Ni dung

Chng I: Tng quan v qu trnh chng n mn v sn ph1. M u2. Vt liu sn ph chng n mn3. Sn ph4. Thit k lp sn ph cho cc cng trnh bin5. X l b mt trc khi sn6. Thi cng sn ph7. Kim tra cht lng cng tc n mn8. Bo dng v sa cha sn phChng II: Chng n mn cho ng ng v b cha du kh1.Gii thiu2.Vt liu cho ng ng du kh3.Chng n mn bn ngoi cho ng ng bin4.Chng n mn bn trong cho ng ng du kh5.Chng n mn bn ngoi cho ng ng trn t lin6.Chng n mn cho b cha du v kh lng: cc loi b cha, vt liu, cc gii php chng n mn

Chng I: Tng quan v qu trnh chng n mn bng sn ph

1. M uChng n mn bng sn ph l bin php to lp bo v trn b mt vt liu chng li cc tc ng n mn (ho hc, in ho) ca mi trng xung quanh. Chng n mn bng bin php sn ph l bin php ph bin v c t lu i. Cc bin php chng r v n mn ph bin hin nay l s dng cc vt liu t b n mn tuy nhin cc vt liu ny thng c gi thnh cao, thng ch lp t nhng ni khng b ngp nc. Bin php chng n mn ph bin nht l dng sn ph bo v. Lp sn ph bo v nhm to mt lp mng chn (barrier) cch ly kim loi vi mi trng. i vi cc cng trnh b ngp nc hay chn trong t th kt hp thm bin php chng n mn cathode (cathode protection). Bin php ny c s dng rng ri trn th gii nh cc gin khoan bin, cu cng, h thng bn b ng ng u c h thng chng n mn cathode. 2. Vt liu sn ph chng n mn Phn loi lp ph chng n mn theo vt liu:- Lp ph sn hu c sn v c - sn tng hp: Sn ph chng n mn c nghin cu pht trin mnh trn th gii. Sn hu c l sn phm ph bin nht v c tng hp t thc vt, than hay du khSn v c l sn phm c tng hp t cc cht kt dnh v c nh natri silicat, canxi silicat Hin c cc loi sn hiu sut cao ca h sn nha km v than c s dng chng n mn cho cc gin khoan v cc kt cu hng hi khc trong vng nc bin ng (tui th 20-30 nm). Vo nhng nm 1970-1980 nhiu loi sn lt ph khc nhau c dng th nh sn chng n mn nng s dng nha tng hp clorua, epoxy, poliester, sn nha c mnh thy tinh hay lp ph cao su, FRP, xi mng, nha tng hp, hp kim ng v niken hay cc bng chng n mn. - Ph kim loi: Bin php chng n mn s dng lp ph kim loi cng c s dng kh ph bin. Bin php ny c th m bo bn c hc cao do lp ph kim loi chu c va p tt hn lp ph hu c. - Lp ph bng hp cht ho hc: Mt bin php sn ph khc l ph vt liu ho hc. To ra mt lp cht ho hc trn b mt kim loi bo v c tnh bn vng cao. Phn loi lp ph theo tnh cht bo v:Lp ph ngn cch: Lp ph loi ny to ra mng ngn cch gia b mt vt liu cn bo v vi mi trng xung quanh (v d nh sn, m kim loi khng n mn). Lp ph m cc: To ra trn mt kim loi cn bo v mt lp kim loi ph c in th m hn. V d ph Zn, Sn, Cd, ... ln trn b mt st, thp. Khi lp ph b khuyt tt cc b th kim loi cn bo v vn khng b n mn.Lp ph c ch: To ra cc cht c ch n mn trn b mt kim loi.3. Sn phSn v vecni l nhng sn phm lng, c th qut hoc phun ln b mt vt liu kim loi hoc phi kim loi trang tr, bo v chng n mn kim loi hoc cch in, dit nm mc... Sn l mt h huyn ph gm cc ht mu (oxit kim loi hoc mui kim loi) phn tn trong cht kt dnh hu c. Phn loi sn ph:Sn du tho mc: Thnh phn cht to mng l du thc vt. Loi sn ny thng khng bn trong mi trng xm thc.Sn du nha: Thnh phn cht to mng l du thc vt v nha (thin nhin hoc nhn to). Loi sn ny thng dng kh ph bin nhng khng thng dng trong k thut.Sn tng hp: Cht to mu l nha tng hp, tn sn theo tn nha nh sn epoxy, alkyd Sn tng hp c s dng rng ri trong c cng nghip v dn dng.Thnh phn sn: a) Pha lng (cht to mng-hot cht):Gm dung mi ho tan cht kt dnh, to ra trn b mt mt mng cht rn lin tc sau khi dung mi bay hi (cht kt dnh c nhiu loi - nha ankyt, bitum, nha than , nha vinyl, nha epoxy, nha polyurethan). Cc ph gia: nhng cht vi mt lng nh cho vo ci thin mng kt dnh, cht lm cho sn mau kh do s tng nhanh qu trnh oxi ha cht kt dnh. Nhng cht ny thng l mui ca mt s kim loi Co, Pb, Mn, Zn, Zr Cht hot ng b mt ci thin thm t ca sn v b mt kim loi. Cht to nh tng lm cho sn dng nh n nh. Cht phn tn c nhim v ui nc ra khi b mt sc t (pigment), lm tng cng bm dnh ca mng sn ngay c khi b mt kim loi b m t. Cht mu (pigment), mu hu c hoc l cc oxit kim loi, mui kim loi. Cht chng lng. Cht tr vi khun, hu h (Cu2O). Cht kt dnh ng rn do b oxi ha trong mi trng khng kh. Sn du thng l cc loi du thc vt: du lanh, du tng, du u tng. Nha alkyt l este ca diaxit v ru a chc. Cht kt dnh ng rn do bc hi dung mi: polymethylmethacrylat. Cht kt dnh ng rn do polymer ha: nha epoxy, nha polyurethan

