 400-600 teev. Silicone roj hmab (siab permeability) 800 mus rau 1,200 teev pib. Tsis muaj gasket (hlau-rau-hlau sib cuag, zoo xoom qhov sib txawv, ntxeem tau interface) Pib ntawm siab tshaj 2000 teev nrog kev tawm tsam me ntsis.

Kev lag luam tawm -tawm yog tias cov gaskets permeable yuav nqus brine thiab o, uas tuaj yeem hloov pauv qhov sib txawv geometry dhau sijhawm. Silicone thiab EPDM tawg rau lub sijhawm ntev (2-5 xyoos) hauv cov brine kub thiab yuav tsum tau hloov.

Clamping Torque thiab tiv tauj siab
Lub siab exerted ntawm lub gasket thiab titanium interface yog ib tug muaj nuj nqi ntawm lub torque siv los zawm lub clamp. Ntau lub zog txhais tau tias cov ntsaws ruaj ruaj uas txhais tau hais tias qhov sib txawv zoo tau txo qis thiab qis dua oxygen yog diffused. Lub zog qis dua (nyob rau hauv cov kev txwv kev sib khi) ua rau muaj qhov sib txawv me ntsis zoo dua, yog li kev pib qeeb qeeb.

Kev ntsuam xyuas lub PTFE gasket ntawm 50 mm inch raj flange nrog saturated NaCl ntawm 50℃muab:

Torque 20 N·m (tsawg) Qhov sib txawv zoo 0.15-0.20 mm Pib 400-600 teev. Torque 40 Nm (tus qauv) Qhov sib txawv zoo 0.08-0.12 hli Pib 200-300 teev Torque 60 N·m (siab): zoo sib txawv 0.04-0.07 hli, pib 50-100 teev.

Txoj hauv kev zoo tshaj plaws rau kev pabcuam ntsev evaporator yog siv qhov tsawg tshaj plaws ntawm torque uas yuav muab lub foob, feem ntau yog 50 mus rau 60 feem pua ​​​​ntawm cov lus pom zoo tshaj plaws rau cov khoom siv gasket. Cov txheej txheem no nce qhov sib txawv zoo yam tsis muaj qhov to.

Crevice tsim daim ntawv thov matrix rau ntsev evaporators
Tsim Parameter nyiam tus nqi rau Extended Life Mechanism Cia siab tias lub sij hawm rau crevice pib (saturated NaCl, 50 degree)
Gap width >0.5 mm (or welded)Oxygen diffusion sustained >5,000 teev (tsis muaj kev tawm tsam)
Qhov dav dav (yog<0.5 mm unavoidable) 0.20-0.30 mmReduces oxygen depletion 500-1000 hrs
Crevice qhov tob<10 mm Anode area limited 300-500 hours
Gasket khoom EPDM los yog silicone (permeable) Gasket oxygen diffusion400 mus rau 1,200 teev.
Clamp torque Min. sealing torque (50-60% ntawm max) Ua kom muaj txiaj ntsig zoo sib txawv 2-3 zaug ntev dua siab zog
Joint tube-tubesheetWelds (tag nrho nkag) Tsis muaj crevice assault (tsuas yog pitting) Tshem tawm qhov crevice
Tswv yim qhia txog ntsev evaporator rhaub
Hauv cov pas dej ntsev evaporation, qhov zoo tshaj plaws tsim rau titanium cua sov raj yog tsim qhov twg tag nrho cov fissures raug tshem tawm los ntawm tag nrho - nkag welded raj- mus rau - tubesheet couplings. Qhov twg yuav tsum tau muaj kev sib txuas, siv lub perforated lossis ribbed gasket los tiv thaiv kev sib cais, thiab qhia qhov sib txawv ntawm 0.20 txog 0.30 mm. Siv EPDM lossis silicone gaskets (nyob rau 60℃brine) es tsis txhob PTFE kom zoo dua nws cov pa permeability. Siv qhov tsawg kawg nkaus clamp torque uas yuav tiv thaiv kom tsis txhob tawg raws li kev txiav txim los ntawm kev sim npuas. Tsim flanges nrog ntiav recesses kom txwv qhov tob tob rau 10 mm lossis tsawg dua. Cov kev xaiv tsim no ua rau lub sijhawm pib crevice los ntawm 200-300 teev (tus qauv PTFE gasket, siab torque) mus rau 2,000-5,000 teev ua ntej yuav tsum tau kuaj xyuas, lossis 3-6 lub hlis ntawm kev ua haujlwm tas mus li. Teem caij tshuaj ntsuam xyuas lub tshuab cua sov txhua xyoo thiab ntxuav txhua qhov kev tawm tsam ntawm kev sib tsoo los ntawm lub teeb polishing rau 24/7 ntsev pas dej ua haujlwm. Rau cov ntawv thov nrog lub sijhawm txij nkawm 5 xyoos, cov pob qij txha welded yog qhov tsim nyog, txawm tias qhov geometry yog qhov zoo.