Nangona uxhathiso lwendalo lwemibhobho yensimbi engenasici, imibhobho yensimbi engenastainless efakwe kwiindawo zaselwandle ifumana iintlobo ezahlukeneyo zomhlwa ngexesha lokuphila kwabo okulindelweyo.Lo mhlwa unokukhokelela ekukhutshweni kwembacu, ilahleko yemveliso kunye nobungozi obunokubakho.Abanikazi beqonga beOffshore kunye nabaqhubi banokunciphisa umngcipheko wokubola ngokuchaza izinto eziluqilima zemibhobho ezibonelela ngokungcono kwi-corrosion yekhemikhali yokumelana ne-corrosion. inaliti, i-hydraulic kunye nemigca ye-impulse, kunye nenkqubo ye-instrumentation kunye nezixhobo zokuva ukuqinisekisa ukuba ukubola akusongeli isidima sombhobho ofakelweyo kunye nokhuseleko olulula.
I-corrosion yendawo inokufumaneka kumaqonga amaninzi, iinqanawa, iinqanawa, kunye nemibhobho kwi-offshore installs.
Umngcipheko we-corrosion mkhulu xa ubushushu bokusebenza besicelo bukhuphuka.Ubushushu bunokukhawuleza ukutshatyalaliswa kwefilimu ye-oxide yangaphandle ekhuselayo ye-tube, ngaloo ndlela ikhuthaza ukubunjwa kwe-corrosion ye-pitting.
Ngelishwa, imingxuma yendawo kunye ne-corrosion yendawo kunokuba nzima ukuyibona, okwenza ezi ntlobo zomhlwa zibe nzima ngakumbi ukuchonga, ukuqikelela kunye noyilo lwalo. Ngenxa yale mingcipheko, abanini beqonga, abaqhubi kunye nabatyunjiweyo kufuneka balumke xa bekhetha imathiriyeli yemibhobho engcono kakhulu yesicelo sabo.Ukukhethwa kwezinto ezibonakalayo ngumgca wabo wokuqala wokuzikhusela kwi-corrosion, ngoko ke ukuyifumana okulungileyo kubalulekile, kodwa banokukhetha ngokufanelekileyo ukusebenzisa i-corrosion yendawo. ukuchasana, i-Pitting Resistance Equivalent Number (PREN) .Iphezulu ixabiso le-PREN lentsimbi, iphakamileyo ukuchasana kwayo kwi-corrosion yendawo.
Eli nqaku liza kuphonononga indlela yokuchonga i-pitting kunye ne-crevice corrosion kunye nendlela yokuphucula ukhetho lwezixhobo ze-tubing kwi-offshore oil kunye ne-gas applications ngokusekelwe kwixabiso le-PREN yezinto.
Umhlwa wendawo wenzeka kwiindawo ezincinci xa kuthelekiswa nomhlwa jikelele, ohambelana ngakumbi kumphezulu wesinyithi.I-Pitting kunye ne-crevice corrosion iqala ukwenza kwimibhobho yentsimbi engatyiwayo engama-316 xa ifilimu yentsimbi yekhromium-etyebileyo yeoksidi yentsimbi igqabhuka ngenxa yokuvezwa kulwelo oludlekayo, kuqukwa nemekobume yetyuwa elwandle kunye nonxweme olunobushushu obuphezulu kunye nonxweme olunxwemeni kunye nolwandle olutyebileyo. ukungcoliseka komphezulu wetyhubhu, kwandisa amandla okuthotywa kwale filimu yokudlula.
pitting.Pitting corrosion kwenzeka xa ifilimu passivation kubude umbhobho kutshatyalaliswa, ukwenza imingxuma encinane okanye imingxuma phezu komhlaba umbhobho.Imingxuma enjalo kusenokwenzeka ukuba zikhule njengoko reactions electrochemical kwenzeka, ebangela intsimbi kwisinyithi ukunyibilika kwisisombululo emazantsi pit.Intsimbi enyibilikisiweyo iya kwandula diffuse ukuya kumphezulu we-tot oxiksidi okanye i-iron oxidi. i-electrochemical reactions ikhawuleza, i-corrosion iqinisa, kwaye inokukhokelela ekubhobhozeni udonga lombhobho kwaye ikhokelela ekuvuzeni.