b) Pha rn: Cc loi cht sc t v cht ph gia. Sc t chng n mn: bt km, bt ch, Pb3O4, ZnCrO4. Sc t gim thm nc: ZnO, TiO2, Fe2O3, graphit. Cht n: SiO2, SbSO4, bt tan, mica, CaCO3... Gia cng sn ph: Qu trnh sn ph thng tun th cc bc:- X l b mt trc khi sn;- Chn loi sn ph theo yu cu;- Sn ph: thng chia lm cc lp sn nn (chng r v lm nn), sn lt (to phng), sn bao ngoi (trang tr).4. Thit k lp sn ph cho cc cng trnh bin+ Cc tiu chun p dng: Thit k h thng chng n mn theo: NACE RP-01-76 (API); + Lp s sn: Vng sn: vng va p sng c xc nh nh sau:SZu=MNTriu cao nht + 60% . H1%SZl=MNTriu thp nht + 40% . H1%. S sn cho tng vng kt cu: trn thng tng, vng nc bn, vng bin ng triu, vng ngp nc.Di y l mt v d s sn ph ca mt cng trnh bin thp cho vng thm lc a pha Nam Vit Nam.Cng trnh thit k c xy dng trong vng bin nhit i c m khng kh thng xuyn ln hn 85%, nhit nc bin thng xuyn ln hn 25C, mn ca nc bin l 3,3%. Trong iu kin kim loi b n mn ph hy rt nhanh, theo qui chun OTC-104-79 ca Lin X (c) ta c th chia cng trnh theo mc n mn sau:-Vng kh quyn: tc n mn thp cacbon l 0,09 mm/nm, y l vng c n mn xm thc mnh trung bnh.-Vng thu triu: Tc n mn thp cacbon l > 0,5 mm/nm, y l vng c tc n mn xm thc rt mnh.-Vng di nc: tc n mn thp cacbon l 0,2mm/ nm, y l vng c n mn xm thc mnh.-Vng di t: tc n mn nh hn 0,01 mm/ nm, l vng c n mn xm thc yu.Chnh v cc vng c n mn khc nhau v c im khc nhau, do ta cn thit k h thng chng n mn cho tng vng khc nhau ph hp vi iu kin c th cho tng vng.S qui trnh sn ph cho tng phn ca cng trnh nh sau. + S 1: Dng cho vng ngp nc ca cng trnh.- Phun ct lm sch n SA 2.5.- Sn mt lp sn lt Sigma EP Universal Primer dy:50 m.- Sn mt lp sn Sigma TCN 300 brown dy:125 m.- Sn mt lp sn Sigma TCN black dy:125m. Tng dy:300 m.* S 2: Cho vng bin ng triu (Vng thm t theo chu k).- Phun ct lm sch n SA 2.5, nhm b mt t t 70 100 m.- Phun ph mt lp nhm dy: 150 m.- Sn mt lp sn Sigmacover Mastic SF dy:250 m.Tng dy : 400 m.* S 3: Dng cho vng khung ni ca chn : (Vng nc bn)- Phun ct lm sch n SA 2.5 nhm b mt t t 70 - 100 m.- Phun ph mt lp nhm dy: 150 m.- Sn mt lp sn Sigma EP dy:250 m.- Sn mt lp sn Sigma CM microcoat dy: 250 m.- Sn mt lp sn Sigmaclur gloss (vng) dy:50 m.Tng dy : 800 m.* S 4: Dng cho phn thng tng: Sn chu lc, sn sn bay, phn kt cu thp Block nh , lan can, tay vn cu thang, l phn cng trnh nm trn kh quyn.- Phun ct lm sch n SA 2.5.- Sn mt lp sn Sigma EP dy:50 m.- Sn mt lp sn CM dy:100 m.- Sn mt lp sn Sigmaclur gloss (trng) dy:50 m. Tng dy:200 m.5. X l b mt trc khi snKhng c loi sn no c kh nng bo v tt khi c sn trn mt b mt khng c chun b k cng. Mng sn ch thc s c hiu qu khi c sn trn b mt c chun b tt v ph hp...Kh nng bo v ca mng sn khng nhng ph thuc vo cht lng sn m cn ph thuc rt nhiu vo cht lng chun b b mt, iu kin thi cng, phng php thi cng cng nh tay ngh ca cng nhn.a) nh hng ca lp g v bn i vi snCc vt bn, vt gc th lm mt kh nng bm dnh ca sn vi b mt cn sn. Vic sn ln mt b mt chun b khng ph hp, s khng to c mt nn tng vng chc bo v b mt chng li s n mn ca mi trng v cc nh hng ha hc khc.B mt sn nhim bn s lm cho bm dnh gia cc lp sn gim i, tng kh nng thm thu ca nc, dn n ph hoi b mt cn bo v. Do vy trc khi sn lp tip theo phi ra nc ngt ton b b mt sau lm kh ri mi sn tip.Mc ch ca cc phng php lm sch b mt l lm sch cc vt bn v cc vt g gip cho mng sn bm dnh tt hn v hiu qu chng n mn cao hn.b)Cc cp g stCp g A: B mt thp c bao bc ton b bi mt lp o tn v c rt t g.Cp gB : B mt thp bt u g v lp o tn bt u bong trc.Cp gC : B mt thp trc ht lp o tn, nhng cc l r vn kh nhn bit bng mt thng.Cp gD : B mt thp g v cc l r nhn bit c bng mt thng.c) Cc phng php lm sch b mtGi s trc khi c x l, b mt thp c lm sch bi v bn, ng thi lp g dy cng c lm sch bt bng g ba.- Lm sch bng bn chi st : Phng php ny tin li, nhng khng ph hp cho vic x l cc mi hn. Nhc im c bn ca phng php ny l d lm cho b mt b bng, do lm gim i bm dnh ca lp sn lt ln b mt nn.- Lm sch bng ba g: G thng kt hp vi bn chi st. Phng php ny i khi thun tin cho nhng sa cha cc b v cho mt vi h sn thch hp. Nhc im ca phng php ny l khng th lm sch b mt t cht lng cao.-Lm sch bng ngn la : Phng php ny lin quan n vic x l nhit, nh thit b t chy (acetylen, oxy). Phng php ny lm sch hu ht lp o tn, nhng km hn khi x l lp g, do khng p ng c cc yu cu ca cc h sn hin i.-Mi a ct ( s dng a mi): L cc a quay ph bng ht nhm (ht mi). Dng cho nhng vng sa cha cc b hoc loi b cc mng g nh. Cht lng ca a ct ngy cng c hon thin do gip x l b mt c tt hn- Lm sch bng phun nc p lc cao: Phng php ny dng ty sch cc lp sn c, cn bn vi p lc t 1.700 bar 2.000 bar (25.000 30.000 psi).- Lm sch bng phun ct t: Lm sch bng hn hp nc v ct, di p sut cao. c dng x l cc mng g ln. Sau khi lm sch do b mt thp b t nn phi c lm kh trc khi qut sn. Phng php ny c u im l khng gy nhim mi trng v khng c bi.- Lm sch bng phun ct kh: y l phng php c dng ph bin, cht lng b mt c chun b rt cao. Cc vt g, cht bn b loi b hon ton ng thi b mt c to nhm tt, bm dnh ca lp sn c ci thin r rt. Nhc im ca phng php ny rt bi nn gy nhim mi trng.d)K thut lm sch b mt bng phng php phun ct.Mt b mt thp b g hoc bn c th lm sch mt cch c hiu qu bng phng php phun ct tc l cc ht ct, , si nh c y ti vi mt tc cao qua ming ng phun s tc ng ln b mt lm sch g v cc cht bn dnh trn n.Kch thc mt ht mi (ct, si) khong t 0,3 n 1,5 mm (12 60 mils) l kch thc c kim nghim hiu qu nht t c cc tiu chun chun b b mt theo quy nh, c bit c hiu qa khi lm sch b mt b lm su. (Vic s dng ht si trong qu trnh chun b b mt thng s dng nhiu hn v hiu qu hn dng bng ct).p lc bnh nn kh thp nht l : 10 kG/cm2.p lc u vi phi t c t : 5 6 kG/ cm2.ng knh vi phun (ch tht) : 8 -10 mm.Gc phun (to vi b mt c phun) : 75o.Vic chun b b mt t hiu qu cao, nhanh chng v kinh t hay khng cn ph thuc vo mc g st, mc r ca b mt cn lm sch. Mt b mt tn cn mi, phng chc chn chi ph cho vic lm sch s t tn km hn so vi mt b mt g, r nhiu.Cc ch trc khi phun ct:* Mi phng cnh sc, gc, mi hn.* Mi lng nhng mi hn g gh, khuyt tt st thp, ty sch ba v hn* Cc l khot nn c ng knh ti thiu 30mm, c kim tra v chp thun trc khi lm sch.e) Cc tiu chun lm sch b mtChun b b mt l mt cng vic ht sc quan trng v cn thit. Do chng ta cn phi hiu r cc tiu chun chun b b mt. Tiu chun lm sch b mt thng thng nht c gi l : Tiu chun chun b cho b mt thp k hiu SIS 05 5900-1967 do Vin nghin cu n mn Thy in son tho vi s hp tc ca Hip hi kim tra v vt liu Hoa k (ASTM) v y ban nghin cu sn cu trc thp (SSPC). Tiu chun ch ra cc cp khc nhau.* Cc cp lm sch b mt bng phng php co v dng bn chi st (phng php th cng) c k hiu bt u bng ch St (St 2; St3).* Cn lm sch bng phng php phun ct l Sa (Sa 1; Sa 2; Sa 2.5; Sa 3). Tuy nhin trong thc t thng s dng 4 loi cp sau:St3Co, ty g v cc cht bn bng bn chi st phi rt cn thn. Vic x l b mt phi loi b lp g v cc vt l. Sau khi lm sch bng khng kh kh nn hay bn chi sch, b mt phi c bng sng ca kim loi.

