Section 4 API-651 Practice Questions

Subject API RP 651 Cathoic P!otection

Issue Da Date 03/98

Revision Da Date 02/99

Page 1

Section 4 - Corrosion of Above Ground Steel Storage Tanks

1" Acco!ing Acco!ing to API API Reco##ene Reco##ene P!actic P!acticee $ 651% the!e the!e a!e &ou! co#'one co#'onents nts in each each co!!osion ce((" )heses co#'onents a!e an anoe an a(( but *hich o& the &o((o*ing+ a, DC cu!!e cu!!ent nt su''( su''(ie ie b- batte batte!ie !iess b, A cathoe c, A #eta((ic #eta((ic 'ath 'ath connecting connecting the the anoe anoe an cathoe cathoe , An e(ec e(ect! t!o( o(-t -tee Re&e!ence. API$651 Pa!ag!a'h "1"1 2" )he base #eta( #eta( goes into into so(ution so(ution co!!oes, co!!oes, b- !e(easin !e(easing g e(ect!ons e(ect!ons an &o!#ing &o!#ing 'ositive 'ositive #eta( ions" )his state#ent esc!ibes *hat taes '(ace at *hat co#'onent o& a co!!osion ce((+ a, b, c, ,

)he ca cathoe )he e(ect!o(-te )he #eta(( #eta((ic ic connecti connection on bet*een bet*een the the cathoe cathoe an an the anoe )he an anoe

Re&e!ence. API$651 Pa!ag!a'h "1"1a, 3" hich o& the the &o((o*ing &o((o*ing is the the #ost co!!ect co!!ect state# state#ent ent !ega!ing !ega!ing the cathoe+ cathoe+ a, oe!at oe!atee co!!osi co!!osion on taes taes '(ace '(ace at the the cathoe cathoe b, 4o co!!osion taes '(ace at the cathoe c, A(( co!! co!!osi osion on taes taes '(ac '(acee at the the cathoe cathoe , A che#ica( che#ica( !eaction !eaction taes '(ace '(ace using using e(ect!ons e(ect!ons !e(ease !e(ease at the e(ect!o(e(ect!o(-te te Re&e!ence. API$651 Pa!ag!a'h "1"1b, " )he e(ect!o(e(ect!o(-te te contains contains ions an an conucts conucts 'ositive 'ositive cu!!ent cu!!ent &!o# &!o# the anoe to to the cathoe" cathoe" )he #ost co##on e(ect!o(-te &o! ete!na( tan bo tto# su!&aces is % *hi(e the #ost co##on &o! inte!na( su!&aces is " a, ate!% te!% s(uge s(uge an #ois #oistt soi( soi( b, oist soi(% *ate! an s(uge c, Aciic Aciic soi(% soi(% *ate! *ate! an an s(uge s(uge , oist oist soi( soi(%% '!ouc '!ouctt an an s(uge s(uge Re&e!ence. API$651 Pa!ag!a'h "1"1, 5" )he t*o #ost #ost co##on co##on t-'es t-'es o& co!!osi co!!osion on to tan tan botto#s botto#s a!e a!e  an an " a, St!ess St!ess co!!os co!!osion ion an ga(van ga(vanic ic b, 7!osion an e!osion/co!!osion c, ene! ene!a( a( an 'itt 'ittin ing g , St!aSt!a- cu!!e cu!!ent nt an bi# bi#eta eta((i ((icc Re&e!ence. API$651 Pa!ag!a'h "1"2

API$653 7a# P!e' Cou!se

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610, 59$9036


Issue Da Date 03/98


Page 2

6" hich t-'e t-'e o& co!!os co!!osion ion !esu(ts !esu(ts in !e(ative( !e(ative(- uni&o!# uni&o!# #eta( #eta( (oss+ (oss+ a, 7!osio 7!osion n an an e!osi e!osion/ on/co! co!!os !osion ion b, St!a- cu!!ent c, ene!a( , Pitting Re&e!ence. API$651 Pa!ag!a'h "1"2 ;" hich t-'e t-'e o& co!!osion co!!osion #a- on(- a&&ect a&&ect !e(ative( !e(ative(- s#a(( a!eas% a!eas% *hi(e *hi(e substantia( substantia( a!eas a!eas o& the su!&ace a!e una&&ecte b- co!!osion+ a, a(vanic b, ene!a( c, !itt(e , Pitting Re&e!ence. API$651 Pa!ag!a'h "1"2 8" Co#'ositio Co#'osition n o& the #eta( #eta( is a &acto! &acto! in ete!#in ete!#ining ing *hich *hich a!eas beco#e beco#e anoes anoes an *hich beco#e cathoes" hat e(se can cause co!!osion+ a, Di&&e!ence Di&&e!encess bet*een bet*een *e( #eta(% #eta(% heat heat a&&ecte a&&ecte


610, 59$9036


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Page 2

6" hich t-'e t-'e o& co!!os co!!osion ion !esu(ts !esu(ts in !e(ative( !e(ative(- uni&o!# uni&o!# #eta( #eta( (oss+ (oss+ a, 7!osio 7!osion n an an e!osi e!osion/ on/co! co!!os !osion ion b, St!a- cu!!ent c, ene!a( , Pitting Re&e!ence. API$651 Pa!ag!a'h "1"2 ;" hich t-'e t-'e o& co!!osion co!!osion #a- on(- a&&ect a&&ect !e(ative( !e(ative(- s#a(( a!eas% a!eas% *hi(e *hi(e substantia( substantia( a!eas a!eas o& the su!&ace a!e una&&ecte b- co!!osion+ a, a(vanic b, ene!a( c, !itt(e , Pitting Re&e!ence. API$651 Pa!ag!a'h "1"2 8" Co#'ositio Co#'osition n o& the #eta( #eta( is a &acto! &acto! in ete!#in ete!#ining ing *hich *hich a!eas beco#e beco#e anoes anoes an *hich beco#e cathoes" hat e(se can cause co!!osion+ a, Di&&e!ence Di&&e!encess bet*een bet*een *e( #eta(% #eta(% heat heat a&&ecte a&&ecte


