Tuyin tap bao cao Hdi nghj KHCN "30 nam Dau khi Viet Nam Cff hdi mdi, thach thiic mdi" 287 LY THUYET v A LTNG DUNG CUA KY THUAT DONG DIEN X O A Y TRONG KIEM TRA KHONG P H A HUY (NDT) Chu Chat Chinh, P[.]
Tuyin tap bao cao Hdi nghj KHCN "30 nam Dau Viet Nam: Cff hdi mdi, thach thiic mdi" 287 LY THUYET v A LTNG DUNG CUA KY THUAT DONG DIEN X O A Y TRONG KIEM TRA KHONG P H A HUY (NDT) Chu Chat Chinh, Phan Duy Lam, Tran Due Minh Vien Ddu Khi TOM TAT Thir nghiem khdng phd hiiy (KPH) bdng phirang phdp ddng diin xody (ECT) Id mpt ndm phuang phdp thir KPH dugc quy dinh tgi cdc Tieu chudn Qudc ti vd Viet Nam thupe linh vuc ndy (bdn phuang phdp khdc Id: sieu dm (UT), thdm thdu chdt long (PT) tir tinh (MT) vd chup tia phdng xg (RT) Bdi viit ndy giai thiiu hi thdng vi khdi niem, nguyin ly hogt dpng, cdc irng dung ciia phirang phdp ddng dien xody, cdc ky thudt kiem tra vd khd ndng ung dung phuang phdp ndy vdo diiu kien Viet Nam vi hien rdt h cdc dan vi nuac vi kiim tra KPH ki cd Tdng cdng ty Ddu Viet Nam, cd logi thiit bi vi thir kiim tra KPH bdng ky thudt ddng diin xody KHAI NIEM Ddng dien xoay kiem tra KPH la mdt ky thuat cd the kiem tra khuyet tat cua vat lieu kim loai ca qua trinh san xuat va qua trinh su dyng vat lieu Day la mgt ky thuat cd chinh xac cao va hoan toan khdng pha buy (vat lieu kiem tra khdng bi pha buy) Kiem tra nhanh chdng, an toan va hieu qua LY THUYET DONG DIEN X O A Y Nguyen ly hoat ddng Khi mdt ddng dien xoay chieu chay mgt cudn day dat sat be mat cua vat lieu dan dien, tu trudng cudn day se cam ung mgt ddng dien xoay tren be mat vat lieu dd (Hinh 1) Bien va pha eua ddng dien xoay se tae dgng len phy tai cua cudn day va dd se anh hudng tdi tdng trd cua cudn day (mach dien) Hinhl Hinh 28g Ly thuyet va dng dung cua ky thuat ddng di^n xoay kiim tra khdng pha huy (NDT) Mdt vlt nut be mat phia dudi cudn day se lam cho ddng dien xoay bj yeu di (do phai di vdng qua vlt nut), dd phu tai tac ddng len cudn day cung yeu di va anh hudng cua nd len tdng trd cua cudn day tang len (Hinh 2) Bien chi thj (tin hieu) tu vlt niit phy thudc chu ylu vao lugng ddng dien xoay bj roi loan bdi vlt nirt Hay ndi each khae: chieu sau, bl rdng va chieu dai cua vet nut se xac dinh su thay ddi chi thj cua vet nut NIU vlt nut nim ngang ddng dien xoay thi kha nang phat hien se tSng len (Hinh 3) V^tndt songsong • khdng phSt hifin dugc vet ndt vudng gdc • phit hien dugc Hinh Cac yeu to anh hu-dng din den ddng dif n xoay - Do dan dien cua vat lieu - Do tham tu Tan sd Hinh dang hinh hgc Kha nang tiep can/Lift-off - Do sau tham thau So- dd trd' khang Day la thi bieu dien tdng trd cua cac mau thu True X the hien trd khang cdn true Y the hien cam img dien khang (Hinh 4) Tuyin tap bao cao Hgi nghj KHCN "30 nam Dau Viet Nam: Cff hdi mdi, thach thde mdi" X, 289 sat tir Vft niit sit Thep Dat khOng khf T VAT LIEU Titanium VAT LIEU KHONG Ve?t niit nh6m Nh6m DO dan didn ting len cua vat ki^m tra •R Hinh Tong trd cuon day - x Man hinh cua thilt bj kilm tra ddng dien xoay la cua sd the bien so dd tdng trd (Hinh 5) Hinh ^^* ^"^ kiem tra vat lieu nhom Cac - phan chinh cua thiet bi Ket cau cudn day Do gia tri tuyet ddi (cudn day don) Do gia tri so sanh (cudn day ddi) Dau dd Ung dung - cua phu-ong phap ddng dien xoay Phat hien khuyet tat vat lieu Phan loai vat lieu (do dan dien) Do be day ldp phu khdng dan dien va dan dien Do chieu day vat lieu - Do cung - Kiem tra dng trao