Sa 2.0B mt lm sch bng phun ct k, cc vt g, cn bn c ty sch l hu ht b mt nn, sau c lm sch li bng khng kh kh nn, hoc bn chi sch.

Sa 2.5B mt c phun ct rt k, hin ln mu kim loi gc. Cc vt g nu cn ch dng vt hoc si mnh, b mt sau c lm sch bng khng kh kh nn, hay bn chi sch.

Sa 3.0B mt c phun ct cc k cho kim loi thun. Loi b hon ton lp g, vt l, sau c lm sch li bng khng kh kh nn hay bn chi sch. B mt sau khi phun ct v lm sch s cho mu sng kim loi ng nht.

f) Cc tiu chun tng ngTrong k thut x l b mt bng phun ct, ngi ta cn s dng cc tiu chun ca Anh (BS) v ca M (SSPC) tng ng vi tiu chun Thy in c a ra di y:Tiu chun Thy inSIS 05 5900Tiu chun Anh-BSTiu chun M-SSPC

Sa 3.0Sa 2.5Sa 2.0Cht lng loi 1Cht lng loi 2Cht lng loi 3SP-5 trng kim loiSP-10 gn trng kim loiSP-6 thng phm

g) Chun b b mt trc khi sn.Nc, hi m, du, m, cc vt g m, vt phn cng nh cc cht bn khng thch hp sn.Chun b b mt kim loi trc khi sn l mt cng vic cc k quan trng, bi l nu b mt c chun b tt th mng sn s bm dnh tt vo b mt nn do nng cao c tui th v cht lng ca mng sn. Ngc li, nu chun b b mt khng tt th mng sn s nhanh chng b bong trc, gy ph hu b mt nn. Do vy, khi chun b b mt nn cn phi tin hnh theo ng cc trnh t sau:h) i vi b mt thp miCc bc chun b c tin hnh theo th t nh sau:- Dng gi tm dung mi ( xng pha sn, du TC1) ty sch cc vt du m bm trn b mt thp.- Dng vi phun nc ra sch cc cn bn (t, ct, bn) sau lm kh bng gi lau hoc thi kh nn.- Cui cng : Dng sng phun ct, my mi hoc giy nhm ty cc g st, vy hn sau c lm sch li bng gi lau hoc kh nn- Mt im cn ht sc lu l: B mt thp sau khi lm sch theo cc bc trn y s b g st tr li rt nhanh chng. V vy, phi sn ngay cng sm cng tt mt lp sn chng g bo v b mt va mi c lm sch khi b g st tr li.i) i vi b mt c lp sn c v b mt b g st nhiuCc bc chun b c tin hnh theo th t nh sau:- Dng gi tm dung mi ( xng pha sn, du TC1) ty sch cc vt du m bm trn b mt - Dng vi phun nc ra sch cc cn bn ( t, ct, bn) sau lm kh bng gi lau hoc thi kh nn.- Dng no, hoc phun nc p lc cao loi b bt lp g.- Cui cng : Dng sng phun ct, my mi hoc giy nhm ty ht lp sn c hoc cc vt g, vy hn sau c lm sch li bng gi lau hoc kh nn v phi c sn ngay mt lp sn chng g.j) Chun b b mt th cp.V mt l do no nh phi ct, hn v b sung, sa cha cc b m sau khi sn xong 1 lp sn chng g, ngi s dng cha c iu kin sn ngay lp sn tip theo. V vy sau khi cc cng vic ct, hn v, sa cha cc b c hon tt, cc bc chun b cho lp sn tip theo c tin hnh nh sau:- Dng my mi, bn chi st, no ty sch cc vy hn, lp sn b chy do hn ct, lp sn b h hng do gia cng c kh sau dng chi sn dm v ngay khu vc bng 1 lp sn chng g, cho sn kh hon ton.- Dng gi tm dung mi lau sch cc vt du, m, sau dng vi phun nc ty sch cc cn bn. Dng gi lau kh hoc kh nn lm kh b mt trc khi sn lp sn k. Mc ch ca x l b mt trc khi sn: lm sch g, m, bi, mui, m tng hiu dnh bm ca sn, tc l tng hiu qu ca h thng sn ph.Cc tiu chun quy phm p dng cho vic x l b mt kim loi: ISO 8501-1, SIS 055900, NACE.Tm li, cc phng php x l b mt bao gm: Cc kiu lm sch bng phng php phun vt liu rn Lm sch bng nc p lc cao C bng bn chi thp C bng mi Co sch cn bng phng php c hc Lm sch bng la Ty bng phng php ngm trong dung dch p bng tay v c bng bn chi thpi vi thp mi: lm sch bng phun ct v sn lt bo v b mt trong qu trnh thi cng. Thng phi lm sch li b mt, thm ch ty lp sn lt sn chnh thc.i vi thp c: p dng tt c cc ni dng trn nhng lu n cc kt cu gn k vi kt cu cn x l.6.Thi cng sn ph+ Tt c cc s sn c tham kho v kim tra qua kinh nghim thc t, c tnh ton sao cho hiu qu bo v cao nht, m bo chi ph nh nht trong sut qu trnh s dng v bo dng.+ Vic thi cng sn phun c tin hnh theo s sn thit k chng n mn.- Trc khi tin hnh sn, sn cn phi pha ng theo t l quy nh v cho thm dung mi ng loi, ng t l, cn phi khuy k sn, tt nht l bng my khuy, trong trng hp khng c my khuy, cn khuy bng tay ti thiu 5 pht.- Tin hnh sn bng thit b phun sn khng c khng kh (v d Graco Buldog, Graco Monak hay Graco King). Cho php sn bng chi cc chi tit nh hoc phc tp nh li, tay vn, lan can trnh lng ph sn khi sn bng sng phun.- Trc khi tin hnh phun sn cn phi thi kh lm sch ht bi v tin hnh sn mt lp bng chi vo cc v tr sn kh bm nh: cc gc cnh, mi hn..- Cn phi chn ng kch thc u phun v p sut phun cho tng loi sn theo tng dy.- Khi bt u sn v trong sut qu trnh sn phi lun kim tra dy t ca my sn, nu thy dy t cn cha ng cn hiu chnh ngay.- Cn phi nghim chnh thc hin ng quy nh k thut phun sn, nht l qui nh a tay: lp sau ln lp trc 50%.- Cn tun th tuyt i theo quy nh thi gian kh gia cc lp.- Sau mi lp cn kim tra dy kh mi lp bng thit b Eclolmeter 345, Ecolmeter 236 hoc Minitest 4000 v ch cho php sn lp tip theo sau khi dy kh ca lp trc phi khng c im no thp hn 5% dy qui nh ca lp .- dy tng cng ca mng sn phi khng c im no thp hn 5%, nu c cn phi sn b sung ngay cho dy.- Cng trnh sau khi sn xong phi ti thiu 7 ngy mi a vo s dng.+ Phn kh quyn l ni c n mn xm thc trung bnh do s sn s dng h Epoxy-polyetan dy 300m l h sn hin i, khng b to phn, i mu trong qu trnh s dng, c thi hn s dng ti thiu l 5 nm, v vng ny vic bo dng, sa cha d dng, khng tn km nn khng cn thit phi tng thi hn s dng ca mng sn.+ Phn di nc c bo v rt tt bng h thng Protector kt hp vi lp sn Epoxy nha than c dy 300 m. V vng ny bo dng sn li hoc thay th Protector rt kh khn tn km nn tnh ton sao cho thi hn s dng v bo v hiu qu khi b n mn l 20 n 25 nm khng cn phi sa cha. + Phn dao ng thy triu l phn cng trnh nm trong vng c mc n mn xm thc mnh, hn na li ch c th bng lp ph, h thng Protector khng bo v c v nht l vic sa cha, bo dng rt kh khn, tn km. Thc t cho thy phn bin ng thy triu, cng trnh b n mn nhanh nht, sn b hng nhanh, sa cha vng thy triu rt tn km, nguy him, chi ph dn gio, tu b rt ln m hiu qu lp sn ph sa cha thc hin ti dn li km rt nhiu so vi khi thi cng trn b. Do cch tt nht l hn ch ti a vic sa cha phn ny. V vy vng ny phi c bo v bng lp ph c bit, ch c mt lp dy ti thiu 2,5 mm, d cho chi ph ban u kh cao, kt hp phun ph mt lp nhm 150 m. + Kim tra cht lng cng tc chng n mn.7. Kim tra cht lng cng tc chng n mn+ Kim tra vt liu: Sn, dung mi, ct, dy nhm.- Tt c mi vt t phi ng chng loi, v s lng, m bo cht lng v thi hn bo qun.+ Kim tra thit b thi cng: Thit b v sng phun sn, my nn kh, sng phun nhm, thit b phun ct. Cn phi kim tra p sut my nn kh, sch v kh ca kh nn, kim tra cc loi u phun sn.+ Kim tra dng c kim tra cht lng: thc o dy t, dy kh ca mng sn.+ Kim tra cht lng b mt kim loi trc khi sn: Theo ISO 8501-1-1998.+ Kim tra iu kin kh hu: o nhit b mt kim loi, nhit khng kh kh, m tng i v xc nh im sng.+ Kim tra cht lng lp sn.- o dy tng lp bng thit b Elcometer 246 hoc tng ng.- Kim tra cng mng sn: bng b bt ch.- Kim tra dnh bm mng sn: bng thit b Elcometer F-106.8. Bo dng v sa cha sn ph (maintenance & repair)Qui trnh v thi gian Bo dng v sa cha sn ph c thc hin theo yu cu quy phm thit k i vi tng vng bin v tng loi cng trnh.