610, 59$9036


Issue Da Date 03/98


Page 3

11" hat is anothe! te!# use &o! >st!a- cu!!ents>+ a, Sho! Sho!tt ci!c ci!cui uits ts b, Positive cu!!ents c, I#'! I#'!es esse se  cu!! cu!!en ents ts , Inte Inte!& !&e! e!en ence ce cu!!e cu!!ent ntss Re&e!ence. API$651 Pa!ag!a'h "2"1 12" )he #ost co##on co##on an 'otentia((- the #ost a#aging st!ast!a- cu!!ents a!e. a, Di!e Di!ect ct cu!! cu!!en ents ts b, A(te!nating cu!!ents c, Inte Inte!# !#it itte tent nt cu!! cu!!ent entss , C(ose C(ose '!oi# '!oi#itit- a(te!n a(te!nati ating ng cu!!ent cu!!entss Re&e!ence. API$651 Pa!ag!a'h "2"1 13" hich o& the &o((o*ing is is not (ie(- to be a sou!ce o& st!a- cu!!ents+ cu!!ents+ a, Stat Static ic e(ec e(ect! t!ic icit it b, e e(ing (ing #achines c, I#'!esse I#'!esse cu!!ent cu!!ent cathoic cathoic '!otect '!otection ion s-ste#s s-ste#s , Rai(!oa oas Re&e!ence. API$651 Pa!ag!a'h "2"1 1" )*o )*o #eta(s *ith i&&e!ent i&&e!ent co#'ositions connecte in an e(ect!o(-te is a gene!a( esc!i'tion o&. a, A batte! b, A cu!!ent su''!esso! su''!esso! c, A sho! sho!tt ci! ci!cu cuit it , a(va a(vani nicc co! co!!o !osi sion on Re&e!ence. API$651 Pa!ag!a'h "2"2 15" A(( but one o& the &o((o*ing &o((o*ing is (iste (iste as #ajo! &acto!s *hich *hich in&(uence the seve!it- o& inte!na( co!!osion" hich is not a &acto!+ a, )he '? (eve( o& the &(ui &(ui in contact contact *ith *ith the the stee( stee( botto# botto# b, )he a#ount o& nit!ogen in the &(ui in contact *ith the stee( botto# c, Sus'ene Sus'ene so(is so(is in the the &(ui &(ui in contact contact *ith *ith the stee( stee( botto# botto# , Conuctivit Conuctivit- o& the &(ui &(ui in in contact contact *ith the the stee( stee( botto# botto# Re&e!ence. API$651 Pa!ag!a'h "2"3 16" )h!ee #ajo! t-'es o& inte!na( inte!na( co!!osion to be consie!e a!e gene!a( co!!osion% 'itting 'itting co!!osion% an to a (esse! etent in tans% envi!on#enta( c!acing" a, )!ue b, @a(se Re&e!ence. API$651 Pa!ag!a'h "2"3 API$653 7a# P!e' Cou!se


610, 59$9036


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Revision Date 02/99

Page 

Answers to API-651 Section 4, corrosion of Aboveground Steel Storage Tanks uestion 4u#be! 1 2 3  5 6 ; 8 9 10 11 12 13 1 15 16

Ans*e! A D   C C D A  C D A A D  A

Shou( -ou &in a #istae o! isag!ee *ith an- ans*e! (iste% '(ease b!ing it to o u! attention &o! co!!ection o! c(a!i&ication" A: )echnica( Associates% Inc" has atte#'te to '!ovie ans*e!s eve(o'e &!o# 'a!ag!a'hs o& the !es'ective Coe% Stana!% o! Reco##ene P!actice" :ou can !each A: )ech b- 'hone at 610, 59$9036% b- &a at 610, 59$2612% o! be$#ai( at b-ag(eBgte"net"



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Section 5 - Determination of Need for Cathodic Protection

1" API Reco##ene P!actice 651 states that the nee &o! cathoic '!otection #ust be ete!#ine &o! a(( sto!age &aci(ities" Decisions gove!ning the nee &o! cathoic '!otection shou( be base on a(( but *hich o& the &o((o*ing+ a, Data &!o# co!!osion su!ve-s an o'e!ating !eco!s b, 4ationa( oa! an AS7 !eco##enations c, P!io! test !esu(ts *ith si#i(a! s-ste#s in si#i(a! envi!on#ents , 4ationa(% state% an (oca( coe !eui!e#ents an the !eco##enations in API$651 Re&e!ence. API RP 651% Pa!ag!a'h 5"1 2" hen shou( co!!osion cont!o( b- cathoic '!otection &o! ne* AS)s be '!ovie+ a, A&te! &ina( *e(ing an be&o!e h-!ostatic testing b, A&te! a(( st!ess !e(ie& has been ca!!ie out c, In the initia( esign , A&te! the tan is in se!vice &o! 6 #onths Re&e!ence. API RP 651% Pa!ag!a'h 5"1"1 3" ene!a((- tans in 'et!o(eu# se!vice use  on the inte!na( su!&aces to cont!o( inte!na( co!!osion" a, AC Cu!!ent instea o& DC cu!!ent cathoic '!otection s-ste#s b, Coatings c, Cathoic '!otection in conjunction *ith coatings , Since 'u!e h-!oca!bon &(uis a!e usua((- not co!!osive e'e!ience sho*s that inte!na( co!!osion *i(( neve! occu! the!e&o!e% co!!osion cont!o( is not necessa!Re&e!ence. API RP 651% Pa!ag!a'h 5"1"3 " Cathoic '!otection is an e&&ective #eans o& co!!osion cont!o( on(- i& it is 'ossib(e to 'ass e(ect!ica( cu!!ent bet*een *hat t*o co#'onents+ a, Anoe an cathoe b, )an she(( an !oo& su''o!t s-ste# c, Roo& to botto# th!ough !oo& su''o!t st!uctu!es , )an she(( an tan botto# Re&e!ence. API RP 651% Pa!ag!a'h 5"1" 5" A &u(( eva(uation o& tan histo!- shou( be 'e!&o!#e '!io! to " a, @i((ing the tan &o! the 25th ti#e b, Painting the ete!io! su!&ace o& the tan c, )e#'o!a!i(- !e#oving the tan &!o# se!vice , Dete!#ining the nee &o! cathoic '!otection Re&e!ence. API RP 651% Pa!ag!a'h 5"2"1



