NGHIEN cuu-TRAO DOI
N/
DANH GIA CAP DO CHAY DAO CUA ONG DAN HOl BANG THEP TRONG NHA MAY NHIET DIEN
TESTING EVALUATING LEVER FATIGUE OF STEAM STEEL PIPE IN THERMAL POWER PLANT
Nguyen Thu Hien', Phan Anh Tu^
'Tmng tam Thu nghiem - Kiem dinh Cdng nghiep, Vien Co khi Nang luang va Md - VINACOMIN
^Trung tam Danh gia hu hdng Vat lieu, Vien Khoa hoc Vat lieu
TOM T A T
De hgn che duac thiet hgi do sir hong hoc cua thiet bi thi viec kiim tra ddnh gid khd ndng Idm viec cua thiet bi tgi hien truang id dieu het sue cdn thiet, ddc biet Id nhirng thiet bi quan trgng Idm viec trong nhimg moi trudng khac nghiet (dp sudt Ion, nhiet do cao,...). Mgt trong nhiing yeu to dien hinh nhdt anh hudng den thai gian Idm viec cua thiet bi duac che tgo bang vat lieu kim logi Id sir bien dgng ddo.
Noi dung cua bdi bdo ndy trinh bdy cdc ket qud nghien cuu ddnh gid cdp do chdy ddo cua cdc dudng ong hai qud nhiet trong cdc nhd mdy nhiet dien de co cdc phuang dn khde phuc, ndng cao hieu qud Idm viec cua thiet bi.
Tit khoa: Ddnh gid cdp do chdy ddo ciia vdi lieu thep.
ABSTRACT
In order to reduce the damage caused by equipment's break-down, it is essential that equipment needs to be regularly checked on-site, especially for important equipment used in severe environments (high pressure, ultra-high temperature, etc). One of the typical factors affecting the duration of metallic eqtdpment is creep deformation. Scope of this paper is to study and evaluate the level of creep deformation for superheating pipe systems in the coal-fueled power plants so that remedies is proposed to improve uerformance effectiveness of the equipment
Keywords: Evaluating level fatigue of material steel.
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NGHIEN cuu-TRAO DOI
l.DATVANDEDdi vdi cac chi tik, ciu kien cua nha may nhiet dien lam viec trong di^u kien nhiet dd va ap suit cao, nhat la cac dng dan hoi qua nhiet thi dang hu hdng thudng gap nhat la hu hdng chay dao. Dudi tac ddng cua nhiet do cao, thep cd the bi bi6n dang cham va lien tuc, tham chi ngay ca khi chiu mdt tai trong khdng ddi, va rdi den mdt luc nao dd se bi nut, gay [1]. Bai bao nay trinh bay ket qua nghien cim qua trinh bien dang dao xay ra trong cac dudng dng hai qua nhiet cua nha may nhiet dien bang phuang phap kiem tra danh gia tai hien trudng trong thdi gian hon 13 thang
2. THIET BI VA PHlTOfNG PHAP NGHIEN CUtJ
Cac dng dan hoi bang thep duoc dan dau cau tnic be mat tai hien trudng theo phuong phap Replica theo tieu chuan ASTM E1351-01 va su
dung cac mang phim xenlulo axetat [2] Cac vi tn dan mEuReplica duoc mai va danh bdng bang may mai chuyen dung Transpol 2/ Struers (Dan Mach).
sau do duoc tam thuc de bien rd cau true te vi. Do dng dan bai duac che tao tu mac thep 9CrliVIo (T91) nen chat tam thuc la dung dich Vilella [1]
Su dung kinh hien vi cam tay PortaMet/Buehler (My) de kigm tra tai cbd cac mau Replica Tiep theo, mang Replica can duo'c phu mdt Idp Ft rSl mdng bing phuong phap bdc bay chup anh cau true tren kinh hien vi quang hoc Axioplan Il/Carl Zeiss (Due) trong phdng thi nghiem ciia Trung tam COMFA va Hitech-LOM, Hinh 1 minh hoa cho qua trinh lay mau kiem tra td chuc te vi tren cac dng hoi qua nhietDN50*5,58 mm Trongthoi gian nghien cuu, tdng sd vi tri kiem tra da tien hanh la 100 va duac chon tren 20 ong hoi cua nha may nhiet dien Vi tri kiem tra duoc lua chon nam d phia tren, phan giiia va phia dudi ciia gian dng hoi
i
a) Tdm thuc vd duac dan mdng phim;
b) Boi muc den len ti-en mdng phim de tdng do tuong phdn;
cj Ddii keo vd tdch mdng phim ra mang ve phong tbi nghiitu:
Hinh J: Hinhdnhqud ninh Idy mau kiim tra tgi vv ///phdn giuagidu dng.
