Pasinei nekupokana kwemararamiro epombi dzesimbi isina tsvina, pombi dzesimbi dzisina simbi dzakaiswa munzvimbo dzemugungwa dziri pasi pemhando dzakasiyana dzekuora mukati mehupenyu hwavo hwesevhisi hunotarisirwa.Kuora uku kunogona kutungamirira kumhepo inopotera, kurasikirwa kwechigadzirwa uye njodzi dzinogona kuitika.Offshore platform varidzi nevashandisi vanogona kuderedza njodzi yekuora nekutsanangura yakasimba pombi zvinhu zvinopa zvirinani kuomarara.Mushure mezvo, ivo vanofanirwa kuramba vakasvinura kana vachiongorora mitsara yejekiseni yemakemikari, hydraulic uye impulse mitsara, uye gadzira chiridzwa uye chiridzwa kuti vaone kuti corrosion haityisidzire kuvimbika kwepombi yakaiswa kana kukanganisa kuchengetedza.
Kuora kwenzvimbo kunogona kuwanikwa pamapuratifomu mazhinji, ngarava, ngarava uye mapaipi ekumahombekombe.Kuora uku kunogona kuva muchimiro chegomba kana kukoromoka kwegomba, chero ipi zvayo inogona kukanganisa mudhuri wepombi uye kuita kuti mvura iburitswe.
Ngozi yekuora inowedzera sezvo tembiricha yekushandisa yekushandisa inowedzera.Kupisa kunogona kukurumidzira kushatisa kwechubhu inodzivirira yekunze passive oxide firimu, nekudaro ichisimudzira gomba.
Nehurombo, gomba renzvimbo uye kukoromoka kwakaoma kuona, zvichiita kuti zviome kuziva, kufanotaura, uye kugadzira marudzi aya ekuora.Tichifunga nezvenjodzi idzi, varidzi vepuratifomu, vashandisi uye vagadziri vanofanirwa kungwarira pakusarudza yakanakisa pombi zvinhu zvekushandisa kwavo.Kusarudzwa kwezvinhu ndiwo mutsara wavo wekutanga wekudzivirira kubva mukuora, saka kuigadzirisa kwakakosha.Sezvineiwo, ivo vanogona kusarudza yakapusa asi yakanyatso shanda chiyero chenzvimbo yekudzivirira ngura, iyo Pitting Resistance Equivalent Number (PREN).Iyo yakakwirira kukosha kwePREN kwesimbi, kunowedzera kupikisa kwayo kune corrosion yemunharaunda.
Ichi chinyorwa chinotarisa maitiro ekuziva gomba uye crevice corrosion, pamwe nekuita optimize tubing zvinhu kusarudzwa kweiyo offshore mafuta uye gasi mashandisirwo zvichienderana neiyo PREN kukosha kwezvinhu.
Localized corrosion inoitika munzvimbo diki kana ichienzaniswa neyakakura ngura, iyo yakawanda yunifomu pamusoro pesimbi.Gomba nekukoromoka kunotanga kuumba pa316 stainless steel tubing apo yekunze chromium-rich passive oxide film yesimbi inoputsika nekuda kwekusangana nezvinwiwa zvinoparadza, kusanganisira mvura yemunyu.Nzvimbo dzemugungwa dzakapfuma mukloridhi, pamwe nekupisa kwakanyanya uye kunyangwe kusvibiswa kwenzvimbo yechubhu, inowedzera mukana wekuparara kweiyi firimu rekufambisa.
pitting Pitting corrosion inoitika apo passivation firimu pane chikamu chepombi inoputsika, ichigadzira makomba madiki kana makomba pamusoro pepombi.Makomba akadaro anogona kukura sezvo electrochemical reactions inoenderera mberi, semugumisiro wekuti iron iri musimbi inonyungudutswa mumhinduro pazasi pegomba.Simbi yakanyungudika inozopararira kumusoro kwegomba uye oxidize kuita iron oxide kana ngura.Sezvo gomba richidzika, maitiro e electrochemical anowedzera, ngura inowedzera, izvo zvinogona kutungamira mukuboborwa kwemadziro epombi uye kutungamirira mukudonha.