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Revision Date 02/99

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6" Such ite#s as site '(an% soi( '!o'e!ties% '!evious !e'ai!s% eisting cathoic '!otection o& nea!b- st!uctu!es% #aintenance histo!-% an e'ecte (i&e shou( be investigate an ete!#ine *hen conucting the " a, 7va(uation o& the (ocation o& a !e&ine! b, P!obabi(it- stu- o& tan sett(e#ent c, 7va(uation o& tan esign/const!uction histo!, 7va(uation o& tan !e'ai!s an a(te!ations Re&e!ence. API RP 651% Pa!ag!a'h 5"2"1"1 ;" =& the &o((o*ing ite#s *hich is not an ite# that shou( be investigate an ete!#ine in the eva(uation o& t-'es o& se!vice+ a, )-'e o& '!ouct sto!e b, P!ouct te#'e!atu!e c, A#bient te#'e!atu!e , P!esence an e'th & *ate! botto#s Re&e!ence. API RP 651% Pa!ag!a'h 5"2"1"2 8" Such ite#s as tan ins'ections 'e! API Stana! 653% co!!osion !ate !eco!s% st!a- cu!!ent '!ob(e#s% esign an 'e!&o!#ance o& '!evious '!otection s-ste#s% an st!uctu!e$to$soi( 'otentia( su!ve-s shou( be investigate an ete!#ine *hen conucting the " a, 7va(uation o& tan !e'ai!/a(te!ation/const!uction histo! b, 7va(uation o& tan esign/const!uction histo!c, 7va(uation o& t-'es o& se!vice , 7va(uation o& ins'ection/co!!osion histo!Re&e!ence. API RP 651% Pa!ag!a'h 5"2"1"3 9" )he cushion #ate!ia( une! the tan has a signi&icant e&&ect on ete!na( co!!osion o& the tan botto#" )he #ate!ia( can a(so in&(uence. a, )he e&&ectiveness an a''(icabi(it- o& ete!na( cathoic '!otection b, )he e&&ectiveness an a''(icabi(it- o& inte!na( cathoic '!otection c, )he ecision to use o! not use a !ecti&ie! o! DC gene!ato! set to su''(- cu!!ent , )he t-'e o& '!ouct that #a- be sto!e in the tan Re&e!ence. API RP 651% Pa!ag!a'h 5"3"1"1 10" hat is an avantage o& using &ine 'a!tic(es &o! the cushion #ate!ia(+ a, )he &ine 'a!tic(es shou( be uni&o!# *hich #aes it easie! to t!ans'o!t b, @ine 'a!tic(es '!ovie a #o!e ense cushion to he(' !euce the in&(u an out&(o* o& o-gen c, @ine 'a!tic(es *i(( not 'e!#it the 'assage o& '!ouct shou( a (ea occu! in the tan botto# , @ine 'a!tic(es *i(( ho( #oistu!e (onge! 'e!#itting it to stabi(i

610, 59$9036


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11" hat is the #ain isavantage in using (a!ge si

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1;" h- *ou( it be #o!e i#'o!tant to '!ovie '!o'e! su''o!t une! cushions o& ne* as'ha(t than &o! conc!ete+ a, As'ha(t is inhe!ent(- a(a(ine an the!e&o!e oes not have the 'otentia( o& '!eventing co!!osion b, As'ha(t is not inhe!ent(- a(a(ine an the!e&o!e oes not have the 'otentia( o& '!eventing co!!osion c, As'ha(t #a- eg!ae an beco#e a co!!osive substance , As'ha(t #a- c!ac a((o*ing #oistu!e to !each the tan botto# *he!e it *i(( !eact vio(ent(- *ith the as'ha(t an the stee( tan botto# Re&e!ence. API RP 651% Pa!ag!a'h 5"3"3"1 18" ?o* can the conition o& the ete!na( su!&ace o& tan botto# an the as'ha(t cushion be ete!#ine+ a, Raise the enti!e tan an ins'ect the tan botto# an the as'ha(t b, )ae a co!e sa#'(e &!o# the as'ha(t &o! testing" )his test *i(( !evea( the a#ount o& stee( that has gone into so(ution an been t!a''e in the as'ha(t c, Conuct a soi( !esistivit- su!ve- a!oun the 'e!i'he!- o& the tan contain#ent , - cutting cou'ons &!o# the tan botto# Re&e!ence. API RP 651% Pa!ag!a'h 5"3"3"2 19" A soi( ana(-sis !evea(s the '? o& a native soi( cushion to be 6"25" )his soi( is consie!e to be. a, oe!ate(- co!!osive b, i((- co!!osive c, Co!!osive , e!- co!!osive Re&e!ence. API RP 651% Pa!ag!a'h 5"3""1 an )ab(e 2 20" A soi( ana(-sis !evea(s the su(&ates (eve( o& a native soi( cushion to be 5525''#" )his soi( is consie!e to be a, oe!ate(- co!!osive b, i((- co!!osive c, Co!!osive , e!- co!!osive Re&e!ence. API RP 651% Pa!ag!a'h 5"3""1 an )ab(e 2 21" hat is the #ost co##on #ate!ia( use as a cushion beneath sto!age tan botto#s+ a, C(ean conc!ete b, C(ean san c, C(ean As'ha(t , C(ean #oi&ie agg!egate Re&e!ence. API RP 651% Pa!ag!a'h 5"3"5



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Revision Date 02/99

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22" )he use o& oi(e san beneath tan botto#s oes not e(i#inate the nee &o! cathoic '!otection an in &act #a- cause cathoic '!otection to be (ess e&&ective because. a, )he oi(e san has highe! !esistivit b, )he san is unab(e to conuct e(ect!ica( cu!!ent c, )he oi( acts as an insu(ato! an b(ocs a(( cu!!ent &(o* , )he oi( c!eates a va'o! bea!e! ent!a''ing *ate! an conta#inants net to the tan botto# Re&e!ence. API RP 651% Pa!ag!a'h 5"3"5 23" )he!e a!e seve!a( *a-s the tan cushion can beco#e conta#inate" )h!ee o& the &o((o*ing a!e #ethos o& cushion conta#ination% *hich one is not+ a, In coasta( a!eas sa(t s'a- #a- be *ashe o*n the sie o& the tan b, @e!ti(i