3. KET QUA VA DANH GIA
Td chirc te vi ciia ciia cac mau nghien cuu tren cac dng dan hoi qua nhiet ch^ tao tir thep T91 d6u cho thiy la mactenxit ram (xem hinh 2, 3 va 4) Ban than td chirc nay da cd cacbit ti^t pha, tuy nhien, khi thdi gian lam viec ciia thi^t bj
trong dieu kien nhiet dd va ap suat cao cang laii thi cacbit tiet pha se bi thd hon Khi cacbit tiet pha nhieu va thd thi kiang Crom trong nen thep bi giam do cacbit cbu yeu cd cdng tbii'c la Cr,,Cj se chiem lay mdt phan Crom trong nen, ket qua !a do ben nhiet, ben an mon va ben dao cua thep bi suy giam nhieu
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NGHIEN Cl/U-TRAO DOI
Hinh 2: Anh to chuc te vi tgi cdc diem phia tren gian ong hai:
a) Bat ddu van hdnh 200x; b) Sau khi van hdnh 1 nam lOOOx.
Hinh 3: Anh id chuc ti vi tgi cdc diem a phdn giiki gidn dug hai:
a) Bdt ddu van hdnh 200x; b) Sau khi van hdnh 1 nam lOOOx.
Hinh 4: Anh to thuc te vi tat cac diem phia dual gidn ong hai:
a) Bdt ddu van hanh 200x, b) Sau khi van hdnh 1 ndm lOOOx.
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NGHIEN CirU-TRAO DOI
* Danh gia va thuc hien cac hanh dong phong ngua lihac phuc ve chay dao cia v$t lieu A
B C D
1 Khong cSn cho den ISn dirng bao duong chinh Ice tiep
Kiem tra cau true bSng Replica sau tii-ng khoang thfri gian thich hgp (kiem tra lai sau 1,5-3 nam)
Van hanh co gioi han den khi sua chua (sira chira / thay the trong vong 6 thang) Lap tu'c sira chira
Damage parameter
A
B C D
Action required None until next major scheduled maintenance outage Replica test at specified interval Limited service until repair Immediate repair
Exposure time
Hinh 6: Su thay ddi cua mire dp (biin dgng) ddo ciia thep theo thdi gian Idm viec.
va cac hdnh dpngphpng ngita cdn thiit [2] du&i gidn dng hai a) a) Bdt ddu van hdnh 200x: b) Sau khi vdn hdnh 1 ndm lOOOx.
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NGHIEN CirU-TRAO DOI
Bang 1. Su thay doi cua cdu true te vi vd miec do hu hong tiiy theo cdp chdy ddo:
Ckp chay dao 0 1
2a 2b 3a
3b
4
5
Cau tnic te vi va mire do hu hdng Cau tnic ban dau nhu liic mdi nhan Cau triic bat dau thay ddi khi chiu tai nhiet- - Tiet pha cacbit min trong ferit
- Pha bainit va peclit bi hda tan dan thanh fent va cacbit, cacbit bau nhu khdng ti^t pha d bien hat - Thep mactenxit cd thd hda cacbit tai bien kim mactenxit.
- Chua xuat hien vi Id rdng.
Tiet pha cacbit tren bien bsit (dang chudi), cd cac vi Id rdng don le.
Cacbit d bien b^t bi tap trung va thd ban, cd nhilu Id rdng phan bd tu do.
Bat dau cd hu hdng chay dao
- Cd nhieu Id rdng phan bd theo dinh hudng.
Cd bien hat rieng le bj tach rdi hay cac vi Id rdng ket hap, ndi lien.
Xuat hien vi nut.
Xuat hien nirt thd dai.
Bien phap can ap dung Khdng can ap dung bien phap gi-
Kbdng can cho den lan dirng bao dudng chinh ke tiep
Xac dinh quy md va su phat tnen cua hu hdng chay dao bang cac dot kiem tra phii hop bang phuang phap Replica Giam nhiet dp, ap suat, neu can thiet phai sua chGa hoac thay thg.