Machubhu anonyanya kukanganiswa negomba kana nzvimbo yavo yekunze yakasvibiswa (Mufananidzo 1).Semuyenzaniso, zvinosvibisa kubva muwelding uye kugaya mashandiro anogona kukuvadza passivation oxide layer yepombi, nekudaro kuumba uye nekukasira pitting.Zvimwe chetezvo zvinoenda nekungobata nekusvibiswa kwepombi.Pamusoro pezvo, sezvo madonhwe emunyu anoputika, makristasi emunyu akanyorova anoumba pamapombi anodzivirira oxide layer uye anogona kutungamirira kugomba.Kuti udzivise kusvibiswa kwemhando idzi, chengeta pombi dzako dzakachena nekudzikwesha nemvura yakachena nguva nenguva.
Mufananidzo 1. 316/316L pombi yesimbi isina tsvina yakasvibiswa neasidhi, saline, uye mamwe madhipoziti inobatwa zvakanyanya negomba.
crevice corrosion.Muzviitiko zvakawanda, pitting inogona kuonekwa nyore nyore nemushandisi.Nekudaro, kukoromoka kwemukova hakusi nyore kuona uye kunoisa njodzi huru kune vanoshanda nevashandi.Izvi zvinowanzoitika pamapombi ane mikaha yakatetepa pakati pezvinhu zvakatenderedza, senge pombi dzakabatwa munzvimbo ine zvisungo kana pombi dzakanyatsonamirwa pedyo neimwe.Kana iyo brine ichipinda mumukaha, nekufamba kwenguva, mushonga wemakemikari acidified ferric chloride solution (FeCl3) inoumbwa munzvimbo ino, izvo zvinoita kuti kukoromoka kuwedzere kukurumidza (Fig. 2).Sezvo mutswe pachawo uchiwedzera njodzi yekuora, kukoromoka kunogona kuitika patembiricha yakadzikira zvakanyanya pane gomba.
Mufananidzo 2 - Crevice corrosion inogona kukura pakati pepombi uye pombi inotsigira (kumusoro) uye kana pombi yakaiswa pedyo nedzimwe nzvimbo (pasi) nekuda kwekugadzirwa kwemakemikari ane hukasha acidified solution yeferric chloride mumukaha.
Kuora kweCrevice kunowanzo kutevedzera kupinza kwegomba kutanga mumukana wakaumbwa pakati pechikamu chepombi uye pombi inotsigira collar.Zvisinei, nekuda kwekuwedzera kwehuwandu hweFe ++ mumvura mukati mekuputsika, funnel yekutanga inova yakakura uye yakakura kusvikira yavhara kuputsika kwese.Pakupedzisira, kuparara kwegomba kunogona kukonzera kupera kwepombi.
Kutsemuka kwakaoma kunomiririra njodzi huru yekuora.Naizvozvo, zvisungiso zvepombi dzinotenderedza chikamu chikuru chedenderedzwa repombi dzinowanzova nenjodzi pane dzakavhurika dzinosungirira, izvo zvinoderedza kusangana kwenzvimbo pakati pepombi nechirambi.Masevhisi matekiniki anogona kubatsira kudzikisira mukana wekukuvadzwa kwecorrosion kana kutadza nekugara achivhura mabhampa uye nekutarisa nzvimbo yepombi kuti iora.
Pitting uye crevice corrosion inogona kudzivirirwa nekusarudza iyo chaiyo simbi alloy yekushandisa.Madiresi anofanirwa kuita hunyanzvi pakusarudza iyo yakakwana pombi zvinhu kuderedza njodzi yekuora zvichienderana nemamiriro ekuita, maitiro ekuita, uye zvimwe zvinosiyana.
Kubatsira vanofananidzira kukwidziridza kusarudzwa kwezvinhu, vanogona kuenzanisa iyo PREN kukosha kwesimbi kuti vaone kuramba kwavo mukuora kwenzvimbo.PREN inogona kuverengerwa kubva kumakemikari alloy, kusanganisira ayo chromium (Cr), molybdenum (Mo), uye nitrogen (N) zvirimo, sezvinotevera:
PREN inowedzera nehuwandu hwezvinhu zvinodzivirira kuora kwechromium, molybdenum uye nitrogen mune alloy.Chiyero che PREN chakavakirwa pane yakakosha pitting tembiricha (CPT) - yakaderera tembiricha panoitika gomba - kune akasiyana simbi isina tsvina zvichienderana nemakemikari anoumbwa.Chaizvoizvo, PREN inoenderana neCPT.Naizvozvo, yakakwirira PREN kukosha inoratidza yakakwira pitting kuramba.Kuwedzera kuduku muPREN kunongoenzana nekuwedzera kuduku kweCPT kana ichienzaniswa nealloy, asi kuwedzera kukuru kwePREN kunoratidza kuwedzera kukuru kwekushanda pane CPT yakakwirira zvikuru.