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2;" ?eate tans o! tans sto!ing hot '!ouct can cause. a, Inc!ease *ate! int!usion ue to causing sno* to #e(t an !un o*n the tan sies b, 7cessive !-ing out o& conc!ete &ounations !esu(ting in '!e#atu!e ete!io!ation an &ai(u!e c, Acce(e!ate co!!osion on the inte!na( su!&ace es'ecia((- in tans *ith *ate! botto#s , Acce(e!ate co!!osion on the ete!na( su!&ace ue to e(evate te#'e!atu!e is the a!ea is *et Re&e!ence. API RP 651% Pa!ag!a'h 5""1 28" )he!e a!e a va!iet- o& #ethos &o! secona!- contain#ent% *hich o& the &o((o*ing is not an acce'te #etho o& secona!- contain#ent" a, Dua( botto# tan esign b, San bags c, Fse o& i#'e!vious c(a- 'a in tan ie , I#'e!vious non#eta((ic #e#b!ane Re&e!ence. API RP 651% Pa!ag!a'h 5""3"1 29" Du!ing the insta((ation o& a ne* stee( botto# ove! an eisting stee( botto#% *hich has been !e'ai!e% i& *ate! o! othe! e(ect!o(-te int!ues into the annu(us% *hat can ha''en+ a, A ga(vanic ce(( #a- &o!# *hich *i(( cause the ne* stee( tan botto# to co!!oe at an acce(e!ate !ate b, An e(ect!oche#ica( !eaction #a- tae '(ace c!eating ha


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Answers to API-651 Section 5, Deterination of !eed for "at#odic Protection uestion 4u#be! 1 2 3  5 6 ; 8 9 10 11 12 13 1 15 16 1; 18 19 20 21 22 23 2 25 26 2; 28 29 30

Ans*e!  C  A D C C D A  C D  A  C  D C D  A D   C D  A 




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Section - !ethods of Cathodic Protection for Corrosion Control

1" hat is the basic '!inci'(e that #aes cathoic '!otection e&&ective" a, Cathoic '!otection is a techniue &o! '!eventing co!!osion b- #aing the enti!e su!&ace o& the #eta( to be '!otecte act as the !ecti&ie! b, Cathoic '!otection is a techniue &o! '!eventing co!!osion b- #aing the enti!e su!&ace o& the #eta( to be '!otecte act as the co!!osion ce(( c, Cathoic '!otection is a techniue &o! '!eventing co!!osion b- #aing the enti!e su!&ace o& the #eta( to be '!otecte act as the cathoe , Cathoic '!otection is a techniue &o! '!eventing co!!osion b- #aing the enti!e su!&ace o& the #eta( to be '!otecte act as the anoe Re&e!ence. API$651% Pa!ag!a'h 6"1 2" hat a!e the t*o s-ste#s o& cathoic '!otection+ a, a(vanic an !e'!esse cu!!ent b, a(vanic an i#'!esse cu!!ent c, a(vanic an !eve!se cu!!ent , a(vanic an inuce cu!!ent Re&e!ence. API$651% Pa!ag!a'h 6"1 3" a(vanic cathoic '!otection s-ste#s use a #eta(% that is #o!e active than the st!uctu!e to be '!otecte% to su''(- the cu!!ent !eui!e to sto' co!!osion" hat is anothe! te!#s, use to esc!ibe this #ate!ia(+ a, Anoe% co##on(- !e&e!!e to as a ga(vanic o! sac!i&icia( anoe b, Cathoe% co##on(- !e&e!!e to as a ga(vanic o! sac!i&icia( cathoe c, Ribbon cathoe% co##on(- !e&e!!e to as a sac!i&icia( !ibbon cathoe , I#'!esse cu!!ent anoe% co##on(- !e&e!!e to as the i#'!esse anoe Re&e!ence. API$651% Pa!ag!a'h 6"2"1 " he!e on the ga(vanic se!ies is c(ean an shin- #i( stee(+ a, C(ean an shin- #i( stee( has a va(ue o& G1"1 vo(ts b, C(ean an shin- #i( stee( has a va(ue o& G1"0 vo(ts c, C(ean an shin- #i( stee( has a va(ue o& G0"8 vo(ts , C(ean an shin- #i( stee( has a va(ue o& G0"5 to $0"8 vo(ts Re&e!ence. API$651% Pa!ag!a'h 6"2"1 an )ab(e 3 5" )he #ost co##on #eta(s use as ga(vanic anoes in soi( a!e. a, Eea an co''e! b, A(u#inu# a((o- 5H


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6" =& the &o((o*ing% *hich is not an avantage o& ga(vanic cathoic '!otection s-ste#s+ a, 4o ete!na( 'o*e! is neee b, Ca'ita( invest#ent is (o* &o! s#a(($ia#ete! tans c, etho is (i#ite to use in (o*$!esistivit- soi(s , Inte!&e!ence '!ob(e#s st!a- cu!!ents, a!e !a!e Re&e!ence. API$651% Pa!ag!a'h 6"2"2 ;" I#'!esse cu!!ent cathoic '!otection s-ste#s use. a, A(te!nating cu!!ent b, Di!ect cu!!ent usua((- '!ovie b- a !ecti&ie! c, Di!ect cu!!ent usua((- '!ovie b- a !- ce(( batte!, 7ithe! i!ect cu!!ent o! a(te!nating cu!!ent e'ening u'on *hich is avai(ab(e Re&e!ence. API$651% Pa!ag!a'h 6"3"1 8" =& the &o((o*ing% *hich is not a isavantage o& i#'!esse cu!!ent cathoic '!otection s-ste#s+ a, ?igh cu!!ent out'ut b, ?igh #aintenance costs c, ?igh o'e!ating costs , ?igh ca'ita( cost &o! s#a(( insta((ations Re&e!ence. API$651% Pa!ag!a'h 6"3"3 9" A cathoic '!otection !ecti&ie! has t*o #ajo! co#'onents *hat a!e the-+ a, A ste'$o*n t!ans&o!#e! to !euce the AC su''(- vo(tage an !ecti&-ing e(e#ents to conve!t DC to AC out'ut b, A ste'$o*n t!ans&o!#e! to !euce the AC su''(- vo(tage an !ecti&-ing e(e#ents to conve!t AC to DC out'ut c, A ste'$o*n t!ans&o!#e! to !euce the DC su''(- vo(tage an !ecti&-ing e(e#ents to conve!t DC to AC out'ut , A ste'$o*n t!ans&o!#e! to !euce the AC su''(- vo(tage an !ecti&-ing e(e#ents to !egu(ate the AC out'ut Re&e!ence. API$651% Pa!ag!a'h 6"3"3 10" I#'!esse cu!!ent anoes use in soi( a!e not #ae o&. a, !a'hite b, ?igh si(icon cast i!on c, Jinc , ie #eta( oies on titaniu# Re&e!ence. API$651% Pa!ag!a'h 6"3"5 11" I#'!esse cu!!ent anoes #a- be insta((e une!neath the tan" a, )!ue b, @a(se Re&e!ence. API$651% Pa!ag!a'h 6"3"5 API$653 7a# P!e' Cou!se