Chng II:Chng n mn cho ng ng v b cha du kh

1. M uVn n mn l mt trong nhng nguyn nhn chnh gy ra h hng ng ng. Trong khi , s an ton ng ng bin c tm quan trng c bit. H hng ng ng dn ti tn tht v con ngi, v kinh t, v c bit l nhim mi trng. V vy, cng tc chng n mn c quan tm c bit c trong giai on thit k ln thi cng v vn hnh ng ng.Mi trng gy n mn ng ng bao gm mi trng trong v ngoi ng. Mi trng bn trong ng ph thuc trc tip vo thnh phn cht truyn dn trong ng c tnh xm thc cao hay thp. Vn tc v nhit dng truyn dn cng c nh hng trc tip n tc n mn. Cc hp cht lng ng to nn cc hin tng g st trong ng to iu kin cho s pht trin ca qu trnh n mn cc b. ng ng lm vic an ton trong i sng thit k, ng ng cn c bo v khin mn c trong ln ngoi.Mt cht kt dnh mnh m ca lp ph bn ngoi trn ton b chiu di ca ng ng s c xu hngngn chn s n mn.Tuy nhin,lun lun c kh nng h hng lp ph trong qu trnh vn chuyn hoc trong khi lp t.Phng php bo v catt bng ant hy sinh c s dng ngn chn n mn nhng khu vc d b h hng.2. Vt liu cho ng ng du kh ng thp C-Mn hn (Welded C-Mn steel linepipe) ng c lin (Seamless C-Mn steel linepipe) ng thp phe rt - xt nt (Ferritic-austenitic (duplex) steel) Cc loi ng ng thp khng g v thp hp kim niken.Ti liu tham kho: DnV - Os-F101: SUBMARINE PIPELINE SYSTEMS_20003. Chng n mn bn ngoi cho ng ng bin3.1. Cc lp ph bn ngoi ngLp ph u tin bn ngoi ng ng c s dng bo v cc ng ng chng n mn. Lp ph n c s dng khi cc ng ng dn sau khi lp t lun trong iu kin tnh, n nh theo phng ngang khi nm trn nn t nh t st hoc ct.Cc lp phb sung c s dng bo v thm, lm tng trng lnggipchong ngvngi c n nh ngang y bin, hocto lp cch nhit.Lp phnhiulpthng c s dngtrong trnghp mi trngbn ngoic xu hngd dngmangilp phbn ngoi(v d,ng ngnmtrn nh nn ,trn vt liu vi,v.v.). Lp cch nhitc s dng duy tr nhit cao cacht lngchybn trongso vinhit mi trng bn ngoi. Vic s dng lp phmt lphoc lp phnhiulpty thucvo mi trngbn ngoiv hocv trhocvic s dngng ng dn.ng ng vngnc sucn c cctnh chtsau: .Kh nng chngli s hp th nc bin.Kh nng chngli cc ha chttrongnc bin.Kh nng chngn mn in. bm dnhvob mtng.Tnh linh hot.Chu c va ngvs mi mn. bnthi tit..Kh nng tng thchvibo vcatt.Mtlp phnlpc th khngthcung cptt ccctnh cht thuctt c cciu kin hot ngcang ng.Trongnhng trng hpnh vylp phnhiu lpc s dng. lp phbm dnh tt vingthp,cn kim tra kb mtng ng khi kt thcqu trnh sn xut. iu nylcn thitvtrong mt s trng hp b mtcang ng hon thin khng th chp nhnth c thdnn mt bm dnhcalp ph. Bctip theolp dnglpph trongphn xng thc hin vic ph ng theo phng php m nh sn xut khuyn ngh.a)Lp ph mt lpEpoxy dnh kt lng thng c chn ph mtlpcho ng ng dn vng nc su. Cc tnh chtv yu cuv lp phc th hin trongBng1.i ving ng dnvng nc su, nikhng cyu cukhcvcc lp phbn ngoi, Epoxy dnh kt lngthng c s dng.i vi hu htcc ng ng vn chuyn du v kh vics dng Epoxy dnh kt lngl v cnghiu qu.Lp phnyc thcs dngkt hp vilp bc lm tng trng lng bng b tng.Bng 1.Lp ph mt lp

Loi lp phNhit ti a (oC)Chiu dy trung bnh ca lp ph (mils)Nh sn xut

Epoxy dnh kt lng901418Dupont, 3M, Lilly, BASF,Jotun

Cng vi lp ph b tng c ths dng cc loi lp ph khc nh nha than menvepoxynhathan vchng c s dngkhi nhit sn phmthp hn.C hai loi lp ph ny l lp ph bitum cgia cbngsi thy tinh.Tuy nhin,hu ht cc lp phbitum khngc khuyn khch bi lutmi trngv s gim hiu qu (vng,nt,thm,vsuy thoiho hc).Li th vicphEpoxy dnh kt lngbao gm:.D dngsa cha.D dngp dnglp ph. bm dnhcaovithp.Ttcho nhit lm vic ca ng ng dn MvAnh,lp phEpoxy dnh kt lngca dngcho ng ng dnngoi bin.b)Lp ph nhiu lpBng 2:Lit knhngs la chnph binnht c sncho lp phnhiulp cho ng ng dnvng nc su.

