Ahakoa te ātete ā-roto o ngā paipa kowiri tira, ka pāngia ngā paipa kowiri tira e whakauruhia ana ki ngā taiao moana e ngā momo waikura rerekē i roto i tō rātou roanga e tumanakohia ana. Ka taea e tēnei waikura te arahi ki ngā tukunga rere, te ngaronga o ngā hua me ngā mōrearea pea. Ka taea e ngā kaipupuri me ngā kaiwhakahaere papaaho o tāwāhi te whakaiti i te mōrearea o te waikura mā te tohu i ngā rauemi paipa kaha ake e whakarato ana i te ātete waikura pai ake. Muri iho, me noho mataara tonu rātou i te wā e tirotirohia ana ngā werohanga matū, ngā raina waipēhi me te nekehanga, me ngā taputapu tukatuka me ngā taputapu pūoko kia kore ai te waikura e whakawehi i te kounga o ngā paipa kua whakauruhia, e whakararuraru hoki i te haumaru.
Ka kitea te waikura ā-rohe i runga i ngā papaaho maha, ngā kaipuke, ngā kaipuke, me ngā paipa i ngā whakaurunga tai. Ka taea e tēnei waikura te puta i te āhua o te waikura poka, te waikura kapiti rānei, ka taea e ēnei te whakangaro i te pakitara o te paipa me te tukunga wai.
Ka nui ake te mōrearea o te waikura ina piki ake te pāmahana whakahaere o te tono. Ka taea e te wera te whakateretere i te whakangaromanga o te kiriata waikura tiaki o waho o te ngongo, ā, ka whakatairanga i te hanganga o te waikura poka.
Engari, he uaua ki te kite i te waikura o te poka me te kapiti, ā, ka uaua ake te tautuhi, te matapae me te hoahoa i ēnei momo waikura. I runga i ēnei mōrearea, me tūpato ngā kaipupuri papaaho, ngā kaiwhakahaere me ngā kaiwhakarite i te wā e whiriwhiri ana i te rauemi paipa pai rawa atu mō tā rātou tono. Ko te whiriwhiri rauemi te rārangi tuatahi o tā rātou parepare ki te waikura, nō reira he mea nui te tika. He waimarie, ka taea e rātou te whiriwhiri mā te whakamahi i tētahi inenga tino māmā engari tino whai hua o te ātete waikura ā-rohe, te Tau Ātete Pitting (PREN). Ko te teitei ake o te uara PREN o tētahi konganuku, ko te teitei ake o tōna ātete ki te waikura ā-rohe.
Ka arotakehia e tēnei tuhinga te tautuhi i te waikura o ngā poka me ngā kapiti, me te pehea hoki te arotau i te kōwhiringa rauemi ngongo mō ngā tono hinu me te hau tai moana i runga i te uara PREN o te rauemi.
Ka puta te waikura ā-rohe i ngā wāhi iti ki te waikura whānui, he rite tonu te āhua i runga i te mata whakarewa. Ka tīmata te waikura poka me te kapiti ki runga i ngā paipa maitai kore waikura 316 ina pakaru te kiriata waikura korehau o waho o te whakarewa nā te pānga ki ngā wai waikura, tae atu ki te wai tote. Ko ngā taiao moana o uta me o uta e nui ana te hauhā, tae atu ki ngā pāmahana teitei me te poke o te mata o ngā ngongo, ka piki ake te kaha o te pirau o tēnei kiriata korehau.
te poka. Ka puta te waikura poka ina pakaru te kiriata whakakore i runga i te roanga o te paipa, ka hanga he kōhao iti, he kōhao rānei i runga i te mata o te paipa. Tērā pea ka tipu ake ēnei kōhao i te wā e puta ai ngā tauhohenga hikohiko, ka rewa te rino i roto i te konganuku ki roto i te wairewa i raro i te kōhao. Ka horapa te rino rewa ki te tihi o te kōhao ka waikura hei hanga waikura rino, waikura rānei. I te hohonu haere o te kōhao, ka tere ake ngā tauhohenga hikohiko, ka kaha ake te waikura, ā, ka taea te arahi ki te poka o te pakitara o te paipa, ka arahi hoki ki ngā turuturu.
He ngāwari ake te waikura o ngā ngongo ina poke tōna mata o waho (Pikitia 1). Hei tauira, ka taea e te poke mai i ngā mahi whakarewa me te huri te kino i te paparanga waikura e kore e uru ki te paipa, ā, ka hangaia, ka tere ake te waikura. Pērā anō hoki mō te whakahaere noa i te poke mai i ngā paipa. Hei tāpiri, i te mimiti haere o ngā pata tote, ka mahi ngā tioata tote mākū e hanga ana i runga i ngā paipa i te mea kotahi hei tiaki i te paparanga waikura, ā, ka arahi pea ki te waikura. Hei ārai i ēnei momo poke, kia ma ō paipa mā te horoi tonu ki te wai māori.