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Answers to API-651 Section 6, $et#ods of "at#odic Protection for "orrosion "ontrol uestion 4u#be! 1 2 3  5 6 ; 8 9 10 11

Ans*e! C  A D C C  A  C A




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Section " # Design of Cathodic Protection S$stems

1" It has been ecie to insta(( an i#'e!vious #e#b!ane une! a ne* sto!age tan being insta((e in a ie a!ea" Cathoic '!otection o& the tan botto# is !eui!e" he!e #ust the anoes be '(ace+ a, Anoes sha(( be '(ace outsie the ie a!ea b, Di!ect(- une! the #e#b!ane beneath the tan c, As c(ose as 'ossib(e to the !ecti&ie! , et*een the #e#b!ane an the tan botto# Re&e!ence. API 651% Pa!ag!a'h ;"2"3"1 2" Ins'ection e'e!ience has isc(ose the nee &o! cathoic '!otection &o! an eisting tan in a ie a!ea" )he!e is a #e#b!ane insta((e une! the tan" hat *ou( be an o'tion &o! insta((ing anoes une! this tan+ a, Kac the tan u' on the sie o''osite the &i(( an ischa!ge (ines an s(ie the !ibbon anoes une! b, o!e une! the tan at a ve!- sha((o* ang(e an insta(( the anoes c, o!e une! the #e#b!ane at a ve!- sha((o* ang(e an insta(( the anoes , Insta(( ee' g!oun be anoes in coe b!ee


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5" Inust!- e'e!ience has sho*n that i& a conuctive e(ect!o(-te eists bet*een an o( an a ne* tan botto#. a, )he cu!!ent &(o* an #eta( (oss *i(( be &!o# the o( botto# b, )he cu!!ent &(o* an #eta( (oss *i(( be &!o# the ne* botto# c, )he cu!!ent &(o* *i(( be &!o# the o( botto# an #eta( (oss *i(( be &!o# the ne* botto# , )he cu!!ent &(o* *i(( be &!o# the ne* botto# an #eta( (oss *i(( be &!o# the o( botto# Re&e!ence. API 651% Pa!ag!a'h ;"2""3 6" )he!e a!e seve!a( avantages to insta((ing a secona!- contain#ent" =& the &o((o*ing% *hich *ou( not be consie!e an avantage+ a, P!ovies a #eans o& etecting an containing (eas an '!eventing g!oun conta#ination b, P!events the natu!a( cu!!ent &(o* bet*een the o( botto# an the ne* botto# c, Pe!#its the aition o& cathoic '!otection at a (ate! ate , a- !euce the ent!- o& g!oun*ate! into the s'ace bet*een the botto#s Re&e!ence. API 651% Pa!ag!a'h ;"2"5"1"1 ;" )he!e a!e seve!a( isavantages to insta((ing a secona!- contain#ent" =& the &o((o*ing% *hich *ou( not be consie!e a isavantage a, )he #e#b!ane #a- act as a basin to contain *ate! o! anothe! e(ect!o(-te that #ight *et the san bet*een the botto#s b, )he #e#b!ane cou( ent!a' h-!oca!bon '!oucts% *hich *ou( !eui!e et!a ca!e &o! hot *o! c, aes the &utu!e aition o& cathoic '!otection vi!tua((- i#'ossib(e , Acts as a ba!!ie! to g!oun*ate! Re&e!ence. API 651% Pa!ag!a'h ;"2"5"1"2 8" hen an ete!na( cathoic '!otection s-ste# is being esigne% the!e a!e seve!a( ite#s to be consie!e" =& the &o((o*ing &ou! ite#s% *hich one *ou( not be a consie!ation+ a, Se(ection an esign o& the cathoic '!otection s-ste# &o! o'ti#u# econo#- o& insta((ation% #aintenance% an o'e!ation b, S'eci&ication o& #ate!ia(s an insta((ation '!actices that #eet a''(icab(e coes% such as 4ationa( 7(ect!ica( anu&actu!e!s Association stana!s% 4AC7 !eco##ene '!actices% an &ee!a(% state% an (oca( !egu(ations c, P!ovisions &o! #onito!ing the cathoic '!otection s-ste# , S'eci&ication o& #ate!ia(s an insta((ation '!actices that #eet a''(icab(e coes% such as A#e!ican Societ- o& echanica( 7nginee!s stana!s% 4AC7 !eco##ene '!actices% an &ee!a(% state% an (oca( !egu(ations Re&e!ence. API 651% Pa!ag!a'h ;"3"2