LpphEpoxy dnh kt lng hai lp c s dng khi c yu cubo vb sung chocclpbn ngoichng hn nhnhit cao,kh nng chng mi mn,v.v..i ving ng vng nc sunhit caocacht lngbn trongmt inhanh chngt nhit mi trng xung quanhtrongvng mtvi dm.Do ,s cn thit phi c mt lp ph nh vyb hn chchoSCRsti khu vctip t ni m smi mncaovlp phb sungc sc khngmi mn caoc s dng.H thngDuvalbao gm mtlp bc trn c s c s Epoxy dnh kt lng (20mils)c dnh kt vi lp ph bng polypropylene ph (20mils). Cclppolypropylenem bo bo v va chm c kh. c) Lp ph 3 lp. Lp ph balppolypropylene (PP)bao gmmtlp epoxy,mtlp ph nha do dnh v chu nhitvlp polypropylene ngoi cng.Polyethylene (PE)vpolypro-pylen (PP)l cc lp ph d c.Cc lp ph nyc s dng b sung chngn mnvthng c s dngcho cch thngng lc nhrisersxin v ni mnhit cacht lngbn tronglcao.Lp ph ng ng ny thng xuyn c s dng cho ng ng c lp ttheo phng phpquay t.Vicphmi lin kt ti hin trng i vi h thngba lp phlkh khn hn p dngvphi mt mtthi gian di hn.Tuy nhin,chu u, cc lp ph PE v PPca thchv chng c bn cao trong mi trng in, knnc, dy,v yu cudng in bo v catt rtt. d) Lp bc gia ti bng b tngLp bc gia ti bng b tngc s dng khitnh n nh ca ng ngtrny binc t ra.Hailoi mt ph bincab tngcs dng l140lb/cu.ftv 190lbs/cu.ft. Mt cao hnt cbng cch thm qungstvo hn hp b tng.Gn y,qungst mt cao hn cs dngc cmt b tng khc nhau, 275-300lbs/cu.ftchoccng ng dnOrmenLange BinBc.e) T chcTiu chunvis k thutlin quan nph ngCc t chcchnhMl:. American Society of Testing Methods (ASTM). Steel Structures Painting Council (SSPC). National Association of Corrosion Engineers (NACE). National Bureau of Standards (NBS). International Organization for Standardization (ISO)In Europe, the more common ones are:. Det Norske Veritas (DNV). Deutsches Institut fur Nurmung (DIN). British Standards (BS). International Organization for Standardization (ISO)3.2. Phng php bo v cathodea) Gii thiu chungBo v cathode l mtphng phpm theo s n mncakim loicn bo v cngn nga.C haiphng phpchnhca Bo v catt lcc h thng antgalvanic(anothde hy sinh) v dng in cng bc (dng in ngoi).i ving ng dnngoi bin,h thnganode galvanicthng c s dng.n mnl mtphn ngin hac lin quan ns mt mtca kim loi.Thc t, iu ny ldo lb mtng ngthpbao gm cc khu vc cattvant phn b ngu nhin,vnc binlcht in phn to nnccpin galvanic.iu nygy racc in t chytmtimkhc n,dn nn mn.Bng cchkt nimt kim loic in th cao hn vi ng ngthp,nc thto ramtpinin ha, trong kim loicth nngthp hns tr thnh mtcathode v cbo v.Lp ph ng nglro cnu tinchng lis n mn.Tuy nhin, sau khi phng ng, qu trnhvn chuynvlp tng ng gy ra mt sh hng cholp ph.Bo v cathode s dngmtkim loikhc m kim loi sb mt in tnhiu hn thp.Cc kim loich yu c s dng nh lanothdehy sinhlhp kimca nhmvkm.Bng cch gnantcacc kim loi nyln cc ng ngthp,th khu vc thp clp phb h hngc bo v khis n mn.Thng thng Antkm khng c dngtrong ccng ng dnvng nc su, v chng km hiu qu vdo i himtkhi lngln hnbo vccng ng. Tuy nhin,Antkmc th ccvomi ni ngvdo khng cn phi s dngcp kt niin vi thp.Km cs dngtrong ccd nkhing ng dncn ckodc theo y binv Antkmc tb va p tung ratrongqu trnh lp t.KmAntkhnghot ng tt chong ngchn dng vn chuyn cht truyn dn nngvc th b n mn dng ht nhit trn50oC.Ngoi ra cn cmtxu hngAntkm bth ng ha nhit trn70oC.Mtkhc, Ant nhm hot ngtt hn nhiu.Chngph hp hncho ng ng dn c chn dng vn chuyn cht truyn dn nng.Ni chung,i vi ng ng dnvng nc su, Anthp kim nhm c gn lin vicc ng nglcc Antvng. CcAntthngc gn ti ch ni ng xng thc hin bc ng theo phng php lp t S-lay v J-lay.Tip xc invi ng ngcthc hinbng cch hnnhit nhm hochndycpt Ant. Trongtrng hplp tccng ngbngphng phpcun,ccAntc lp t trn cctunmtrongkhi ng khng quay v c cng thng.Trong trng hp ny,cc Antvng cgn ving ngbngbu-lngvgncp bng hnnhit nhm vi ng ng.Ccthit kcacc h thngBo v catt phixem xtkh nng tc dng gy hi cah thngBo v cattnh s gin hydrca thp vng sut cc b l nhng tc dng c th dnns nt do ng sutgy radohydr.b)Phng phpthit kbo v catttin hnhthit kbo v cattchomt ng ng dnvng nc su,cc thng scnphi c bit nl:.Thi hn phc v/thit k (nm).S h hng lp ca lp ph(%).Mt dng in bo v(mA/m)ng c chnhockhng c chn.. in tr sut ca nc bin (m-cm).in tr sutca t(m-cm). Th nng bo vng ng (bnh thng,900mVWRTAg/AgCl).Anodeu ra(A.h/kg).Th nng ca Anode (mVw.r.t.Ag/AgCl).H s s dng Anode (%).Nhit nc bin.Nhit ng ng dn.. suln/ su vi cang ng i sngthit kcang ngcda trn vic nltuyn ng ng dn duhay ng ng ni b m.Thi hn lm vic catuyn ng ng dn duc thdi n40nm, trong khi mtngni m bnh thngl 20 nm.H s h hnglpph ph thucvo loilp ph.Crtt d liuv vn ny.DNV(RP-F103)vNACE(RP-01-76) nghcc gi trdavo loilp phng ng.Bagi trcas h hng lp ph in hnh l ban u,trung bnh vkt thc.Mt dng in,in tr sut vnhit ph thucvov tr a l nilp t ng ng.Trongng ng dnvng nc su,nhit nc binnm trong khong t 1.78Cn7.58C.DnVvNACEa ragi tr chomt dng inv in tr sutcho ccv tra l ngoi bin.i vithptrnb chn vitrong cc trm tch,DNV khuyn co ly mt dng in thit k0:020A=m2. LoiAntc s dngxc nhtnh chtin haca n.V d, Galvalum III 1 ccng sutra ca Antkhong2250A.h/kg trongnc bin c nhit nh hn258Cvth nng ca n khong1050mV.Cc nh sn xutAntcung cpnhng tnh cht nychothit k.Yu t s dng Ant ph thuc vo hnh dng s dng thc t (application) ca Another. Another vng thng c gi nhls dng80% vocui i sngca n,trong khi Antlp t cch xa ng ng cs dng stand-off.i vinhit ng ng trn 258C,mt dng in thit k tngln.i vi mitrnnhit 258Cmt dng in tng gn 0:001A=m2.Ccphng phpthit ktng kt ysauc a ra trong DNVRPB401.Thit kphip nghaiyu cu: Tngkhi lngtnh ca Antphi p ngnhu cudng in tng cng trong sut i sng thit k. B mttip xc vi bn ngoi ca Ant phi cung cp dng in yu cu cui i sng thit k (khu vc phi p ngnhu cudng in kt thccuc sngthit k(b mttip xc vi bn ngoi ca Antc tnhtkch thc ban u Ant,khi lngtnh,vh ss dng ant).Trc ht,cn tnh tondng in yu cu,(Ic),choban u,trung bnh,vgiai oncui cngca i sng thit k.dng inyu cu bo vming ng ctnhbngcch nhn tngdin tchbn ngoi(Ac)vimt dng in thit k thch hp(ic)vh s ph hy lp bc(fb):

Dng in yu cu chophn ccban u,Ici,vcho tiphn cccuicai sngthit k,Icf,thngctnh cngvi dng inyu cu trung bnh Icmcn thit duy trbo v catt trong sutthi gianthit k.Khng cn thit phi tnh ton dng inyu cu cn thit chos phn ccban u,Ici,bi v,ban u,cclp phchng n mn ng nglm gim ng knhu cudng invthi gian cn thitchos phn ccban u.Cc h s h hng ca lp ph khc nhau,tc l h s h hng ban u,h s h hng trung bnh,v h s h hng cui cng,c a ratrongn phmca DnV v NACE.V d, vnh Mexico,i vi lp phFBEvimtcuc sngthit k l 20nm,th h s h hng ban u,trung bnh,vcui cngtng ng l1%,3%,v5%.Tngkhi lngtnh Mtca anodecn thit duy trbo v catt cang ngtrong sut i sng thit ktd(nm)c chobi cng thc sau:

trong : - dng in yu cu trung bnh

- hiu qu in ha (A-h/kg) (the electrochemical efficiency)