I-tubing ichaphazeleka ngakumbi kwi-pitting corrosion xa umphezulu wayo wangaphandle ungcolisekile (Umfanekiso 1) .Ngokomzekelo, ukungcoliswa kwe-welding kunye nokusebenza kokusila kungonakalisa i-oxide ye-passivating oxide yombhobho, ngaloo ndlela yenze kwaye ikhawuleze i-corrosion. imibhobho yenza okufanayo ukukhusela umaleko weoksidi kwaye kunokukhokelela kwi-corrosion.
Umzobo 1 - 316 / 316L umbhobho wensimbi engenasici ongcolileyo nge-asidi, i-brine kunye nezinye iidiphozithi zisengozini kakhulu kwi-corrosion.
Kwimeko ezininzi, i-pitting ingachongwa ngokulula ngumqhubi.Nangona kunjalo, i-crevice corrosion ayilula ukuyibhaqa kwaye ibeka umngcipheko omkhulu kubasebenzi kunye nabasebenzi. Ngokuqhelekileyo kwenzeka kwimibhobho enezithuba ezixineneyo phakathi kwezinto ezijikelezileyo, njengemibhobho ebanjwe kwindawo kunye neziqeshana okanye imibhobho efakwe ngokuqinileyo ecaleni. (FeCl3) iifom zesisombululo kummandla ekuhambeni kwexesha kwaye ibangela ukuthotywa kwemingxuma ekhawulezileyo (Umfanekiso 2).
Umzobo we-2 - I-Crevice corrosion ingaphuhliswa phakathi kombhobho kunye nenkxaso yombhobho (phezulu) kwaye xa umbhobho ufakwe kufuphi neminye imiphezulu (ezantsi) ngenxa yokwenziwa kwesisombululo se-acidified ferric chloride eyingozi kwi-crevice.
I-Crevice corrosion idla ngokufanisa i-pitting corrosion kuqala kwi-crevice eyenziwe phakathi kobude bombhobho kunye ne-clip yenkxaso yombhobho.Nangona kunjalo, ngenxa yokunyuka kwe-Fe ++ yoxinaniso kulwelo olungaphakathi kweqhekeza, i-crater yokuqala iba nkulu kwaye ibe nkulu de ivale yonke i-fracture.
Iintanda eziqinileyo zingowona mngcipheko mkhulu wokuthotywa.Ngoko ke, izithinteli zemibhobho ezisonga ubuninzi besangqa sombhobho zikholisa ukubonisa umngcipheko omkhulu kuneeclamps ezivulekileyo, ezinciphisa indawo yokudibanisa phakathi kombhobho kunye ne-clamp.
I-pitting kunye ne-crevice corrosion inokuthintelwa ngokufanelekileyo ngokukhetha i-alloy yensimbi efanelekileyo kwisicelo.Abachazi kufuneka basebenzise inkuthalo ukukhetha eyona imathiriyeli yombhobho ukunciphisa umngcipheko wokuhlwa ngokusekelwe kwimeko yokusebenza, iimeko zenkqubo kunye nezinye izinto eziguquguqukayo.
Ukunceda abacacisi baphucule ukhetho lwezixhobo, banokuthelekisa amaxabiso esinyithi e-PREN ukumisela ukuxhathisa kwabo kwi-corrosion yendawo.PREN ingabalwa kwimichiza ye-alloy, kubandakanywa ne-chromium (Cr), i-molybdenum (Mo), kunye nomxholo we-nitrogen (N), ngolu hlobo lulandelayo:
I-PREN iyanda kunye nomxholo wezinto ezinganyangekiyo kwi-chromium, i-molybdenum kunye ne-nitrogen kwi-alloy.Ubudlelwane be-PREN busekelwe kwiqondo lokushisa elibalulekileyo (CPT) - iqondo lokushisa eliphantsi kakhulu apho i-pitting corrosion ibonwa khona - kwiindidi zensimbi ezingenasici ngokumalunga nokubunjwa kweekhemikhali. Ukuchasana.Ukunyuka okuncinci kwi-PREN kufana kuphela nokunyuka okuncinci kwe-CPT xa kuthelekiswa ne-alloy, kanti ukunyuka okukhulu kwe-PREN kubonisa ukuphuculwa okuphawulekayo kwintsebenzo kwi-CPT ephezulu kakhulu.