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9" In&o!#ation that is use&u( &o! esign o& an ete!na( cathoic '!otection s-ste# can be ivie into th!ee catego!ies. a, S'eci&ications% site conitions% an ju!isictiona( !eui!e#ents b, S'eci&ications an '!actices% site conitions% an F"S" eo(ogica( su!ve- !e'o!ts c, S'eci&ications an '!actices% site conitions% an &ie( su!ve-% co!!osion test ata% an o'e!ating e'e!ience , S'eci&ications an '!actices% tan she(( conitions% an &ie( su!ve-s Re&e!ence. API 651% Pa!ag!a'h ;"3"3 10" hat a!e the t*o t-'es o& cathoic '!otection s-ste#s #ost co##on(- use+ a, a(vanic cathoe s-ste# an i#'!esse vo(tage s-ste# b, a(vanic anoe s-ste# an i#'!esse cu!!ent s-ste# c, a(vanic anoe s-ste# an inte!&e!ence cu!!ent s-ste# , a(vanic anoe s-ste# an inte!&e!ence vo(tage s-ste# Re&e!ence. API 651% Pa!ag!a'h ;"3"5"1 an ;"3"5"2 11" a(vanic cathoic '!otection s-ste#s a!e #o!e econo#ica( on. a, S#a(($ia#ete! tans b, Ea!ge$ia#ete! tans c, a!e% 'oo!(- coate st!uctu!es , u(ti'(e (a!ge tans in a ie a!ea Re&e!ence. API 651% Pa!ag!a'h ;"3"5"1"1 12" )he th!ee #ost co##on ga(vanic anoe #ate!ia(s use &o! soi( insta((ations a!e. a, ?igh 'otentia( #agnesiu# a((o-s%


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1" )he nu#be! o& anoes !eui!e to '!ovie cathoic '!otection e'ens u'on *hat t*o &acto!s+ a, )he istance &!o# the ga(vanic anoe to the tan botto# an soi( ischa!ge !ate b, )ota( cu!!ent !eui!e#ents an the e'ecte iniviua( anoe ischa!ge !ate in the soi( c, )ota( st!a- cu!!ents e'ecte an the tota( cu!!ent !eui!e#ents , )ota( cu!!ent !eui!e#ents an the e'ecte iniviua( cathoe ischa!ge !ate in the soi( Re&e!ence. API 651% Pa!ag!a'h ;"3"5"1" 15" In '(acing the anoes% ho* is bette! cu!!ent ist!ibution an #o!e uni&o!# 'o(a!i

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19" =& the &o((o*ing% *hich is not the best #ate!ia( &o! i#'!esse cu!!ent anoes use in *ate! insta((ations a, )itaniu# b, )anta(u# c, Co''e! , P(atini


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23" )he cu!!ent !eui!e#ent test can on(- be 'e!&o!#e on eisting tans using a te#'o!a!g!ounbe an an a''!o'!iate sou!ce o& i!ect cu!!ent" De'ening on the cu!!ent !eui!e% the 'o*e! sou!ce can va!- b- ho* #uch+ a, @!o# a 2 vo(t sto!age batte!- to a 300$a#' *e(ing unit b, @!o# a 12 vo(t sto!age batte!- to a 300$a#' *e(ing unit c, @!o# a 6 vo(t sto!age batte!- to a 300$a#' *e(ing unit , @!o# a 1"2 vo(t so(a! 'ane( to a 300$a#' *e(ing unit Re&e!ence. API 651% Pa!ag!a'h ;"3"5"2"2"1 2" Du!ing the cu!!ent !eui!e#ent test% ho* is #ai#u# contact o& the tan botto# *ith the cushion #ate!ia( ensu!e+ a, )he tan is &i((e to an aeuate (iui (eve( to ensu!e #ai#u# botto# contact b, )he tan is '!essu!i


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28" Conition an t-'e o& coating i& an-,% #ini#u# an #ai#u# *ate! (eve( in tan% co#'atibi(it- o& sto!e (iui *ith anoes an cab(es% a n inte!na( ins'ection inte!va( o& tan *hich a&&ects esign (i&e a!e a(( &acto!s that. a, In&(uence the esign o& an ete!na( cathoic '!otection s-ste# b, In&(uence the esign o& a e'!esse cu!!ent cathoic '!otection s-ste# c, In&(uence the esign o& an inte!na( cathoic '!otection s-ste# , In&(uence the esign o& the !ecti&ie! use in a cathoic '!otection s-ste# Re&e!ence. API 651% Pa!ag!a'h ;""1

Answers to API-651 Section %, Design of "at#odic Protection S&stes uestion 4u#be! 1 2 3  5 6 ; 8 9 10 11 12 13 1 15 16 1; 18 19 20 21 22 23 2 25 26 2; 28

Ans*e! D  C A  C D D C  A C C  D  D  C A C D  A  D A C

Shou( -ou &in a #istae o! isag!ee *ith an- ans*e! (iste% '(ease b!ing it to o u! attention &o! co!!ection o! c(a!i&ication" :ou can !each A: )ech b- 'hone at 610, 59$9036% b- &a at 610, 59$2612% o! b- e$#ai( at b-ag(eBgte"net" API$653 7a# P!e' Cou!se


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Section % # Criteria for Cathodic Protection

1" API$651 '!ovies c!ite!ia &o! ete!#ining the aeuac- o& cathoic '!otection o& aboveg!oun sto!age tans" hat ocu#ent is !e&e!ence &o! a #o!e etai(e esc!i'tion+ a, AS7 Section % 4onest!uctive 7a#ination b, API$Stana! 650% e(e Stee( )ans &o! =i( Sto!age c, API$Stana! 653% )an Ins'ection% Re'ai!% A(te!ation% an Reconst!uction , 4AC7 RP$01$69 Re&e!ence. API$651% Pa!ag!a'h 8"2"1 2" In ete!#ining i& aeuate cathoic '!otection is being achieve% *hich o& the &o((o*ing *ou( be co!!ect+ a, A negative cathoic, 'otentia( o& at (east 850 # *ith cathoic cu!!ent a''(ie b, A 'ositive cathoic, 'otentia( o& at (east 850 # *ith cathoic cu!!ent a''(ie c, A negative cathoic, 'otentia( o& at (east 85"0 # *ith cathoic cu!!ent a''(ie , A 'ositive cathoic, 'otentia( o& at (east 85"0 # *ith cathoic cu!!ent a''(ie Re&e!ence. API$651% Pa!ag!a'h 8"2"2"1 3" ?o* #ust the !eui!e negative 'otentia( be #easu!e+ a, )his 'otentia( sha(( be #easu!e *ith !es'ect to a satu!ate co''e!/co''e! su(&ate !e&e!ence e(ect!oe CS7, contacting the #eta( tan botto# b, )his 'otentia( sha(( be #easu!e *ith !es'ect to a satu!ate co''e!/co''e! su(&ate !e&e!ence e(ect!oe CS7, contacting the e(ect!o(-te c, )his 'otentia( sha(( be #easu!e *ith !es'ect to a satu!ate co''e!/co''e! su(&ate !e&e!ence e(ect!oe CS7, contacting the #eta( casing o& the !ecti&ie! , )his 'otentia( sha(( be #easu!e *ith !es'ect to a satu!ate co''e!/co''e! su(&ate !e&e!ence e(ect!oe CS7, contacting the 'ositive te!#ina( o& the 'o*e! sou!ce Re&e!ence. API$651% Pa!ag!a'h 8"2"2"1 " In ete!#ining i& aeuate cathoic '!otection is being achieve% *hich o& the &o((o*ing *ou( be co!!ect+ a, 4egative 'o(a!i
a co##on #etho o& #easu!ing 'o(a!i
Re&e!ence. API$651% Pa!ag!a'h 8"2"2"2 API$653 7a# P!e' Cou!se


