Naphezu kokumelana nokugqwala okungokwemvelo kwamapayipi ensimbi engagqwali, amapayipi ensimbi engagqwali afakwe ezindaweni zasolwandle angaphansi kwezinhlobo ezahlukene zokugqwala ngesikhathi sokuphila kwawo okulindelekile.Lokhu kugqwala kungaholela ekukhiqizweni okungekho emthethweni, ukulahlekelwa komkhiqizo kanye nezingozi ezingase zibe khona.Abanikazi bepulatifomu yasogwini kanye nabaqhubi banganciphisa ingozi yokugqwala ngokucacisa izinto eziqinile zamapayipi ezinikeza ukumelana namakhemikhali, i-corrosion ye-corrosion ehlinzeka kangcono. imigqa ye-aulic ne-impulse, futhi icubungule izinsimbi nezisetshenziswa zokuzwa ukuze kuqinisekiswe ukuthi ukugqwala akusongeli ubuqotho bamapayipi afakiwe kanye nokuphepha engozini.
Ukugqwala kwendawo kungatholakala ezinkundleni eziningi, emikhunjini, emikhunjini, kanye namapayipi ezindaweni ezifakwe ngasogwini lolwandle.Lokhu kugqwala kungaba ngendlela yokugqwala kwemigodi noma ukugqwala, okungaguguleka udonga lwamapayipi futhi kubangele ukuphuma koketshezi.
Ingozi yokugqwala inkulu uma izinga lokushisa lokusebenza likhuphuka.Ukushisa kungasheshisa ukubhujiswa kwefilimu ye-oxide yangaphandle eyisivikelo ye-tube, ngaleyo ndlela kukhuthaze ukwakheka kokugqwala kwe-pitting.
Ngeshwa, ukugqwala kwendawo kanye nokugqwala kungase kube nzima ukukubona, okwenza lezi zinhlobo zokugqwala kube nzima kakhulu ukuzibona, ukubikezela kanye nokuklama kwazo. Uma kubhekwa lezi zingozi, abanikazi benkundla, o-opharetha nabakhethiwe kufanele baqaphele lapho bekhetha okokusebenza kwamapayipi okungcono kakhulu okuzosetshenziswa. i-sistance Equivalent Number (PREN).Uma liphakama inani le-PREN lensimbi, liphakama ukumelana nokugqwala kwendawo.
Lesi sihloko sizobuyekeza indlela yokubona ukugqwala kwe-pitting kanye ne-crevice kanye nendlela yokuthuthukisa ukukhethwa kwezinto zamashubhu ku-offshore oil ne-gas applications ngokusekelwe kunani le-PREN yezinto ezibonakalayo.
Ukugqwala okusendaweni kwenzeka ezindaweni ezincane uma kuqhathaniswa nokugqwala okuvamile, okufana kakhulu endaweni yensimbi. Ukugqwala kwemigodi nokuqhekeka kuqala ukwakheka emapayipini ensimbi engagqwali angu-316 lapho ifilimu yensimbi ecebile ye-chromium ye-passive oxide igqabuka ngenxa yokuchayeka oketshezini olubolayo, okuhlanganisa namanzi anosawoti. i-bing surface, yandise amathuba okucekelwa phansi kwale filimu ye-passivation.
I-pitting.Ukugqwala kwe-pitting kwenzeka lapho ifilimu yokudlula kubude bepayipi ibhujiswa, yenza imigodi emincane noma imigodi ebusweni bepayipi.Imigodi enjalo ingase ikhule njengoba ukusabela kwe-electrochemical kwenzeka, okubangela ukuba insimbi esensimbi incibilike ibe yikhambi elingaphansi komgodi.Insimbi encibilikisiwe izobe isisakazekela phezulu komgodi ukuze ifake i-iron oxidis ejulile futhi yenze i-electrochemical reaction. i-celerate, ukugqwala kuyaqina, futhi kungaholela ekubhobozeni udonga lwamapayipi futhi kuholele ekuvuzeni.
I-Tubing isengozini enkulu yokugqwala kwemigodi lapho ingaphandle layo lingcolile (Umfanekiso 1). Isibonelo, ukungcoliswa okuvela emisebenzini yokushisela nokugaya kungalimaza ungqimba lwe-oxide edlulayo yepayipi, ngaleyo ndlela kwakhe futhi kusheshise ukugqwala kwe-pitting. Okufanayo kuya nangokubhekana nokungcoliswa okuvela kumapayipi. Ngaphezu kwalokho, ukwakheka kwe-crystal doncelet kumapayipi kasawoti afanayo nosawoti ophuma kusawoti. ukuvikela ungqimba lwe-oxide futhi kungaholela ekugqwaleni kwe-pitting. Ukuze uvimbele lezi zinhlobo zokungcola, gcina amapayipi akho ehlanzekile ngokuwageza njalo ngamanzi ahlanzekile.