- h s s dng ant

- i sng thit kDng inyu cu u ra(ban u/kt thc)v in dung dng in i vi mt sant c trng xc nhkch thcyu cu vkhi lng tnh yu cu caAnt.Ccyu cusau phi cp ngbiccthit kh thngbo v catt:

(ban u/kt thc) (ban u/kt thc)

trong - s lng ant

- dung in ca ant (A-h)

- dng in u ra ca ant (A)Dung in ca ant c xc nh bi cng thc:

trong - khi lng tnh ca mt ant. Dng in ra ca ant () c tnh ton theo nh lut m:

trong

- th nng thit k ca mch khp kn ca ant

- th nng bo v thit k

- in tr ca ant

Th nng bo v thit k () i vi thp cc bon l (-0,80 V) (rel. Ag/AgCl/nc bin) khi nc bin c ngm kh v (-0,90 V) (rel. Ag/AgCl/nc bin) khi mi trng k kh bao hm c trm tch. Ti liu thit k khuyn ngh s dng cho tt c cc tnh ton bi v mt dng in thit k ban u v kt thc u quy v hiu in th bo v.

Th nng mch ant khp kn () i vi ant nhm c ly bng -1,1 V cho ng ng bin nhit mi trng xung quanh v bng -1,085 V i vi ng ng nhit cao hn. in tr ca ant (Ra) dng vng c xc nh theo cng thc sau:

trong - in tr sut ca mi trng

- din tch b mt l thin ca ant

S lng ant yu cu, , c xc nh theo cng thc sau:

trong :

- dng in yu cu tng cng cui cng i vi ng ng

- dng in ra ca mt antSau mt sln lp lic th p ngyu cuca c hai tngkhi lngAntnet,Mt,vtng sanodecui cngdng inu ra (naIaf).Ni chung,khong cch ti a ca ccAntc nghl 300m.Tuy nhin,phng phptnh tonsuy gimtim nngbo v vikhong cchc thc s dng xc nhkhi lngvkhong cch gia ccAnt.Vic tnh tons suy gim lcn thit xc nhAnt cho thit kBo v catt carisers thp (Steel Catenary Risers - SCR).TrongRisers thp dng dy neo, Antc tnhiu hn phnvng,mt s Ant c th c ttrn nhng onng ngtnhquaimtip t.Phng phpnycng hu chchong ng dn dungn (lnn3dm)cko st y vi xe trt hai u ng.Thay vt cc Antvng cch nhau dc theong,tt c tng khi lng cacc Antcn thit chong ngc th t trnccxe trt .Vic t cc xe trt cui ng ngngn chns c va pvs ri Ant vng tcc ng ngckodc theoy bin.Tnh ton s suy gim cho thy nu dng in lu thng t 2 im ca ng ng, s thay i th nng ca ng ng c th c tnh ton bng cc phng trnh sau:

trong - s thay i th nng ti im x

- s thay i th nng ti im drain

- bn knh ng ng

- s thay i th nng im gia hai im

- bn tuyn tnh ca ng ng

- dng in tng cng cn c (pick up)

- khong cch gia hai im

- khong cch t im drain point

- dc phn cc

- din tch thc t ca ct thp trn chiu di thng ca ng ng.Rng bucb sungl:.Dng in,IA,phibng dngin c thcphn phi bicc dyanodegp..EAphibngth nngantnh hns gim IR khi s dngkhngtr ca dy ant. .Khi lng antphi vt qutrng lngcn thitbo vccphnca ng ngtrong i sngthit kquy nh.S dngccphng trnhtrnvcc rng buc trn,cth tnh ton ckhong cchln nht ca t s yu cu l khi lng/dyccAnt.a. Chng n mn bn trong cho ng ng du khHu ht cc cht lng vn chuyntrongcc h thngng ng ckh nngn mnvt liu ng ng thp C-Mn(cc bon-mng gan).Vic la chnmth thngbo vchng n mnbntrongng ngvriserscnh hngln nthit kchi titv do phi cnh gitrong qu trnhthit kphng n.Cc ty chnsau ykim sots n mnc thcxem xt:a)X l cht lngloi bccnc dng lngv/hoccc cht gy n mnb)S dngng nghoclt(kim loi)bn trong c kh nngchng n mn;c)S dng lp phhu c chngn mn bo vhoclp lt (thngs dng kt hpvia)hocd));d)X l ha hc,tc lb sungcccht ha hccchc nng gim n mn.Kim sotn mnbng cch x lcht lngc thlin quan nloi bnc khidu/kh(dehydration),hocloi b -xy t nc bin phun(deoxygenation). Bo vchng n mnbn trong bng cchs dngng ng bng Hp kimchngn mn Thng thngvic la chnvt liuchng n mn c nh gi trc vic chnthpC-Mn, khi m vt liu ckt lunkhng an ton, m bo tin cy v/hoc hiu quchi phchohot ng.Tip theo,cc thng sch yusau ys cxem xt khi la chn cavt liuchng n mn:-c tnh c hc-Dch to, c bitl tnh hn c-C kh nngchng n mn bn trong v bn ngoi,c bit i rn nt do mi trng gy ra. Bo vchng n mnbn trong bng lp phhu c hocltNulp ph hocltbn trong s cnh gilmt ty chnkim sots n mn,th ccthng sch yu sau y s cxem xt:-Tnh tng thchha hc vitt c cccht lng cvn chuynhoc c lin quantrong khi lp t,vn hnhv khai thc,bao gm cnhng tc ngcabt kcht ph giano. -Kh nng chngxi mnbicht lngvh hng c hc do phng thoi no sch lng ng (pigging operations) pigginghot ng;- bn khi kh p nhanh;- tin cy i vi kim sotcht lng trong thi gianng dnglp ph,- tin cycacc h thngph ch u nitrong ni b m (nu c); -Hu qucatht biv k thutd phngi vi sgim thius n mn.Lp phbn trong ng ng dn(v d nhbng mng mngepoxytng hp)ch yucp dngvi mc ch gimma sttrong ccng ngkh tkh("flow coatings").Mc d lp phbn trongc th khng em li hiu quy trong vic ngn ngan mntn cng nucht lngc tnh cht n mn cc vn chuyn,mtlp ph bt k viy tnhcht vnc thc hiu qutrong vic gims hnh thnh ng sut mng do n mn tn cngvdo ,kh nngduy tr p lcng ng. Chng n mn bn trongbng cch x l ha hc X l ha hc cc cht lng kim sot n mnc th bao gm:-Cc cht c chn mn(v d:"to mng");-mho cht giu pH;-Bi xt(gim thiu n mn do vi khun);-Glycolhocmethanol(cho thmnng cao chos c chhydrat, pha longtrong phanc);-Cht phn tn( nh tngha ncc trongdu);-Cht loi bccthnh phnn mn nng thp. tin cycax l ha hc cnh gi c thtrongthit kphng n.Thng squan trng cxem xtl:-Hiu qu gim thius n mnd kin i vi cht lngthc t cxem xt,bao gm ccc hiu ngc thca t l, cht lng,v.v..lin quan ncht lng; -Kh nngcacht lng vn chuyndch trong ng phn phi cccht c chtrong h thngng ngdc theoton b chiu di vchu vica n,-Tng thchvitt c cch thngng ngv vt liu u ra,c bit lcht n hivlp phhu c, -Tng thchvibt kcht ph giakhccphun vo-Mi nguy himi vi sc khevkh nng tng thchmi trng,-Quy nhphunvk thut/th tcgim sthiu quc ch, -Hu qucas tht bit cs bo vy , vd phngk thut.Hng dn :i ving ngdn cht lngkhng qua x lhoc cht lngkhcc n mncaovcyu cucaov an tonv tin cy,cn phixc minhtnh hiu qu cavic x l bngha chtbng cch gim sts ton vnbng cch s dngmtcng ccho phpo dythnhng dc theoton b chiu dicang ng. b. Chng n mn bn ngoi cho ng ng trn t linMi trng n mn ngoi ng ca tuyn ng trn b ch yu l t. mi vng, mi khu vc, tnh xm thc ca t ln ng ng l khc nhau, n ph thuc vo cc yu t ch yu sau: thm nhp ca khng kh v nc vo trong t, ph thuc vo cu to ht v xp ca t. m ca t. mui c trong t. dn in ca t.Ngoi s n mn do tnh xm thc ca t ln ng ng, cc yu t nh: cc loi vi sinh vt, tnh acid, nhit ca t cng nh hng khng nh n s n mn bn ngoi ca ng ng.Qu trnh n mn bn ngoi ca ng ng trong t c th hiu nh sau: v t l mt mi trng khng ng nht, do s xm thc ca khng kh (trong c kh oxy O2) v nc vo trong t l khng u nhau mi ch. Trong t c acid v nc khi gp kim loi s xy ra phn ng ha hc lm mt i mt phn kim loi. Phn ng ny xy ra khc nhau mi on ng, mt phn kim loi c xu hng tr thnh catt, phn khc tr thnh ant (ni s kh oxy din ra mnh hn). Kt qu l ng ng b n mn m hin tng nhn thy l s xut hin cc h, cc im r mt v ch yu l pha di ng ng. chng n mn cho ng ng trn t lin c th s dng cc phng php sau.a) Chng n mn bn trong ngPhng php 1: S dng thp ht chn khng, nc bin trc khi cho vo ng ng s qua thp ht chn khng, ton b kh s c tch khi nc. Phng php 2: S dng ha cht c chng phun vo trong lng ng.b) Chng n mn bn ngoi ngb-1) Chng n mn ch ng: Hin tng n mn bn cht l phn ng in ha ca kim loi hoc hp kim cng vi mi trng xung quanh m kt qu l lm mt mt phn kim loi hoc hp kim . Mt phn trong kim loi c xu hng tr thnh dng cc (anodic) v phn khc tr thnh catt (cathodic). Ti dng cc, kim loi b ha tan v hin tng n mn xy ra. Qu trnh ny c th b ngn chn bng cch lm cho vng anodic v cathodic c cng hoc gn mt in th. Phng php nh vy c gi l chng n mn in ha hay chng n mn ch ng. Phng php ny chia ra lm hai cch chnh l dng anod hy sinh v phng php dng in p ngoi.

