ʻOiai ke kūpaʻa ʻana o ka corrosion o nā paipu kila kila, ʻo nā paipu kila kila i hoʻokomo ʻia i loko o nā kaiapuni kai e pili ana i nā ʻano ʻino like ʻole i ko lākou ola lawelawe i manaʻo ʻia. Hiki i kēia ʻino ke alakaʻi i ka hoʻokuʻu ʻana i ka mahuka, ka nalowale o nā huahana a me nā pōʻino. Hiki i nā mea nona ka paepae a me nā mea hoʻohana ke hōʻemi i ka pilikia o ka ʻinoʻino ma o ka wehewehe ʻana i nā mea paipu ikaika e hāʻawi i ka pale ʻana i ka corrosion. Ma hope iho, pono lākou e makaʻala i ka nānā ʻana i nā laina hoʻoheheʻe kemika, nā laina hydraulic a me nā laina impulse, a me ka hana ʻana i nā mea kani a me nā mea kani e hōʻoia ai ʻaʻole e hoʻoweliweli ka corrosion i ka kūpaʻa o ka paipa i hoʻokomo ʻia a i ʻole ka palekana palekana.
Hiki ke ʻike ʻia ka corrosion kūloko ma nā kahua he nui, nā moku, nā moku a me nā paipu o waho. Hiki i kēia ʻino ma ke ʻano o ka lua a i ʻole ka crevice corrosion, ʻo ia ka mea hiki ke hoʻopau i ka pā paipu a hoʻokuʻu ʻia ka wai.
Piʻi ka pilikia o ka corrosion i ka piʻi ʻana o ka mahana hana o ka noi. Hiki i ka wela ke hoʻoikaika i ka hoʻohaʻahaʻa ʻana o ke kiʻiʻoniʻoni passive oxide pale o ka paipu, a laila e hoʻoikaika ai i ka lua.
ʻO ka mea pōʻino, paʻakikī ka ʻike ʻana i ka lua a me ka ʻāʻī ʻana, no laila paʻakikī ke ʻike, wānana, a me ka hoʻolālā ʻana i kēia mau ʻano ʻino. Ma muli o kēia mau pilikia, pono nā mea nona ka paepae, nā mea hana a me nā mea i koho ʻia e makaʻala i ke koho ʻana i nā mea paipu maikaʻi loa no kā lākou noi. ʻO ke koho ʻana i nā mea waiwai ko lākou lālani mua o ka pale ʻana i ka corrosion, no laila he mea nui ka hoʻokō pono ʻana. ʻO ka mea pōmaikaʻi, hiki iā lākou ke koho i kahi ana maʻalahi akā maikaʻi loa o ke kūpaʻa corrosion kūloko, ka Pitting Resistance Equivalent Number (PREN). ʻOi aku ka kiʻekiʻe o ka waiwai PREN o kahi metala, ʻoi aku ka kiʻekiʻe o kona kūʻē ʻana i ka corrosion kūloko.
E nānā ana kēia ʻatikala pehea e ʻike ai i ka ʻinoʻino o ka lua a me ka ʻāʻī, a me ke ʻano o ka koho ʻana i nā mea paipu no nā noi aila a me ke kinoea waho ma muli o ka waiwai PREN o ka mea.
Hiki ke ʻino ʻia i loko o nā wahi liʻiliʻi ke hoʻohālikelike ʻia me ka ʻino maʻamau, ʻoi aku ka like o ka ʻili metala. Hoʻomaka ka ʻino ʻana o ka lua a me ka ʻāʻī ma luna o ka paipu kila kuhili ʻole 316 i ka wā e haki ai ka kiʻiʻoniʻoni passive oxide o waho o ka metala ma muli o ka ʻike ʻana i nā wai ʻino, me ka wai paʻakai. ʻO nā kaiapuni moana i waiwai i nā chlorides, a me nā wela kiʻekiʻe a me ka hoʻohaumia ʻana o ka ʻili o ka paipu, e hoʻonui i ka likelihood o ka degradation o kēia kiʻi passivation.