ddi nhiet (sit tir va sit khdng tu) 290 Ly t h u y i t va dng dung ciia ky thuat ddng dien xoay k i i m tra khong pha huy (NDT) Dudng kiem tra ASME (Hinh 6) Hinh Dirdng kiem tra ASTM a De ddng, thudn lgi Keo dau dd qua dng va nhan dugc tin hieu nhat tu mdi khuyet tat (Hinh 7) - Ld thdng - Ld sau 80% ben ngoai - Ld sau 60% ben ngoai - Ld sau 40% ben ngoai - Ld sau 20% ben ngoai - Mdp b Khd khan - Ong dudng kiem tra dugc dd bdi tam dd va hau het cac sai sd xay khuyet tat nam canh tam dd (Hinh 8) Hinh - Tin hieu tu tam dd trdn lan vdi tin hieu cua khuyet tat, rit khd xac djnh c Anh huang ciia tdm dd' nhu sau: OO&SO b OD Sjppcft ^kit.j resulting iivlkil Hinh d Gidi phdp Dua vao mot kenh tin hieu de hda tron va loai tru tin hieu cua tam dd Tuyin tap bao cao Hdi nghj KHCN "30 nam DjuJ^hi Viet Nam^: Co hdi mdi, thach thuc mdi" 291 e Kit qud (Hinh 9) Hinh Ky thuat kiem tra cac ong thep tir (thep caebon) - Can tan sd thap de tham thau - Cd hai ky thuat kiem tra: Cdng nghe tu trudng xa (RFT) va Cdng nghe tu trudng gin (NFT) Sy gidng giua hai ky thuat (RFT & NFT) la deu su dyng tan sd thap de tham thau vao vat lieu a Ky thuat tir trudng xa (RFT) Ky thuat tu trudng xa (RFT) la ky thuat phat nhan xuyen qua dng, su dyng cac cudn phat nhan rieng biet each 2,5 lan dudng kinh dng RFT phy thudc vao tinh trang cua dng gan cac cudn phat nhan va giua cae cudn dd Vi thiet bi chay ben ngoai dng nen cac tin hieu phy thudc nhieu vao ket eau gia dd nhu tam dd gida cac cudn phat nhan • Uu diim Do dugc chinh xac sau cac khuyet tat Rat phu hgp de phat hien cac khuyet tat ben ngoai dng • Nhugc diim - Do dac diem thiet ke nen rat khd kiem tra mdt vai em dau dng - Rat khd phan biet tin bieu khuyet tat ben va ben ngoai - Khdng the xac dinh chinh xac cac khuyet tat sat tam dd - Khdng the kiem tra dugc vung dudi tam b Ky thugt tir trudng gan (NFT) Cac cudn day cam bien nam rat gan va day khdng phai la ky thuat xuyen qua dng NFT phy thudc vao tinh trang cua dng d gan cac cudn day va phu thudc chut it vao ket cau tam dd vi tin hieu khdng xuyen qua dng • Uu diim - Cd the kiem tra dugc tu dau mep dng - Cd sy phan biet rd rang tin hieu giua cae khuyit tat ben va ben ngoai ong - Kiem tra dugc cac khuyet tat gin va dudi tim dd Ly thuyit va ung dung eiia ky thuat dong dien xoay kiim tra khdng pha hiiy (NDT) 292 • Nhugc diim - Khd su dung cho cac khuyet tat ben ngoai vi gdc pha la ngau nhien Tdm lai RFT kiem tra bang ky thuat tu trudng xa cd chinh xac cao hon ddi vdi cac khuyet tat nhd xa tam dd NFT kiem tra bang ky thuat tu trudng gin de dang phan tich cac tin bieu han NFT kiem tra bang ky thuat tu trudng gan phu hgp ban kbi kiem tra cac vung gan va dudi tam dd b Thir nghiem hien trudng Quyet dinh the nao? Dung ky thuat tu trudng xa hay gan hay dung ca hai? • Gidi phdp Su dyng ket hgp ea hai ky thuat tu trudng xa va gan de kiem tra chum dng bang vat lieu tu tinh Cae man hinh dudi day the bien khuyet tat khe nut 25 50 va 75% cua dng (Hinh 10) NF-LF NF-HF NF-VHF ffinh 10 Remote Field • Kit qud - Cac tin hieu NF-LF, NF-HF va RF dua cac dai pha rdng rit dl dang eho viec phan tich du lieu Tin bieu NF-VHF ed nhay rit kem tin so cao - Mui ten chi tin hieu gia tu cudn phat diu dd cua ky thuat tu trudng xa Cac man hinh dudi day thi hien khuyit tat khe nut 25% va 25% ngoai (Hinh 11) ffinh 11 emote FieW Tuygn tap bao cao Hdi nghj KHCN "30 nam DSu Viet Nam: Cff hgi mdi, thach thde mdi" 