Body of Knowledge for API.

8/20/2019 Body of Knowledge for API.

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API-653BODY OF KNOWLEDGE FOR API-653

Aboveground Storge !n" In#$e%t&on 'ert&(&%t&on E)*&nt&on+nur, re$%e# Augu#t .//01

I-

Reference:API-575 Inspection of Atmospheric and Low-Pressure Storage TanksAPI- 65 !e"ded Stee" Tanks for #i" StorageAPI-65$ %athodic Protection of A&o'eground Petro"eum Storage TanksAPI-65( Tank Inspection) Repair) A"teration) and ReconstructionAPI-*$5 %"eaning Petro"eum Storage TanksAPI-**7 Preparing Tank +ottoms for ,ot !ork

AS./ Pu&"ications:AS./ Section 0 1ondestructi'e /2aminationAS./ Section I3 !e"ding and +ra4ing ua"ifications

.1 'ORROSION RA!ES AND INSPE'!ION IN!ER2ALS API-545 Prgr$ 4167

a .eta" Loss inc"uding corrosion a'eraging-API-65() Section * & %orrosion Rates see &e"owc Remaining Life see &e"owd Remaining %orrosion A""owance API-65() Section 8e Inspection Inter'a" API-65() Section 8

Remaining Life 9ears ;t< actua" - ;t< minimum%orrosion rate

=Inches mi""imeters per 9ear>

!here:

;t< actua" the thickness) in inches mi""imeters recorded at the time of inspection for a gi'en "ocation or component

;t< minimum minimum a""owa&"e thickness) in inches mi""imeters) for a gi'en "ocation or component

;t< pre'ious the thickness) in inches mi""imeters) recorded at the same "ocation as ;t< actua" measuredduring pre'ious inspection

%orrosion Rate ;t< pre'ious - ;t< actua"?ears &etween ;t< actua" - ;t< pre'ious

;t< pre'ious the thickness) in inches mi""imeters recorded a the same "ocations as ;t< actua" measuredduring a pre'ious inspection

8- +OIN! EFFI'IEN'IES

a @oint T9pe API-65( Section *) Ta&"e *-$ & T9pe and /2tent of radiograph9 performed API-65() Ta&"e *-$) Section $ API-65) Section

6$) Bigure 6-$c @oint efficienc9 &9 reading API-65() Ta&"e *-$

Cetermining Doint efficienc9 ma9 &e part of a minimum thickness or ma2imum fi"" height pro&"em since Doint efficienc9) ;/


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, S 2 / 2 ;t< min *6 2 C 2 F

=- WELD SI>ES FOR S


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6- SE!!LE9EN! E2AL;A!ION7 Edge Sette*ent API-653 A$$end&) B18137

+*($ /dge sett"ement occurs when the tank she"" sett"es sharp"9 around the peripher9) resu"tingin deformation of the &ottom p"ate near the she""-to-&ottom corner Dunction Big +-5 I""ustratethis sett"ement+*(* The formu"a gi'en in +(( can &e used to e'a"uate this criteria A"ternati'e"9) a rigorousstress ana"9sis can &e carried out for the deformed profi"e .easure the edge sett"ement carefu""9

b7 Botto* Sette*ent Ner te !n" Se API-653 A$$end&) B181= F&gure# B-6 B-.@ B-..

B-.87

+*8$ Big +-7 i""ustrate this t9pe of sett"ement+*8* The formu"a gi'en in +(( can &e used to e'a"uate this criteria A"ternati'e"9) a rigorousstress ana"9sis can &e carried out for the deformed profi"eRead a"" notes on the figures

%7 Lo%&ed Botto* Sette*ent Re*ote (ro* te !n" Se API-653 B18157+*5$ There are depressions or &u"ges that occur in a random manner) remote from the she""see fig +-J+*5* Accepta&i"it9 of these "oca"i4ed sett"ements is dependent upon "oca"i4ed stresses in the

&ottom p"ate) design and Eua"it9 of the "ap we"ds sing"e pass or mu"tipass) and 'oids &e"ow the &ottom p"ate The formu"a gi'en in +(( can &e used to e'a"uate this criteria This limit areapplicable to bottoms which have single pass lap-welded joints.