pitting Pitting corrosion i ka wā e haki ai ke kiʻiʻoniʻoni passivation ma kahi ʻāpana o ka paipu, e hana ana i nā lua liʻiliʻi a i ʻole nā ​​lua ma ka ʻili o ka paipu. E ulu paha ia mau lua i ka hoʻomaka ʻana o nā hopena electrochemical, ma muli o ka hoʻoheheʻe ʻia ʻana o ka hao i loko o ka metala i ka hopena ma lalo o ka lua. A laila e laha ka hao i hoʻoheheʻe ʻia i luna o ka lua a hoʻoheheʻe ʻia e hana i ka hao a i ʻole ka pala. I ka hohonu o ka lua, e wikiwiki ana nā hopena electrochemical, piʻi ka corrosion, hiki ke alakaʻi i ka perforation o ka paia paipu a alakaʻi i nā leaka.
ʻOi aku ka maʻalahi o nā paipu i ka lua inā haumia ko lākou ʻili waho (Figure 1). No ka laʻana, hiki i nā mea haumia mai ka hana wili a me ka wili ʻana ke hoʻopōʻino i ka papa passivation oxide o ka paipu, a laila e hoʻokumu a wikiwiki i ka lua. Pela no ka hana wale ana i ka haumia o na paipu. Eia kekahi, i ka wā e hoʻoheheʻe ʻia ai nā kulu paʻakai, ʻo nā kristal paʻakai mākū i hana ʻia ma luna o nā paipu e pale i ka ʻāpana okisa a hiki ke alakaʻi i ka lua. No ka pale ʻana i kēia mau ʻano ʻino, e hoʻomaʻemaʻe i kāu mau paipu ma ka holoi pinepine ʻana iā lākou me ka wai hou.
Kiʻi 1. 316/316L paipu kila kila i hoʻohaumia ʻia me ka waika, paʻakai, a me nā waihona ʻē aʻe e maʻalahi loa i ka lua.
ʻinoʻino māwae. I ka hapanui o nā hihia, hiki ke ʻike maʻalahi ka lua e ka mea hoʻohana. Eia nō naʻe, ʻaʻole maʻalahi ka ʻike ʻana i ka corrosion crevice a ʻoi aku ka pilikia o nā mea hana a me nā limahana. Hana ʻia kēia ma luna o nā paipu i loaʻa nā āwaha liʻiliʻi ma waena o nā mea a puni, e like me nā paipu i paʻa i kahi me nā paʻi a i ʻole nā ​​paipu i hoʻopaʻa paʻa ʻia ma ka ʻaoʻao o kekahi. Ke komo ka brine i loko o ka ʻāwaʻa, i ka manawa lōʻihi, ua hoʻokumu ʻia kahi solution ferric chloride chemically aggressive acidified ferric chloride (FeCl3) ma kēia wahi, kahi e wikiwiki ai ka ʻino ʻana (Fig. 2). Ma muli o ka hoʻonui ʻana o ka crevice i ka pōʻino, hiki ke ʻano ʻino ka crevice i nā mahana haʻahaʻa haʻahaʻa ma mua o ka pitting.
Kiʻi 2 - Hiki ke hoʻomohala ʻia ka ʻino ma waena o ka paipu a me ke kākoʻo paipu (luna) a i ka wā e hoʻokomo ʻia ai ka paipu kokoke i nā ʻaoʻao ʻē aʻe (lalo) ma muli o ka hoʻokumu ʻia ʻana o kahi solution acidified ferric chloride i loko o ka āpau.
Hoʻohālike maʻamau ka ʻino ʻana o Crevice i ka lua mua ʻana i loko o ke āpau i hana ʻia ma waena o ka ʻāpana paipu a me ke kola kākoʻo paipu. Eia naʻe, ma muli o ka piʻi ʻana o ka Fe ++ i loko o ka wai i loko o ka haʻihaʻi, ʻoi aku ka nui o ka funnel mua a hiki i ka uhi ʻana i ka haki holoʻokoʻa. ʻO ka hope loa, hiki i ka corrosion crevice ke alakaʻi i ka perforation o ka paipu.
