Ntawm Qhov Kev Sib Txuas Tshwj Xeeb ntawm Chloride Concentration thiab Sheath Surface Temperature Puas Yog 1.6 millimeter 316 Stainless Steel Sheath Hloov los ntawm Passive mus rau Active Pitting Corrosion hauv Atmospheric Storage Tank Heating Service?

Rau cov txheej txheem engineers lub luag hauj lwm rau hluav taws xob immersion heaters nyob rau hauv atmospheric cia tso tsheb hlau luam uas muaj cov kev daws teeb meem uas muaj chloride bearing, xws li tsim cov dej, desalter effluents, thiab industrial ntxuav dej, qhov sib txawv ntawm passive thiab nquag pitting corrosion yog qhov txawv ntawm ib tug 316 stainless hlau sheath uas kav kaum xyoo los yog kaum lub lis piam. Tab sis qhov xwm txheej nyob rau hauv cov huab cua cia tso tsheb hlau luam yog zoo li qub los yog qeeb txav nrog ntau yam chloride concentrations vim evaporation thiab stratification whereas tshiab tov yog tas li nyob rau hauv kov nrog lub sheath nyob rau hauv tas li ntawd flow systems. Cov phab ntsa tuab yog 1.6 hli. Nws yog ib qho kev sib haum xeeb ntawm cov neeg kho tshuab lub zog thiab cov tswv yim hloov hluav taws xob. Qhov tseem ceeb pitting kub thiab qhov tseem ceeb chloride concentration rau 316 tsis yog tus lej zoo li qub, tab sis cuam tshuam nrog qhov kub siab ntawm lub plhaub saum npoo vim yog siv watt ntom. Daim ntawv no nthuav tawm cov tshuaj chloride concentration thiab sheath qhov kub thiab txias ntawm 1.6 hli phab ntsa hloov ntawm passive (corrosion npaum li cas.<0.05 mm/year) to active pitting (penetration within months).

Qhov ntsuas kub tseem ceeb thiab kev sib cuam tshuam nrog chloride
Qhov tseem ceeb pitting kub ntawm 316 stainless hlau nyob rau hauv ib tug muab tshuaj chloride concentration yog qhov kub ntawm qhov chaw ruaj khov muaj peev xwm nucleate thiab loj hlob. Hauv qab no qhov kub thiab txias zaj duab xis passive tseem nyob twj ywm thiab tus nqi corrosion tsis tseem ceeb. Nws yog inverse kev sib raug zoo. Qhov siab dua cov chloride concentration, qhov qis dua qhov tseem ceeb pitting kub. Qhov tseem ceeb pitting kub yog nyob ib ncig ntawm 80oC hauv 100 ppm chloride. Hauv 1,000 ppm chloride nws txo qis rau 55 degree. Ntawm 5,000 ppm chloride nws poob rau 35 C. Ntawm 10,000 ppm chloride (1% NaCl), qhov tseem ceeb pitting kub yog li 25 degree. Lub tshav kub flux los ntawm immersion heaters ua rau lub sheath saum npoo kub yog 15-40℃saum toj no lub tank kub. Qhov ntsuas kub ntawm lub tank ntawm 40℃nrog rau 8 W / cm² rhaub yuav yog 60-70 degree. Yog hais tias cov tshuaj chloride concentration nyob rau hauv lub tank yog 1,000 ppm, qhov tseem ceeb pitting kub ntawm 55℃yog tshaj thiab pib ntawm pitting yuav tshwm sim nyob rau hauv lub lis piam. Lub sij hawm rau perforation ib zaug pitting pib yog tswj hwm los ntawm phab ntsa thickness ntawm 1.6 hli, uas ntawm ib txwm propagation tus nqi ntawm 0.5-2.0 hli ib hlis txhais tau tias tsis ua hauj lwm nyob rau hauv 1-3 lub hlis.

1.6 millimeter Sheath Critical Transition Thresholds
Kev ntsuam xyuas immersion nrog 316 cov qauv nrog cov yam ntxwv ntawm qhov sib txawv ntawm cov khoom siv hluav taws xob swaged tau tsim cov kev hloov pauv hauv qab no rau phab ntsa 1.6 hli ntawm watt ntom ntawm 6-10 W / cm2. Qhov ntsuas kub ntawm lub tank yuav tsum yog 10-20℃hauv qab qhov kub ntawm qhov sheath nto.

Chloride Concentration (ppm) Critical Pitting Temperature for 316 (degree) Yam tsawg kawg nkaus Sheath Surface Temperature for Passive-to-Active Transition Safe Bulk Tank Temperature for 1.6 mm Sheath at 8 W/cm2Above expect service life Transition
< 100 ppm < 80°C 80°C < 65°C 5-10 years 100 - 500 ppm 65 - 80°C 65 - 80°C < 50 - 65°C 2-5 years 500 - 1,000 ppm 55 - 65°C 55 - 65°C < 40 - 50°C 1-2 years 1,000 - 2,000 ppm 45 - 55°C 45 - 55°C < 30 - 40°C 6-12 months 2,000 - 5,000 ppm 35 - 45°C 35 - 45°C < 20 - 30°C 3-6 months 5,000 - 10,000 ppm 25 - 35°C 25 - 35°C < 10 - 20°C 1-3 months
>10,000 ppm< 25 °CBelow 25 degrees CNot safe regardless of temperature Weeks to months
Rau lub tank ntim nrog qhov kub ntawm 50 deg C thiab 1.6 hli sheath ntawm 8 W / cm 2 lub sheath nto kub yog nyob ib ncig ntawm 65-70 deg C. Cov chloride concentration yuav tsum tsawg tshaj li 500 ppm kom nyob twj ywm saum toj no qhov tseem ceeb pitting kub. Active pitting yuav pib nyob rau hauv lub lis piam ntawm qhov tseem ceeb ntawm 55℃nrog chloride theem ntawm 1,000 ppm thiab saum npoo kub. Yog tias cov ntsiab lus chloride hauv lub tank ntau dua 2,000 ppm, 316 tsis tsim nyog ntawm qhov ntsuas kub ntawm cov khoom siv, vim tias qhov kub thiab txias ntawm lub plhaub yuav tsum tau tsim txawm tias cov cua sov me me yuav dhau qhov kub tseem ceeb rau pitting.