4- N;9BER OF SE!!LE9EN! POIN!S7 !o %%ute te nu*ber o( #urve, $o&nt# (or deter*&n&ng tn" #ette*ent API-653 [email protected]

A$$end&) B F&gure B-. F&gure B-87$5$* Tank sett"ement sha"" initia""9 &e sur'e9ed with the tank empt9 using the num&er of

&ottom p"ate proDection e"e'ation measurement points) 1) uniform"9 distri&uted around thecircumference) as indicated &9 the fo""owing formu"a:

N C D.@!here:N minimum reEuired num&er of sett"ement measurement points) &ut no "ess that eight A""

fractiona" 'a"ues sha"" &e round to the ne2t higher who"e num&er The ma2imum spacing &etweensett"ement measurement point sha"" &e (* feet

D Tank diameter in feet

0- I9PA'! !ES!ING

7 !n" de#&gn *et te*$erture API-65@ 8181/13 ? F&gure 8-87**M( Nn"ess e2perience or specia" "oca" conditions Dustif9 another assumption) the design

meta" temperatures sha"" &e assumed to &e J° % $5° B a&o'e the "owest one-da9 means am&ient

temperature of the "oca"it9 where the tank is to &e insta""ed Isotherma" "ines of "owest one-da9means temperatures are shown in Big ** The temperature are not re"ated to refrigerated-tanktemperatures see $$$

b7 9ter& Grou$ Nu*ber (or Pte API-65@ !be 8-37Stud9 ta&"e

%7 I( &*$%t te#t&ng reu&red API-65@ F&gure 8-.7

.inimum Permissi&"e Cesign .eta" Temperature for materia"s Nsed in Tank She""s withoutImpact Testing Stud9 ta&"e

d7 I( &*$%t te#t vue# re %%e$tbe API-65@ !be 8-=7.inimum Impact Test ReEuirements for P"ates see 1ote

(


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Stud9 ta&"e

/- E:IS!ING !ANK S


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7 Deter*&ne SdH obe #tre## (or de#&gn %ond&t&on API-65@ tbe 3-8 API-653 61=187b7 Deter*&ne StH obe #tre## (or ,dro#tt&% te#t %ond&t&on API-653 813181.1b ? F&gure

8-.7%7 Deter*&ne t.H verge t&%"ne## (or %orroded re API-653 813181.1% 813181.1d F&gure

8-.7d7 Deter*&ne t *&nH (or te %orroded re


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AS9E Se%t&on I:- Wed&ng nd Br&ng u&(&%t&on#

A7 !e &n#$e%tor #oud ve te "noedge nd #"& reu&red to rev&e Pro%edure u&(&%t&onRe%ord nd Wed&ng Pro%edure S$e%&(&%t&on or to n#er reu&r&ng te #*e eve o( "noedgend #"&1 ue#t&on# %over&ng te #$e%&(&% rue# o( Se%t&on I: & be &*&ted &n %o*$e)&t, nd #%o$eto te S9AW nd SAW ed&ng $ro%e##e#1

.7 ue#t&no# & be b#ed on7 No *ore tt one $ro%e##b7 F&er *et# &*&ted to one%7 E##ent& no-e##ent& vr&be# on, & be %overedd7 Nu*ber !,$e nd Re#ut# o( *e%n&% te#t#e7 B#e *et &*&ted to P.(7 Add&t&on e##ent& vr&be# reu&red b, AIP-65@ or API- 653

87 !e (oo&ng# re #$e%&(&%, e)%uded

B7 !e &n#$e%tor #oud "no tt te WPS *u#t re(eren%e t $$&%be PR n tt tePR *u#t be #&gned nd dted1