Tafura 1 inofananidza kukosha kwePREN kune akasiyana alloys anowanzo shandiswa muindasitiri yemafuta uye gasi.Inoratidza kuti kutsanangurwa kunogona sei kunatsiridza corrosion kuramba nekusarudza yepamusoro mhando pombi alloy.PREN inowedzera zvishoma kubva pa316 SS kusvika pa317 SS.Super Austenitic 6 Mo SS kana Super Duplex 2507 SS yakanakira kuwedzera kukuru kwekuita.
Yakakwira nickel (Ni) kutariswa musimbi isina tsvina inowedzerawo kusaita ngura.Nekudaro, iyo nickel yemukati yesimbi isina tsvina haisi chikamu chePREN equation.Chero zvazvingava, zvinowanzobatsira kusarudza simbi dzisina tsvina dzine nickel yepamusoro, sezvo chinhu ichi chinobatsira kudzorerazve nzvimbo dzinoratidza zviratidzo zvekuora kwenzvimbo.Nickel inodzikamisa austenite uye inodzivirira kuumbwa kwemartensite paunokotama kana kutonhora kudhirowa 1/8 pombi yakaoma.Martensite chikamu chisingadikanwi checrystalline mumasimbi chinodzikisira kuramba kwesimbi isina tsvina kusvika pakuora kwenzvimbo pamwe nekutsemuka kwekloridi-induced stress.Iyo yakakwira nickel yeinenge 12% mu316/316L simbi inodiwa zvakare kune yakanyanya kudzvanywa hydrogen gasi kushandiswa.Iyo shoma nickel concentration inodiwa paASTM 316/316L simbi isina tsvina i10%.
Localized corrosion inogona kuitika chero kupi zvako pamapombi anoshandiswa munzvimbo dzemugungwa.Zvisinei, gomba rinonyanya kuitika munzvimbo dzinenge dzatosvibiswa, nepo kuparara kwemukova kunowanzoitika munzvimbo dzine mikaha yakamanikana pakati pepombi nemidziyo yekuisa.Uchishandisa PREN sehwaro, iyo inofananidzira inogona kusarudza yakanakisa pombi alloy kudzikisa njodzi yechero mhando yekuora kwenzvimbo.
Zvisinei, ramba uchifunga kuti kune zvimwe zvakasiyana-siyana zvinogona kukanganisa njodzi yekuora.Semuyenzaniso, tembiricha inokanganisa kumira kwesimbi isina tsvina pagomba.Kumamiriro ekunze anopisa emugungwa, super austenitic 6 molybdenum simbi kana super duplex 2507 pombi dzesimbi isina tsvina dzinofanirwa kutariswa zvakanyanya sezvo zvinhu izvi zvine kupikisa kwakanakisa kuvhuvhu uye kuputika kwechloride.Kumamiriro ekunze anotonhorera, pombi ye316/316L inogona kukwana, kunyanya kana paine nhoroondo yekushandiswa kwakabudirira.
Offshore platform varidzi nevashandisi vanogonawo kutora matanho ekudzikisa njodzi yekuora mushure mekunge tubing yaiswa.Vanofanira kuchengeta pombi dzakachena uye dzichigara dzichigezwa nemvura yakachena kuderedza njodzi yekupinza.Vanofanirwa zvakare kuve nevashandi vekuchengetedza vakavhura mapombi mapombi panguva yekuongorora nguva nenguva kuti vatarise kana crevice corrosion.
Nekutevera nhanho dziri pamusoro, varidzi vepuratifomu nevashandisi vanogona kuderedza njodzi yekuora kwepombi uye kudonha kwakabatana munzvimbo yegungwa, kuvandudza kuchengetedzwa uye kushanda zvakanaka, uye kuderedza mukana wekurasikirwa kwechigadzirwa kana kuburitswa kwemhepo.
Brad Bollinger is the Oil and Gas Marketing Manager for Swagelok. He can be contacted at bradley.bollinger@swagelok.com.
The Journal of Petroleum Technology ndiyo inotungamira magazini yeSosaiti yePetroleum Injiniya, ine zvipfupiso zvine chiremera uye zvinyorwa pamusoro pekufambira mberi kwe tekinoroji yepamusoro, nyaya dzeindasitiri yemafuta negasi, uye nhau nezve SPE nenhengo dzayo.