1.6 hli Jacket Safe Operating Envelope Matrix
Cov lus hauv qab no teev qhov siab tshaj plaws kev nyab xeeb bulk tank kub rau 1.6 hli 316 sheath ntawm ntau yam watt ntom thiab chloride concentrations. Cov txiaj ntsig no ua kom ntseeg tau tias qhov kub ntawm cov ntaub npog qhov chaw yog tsawg kawg 5℃hauv qab qhov kub ntawm qhov tseem ceeb rau qhov chloride concentration.

Chloride Concentration (ppm) SHEATH SurfACE TEMPERATURE SHEATH NTAWM TEMPERATURE SHEATH NTAWV TEMPERATURE (5 W/cm2) (8 W/cm2) Maximum Safe Maximum Safe Maximum Safe Bulk Temperature 12W/cm²
Hauv qab 100 ppm 75℃65℃60℃50℃100 - 250 ppm 70℃60℃55℃45℃250 - 500 ppm 65℃55℃50℃40℃500 - 750 ppm 505℃500℃1,000 ppm 55℃45℃40℃30℃1,000 - 1,500 ppm 50℃40℃35℃25℃1,500 - 2,000 ppm 45℃35℃30℃20 degree
2000ppm Tsis muaj kev nyab xeeb Tsis nyab xeeb Tsis nyab xeeb Tsis ruaj ntseg
Yog hais tias qhov ntsuas kub ntawm lub plhaub saum npoo yog siab dua qhov tseem ceeb pitting kub rau cov ntsiab lus chloride qhia, ces pitting tsis ua hauj lwm yog tsis muaj kev zam rau txhua daim ntawv thov. Lub 1.6 hli phab ntsa tuab muab qee lub sijhawm nthuav tawm, txawm li cas los xij lub tshuab rhaub yuav tsum pom tias muaj kev ua haujlwm ntev, kwv yees lub neej ua haujlwm hauv lub hlis ntau dua li xyoo.

Tsim Kev Hloov Kom Tsis txhob Pitting Hloov
Nyob ze ntawm tus ciam teb ntawm passive mus rau kev hloov pauv ntawm cov txheej txheem, peb qhov kev hloov kho ntawm tus qauv tsim tuaj yeem siv los ua kom tsis txhob muaj pitting yam tsis hloov cov ntaub ntawv sheath lossis phab ntsa thickness. Thawj yog kom txo wattage ceev. Thaum qhov kub ntawm qhov kub ntawm qhov kub ntawm 15-25 degrees ntawm 5 W / cm² es tsis txhob ntawm 10 W / cm², lub active tsoom fwv yuav hloov mus rau passive tsoom fwv. Qhov kev hloov thib ob yog txhawm rau txhawb txoj kev ncig thoob plaws tag nrho saum npoo ntawm lub plhaub. Lub twj tso kua mis me me lossis cov twj tso kua mis tuaj yeem txo qhov kub ntawm qhov kub ntawm qhov kub ntawm 40-60%, ua kom lub hauv siab qis dua qhov tseem ceeb txawm tias nyob rau nruab nrab watt ntom ntom. Qhov kev hloov pauv tom ntej no yog txhawm rau txhawm rau saib xyuas kev tiv thaiv corrosion, me me 316 daim coupon hluav taws xob txuas nrog rau lub tshuab cua sov. Ib qho kev nce ntxiv hauv galvanic tam sim no qhia txog qhov pib ntawm kev ua haujlwm pitting thiab muab lus ceeb toom ntxov ntawm kev nkag mus rau hauv cov ntaub. Yog hais tias cov tshuaj chloride concentration nyob rau hauv lub tank sib txawv vim evaporation los yog batch hloov, engineers yuav tsum tau qhia 316L nrog ib tug ntau dua pitting kuj sib npaug tus naj npawb thiab xav txog kev kho dua tshiab rau 317 stainless hlau (3.5% molybdenum) los yog Alloy 825 rau txhim khu kev qha kev pab mus sij hawm ntev. Tus nqi nce ntxiv ntawm cov hlau tsis muaj zog yog feem ntau tsawg dua tus nqi ntawm ib qho kev ua tsis tiav hauv ib lub tank cia, nrog rau cov khoom sib kis, tso dej tawm thiab hloov lub rhaub. • Thaum qhia cov cua sov rau cov tshuaj chloride nqa lub tank, ib txwm ntsuas qhov tseeb chloride concentration ntawm qhov ntsuas kub ua haujlwm. Xam cov sheath saum npoo kub ntawm qhov pom zoo watt ceev. Rau lub sij hawm ntev siv nrog 1.6 hli 316 sheath muaj kev nyab xeeb tsis tsawg kawg yog 10℃hauv qab qhov tseem ceeb pitting kub yog qhia.