Lp t ant manh ch to sn Bo v bng dng in ngoi

b-2. Chng n mn b ng: L phng php to s cch li gia vt cn chng n mn vi mi trng c tnh n mn bng cc loi vt liu bc bn ngoi ng. c im ca vt liu chng n mn: Bm dnh tt, c kh nng chng li cc tc ng ca mi trng. C kh nng chng li cc tc ng ha hc, vt l, c tnh chng lo ha. C kh nng lm vic c trong mi trng thit k. C tnh tng thch ha hc vi cc lp bc khc nhau v bn thn vt cn chng n mn.Cc loi vt liu dng bc ng chng n mn ph bin: Glass flake epoxy. Fussion Bouded epoxy. Coal tar epoxy. Intumescent epoxy. Asphalt Enamel. Fussion bouded epoxy kt hp vi Adhesive+Polyethylene. Cao su PolyChloprence. Cao su chuyn dng Neoprence...b-3) Bo v kt hp: Phng php ny kt hp c c vic chng n mn bng sn ph v chng n mn bng in ha. Phng php ny c u im: Phn b dng in bo v tt hn. Kinh t hn cc phng php ring l. Trnh c nhng hn ch ca cc phng php trn khi dng ring l. Gim tc ha tan anode.c) V d tnh ton chng n mn cho tuyn ng b PM3Khng bc chng n mn trong ng. Bc chng n mn ngoi ng bng phng php kt hp (kt hp gia chng n mn ch ng v b ng). Vt liu bc chng n mn l Asphalt Enamel, phng php chng n mn ch ng: s dng chng n mn in ha bng anode hy sinh.c-1) Tnh ton thit k h thng bo v cathode+ Mc ch: La chn Anode (dng Anode, kch thc Anode, in th lm vic ca Anode, khi lng Anode). Tnh ton s lng Anode cn thit cho tuyn ng.+ Phng php tnh tonTnh ton thit k anode c thc hin theo cc bc sau:Bc 1: Xc nh din tch b mt ca tuyn ng Sa.

Trong ,Sa:din tch b mt tuyn ng. [m2].D:ng knh ngoi ca ng.[m]L:chiu di tng cng ca tuyn ng. [m]

Bc 2: Xc nh dng in yu cu ca anode.

Trong :Idc:dng in yu cu ca anode. [A]Id:mt dng yu cu. [mA/m2]Cb:h s hng ca lp bc. SF:h s an ton.Bc 3: xc nh s lng anode:

Trong :Ianode:dng in ra ca mt anode. [A]Ianode=sc in ng/ in tr ca mch.Sc in ng=in th ca anode - in th kt cu yu cu.in tr mch=in tr anode + in tr ca t + in tr ca ng trong lp bc + in tr ca lp bc trong t + in tr cp.Vi ng c bc tt, in tr ca ng trong lp bc lun ln hn in tr ca ng trn. S ln hn v in tr sut ny cho php trong bt k trng hp no th dng in lun nh hn dng in cho php. V vy, ta thng b qua in tr ca ng trong lp bc v in tr ca lp bc trong t.in tr cp l in tr ca dy cp ni anode vi ci gp in. Cp ny c ch to theo tiu chun sn xut ca nh my v c gi tr in tr khng ng k.Vy:in tr mch=in tr anode + in tr ca t.Do , vi k hiu:

Rn:in tr mch.

R1:in tr anode.

R2:in tr ca t.Ta c:Rn=R1+R2Vi R1, R2 tnh theo cng thc sau:

Trong :

Pb, Ps: in tr ca anode v ca t. La, Lc: chiu di ca anode khng k lp bc, v chiu di ca anode c k lp bc. [m]da, dc: ng knh ca anode khng k lp bc, v ng knh anode k c lp bc.Bc 4: Xc nh khi lng anode:

Trong :m:khi lng anode. [kg]Z:s tiu hy thc t ca anode trng km.[kg/A nm]t:tui th thit k ca h thng. [nm]Ianode:dng in ra ca anode. [A]D:h s hiu qa ca dng in anode. [%]u:h s s dng ca anode. [%]+ S liu tnh ton Cc thng s u voK hiuGi trn v

Chiu di tng cng tuyn ng bL27000[m]

ng knh ngoi ca ngD0.508[m]

Mt dng yu cuId30[mA/m2]

H s hng lp bcCb5[%]

H s an tonSF1.1

in th kt cu yu cu0.85[V]

in th ca anode1.1[V]

in tr sut ca anodePb250[.cm]

in tr sut trung bnh ca tPs1000[.cm]

Chiu di ca anode khng k lp bcLa114.3[cm]

ng knh anode khng k lp bcda5.08[cm]

Chiu di ca anode k c lp bcLc129.54[cm]

ng knh anode k c lp bcdc12.7[m]

S tiu hy thc t ca anode Z12[kg/A.nm]

Tui th thit k ca anodet30[nm]

H s hiu qu ca dng in anodeD90[%]

H s s dng ca anodeu85[%]

Anode c chn nh sau: Loi Anode: anode trng km ( Zinc anode) c hnh dng thanh.