Umfanekiso 1 – 316/316L wepayipi lensimbi engagqwali elingcoliswe i-asidi, amanzi ahlanzekile nezinye izinto ezifakwayo kulula kakhulu ukugqwala.
I-crevice corrosion.Ezimweni eziningi, ukubola kungabonakala kalula ngumsebenzisi. Nokho, ukugqwala kwe-crevice akulula ukukubona futhi kubangela ingozi enkulu kubaqhubi nabasebenzi. Ngokuvamile kwenzeka kumapayipi anezikhala eziqinile phakathi kwezinto ezizungezile, njengamapayipi abanjwe endaweni eneziqeshana noma amapayipi afakwe ngokuqinile eceleni. endaweni ngokuhamba kwesikhathi futhi kubangela ukugqwala kwemifantu kusheshise (Umfanekiso 2).Ngenxa yokuthi imifantu ngokwayo yandisa ingozi yokugqwala, ukugqwala kwemifantu kungenzeka emazingeni okushisa aphansi kakhulu kunokugqwala kwemigodi.
Umfanekiso wesi-2 – Ukugqwala kungase kuthuthuke phakathi kwepayipi nesixhaso sepayipi (phezulu) nalapho ipayipi lifakwe eduze kwezinye izindawo (ngezansi) ngenxa yokwakheka kwesisombululo se-acidified ferric chloride esinamakhemikhali emfantwini.
Ukugqwala kwe-Crevice ngokuvamile kulingisa ukugqwala komgodi kuqala emfantwini owakheke phakathi kobude bepayipi nesiqeshana sokusekela ipayipi.Nokho, ngenxa yokukhula kokugxila kwe-Fe++ oketshezini olungaphakathi kokuphuka, i-crater yokuqala iba nkulu futhi ibe nkulu ize ivale yonke indawo.
Ukuqhekeka okuqinile kuyingozi enkulu kakhulu yokugqwala. Ngakho-ke, izinsimbi zamapayipi ezisonga ingxenye enkulu yesiyingi sepayipi zivame ukuveza ubungozi obukhulu kunezinsimbi ezivulekile, ezinciphisa indawo yokuthintana phakathi kwepayipi ne-clamp. Ochwepheshe bezokulungisa bangasiza ekunciphiseni amathuba okugqwala okudala umonakalo noma ukwehluleka ngokuvula njalo izinsimbi kanye nokuhlola ukugqwala kwendawo.
Ukugqwala kwemigodi nokuqhekeka kungavinjelwa kangcono ngokukhetha ingxubevange yensimbi efanele yohlelo lokusebenza.Izicacisi kufanele zicophelele ukuze zikhethe okokusebenza kwamapayipi okuphelele ukuze kuncishiswe ubungozi bokugqwala ngokusekelwe endaweni yokusebenza, izimo zenqubo nokunye okuhlukile.
Ukuze usize izicacisi zithuthukise ukukhethwa kwezinto, zingaqhathanisa amanani ensimbi e-PREN ukuze zinqume ukumelana kwazo nokugqwala kwendawo.PREN ingabalwa kusukela ekwakhekeni kwamakhemikhali engxubevange, okuhlanganisa nokuqukethwe kwayo kwe-chromium (Cr), i-molybdenum (Mo), ne-nitrogen (N), ngendlela elandelayo:
I-PREN ikhuphuka ngokuqukethwe kwezakhi ezimelana nokugqwala i-chromium, i-molybdenum ne-nitrogen ku-alloy.Ubudlelwano be-PREN busekelwe kumazinga okushisa abalulekile (CPT) - izinga lokushisa eliphansi kakhulu lapho ukugqwala kwe-pitting kubonwa khona - kuma-stainless steels ahlukahlukene ngokuphathelene nokwakheka kwamakhemikhali.Okubalulekile, ukufaneleka kwe-PREN ukukhuphuka kwenani eliphakeme, i-PREN iphakamisa inani eliphakeme. ku-PREN ilingana kuphela nokunyuka okuncane kwe-CPT uma kuqhathaniswa ne-alloy, kanti ukwanda okukhulu kwe-PREN kubonisa ukuthuthukiswa okuphawulekayo ekusebenzeni ku-CPT ephakeme kakhulu.