Itheyibhile 1 ithelekisa amaxabiso e-PREN ee-alloys ezahlukeneyo ezisetyenziswa ngokuqhelekileyo kwi-oyile ye-offshore kunye ne-gas applications.Ibonisa indlela ukucaciswa kunokuphucula ngokuphawulekayo ukuxhatshazwa kwe-corrosion ngokukhetha i-alloy ye-alloy yombhobho ophezulu.PREN inyuka kuphela xa idlula kwi-316 ukuya kwi-317 insimbi engenasici. isetyenziswe ngokufanelekileyo.
Uxinzelelo oluphezulu lwe-nickel (i-Ni) kwinsimbi engenasici iphinda ikhulise ukumelana nokugqwala.Nangona kunjalo, umxholo we-nickel wensimbi engenasici awuyonxalenye ye-equation ye-PREN.Kuyo nayiphi na imeko, kudla ngokuba luncedo ukucacisa iintsimbi ezingenasici kunye noxinzelelo oluphezulu lwe-nickel, njengoko le nto inceda ukuphinda i-passivate iindawo ezibonisa iimpawu ze-corrobilisten ye-corrobilisten okanye i-marsite ye-corrobilisten okanye i-marsite ye-corrobilisten. umzobo obandayo we-1/8 umbhobho onzima.I-Martensite yinqanaba lekristale elingafunwayo kwiintsimbi ezinciphisa ukuxhathisa kwensimbi engenasici kwi-corrosion yendawo kunye ne-chloride-induced stress cracking.Umxholo we-nickel ophezulu ubuncinane we-12% kwi-316 / 316L nayo iyanqweneleka kwizicelo ezibandakanya uxinzelelo oluphezulu lwe-33L yegesi ye-nickel 31L. insimbi engenasici kwi-ASTM ye-standard specication yi-10%.
I-corrosion yendawo ingenzeka naphi na kwimibhobho esetyenziswa kwiindawo zaselwandle.Nangona kunjalo, ukubola kwemingxuma kunokwenzeka ukuba kwenzeke kwiindawo esele zingcolisekile, ngelixa i-corrosion ye-crevice inokwenzeka ukuba yenzeke kwiindawo ezinezikhewu ezimxinwa phakathi kombhobho kunye ne-hardware ekhwelayo.
Nangona kunjalo, khumbula ukuba kukho ezinye iinguqu ezinokuchaphazela umngcipheko wokugqwala.Ngokomzekelo, ubushushu buchaphazela ukuchasana kwe-pitting yensimbi engenasici.Kwimozulu yaselwandle eshushu, i-6 molybdenum super austenitic okanye i-2507 super duplex ipayipi yensimbi engenasici kufuneka ithathelwe ingqalelo nzulu kuba ezi zixhobo zinokuchasana okugqwesileyo kwi-corrosion yendawo kunye ne-chloride yoxinzelelo lwe-3616 yemozulu epholileyo, i-3L ye-chloride yoxinzelelo lwe-3616 yemozulu epholileyo inokuba yi-3L. ngokwaneleyo, ngakumbi ukuba imbali yokusetyenziswa ngempumelelo iye yasekwa.
Abanini bamaqonga angaphandle konxweme kunye nabasebenzisi nabo banokuthatha amanyathelo okunciphisa umngcipheko wokuhlwa emva kokuba kufakwe iityhubhu. Kufuneka bagcine imibhobho icocekile kwaye igungxulwe ngamanzi amatsha rhoqo ukunciphisa umngcipheko wokurhwalala kwemingxuma.
Ukulandela amanyathelo achazwe ngasentla, abanikazi beqonga kunye nabaqhubi banokunciphisa umngcipheko wokubola kweetyhubhu kunye nokuvuza okuhambelanayo kwiindawo ezihlala elwandle, ukuphucula ukhuseleko kunye nokusebenza kakuhle, ngelixa kunciphisa ithuba lokulahleka kwemveliso okanye ukukhutshwa kokukhutshwa kwe-emissions.
Brad Bollinger is the Oil and Gas Marketing Manager for Swagelok Company.He can be reached at bradley.bollinger@swagelok.com.
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