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6" In ete!#ining i& aeuate cathoic '!otection is being achieve% *hich o& the &o((o*ing *ou( be co!!ect+ a, A #ini#u# o& 1000 # o& cathoic 'o(a!i


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10" Co!!ection &o! IR !o' in the soi( is o&ten necessa!- &o! #easu!e#ents #ae at the tan 'e!i#ete! even i& the !e&e!ence e(ect!oe is '(ace i##eiate(- ajacent to the tan" )his is es'ecia((- t!ue i&  is/a!e c(ose to the tan" a, Dist!ibute anoes b, )he cathoic '!otection 'o*e! su''(- !ecti&ie! c, )he sac!i&icia( anoe , )he DC 'o*e! su''(- batte!-, Re&e!ence. API$651% Pa!ag!a'h 8"3"2 11" onito!ing the actua( st!uctu!e$to$soi( 'otentia( une! the tan shou( be consie!e" ?o* can this be acco#'(ishe+ a, Pe!#anent(- insta((e !e&e!ence e(ect!oe o! b- bu!-ing !e&e!ence e(ect!oe eve!20 &eet a!oun the 'e!i#ete! o& the tan b, Inse!ting a !e&e!ence e(ect!oe une! the tan th!ough a 'e!&o!ate tube o! attaching a !e&e!ence e(ect!oe to the tan she(( c, Pe!#anent(- insta((e !e&e!ence e(ect!oe o! b- inse!ting a !e&e!ence e(ect!oe une! the tan th!ough a 'e!&o!ate tube , Pe!#anent(- insta((e ba!e co''e! *i!e connecte to the tan botto# o! binse!ting a !e&e!ence e(ect!oe une! the tan th!ough a 'e!&o!ate tube Re&e!ence. API$651% Pa!ag!a'h 8"3" 12" =the! stana! !e&e!ence e(ect!oes #a- be substitute &o! the satu!ate co''e!/co''e! su(&ate !e&e!ence e(ect!oe" hich o& the &o((o*ing is not a co##on substitute+ a, Re&e!ence e(ect!oe  Jinc% o(tage  L0"25 b, Re&e!ence e(ect!oe  Satu!ate OCI ca(o#e( o(tage  $0";8 c, Re&e!ence e(ect!oe  Si(ve!/si(ve! ch(o!ie o(tage  $0"80 , Re&e!ence e(ect!oe  A(u#inu# a((o- 5H


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Answers to API-651 Section ', "riteria for "at#odic Protection uestion 4u#be! 1 2 3  5 6 ; 8 9 10 11 12

Ans*e! D A  C D C C C  A C D




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Section & - 'nstallation of Cathodic Protection S$stems

1" Insta((ation o& cathoic '!otection s-ste#s sha(( be in st!ict acco!ance *ith the !a*ings an s'eci&ications" 7ce'tions #a- be #ae on(- *ith the a''!ova( o& *hich o& the &o((o*ing+ a, )he API$653 Ins'ecto! o! 'e!sonne( ua(i&ie an t!aine b- the Ins'ecto! b, )he 4ationa( oa! Ins'ecto! o! 'e!sonne( ua(i&ie an t!aine b- the Ins'ecto! c, )he o*ne!% o'e!ato!% o! 'e!sonne( ua(i&ie b- the o*ne! o! o'e!ato! , )he #anu&actu!e! o& the tan o! the autho!i

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6" In an i#'!esse cu!!ent cathoic '!otection s-ste#% ca!e #ust be taen not to c!ac o! a#age the anoe u!ing han(ing an insta((ation" =& the &o((o*ing% *hich *ou( be a t!ue state#ent+ a, Anoes *ith ve!- s#a(( c!acs nea! the botto# o& the anoe #a- be use *ithout !e'ai! b, C!ace anoes shou( be ins'ecte to ensu!e the insu(ation on the (ea *i!es is not a#age be&o!e insta((ing the anoe c, Anoes *ith c!acs g!eate! than 0"0625> in *ith sha(( not be use , C!ace anoes shou( not be use Re&e!ence. API$651% Pa!ag!a'h 9"3"1"1 ;" ?o* can the (i&e o& an i#'!esse cu!!ent anoe be inc!ease+ a, - insta((ing a ti#ing evice that activates the cu!!ent at thi!t-$secon inte!va(s b, P!o'e!(- insta((ing the bac&i(( #ate!ia( c, Fse a substitute anoe #ate!ia( , Fsing AC cu!!ent instea o& DC cu!!ent Re&e!ence. API$651% Pa!ag!a'h 9"3"1"2 8" =& the &o((o*ing% *hich is not a '!inci'a( 'oint that nees to be obse!ve in the insta((ation o& i#'!esse cu!!ent anoes+ a, )he anoe shou( be insta((e so that at (east one sie is in contact *ith the soi( b, u!ie connections #ust be '!otecte against the ent!ance o& #oistu!e c, Anoes an cab(e shou( be insta((e at a su&&icient e'th to '!otect against accienta( a#age , Ca!e shou( be taen to '!otect the cab(e connection to the anoe Re&e!ence. API$651% Pa!ag!a'h 9"3"1"3 9" @o! a t-'ica( ve!tica( anoe insta((ation% the ho(e is ecavate  inches in ia#ete! ba''!oi#ate(-  &eet ee'" a, Si to ten% &ive to ten b, 7ight to t*e(ve% ten to t*entc, )*e(ve to eighteen% t*e(ve to t*ent-$&ou! , 7ighteen to t*ent-$&ou!% eighteen to thi!tRe&e!ence. API$651% Pa!ag!a'h 9"3"2"1 10" hen it is necessa!- to insta(( an i#'!esse cu!!ent anoe in the ho!i