Hōʻike nā māwae mānoanoa i ka pōʻino nui loa. No laila, ʻoi aku ka pilikia o nā paipu paipu e hoʻopuni ana i kahi ʻāpana nui o ka pōʻai o ka paipu ma mua o nā pipili hāmama, e hōʻemi ana i ka ʻili pili ma waena o ka paipu a me ka paʻi. Hiki i nā ʻenehana lawelawe ke kōkua i ka hōʻemi ʻana i ka pōʻino o ka crevice corrosion a i ʻole ka hāʻule ʻana ma o ka wehe mau ʻana i nā pipili a nānā i ka ʻili o ka paipu no ka corrosion.
Hiki ke pale ʻia ka ʻino ʻana o ka lua a me ka ʻāʻī ma ke koho ʻana i ka huila metala kūpono no ka noi. Pono nā mea kikoʻī e hoʻoikaika pono i ke koho ʻana i nā mea paipu maikaʻi loa e hōʻemi i ka pilikia o ka ʻino ma muli o ke kaiapuni kaʻina, nā kūlana kaʻina, a me nā ʻano ʻē aʻe.
No ke kōkua ʻana i nā mea kikoʻī i ka koho ʻana i nā mea waiwai, hiki iā lākou ke hoʻohālikelike i nā waiwai PREN o nā metala e hoʻoholo ai i ko lākou kū ʻana i ka corrosion localized. Hiki ke helu ʻia ka PREN mai ke kemika o ka alloy, me kona chromium (Cr), molybdenum (Mo), a me ka nitrogen (N), penei:
Hoʻonui ka PREN me nā mea o ka corrosion-resistant element o chromium, molybdenum a me ka nitrogen i loko o ka alloy. Hoʻokumu ʻia ka lakio PREN ma luna o ka mahana pitting koʻikoʻi (CPT) - ka wela haʻahaʻa loa e puka ai ka lua - no nā kila kuhili ʻole ma muli o ka haku mele. ʻO ka mea nui, pili ka PREN i ka CPT. No laila, ʻoi aku ka kiʻekiʻe o nā waiwai PREN e hōʻike ana i ke kūpaʻa pitting kiʻekiʻe. ʻO kahi hoʻonui liʻiliʻi o ka PREN ua like wale ia me kahi piʻi liʻiliʻi o ka CPT i hoʻohālikelike ʻia me ka huila, ʻoiai ka piʻi nui o ka PREN e hōʻike ana i kahi hoʻomaikaʻi nui o ka hana ma luna o kahi CPT kiʻekiʻe loa.
Hoʻohālikelike ka Papa 1 i nā waiwai PREN no nā ʻano ʻano like ʻole i hoʻohana maʻamau ʻia i ka ʻoihana ʻaila a me ke kinoea. Hōʻike ia pehea e hiki ai i nā kikoʻī ke hoʻomaikaʻi maikaʻi i ka pale ʻana i ka corrosion ma ke koho ʻana i kahi hui paipu ʻoi aku ka maikaʻi. Piʻi iki ka PREN mai 316 SS a i 317 SS. He kūpono ka Super Austenitic 6 Mo SS a i ʻole Super Duplex 2507 SS no ka piʻi nui ʻana o ka hana.
