Ukushisela amapayipi ensimbi engagqwali kanye namapayipi kuvame ukudinga ukuhlanza i-back-purging nge-argon uma usebenzisa izinqubo zendabuko ezifana nokushisela i-gas tungsten arc (GTAW) kanye nokushisela i-arc yensimbi evikelwe (SMAW). Kodwa izindleko zegesi kanye nesikhathi sokusetha inqubo yokuhlanza kungabaluleka, ikakhulukazi njengoba ububanzi bepayipi nobude bukhula.
Lapho beshisela insimbi engagqwali yochungechunge lwama-300, osonkontileka bangasusa ukubuyiselwa emuva kokushisela kwemisele evulekile ngokushintsha kusuka ku-GTAW noma i-SMAW yendabuko baye enkambisweni yokushisela ethuthukisiwe, ngenkathi besathola ikhwalithi ephezulu yokushisela, balondoloze ukumelana nokugqwala kwezinto, futhi bahlangabezane ne-Welding Procedure Specification (WPS) idinga inqubo yokushisela insimbi yensimbi ye-arc yegesi ye-short-circuit (GMAW). Inqubo ye-GMAW ye-short-circuit ethuthukisiwe iletha nezinzuzo ezengeziwe ekukhiqizeni, ekusebenzeni kahle kanye nokulula kokusetshenziswa, okusiza ekuthuthukiseni inzuzo.
Njengoba ithandwa ngenxa yokumelana kwayo nokugqwala kanye namandla ayo, ama-alloy ensimbi engagqwali asetshenziswa ezinhlelweni eziningi zamapayipi kanye namapayipi, okuhlanganisa uwoyela negesi, i-petrochemical, kanye ne-biofuels. Nakuba i-GTAW ibilokhu isetshenziswa ezinhlelweni eziningi zensimbi engagqwali, inezinkinga ezithile ezingaxazululwa nge-GMAW ethuthukisiwe ye-short-circuit.
Okokuqala, njengoba ukushoda kwabashiseli abanekhono kuqhubeka, ukuthola abasebenzi abajwayelene ne-GTAW kuyinselele eqhubekayo. Okwesibili, i-GTAW akuyona inqubo yokushisela esheshayo, evimbela izinkampani ezifuna ukwandisa umkhiqizo ukuze zihlangabezane nezidingo zamakhasimende. Okwesithathu, idinga ukuhlanza amapayipi ensimbi engagqwali okuthatha isikhathi futhi okubizayo.
Kuyini i-blowback? I-Purge ukungenisa igesi ngesikhathi senqubo yokushisela ukuze kususwe ukungcola futhi kuhlinzekwe ukwesekwa. I-backside purge ivikela i-backside ye-weld ekwakheni ama-oxide asindayo lapho kukhona umoya-mpilo.
Uma ingemuva lingavikelwe ngesikhathi sokushisela umsele wezimpande ovulekile, umonakalo ungase uvele ku-substrate. Lokhu kuphuka kubizwa ngokuthi i-saccharification, okubizwa kanjalo ngoba kuphumela endaweni ebukeka njengoshukela ngaphakathi kwe-weld. Ukuze kuvinjelwe ukuxubha, umshiseli ufaka ipayipi legesi kolunye uhlangothi lwepayipi bese exhuma ukuphela kwepayipi ngedamu lokuhlanza. Baphinde bakhe umoya komunye umkhawulo wepayipi. Bavame futhi ukufaka iteyipu nxazonke kwesikhala sejoyinti. Ngemva kokuhlanza ipayipi, bakhipha ingxenye yeteyipu nxazonke kwejoyinti baqale ukushisela, bephinda inqubo yokukhumula nokushisela kuze kube yilapho i-root bead isiqediwe.
Susa i-blowback. Ukulandelela kungadla isikhathi esiningi nemali, kwezinye izimo kunezela izinkulungwane zamaRandi kuphrojekthi. Ukushintshela enkambisweni ye-short-circuit GMAW ethuthukisiwe kwenze inkampani yakwazi ukuqedela ama-root pass ngaphandle kokusebenzisa i-backflushing ezicelweni eziningi zensimbi engagqwali. Izicelo zokushisela zezinsimbi ezingagqwali ezingu-300 zifaneleka kahle kulokhu, kuyilapho izinhlelo zokushisela zezinsimbi ezingagqwali ze-duplex ezihlanzekile kakhulu okwamanje zidinga i-GTAW ukuze kusetshenziswe i-root pass.
Ukugcina okokufaka ukushisa kuphansi ngangokunokwenzeka kusiza ukugcina ukumelana nokugqwala kwento yokusebenza. Ukunciphisa inani lokudlula kokushisela kuyindlela eyodwa yokunciphisa okokufaka ukushisa. Izinqubo ze-GMAW ezithuthukisiwe ze-short-circuit, njenge-Regulated Metal Deposition (RMD®), zisebenzisa ukudluliselwa kwensimbi okulawulwa ngokunembile ukuze kuhlinzekwe ukufakwa kwamaconsi afanayo. Lokhu kwenza kube lula ngomshini wokushisela ukulawula ichibi lokushisela, elilawula okokufaka ukushisa kanye nesivinini sokushisela. Okokufaka ukushisa okuphansi kuvumela ichibi lokushisela ukuba liqine ngokushesha.