Van hanh cd gidi ban den khi sua chiia (sua chira / thay the trong vdng 6 thang)
Khdng van hanh tiep, siia chiia hoac thay the
Doi voi qua trinh dao cua thep T91 cOng nhu thep khong ri mactenxit, 16 r6ng khong bat diu xuat hien a bien hat, ma xuit hien a bien hat austenit nguyen thuy hay bien phien mactenxit c a p chay dao cao nhit d6i voi T91 la 2b, dieu nay la do hanh vi chay dao ciia loai thep nay khac 50 voi cac mac thep chiu nhiet cu - rit b6n a giai loan d i u con sau khi dao (co 16 rdng) thi rit nhanh 51 nirt hong [3] D6i voi cac vi tri kiem tfa co cip
;hay dao ni 3a tro xu6ng yeu cau tien hanh kiem ra lap lai t6 chiic t6 vi tai do sau khoang thoi gian TAP
hi 1 nam ke tii lan kiem tra nay. Cac vi tri kiem tra CO cap chay dao len toi 3a-3b dugc coi la gioi han cho phep lam viec cua thiet bi vi khi cap chay dao la 3b da can phai ap dung cac bien phap an toan nhu giam ap suat, nhiet do,.. Trong thuc t^ van hanh nha may nhiet dien thi kho thuc hien dugc dieu nay, vi the nen c6 phuong an thay the cac 6ng qua nhiet nay, hay can theo doi chiing chat che trong qua trinh van hanh va c6 phugng an sira chira/thay the kip thoi.
Voi to chirc te vi cua vat lieu tai cac vi tri C H l C O KHI VIET NAM, So 1+2 nam 2014
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NGHIEN CirU-TRAO 001
da kiem tra thi chua thiy xuSt hien cac Id rdng dao, tuy nhien cac vj tri hat cacbit thd da co cap chay dao tien rat gan den cap 2a, dieu nay yeu cau tien hanh kiem tra lap lai td chirc t^ vi tai do sau khoang thdi gian tir 1- 2 nam iTng vdi moi mdt cap dp chay dao thi cung can ap dung nhirng hanh ddng phdng ngira nhit dinh
Trong qua trinh bien dang dao, td chuc te vi ciia thep ciing thay ddi tir ciu triic ban diu cho den khi xuat hien cac Id rdng dan le {chii y6u d bien hat) rdi cac Id rdng ngay cang nhigu, cd
dinh hudng. Neu nhu dudng dng tiep tuc lam vi§) trong dieu kien nhiet do va ap suit cao se xua hien cac vet nut te vi do cac Id rdng kdt noi IEU r6i tiep theo la niit thd dai Dieu nay hoan toan phij hop vdi anh td chirc te vi cua thep dng gian hm qua cac thdi ky nhu trong binh 6 Trong tit ca cac mau kiem tra, cacbit tiet pha the bien rd va cd kich thudc kha thd, cac hat cacbit tap hop thanh chu6i d bien hat, cac vi Id rdng bat dau xuit hien. Tit ca nhiing hien tuong tren se lam giam co tinh va d$
ben dao ciia vat lieu.
c) Cdc 16 rdng phdi triin tho dgi.
Hinh 6: Su thay ddi td chuv ti
d) Cdc Id rong theo dinh huxmg vd ndi liin.
VI cua dng gidn hai (xlOOO).
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NGHIEN CIIU-TRAODOI
4. KET L U A N
Cac ket qua ki6m tra cho thiy sau thdi gian
dao). Cacbit tiet pha cd kich thudc thd, bi tap hop thanh chudi. De bao dam an toan v&n hanh cho he thdng Id hoi, can tien hanh kiem tra dinh ky td lam viec lien tuc, vat lieu cua cac dng d k boi qua ^buc t6 vi trong qua trinh van hanh d6 cd phuang nhiet da bi suy thoai ro rang vg ciu tnic (chay an sira chiia, thay the kip thdi. •
Ngay nhan bai 05/01/2014 Ngay phan bien: 10/02/2014
Ngu-oi phan bien: PGS, TS Bui Anh Hda, Vien Khoa hpc va Ky thuat Vat lieu, Trudng D?ii hoc Bach Khoa Ha Ndi.
Tai lieu tham khao:
[1]. R. Viswanathan "Damage Mechanisms and Life Assessment of High Temperature Components", ASM hitemational, Metals Park, Ohio 44073, 1995
[2]. ASTM E 1351:2001 "Standard Practice for Production and Evaluation of Field Metallographic Rephcas", reapproved 2006.
[3], Pertti Auerkari, Jonna 'VGB-TW 507 - Microstructure Rating Charts for Evaluating the Microstructure and Creep Damage of High- Temperature Steels for High- Pressure Piping and Boiler Components", 2"^ Edition, 2005 [4]. Cdc bdo cdo ddnh gid qud trinh chdy ddo cua Viin Ca khi Ndng lugng vd Md vd Trung tdm Comfa.
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