Ithebula 1 liqhathanisa amanani e-PREN ama-alloys ahlukahlukene avame ukusetshenziswa ekusetshenzisweni kukawoyela negesi angasogwini. Libonisa ukuthi ukucaciswa kungathuthukisa kanjani ukumelana nokugqwala ngokukhetha ingxubevange yamapayipi ebanga eliphakeme.PREN inyuka kancane kuphela lapho isuka ku-316 iye ku-317 insimbi engagqwali.Ngokwenyuka kokusebenza okubalulekile, i-6 Moinless stain7 insimbi eyi-super austenitic eyi-2 ekahle isetshenziswa insimbi engagqwali engu-6 Moinless 7 noma insimbi engagqwali engu-2.
Ukugxila okuphezulu kwe-nickel (Ni) kunsimbi engagqwali nakho kuthuthukisa ukumelana nokugqwala.Nokho, okuqukethwe kwe-nickel yensimbi engagqwali akuyona ingxenye yezibalo ze-PREN.Kunoma ikuphi, kuvame ukuzuzisa ukucacisa izinsimbi ezingenasici ezinokugxilisa kwe-nickel okuphezulu, njengoba le nto isiza ukudlula kabusha izindawo ezibonisa izimpawu zokugqwala kwendawo lapho kugqwala ukugqwala noma ukwakheka okubandayo kwe-marte kuvimbela ukugqwala. 8 ipayipi eliqinile.I-Martensite iyisigaba sekristalu esingafunwa ezinsimbi esinciphisa ukumelana kwensimbi engagqwali ekugqwaleni kwendawo kanye nokuqhekeka kokucindezeleka okubangelwa i-chloride.Okuqukethwe kwe-nickel okuphezulu okungenani okungu-12% ku-316/316L kuyafiseleka ekusetshenzisweni okubandakanya i-high pressure gaseous corrosion indinganiso ye-nickel TM3 edingekayo i-stadium ethize ye-AS3LTM3 ethize ethize ye-nickel61insimbi ethize ye-nickel61. 10%.
Ukugqwala kwendawo kungenzeka noma kuphi emapayipini asetshenziswa ezindaweni zasolwandle.Kodwa-ke, ukugqwala kwemigodi kungenzeka kakhulu ezindaweni esezingcolile kakade, kuyilapho ukugqwala kwemigodi kungenzeka kakhulu ezindaweni ezinezikhala ezincane phakathi kwepayipi ne-hardware ekhuphukayo. Ngokusebenzisa i-PREN njengesisekelo, isicacisi singakhetha ingxubevange yamapayipi engcono kakhulu ukuze kuncishiswe noma iyiphi ingcuphe yohlobo oluthile lwensimbi yendawo.
Kodwa-ke, khumbula ukuthi kunezinye izinto eziguquguqukayo ezingathinta ingozi yokugqwala.Isibonelo, izinga lokushisa lithinta ukumelana komgodi wensimbi engagqwali.Ezimweni zezulu ezishisayo zasolwandle, i-6 molybdenum super austenitic noma ipayipi lensimbi engagqwali engu-2507 super duplex kufanele ibhekwe ngokujulile ngoba lezi zinto zinokumelana okuhle kakhulu nokugqwala kwendawo kanye nomlando we-chloride 16 okwanele, umlando okwanele wepayipi le-chloride 16 kungase kube ukuqhekeka kwe-3 L. ukusetshenziswa ngempumelelo sekusunguliwe.
Abanikazi benkundla yasogwini kanye nabaqhubi bangakwazi futhi ukuthatha izinyathelo zokunciphisa ingozi yokugqwala ngemva kokufakwa kweshubhu.Kufanele bagcine amapayipi ehlanzekile futhi eshaywa ngamanzi ahlanzekile njalo ukuze kuncishiswe ingozi yokugqwala kwemigodi.Kufanele futhi babe nochwepheshe bezokulungisa bavule izinsimbi zokubopha amashubhu ngesikhathi sokuhlolwa okujwayelekile ukuze babheke ukuthi kukhona ukugqwala komgodi.
Ngokulandela izinyathelo ezishiwo ngenhla, abanikazi benkundla nabaqhubi banganciphisa ingozi yokugqwala kwamashubhu nokuvuza okuhlobene ezindaweni zasolwandle, bathuthukise ukuphepha nokusebenza kahle, kuyilapho benciphisa ithuba lokulahleka komkhiqizo noma ukukhishwa kwezisi ezibalekile.
Brad Bollinger is the Oil and Gas Marketing Manager for Swagelok Company.He can be reached at bradley.bollinger@swagelok.com.
I-Journal of Petroleum Technology ingumagazini ohamba phambili we-Society of Petroleum Engineers, ehlinzeka ngamafuphi nezici ezigunyaziwe mayelana nenqubekelaphambili yobuchwepheshe bokuhlola nokukhiqiza, izindaba zemboni kawoyela negesi, kanye nezindaba mayelana ne-SPE namalungu ayo.