Ngokudluliselwa kwensimbi okulawulwayo kanye nokubanda okusheshayo kwechibi lokushisela, ichibi lokushisela alinazo izivunguvungu eziningi futhi igesi yokuvikela ishiya isibhamu se-GMAW singaphazanyiswa kangako. Lokhu kuvumela igesi yokuvikela ukuthi idlule empandeni evulekile, isuse umoya futhi ivimbele ukusatshalaliswa noma ukubola ngemuva kwe-weld. Lokhu kuhlanganiswa kwegesi kuthatha isikhathi esifushane ngoba amadaka aqina ngokushesha kakhulu.
Ukuhlola kukhombisile ukuthi inqubo ye-GMAW ye-short-circuit eguquliwe ihlangabezana nezindinganiso zekhwalithi yokushisela ngenkathi igcina ukumelana nokugqwala kwensimbi engagqwali njengalapho i-root bead ishiselwa nge-GTAW.
Ushintsho enqubweni yokushisela ludinga inkampani ukuthi iphinde iqinisekise i-WPS yayo, kodwa ukushintsha okunjalo kungaletha imbuyiselo enkulu yesikhathi kanye nokonga izindleko zomsebenzi omusha wokukhiqiza nokulungisa.
Ukushisela umsele wezimpande ovulekile kusetshenziswa inqubo ye-GMAW yesikhashana ethuthukisiwe kunikeza izinzuzo ezengeziwe ekukhiqizeni, ekusebenzeni kahle kanye nokuqeqeshwa kwabashiseli. Lokhu kufaka phakathi:
Kuqeda amathuba okuba neziteshi ezishisayo ngenxa yokukwazi ukufaka insimbi eyengeziwe ukuze kwandiswe ukujiya kwesiteshi sezimpande.
Ukubekezelela okuhle kakhulu kokungalingani okuphezulu nokuphansi phakathi kwezingxenye zamapayipi. Ngenxa yokudluliselwa kwensimbi okubushelelezi, inqubo ingavala kalula izikhala ezifika ku-1/2 amasentimitha.
Ubude be-arc buyahambisana kungakhathaliseki ukuthi i-electrode inwetshiwe, okukhokhela abaqhubi abanenkinga yokugcina i-extension inwetshiwe njalo. I-weld puddle elawulwa kalula kanye nokudluliselwa kwensimbi njalo kunganciphisa isikhathi sokuqeqeshwa kwabashiseli abasha.
Nciphisa isikhathi sokungasebenzi kokushintsha kwenqubo. Ucingo olufanayo kanye negesi yokuvikela ingasetshenziswa eziteshini zezimpande, zokugcwalisa kanye nezesivalo. Inqubo ye-GMAW evunguziwe ingasetshenziswa uma nje iziteshi zigcwele futhi zivaliwe ngegesi yokuvikela i-argon okungenani engu-80%.
Ngemisebenzi efuna ukuqeda i-backflush ekusetshenzisweni kwensimbi engagqwali, kubalulekile ukulandela amathiphu amahlanu ayisihluthulelo empumelelo lapho ushintshela enqubweni ye-GMAW ye-short-circuit eguquliwe.
Hlanza ingaphakathi nengaphandle lamapayipi ukuze ususe noma yikuphi ukungcola. Sebenzisa ibhulashi lensimbi elenzelwe insimbi engagqwali ukuze uhlanze ingemuva lejoyinti okungenani i-intshi elilodwa ukusuka emaphethelweni.
Sebenzisa insimbi engagqwali yokugcwalisa insimbi enokuqukethwe okuphezulu kwe-silicon, njenge-316LSi noma i-308LSi. Okuqukethwe okuphezulu kwe-silicon kusiza ekumanziseni ichibi lokushisela futhi kusebenza njenge-deoxidizer.
Ukuze usebenze kahle kakhulu, sebenzisa ingxube yegesi yokuvikela eyenzelwe ngokukhethekile inqubo, njenge-helium engu-90%, i-argon engu-7.5%, kanye ne-carbon dioxide engu-2.5%. Enye inketho i-argon engu-98% kanye ne-carbon dioxide engu-2%. Umhlinzeki wegesi yokushisela angase abe nezinye izincomo.
Ukuze uthole imiphumela emihle kakhulu, sebenzisa i-tip enciphile kanye ne-nozzle ukuze uqondise impande ukuze uthole ukumbozwa kwegesi. I-nozzle eyindilinga ene-gas diffuser eyakhelwe ngaphakathi inikeza ukumbozwa okuhle kakhulu.
Qaphela ukuthi ukusebenzisa inqubo ye-GMAW ye-short-circuit eguquliwe ngaphandle kwegesi esekelayo kukhiqiza inani elincane lesikali ngemuva kwe-weld. Lokhu kuvame ukufiphala njengoba i-weld iphola futhi ihlangabezana nezindinganiso zekhwalithi ze-petroleum, i-power plant kanye ne-petrochemical applications.
UJim Byrne unguMphathi Wezokuthengisa Nezicelo weMiller Electric Mfg. LLC, 1635 W. Spencer St., Appleton, WI 54912, 920-734-9821, www.millerwelds.com.
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