293 • Kit qud - Trong trudng hgp NF-LF tin hieu dung la cua khe nut 25% ngoai va tin hieu nam ngang la cua khe nut 25% ngoai - Tin hieu NF-VHF cho tin hieu phan hdi cua vet nut va khong co tin hieu phan hdi cua vet nut ngoai vi su dung tan sd cao - Tin hieu RF cho tin hieu chdng len cua 25% vet nut va 25% vlt nut ngoai bdi vi su dyng ky thuat xuyen qua dng, dd khdng phan biet dugc cac khuyet tat giua va ngoai d Ket ludn Bang each ket hgp cam bien tu trudng gan vdi cam bien tu trudng xa, ta cd the cd dugc: - Kha nang chinh xac cac khuyet tat gan sat vdi tam dd va tam bgc dng - Kha nang phat hien nhiing Id dudi tam dd - Kha nang phan biet dugc cac khuyet tat ben va ben ngoai dng Ky thuat mdi - Bien ddi tan sd vdi ma mau a Sir cdn thiet Hay xem cac tin hieu dudi day (Hinh 12 va 13): ^v A \\^ Hinh 12a Tin hieu bao gom tir tinh ••'' Hinh 12b Tin hieu cua 16 thong •^ N Hinh 12c Tin hieu cua vet nth - Khdng cd kha nang phan biet giira cae tin hieu vdi tan sd don - Thiet bi da tan se giup phan biet cae khuyit tat - Bude tiep theo - Bien ddi tin sd ^ Cac kenh tan sd ao se chi cac dau hieu cac tan sd khae ^ Tat ca cac kenh tan sd ao dat chdng len ^ Dieu dua mdt dang mau nhit eho tung loai khuyit tat 294 Ly thuygt va dng dung eiia ky thuat dong dien xoay kigm tra khdng pha hiiy (NDT) ••N ' i ' v "\ 'V 'i i '^ ) i ^, ^* t ^\ i, i X 'i "i i 'i ••: v, i ') i Hinh 13a Tin hieu bao gom td tinh \ \ Hinh 13b Tin hieu cua 16 th6ng I I I Hinh 13c Tin hieu cua vet ntrt Cdng them mau Hinh 14: Bien doi tan s6 tir thap den cao Hinh 15: Bien d6i tan so td cao den thap Hinh 16: Bien d6i tan so diem cuoi Hinh 14b ffinh 15b ffinh 16b ffinh 14a ffinh 15a ffinh 16a Tuyin tap bao cao Hdi nghj KHCN "30 nam D5u Viet Nam: Co hdi moi, thach thde mdi" 295 b Lgi ich cda viec bien ddi tdn sd - De dang phat hien va nhan dang khuyet tat - Khdng can thiet phai cd chieu dai toan bg cua tin hieu khuyet tat de phan tich KHA NANG UNG DUNG TAI VIET NAM • Thiet bi kiem tra RFECT rat hien dai dung chu yeu cho vat lieu sat tu Hien nay, tai Viet Nam chua cd cdng ty nao mua thiet bi Chua cd dugc dao tao bai ban ve ky thuat • Cac ung dung cy the tai hien trudng hien chua cd bdi vi chua cd nhieu ngudi biet ve thiet bi • Cac nha may lge dau se cd tuang lai, do dau tu bay gid la thich hgp • Day la mgt ky thuat hien dai, khd hon cac ky thuat NDT khae nen phai dau tu sdm tu bay gid de - nam sau cd cac chuyen gia gidi ve ITnh vyc ôãã' r%4bô O w ã> ã ô • umm " •|BHi v:; -i — t=r?|Ht /ffi M.ga» ^ J ^Kj- — ^ Hinh 16: Thiet bj kiem tra bang dong dien xoay ECT 48AT TAI LIEU THAM KHAO ASME V: Boiler and pressure vessel code, non-destructive examination ASME B31.3: ASME code for pressure piping - Chemical plant and refiner\- piping ASTM-E709-85 Standard practice for magnetic particle testing www.russelltech.com ... Kiem tra dng trao ddi nhiet (sit tir va sit khdng tu) 290 Ly t h u y i t va dng dung ciia ky thuat ddng dien xoay k i i m tra khong pha huy (NDT) Dudng kiem tra ASME (Hinh 6) Hinh Dirdng kiem tra. .. didn ting len cua vat ki^m tra •R Hinh Tong trd cuon day - x Man hinh cua thilt bj kilm tra ddng dien xoay la cua sd the bien so dd tdng trd (Hinh 5) Hinh ^^* ^"^ kiem tra vat lieu nhom Cac - phan... khuyit tat ben va ben ngoai ong - Kiem tra dugc cac khuyet tat gin va dudi tim dd Ly thuyit va ung dung eiia ky thuat dong dien xoay kiim tra khdng pha hiiy (NDT) 292 • Nhugc diim - Khd su dung