Ahua 1 – Ko te paipa maitai kore waikura 316/316L kua poke i te waikawa, te tote me ētahi atu putunga ka tino pāngia e te waikura.
Te waikura o te kapiti. I te nuinga o te wā, ka taea e te kaiwhakahaere te tautuhi ngāwari i te pakaru. Heoi, ehara i te mea ngāwari te kite i te waikura o te kapiti, ā, he nui ake te mōrearea ki ngā kaiwhakahaere me ngā kaimahi. I te nuinga o te wā ka puta i runga i ngā paipa he iti ngā āputa i waenga i ngā rauemi e karapoti ana, pērā i ngā paipa e puritia ana ki te wāhi me ngā topenga, ngā paipa rānei e tāutahia ana ki te taha. Ina mimiti te wai tote ki roto i te kapiti, ka puta he wairewa waikawa ferric chloride (FeCl3) kaha ki te rohe i roto i te wā, ā, ka tere ake te waikura o te kapiti (Pikitia 2). Nā te mea ka nui ake te mōrearea o te waikura i ngā kapiti, ka puta te waikura o te kapiti i ngā pāmahana he iti iho i te waikura o te kapiti.
Pikitia 2 – Tērā pea ka puta te waikura i waenganui i te paipa me te tautoko o te paipa (runga) me te wā e tāutahia ana te paipa ki te taha o ētahi atu mata (raro) nā te hanganga o te wairewa konukōre waikawa kaha ki te matū i roto i te kapiti.
Ko te waikura o te kapiti he rite tonu ki te waikura o ngā rua i te kapiti i hangaia i waenganui i te roa o te paipa me te topenga tautoko o te paipa. Heoi, nā te pikinga o te kukū Fe++ i roto i te wai i roto i te whati, ka nui haere te kapiti tuatahi tae noa ki te kapi i te whati katoa. Hei whakamutunga, ka taea e te waikura o te kapiti te poka i te paipa.
Ko ngā kapiti kikī te mea tino mōrearea o te waikura. Nō reira, ko ngā rawhi paipa e takai ana i te nuinga o te porowhita o te paipa he nui ake te mōrearea i ngā rawhi tuwhera, e whakaiti ana i te mata pa i waenga i te paipa me te rawhi. Ka taea e ngā tohunga tiaki te āwhina ki te whakaiti i te tūponotanga o te waikura kapiti e puta ai te kino, te pakaru rānei mā te whakatuwhera i ngā rawhi me te tirotiro i te mata o te paipa mō te waikura.
Ko te huarahi pai ki te ārai i te waikura o ngā rua me ngā kapiti mā te whiriwhiri i te koranu whakarewa tika mō te tono. Me āta tirotiro ngā kaiwhakatakoto whakaaro ki te whiriwhiri i te rauemi paipa tino pai hei whakaiti i te mōrearea o te waikura i runga i te taiao whakahaere, ngā āhuatanga tukanga me ētahi atu taurangi.
Hei āwhina i ngā kaiwhakatakoto whakaaro ki te arotau i te kōwhiringa rauemi, ka taea e rātou te whakataurite i ngā uara PREN o ngā konganuku hei whakatau i tō rātou ātete ki te waikura ā-rohe. Ka taea te tatau i te PREN mai i te hanganga matū o te koranu, tae atu ki tōna ihirangi chromium (Cr), molybdenum (Mo), me te hauota (N), penei:
Ka piki ake te PREN me te nui o ngā huānga ātete-waikura, arā, te chromium, te molybdenum me te hauota i roto i te koranu. Ko te whanaungatanga PREN e hangai ana ki te pāmahana poka nui (CPT) – te pāmahana iti rawa e kitea ai te waikura poka – mō ngā momo maitai kore waikura e pā ana ki te hanganga matū. Ko te tikanga, he ōrite te PREN ki te CPT. Nō reira, ko ngā uara PREN teitei ake e tohu ana i te ātete poka teitei ake. Ko te pikinga iti o te PREN he rite noa ki te pikinga iti o te CPT ki te whakataurite ki te koranu, engari ko te pikinga nui o te PREN e tohu ana i te whakapainga nui o te mahi ki te CPT teitei ake.