Kch thc: bc . in th lm vic ca anode : -1.1V.+ Kt qu tnh tonThng s kt quK hiuGi trn v

Din tch b mt ngSa43090.1[m2]

Dng in yu cu ca anodeIdc71.0986[A]

in tr ca anodeR11.80568[]

in tr ca tR25.40209[]

in tr ca mchRn7.20777[]

Dng in ra ca mt anodeIanode0.03468[A]

S lng anodeN2049.85[ci]

Khi lng mt anodem16.3223[kg]

T bng kt qu tnh ton trn, ta ly s lng anode l 2050 ci. 6. Chng n mn cho b cha du v kh lng6.1) Cc loi b cha B cha l mt cng trnh xy dng nhm mc ch phc v cho cng tc tng tr cc sn phm du (xng, du ho), kh ho lng, nc, axt, cn cng nghipa) Phn loi theo hnh dng b:- B cha hnh tr (tr ng, tr ngang);- B hnh cu;- B hnh git nc

Hnh 1: B cha tr ng p lc thpHnh 2. B cha tr ngang

Hnh 1: B cha cuHnh 2. B cha hnh git nc

b) Phn loi theo v tr ca b trong khng gian:B c th t cao hn mt t (trn gi ta), t trn mt t , ngm hoc na ngm di t hoc di nc.c) Phn loi theo mi b:- B cha c th tch khng i (mi tnh - c nh).- B cha c th tch thay i (mi phao ngoi mi c nh cn c phao ni trn mt cht lng; hoc mi ni - bn thn l mi phao)d) Phn loi theo p lc d (p lc do cht lng bay hi):- B cha p lc thp: khi p lc d pd 0,002MPa v p lc chn khng (khi x ht cht lng) po 0,00025Mpa (0,0025 kG/cm2). - B cha tr ng p lc cao: khi p lc d pd > 0,002MPa.1) Vt liu: Thp B tng ct thp2) Cc gii php chng n mnCc b cha c bo v chng n mn bng: Sn ph Phng php bo v cattC th p dng phng php bo vcattchocc b cha bo vb mtbntrong,b mtbn ngoi,i vitrng hp bngmhocb chatip xc vit, hocc bn trong/bn ngoi. Ty thucvoloicht lngcha trongccb chacn cbo v c th s dngantpin in (ant galvanic)hocdng in cng bc (impressed current). Thng thngccb mtcn cbo vtheo phng php bo v cattcng cphgim btcc yu cuv dng invtngtui thcacc antgalvanic. Trong cc h thng anodehy sinhcc electronnng lngcao cn thitbo vcattccung cpbis n mncamtkim loihot tnh. iu ny c m t bi hnh di y.K hiu trn hnh v:Active Metal (Anode) = Kim loi hot tnh (ant)Protected Metal (Cathode) = Kim loi c bo v (catt)

Bo v bng dng in cng bc (dng in ngoi)

Cc vt lius dng choanthy sinhhoc l kim loihot tnh tng itinh khit, chng hnnhkmhocmagi,hoclcc hp kimmagi, hp kim nhm.Khivic bo vcatt chob chac thc hin viant b chn vi,mt vt liuc bitpbao quanh antbo mrngccants chokt qumong mun.Trongqu trnhcung cpcc in tbo vcatt chomtkim loit hot tnh hn kim loihot tnh hn b n mn. Cckim loihot tnh hn(ant-ant)lhy sinh bo v cckim loithot tnh(catt).S lngn mnph thuc vokim loi c s dng nhantt l thunvi lngdng in ccung cp.Ccantc s dng trongbo vcattchob cha phi cnh kkim travthay thkhi b n mn ti mc ti a.3.1) Bo vcatt cho b ngm Bo v catt lmtty chnbo vmtbchangm(BCN) khi b n mn.Chailoih thngbo vcatt:anodehy sinhdng in cng bc (dng in ngoi)Anthy sinhc thcgnvomtBCNthp c sn ph bo vchng n mn.Anthy sinh l cc phnkim loi hot tnhhn v mt in so viBCNthp. Bi v ccantc ch ng hn,dng in n mnsi ra t chng.Nh vy,BCNc bo vtrong khicc antnh km lhy sinh.Anthtphi cthay th bo vchng n mntip tcBCNny.Mt h thng bo v bng dng in cng bc s dngmtb chnh luchuyn idng in xoay chiuthnh dng in mt chiu.Dng in nyc truyn quamtdycch inviant, lcc thanhkim loic bitb chn vitrongtgnBCN. Dng insau chyquattih thngBCNv tr vchob chnh luthng quamtdycch inthucBCNny.H thngBCN c bo vbi vdng in i ti BCNsvt qu dng in gy nnn mnthngchyrat h thngBCN.Cc tiu chun thit kquy nhyu cuh thngbo vcatt c lp ttiBCNc thit k bimtchuyn gian mn.H thng bo vcatt ca BCN phi ckim tra trong vng suthngci tvc t nhtbanmsau .Cn phigikt qucahailn kim tracui cngchng minh rngvic bo vcatt ang lm vic.Ngoi ra, phikim tra mth thngdng in ngoic mi 60ngyxc minhrngh thngang hot ng.Gikt qucabaln kim tra 60-ngy cui cngchng minhrngh thngdng in ngoiang hot ngng cch.

Bo v bng ant hy sinhElectrical Isolation (Bushings) = Cch in (Tm lt)Dieletric protection coating = lp ph bo v in miCathodic Protection (Anode) = Bo v catt (ant)

Bo v catt bng dng in cng bc (dng in ngoi)

Cclp phphilmtvt liuin mithch hp(v d, mtlp ph cho b cha ngm cchly v in i vi mi trngxung quanhv p ngcc tiu chunngnh cng nghipp dng).Mtlp phnha asphan c xem llp phin mi khng ph hp.3.2) Bo v catt cho b cha nm trn mt tCc dng n mn gm c:

n mn bn ngoi y b chan mn pin in do vt liu bn ngoi trong ct m

n mn do thot nc kmThp mi v thp c kt hp vi nhau

Bo v catt kiu pin in (Galvanic)

Bo v catt bng dng in ngoi

Cc loi ant : Ant nng Ant su

Ant nng (Shallow Anodes)

Ant su (Deep Anode)

o in th xung quanh y bGim st dng in

Mt loi ant in hnhH thng ant xuyn ngang di y b

n mn bn trong b

Lp t ant bn trong y bCc loi ant

B tr h thng chng n mn di y b

3.3 Kim trav gim stcch thngbo vcattTh nghimquan trngnhtc s dng trongvic gim st cc h thngbo v catt l o in th gia kt cu v cht in phn.Ni chungiu ny c thc hinbng cchkt nikt cu vi in cc tham chiu c hiu chnh thng quamtvn kvo s khc bitca in th.in cc tham chiuin hnh s dngtrongt vnclng, sulphateng,bc, clorua bc hoc clorua km.Cc in cctham chiuthng c ci tthng xuyn c hoc khng cphiu gim gi(din tchtrnca kim loi)hocdi ng.Vic o in th phi l "IRt do", loi b hiu ngcavic p dngmtin p(h thngbo v catt)lnkt cu. Cc php o khc ca h thng bo v catt l:- Tnh ton vn ca mp cch ly v ch ni c s dng IF tester- Gim st dng in bng ng h kp hoc ng h ngoi.- o hiu in th v dng in t ngun cung cp bng dng c o in- o in tr sut ca t trc khi thit k h thng bo v catt. iu ny quyt nh vic chn kch thc ca ant v lp m di t. 3.4 Tiu chun bo vTiu chunbo vin hnhi vi th nng gia kt cu v cht inphn (tip xc vit/nc) ckhuyn nghtrongtiu chuncng nghipvtm tt nh sau:-850mVso viCu|CuSO 4in cctham chiuchothptrongtc ga/nc.-950mVso viCu|CuSO 4in cctham chiuchothptrong tym kh xc nhns hin dincavi khun khsulphatehot ng.Tt c cctim nngtrnlIRtwj dohoc"tt"th nng.Thay thtiu chun-ti thiu l100mVphn catt ccgiacc c cuvinn nhlin lc viin.S hnh thnhhocphn r cas phn ccc th c o p ng cctiu ch ny.31/31