ʻOi aku ka nui o ka nickel (Ni) i loko o ke kila kuhili ʻole e hoʻonui i ka pale ʻana i ka corrosion. Eia naʻe, ʻaʻole ʻāpana o ka hoʻohālikelike PREN ka maʻiʻo nickel o ke kila kila. I kēlā me kēia hihia, ʻoi aku ka maikaʻi o ke koho ʻana i nā kila kila me ka ʻoi aku ka nickel kiʻekiʻe, no ka mea, kōkua kēia mea i ka hoʻololi hou ʻana i nā papa e hōʻike ana i nā hōʻailona o ka corrosion localized. Hoʻopaʻa ʻo Nickel i ka austenite a pale i ka hoʻokumu ʻana o martensite i ka wā e kulou ai a i ʻole ke kaha anu 1/8 paipu paʻa. ʻO Martensite kahi māhele crystalline maikaʻi ʻole i nā metala e hōʻemi ana i ke kūʻē ʻana o ke kila kila i ka corrosion localized a me ka chloride-induced stress cracking. ʻO ka maʻiʻo nickel kiʻekiʻe o ka liʻiliʻi he 12% i ke kila 316/316L makemake pū ʻia no nā noi hau hydrogen kaomi kiʻekiʻe. ʻO ka haʻahaʻa haʻahaʻa nickel i koi ʻia no ka ASTM 316/316L stainless steel he 10%.
Hiki ke ʻino ʻia ma nā wahi a pau ma nā paipu i hoʻohana ʻia i nā kaiapuni kai. Eia nō naʻe, ʻoi aku ka nui o ka pitting ma nā wahi i haumia ʻia, ʻoiai ʻoi aku ka nui o ka ʻino ʻana ma nā wahi me nā āpau haiki ma waena o ka paipu a me nā mea hoʻokomo. Ke hoʻohana nei i ka PREN ma ke ʻano he kumu, hiki i ka mea kikoʻī ke koho i ka huila paipu maikaʻi loa e hōʻemi i ka pilikia o kēlā me kēia ʻano o ka corrosion kūloko.
Eia nō naʻe, e hoʻomanaʻo ʻia aia kekahi mau ʻano ʻē aʻe e hiki ke hoʻopilikia i ka pilikia o ka corrosion. No ka laʻana, pili ka mahana i ke kūpaʻa o ke kila kila i ka lua. No ka piʻi ʻana o ka moana wela, pono e noʻonoʻo nui ʻia nā paipu kila kila super austenitic 6 molybdenum a i ʻole super duplex 2507 no ka mea ʻoi aku ka maikaʻi o kēia mau mea i ka corrosion localized a me ka pohā chloride. No nā piʻi anuanu, lawa paha ka paipu 316/316L, ʻoi aku ka nui inā loaʻa kahi moʻolelo o ka hoʻohana kūleʻa.
Hiki i nā mea nona ka paepae a me nā mea hoʻohana ke hana i nā hana e hōʻemi i ka pilikia o ka pala ma hope o ka hoʻokomo ʻia ʻana o ka paipu. Pono lākou e hoʻomaʻemaʻe i nā paipu a holoi pinepine ʻia me ka wai hou e hōʻemi i ka pilikia o ka lua. Pono e loaʻa iā lākou nā ʻenehana mālama e wehe i nā paipu paipu i ka wā o ka nānā maʻamau e nānā i ka corrosion crevice.
Ma ka hahai ʻana i nā ʻanuʻu i luna, hiki i nā mea nona ka paepae a me nā mea hoʻohana ke hōʻemi i ka hopena o ka ʻino o ka paipu a me nā leaks pili i loko o ke kai moana, hoʻomaikaʻi i ka palekana a me ka pono, a e hōʻemi i ka manawa o ka nalowale o ka huahana a i ʻole nā ​​​​huka lele.
Brad Bollinger is the Oil and Gas Marketing Manager for Swagelok. He can be contacted at bradley.bollinger@swagelok.com.
ʻO ka Journal of Petroleum Technology ka puke pai alakaʻi o ka Society of Petroleum Engineers, e hōʻike ana i nā hōʻuluʻulu mana a me nā ʻatikala e pili ana i ka holomua o ka ʻenehana upstream, nā pilikia ʻoihana aila a me ka hau, a me nā nūhou e pili ana iā SPE a me kona mau lālā.