E whakataurite ana te Ripanga 1 i ngā uara PREN o ngā momo koranu e whakamahia whānuitia ana i roto i ngā tono hinu me te hau o tai. E whakaatu ana me pēhea te whakatakotoranga e taea ai te whakapai ake i te ātete waikura mā te whiriwhiri i tētahi koranu paipa kounga teitei ake. Ka piki ake te PREN i te wa e neke ana mai i te 316 ki te 317 kowiri tira. Mō te pikinga mahi nui, ko te kowiri tira super austenitic 6 Mo, ko te kowiri tira super duplex 2507 rānei te mea tino pai.
Ka whakanui ake hoki te nui o te nikara (Ni) i roto i te maitai kore waikura i te ātete ki te waikura. Heoi, kāore te nui o te nikara o te maitai kore waikura i roto i te whārite PREN. Ahakoa pēhea, he pai te tohu i ngā maitai kore waikura he nui ake te nui o te nikara, nā te mea ka āwhina tēnei huānga ki te whakaora anō i ngā mata e whakaatu ana i ngā tohu o te waikura ā-rohe. Ka whakaū te nikara i te austenite me te ārai i te hanganga martensite i te piko, i te tō matao rānei i te 1/8 o te paipa mārō. Ko te Martensite he wāhanga tioata kāore e hiahiatia ana i roto i ngā konganuku e whakaiti ana i te ātete o te maitai kore waikura ki te waikura ā-rohe me te pakaru ahotea i puta mai i te hauhāora. He mea hiahia hoki te nui ake o te nikara o te 12% i roto i te 316/316L mō ngā tono e whai wāhi ana ki te hauwai hau pēhanga teitei. Ko te iti rawa o te kukū nikara e hiahiatia ana mō te maitai kore waikura 316/316L i roto i te whakatakotoranga paerewa ASTM he 10%.
Ka taea te waikura ā-rohe te puta i ngā paipa katoa e whakamahia ana i roto i ngā taiao moana. Heoi, he nui ake te tūponotanga o te waikura poka i ngā wāhi kua poke kē, engari he nui ake te tūponotanga o te waikura kapiti i ngā wāhi he whaiti ngā āputa i waenga i te paipa me te taputapu whakairi. Mā te whakamahi i te PREN hei pūtake, ka taea e te kaiwhakatakoto whakaaro te kōranu paipa pai rawa atu hei whakaiti i te tūponotanga o tētahi momo waikura ā-rohe.
Heoi, kia maumahara kei reira ētahi atu taurangi ka pā ki te mōrearea o te waikura. Hei tauira, ka pā te pāmahana ki te ātete o te maitai kore waikura ki te pakaru. Mō ngā āhuarangi moana wera, me whai whakaaro nui ki te paipa maitai kore waikura 6 molybdenum super austenitic, 2507 super duplex rānei, nā te mea he tino pai te ātete o ēnei rauemi ki te waikura ā-rohe me te pakaru ahotea chloride. Mō ngā āhuarangi matao, he rawaka pea te paipa 316/316L, inā koa mēnā kua whakapumautia he hītori o te whakamahinga angitu.
Ka taea hoki e ngā kaipupuri me ngā kaiwhakahaere o ngā papaaho moana te mahi i ngā mahi hei whakaiti i te tūponotanga o te waikura i muri i te tāutanga o ngā ngongo. Me pupuri e rātou ngā paipa kia ma, kia horoia hoki ki te wai māori i ia wā hei whakaiti i te tūponotanga o te waikura. Me tono hoki rātou ki ngā tohunga tiaki kia whakatuwhera i ngā rawhi ngongo i ngā wā tirotiro noa hei tirotiro i te kitea o te waikura kapiti.
Mā te whai i ngā kaupae kua whakarārangihia i runga ake nei, ka taea e ngā kaipupuri me ngā kaiwhakahaere papaaho te whakaiti i te mōrearea o te waikura o ngā ngongo me ngā turuturu e pā ana ki roto i ngā taiao moana, me te whakapai ake i te haumaru me te whai huatanga, me te whakaiti anō hoki i te tūponotanga o te ngaronga o te hua, te tukunga rānei o ngā tukunga rere.
Brad Bollinger is the Oil and Gas Marketing Manager for Swagelok Company.He can be reached at bradley.bollinger@swagelok.com.
Ko te Journal of Petroleum Technology te maheni matua o te Society of Petroleum Engineers, e whakarato ana i ngā whakamārama me ngā kaupapa whai mana mō ngā whanaketanga o te hangarau tūhura me te whakaputa, ngā take o te umanga hinu me te hau, me ngā purongo mō SPE me ōna mema.