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11" @o! i#'!esse cu!!ent cathoic '!otection s-ste#s% *hen *ou( insta((ation o& the anoe in the ho!i


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15" hat is the '!e&e!!e #eans o& connecting the negative !ecti&ie! (ea *i!e to the st!uctu!e to be '!otecte+ a, A 'o*e! *e( connection Ca*e(% )he!#ite% o! euiva(ent, b, !a

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20" h- is it a goo '!actice to insta(( 'e!#anent test (eas% g!ouning (ugs% o! sho!t 'ieces o& cab(e &o! #easu!ing tan$to$soi( 'otentia(+ a, Re'eate contact *ith the tan b- a ni&e o! ice 'ic *i(( eventua((- 'unctu!e the tan b, Re'eate contact *ith the tan b- a ni&e o! ice 'ic can cause sho!t ci!cuiting o& the cathoic '!otection s-ste# c, Re'eate contact *ith the tan b- a ni&e o! ice 'ic can cause ea!(- &ai(u!e o& the tans 'aint s-ste#" , Re'eate contact *ith the tan b- a ni&e o! ice 'ic can cause st!ess !ise!s ue to cutting the tan su!&ace Re&e!ence. API$651% Pa!ag!a'h 9"";

Answers to API-651 Section (, Installation of "at#odic Protection S&stes uestion 4u#be! 1 2 3  5 6 ; 8 9 10 11 12 13 1 15 16 1; 18 19 20

Ans*e! C D A  C D  A   C D C D A  C D  C




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Section () - 'nterference Currents

1" hat can be a '!ob(e# cause b- the insta((ation o& a ne* i#'!esse cu!!ent cathoic '!otection s-ste#+ a, A ne* i#'!esse cathoic '!otection s-ste# #a- cause an unacce'tab(e !ain on the e(ect!ica( substation &o! the !e&ine! b, A ne* i#'!esse cathoic '!otection s-ste# #a- cause inte!&e!ence *ith neighbo!ing st!uctu!es c, A ne* i#'!esse cathoic '!otection s-ste# #a- cause inte!&e!ence *ith ce!tain !aio signa(s , A ne* i#'!esse cathoic '!otection s-ste# #a- cause inte!&e!ence *ith o'e!ating cont!o(s o& nea!b- '!ocess units Re&e!ence. API$651% Pa!ag!a'h 10"1"1 2" hat is the #ost co##on sou!ce o& >constant cu!!ent> inte!&e!ence cu!!ents+ a, Recti&ie!s ene!gi&(uctuating cu!!ent>% *hich o& the &o((o*ing is not a no!#a( sou!ce &o! this t-'e o& st!a- cu!!ent+ a, Fne!g!oun #ining e(ect!ica( s-ste#s b, 7(ect!ic !ai(*a-s c, Ra'i t!ansit s-ste#s , AC to DC !ecti&ie!s Re&e!ence. API$651% Pa!ag!a'h 10"2"2 " Du!ing a co!!osion cont!o( su!ve-% the ins'ecto! notice a 'ositive shi&t o& the st!uctu!e$ to$soi( 'otentia( on the a&&ecte st!uctu!e at a 'oint *he!e cu!!ent #a- be ischa!ge &!o# the a&&ecte st!uctu!e" hat *ou( this inicate+ a, Inte!&e!ence &!o# the cathoic '!otection s-ste# !ecti&ie! b, Inte!&e!ence &!o# a nea!b- (ighting ci!cuit c, Inte!&e!ence &!o# a neighbo!ing sou!ce , Inte!&e!ence &!o# a ga(vanic anoe s-ste# Re&e!ence. API$651% Pa!ag!a'h 10"3 5" Inte!&e!ence cu!!ents have been etecte" ?o* cou( this '!ob(e# be !eso(ve+ a, Design% '!o'e! boning% an use o& sac!i&icia( anoes b, Design% !e(ocation o& the tan% use o& sac!i&icia( anoes c, Design% '!o'e! boning% !e#ova( o& cathoic '!otection s-ste# , Design% '!o'e! boning% i&&e!ent choice o& coating on the st!uctu!e Re&e!ence. API$651% Pa!ag!a'h 10""1 API$653 7a# P!e' Cou!se


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Answers to API-651 Section 1), Interference "urrents uestion 4u#be! 1 2 3  5

Ans*e!  A D C A




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Section (( - *+eration and !aintenance of Cathodic Protection S$stems

1" h- is it i#'o!tant to conuct 'otentia( su!ve-s *hen the!e is an aeuate (iui (eve( in a tan+ a, otto#$to$e(ect!o(-te 'otentia( !eaings #a- inicate aeuate '!otection &o! the 'o!tion o& the tan in contact *ith the soi( but *hen the tan is &u(( an a(( o& the botto# is in contact% '!otection #a- not be su&&icient b, otto#$to$anoe 'otentia( !eaings #a- inicate aeuate '!otection &o! the 'o!tion o& the tan in contact *ith the soi( but *hen the tan is &u(( an a(( o& the botto# is in contact% '!otection #a- not be su&&icient c, otto#$to$cathoe 'otentia( !eaings #a- inicate aeuate '!otection &o! the 'o!tion o& the tan in contact *ith the soi( but *hen the tan is &u(( an a(( o& the botto# is in contact% '!otection #a- not be su&&icient , otto#$to$e(ect!o(-te 'otentia( !eaings #a- inicate aeuate '!otection &o! the 'o!tion o& the tan in contact *ith the soi( but *hen the tan is &u(( an a(( o& the botto# is in contact% '!otection #a- be &a! #o!e than necessa!Re&e!ence. API$651% Pa!ag!a'h 11"1"3 2" easu!e#ents o& the native st!uctu!e$to$soi( 'otentia( shou( be #ae " a, I##eiate(- a&te! an- cathoic '!otection s-ste# is ene!gi


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Section 4 API-651 Practice Questions

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