'7 API-65@ nd API-653 Gener ed&ng reu&re*ent#

.7 API-65@ Wed&ng Stee !n"# (or O& Storge

;nder#tnd te rue# (or ed&ng &n API-65@ Se%t&on 4 nd oter rue# (or ed&ng &n API-65@ #u%# to#e (or

7 t,$&% o&nt nd de(&n&t&on#b7 ed #&e#%7 re#tr&%t&on# on o&nt#d7 *)&*u* obe re&n(or%e*ent

e7 &n#$e%t&on reu&re*ent#

87 API-653 !n" In#$e%t&on Re$&r# Atert&on nd Re%on#tru%t&on ;nder#tnd tegener rue# (or ed&ng &n API-653 Se%t&on /1

III1 NONDES!R;'!I2E E:A9INA!ION

AS9E Se%t&on 21 Nonde#tru%t&ve E)*&nt&on

7 Art&%e-. Gener reu&re*ent#b7 Art&%e-8 Rd&ogr$,%7 Art&%e-5 ;!d7 Art&%e-6 L&u&d Penetrnte7 Art&%e-4 9gnet&% Prt&%e !e#t&ng

(7 API-653 Gener nonde#tru%t&ve e)*&nt&on reu&re*ent#

.7 API-65@ Weded Stee !n"# (or O& Storge;nder#tnd te gener rue# (or NDE I API-65@ Se%t&on 61

87 API-653 !n" In#$e%t&on Re$&r Atert&on nd Re%on#tru%t&on ;nder#tnd te genrrue# (or NDE &n API-653 Se%t&on .@

6


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I21 PRA'!I'AL KNOWLEDGE- GENERAL

A7 !e (oo&ng to$&%# *, be %overed

.7 Orgn&t&on nd 'ert&(&%t&on Reu&re*ent#87 !,$e# nd De(&n&t&on# o( In#$e%t&on#37 !,$e# 'orro#&on nd Deter*&nt&on

=7 9ter&# nd Fbr&%t&on# Probe*#57 Wed&ng67 Nonde#tru%t&ve E)*&nt&on NDE7 9etod#47 'orro#&on nd 9&n&*u* !&%"ne## Evut&on07 E#t&*ted Re*&n&ng L&(e/7 In#$e%t&on Interv Deter*&nt&on nd I##ue# A((e%t&ng Interv#.@7 In#$e%t&on Re&e( Dev&%e#..7 In#$e%t&on S(et, Pr%t&%e#.87 In#$e%t&on Re%ord# nd Re$ort#.37 Re$&r# nd Atert&on#.=7 D##e*b, nd Re%on#tru%t&on.57


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.7 ;nder#tnd API-653 gener $r%t&%e#

7 !,$e# o( tn"# %overedb7 A$$&%be &n#$e%t&on t#"# (or &ntern nd e)tern &n#$e%t&on e1g1 API- Stndrd

653 A$$end&) ' %e%"t (or !n" In#$e%t&on7%7 S(e or"&ng $r%t&%e#d7 !&%"ne## nd d&*en#&on *e#ure*ent# nd toern%e#

e7 Reu&re*ent# o( te tree t,$e# o( e)tern &n#$e%t&on# nd n &ntern &n#$e%t&on(7 Freuen%&e# nd &nterv# (or e)tern nd &ntern &n#$e%t&ong7 Aternt&ve to te reu&red &ntern &n#$e%t&on &nterv#7 NDE $ro%edure nd NDE $er#onne u&(&%t&on reu&re*ent#&7 !,$e# o( root# nd #e# nd t,$e# o( deter&ort&on 7 Re#on (or &n#$e%t&on nd %u#e# o( deter&ort&on o( #torge tn"#"7 Pro%edure# to %e%" or te#t #torge tn"# (or e"#7 !oo# nd eu&$*ent (or tn" &n#$e%t&on*7 F&ure ##e##*ent nd deter&ort&on o( u)&&r, eu&$*entn7 Su&tb&&t, (or %ont&nued #erv&%e#o7 'nge-o(-#erv&%e e((e%t# on #u&tbe (or %ont&nued #erv&%e$7 Evut&on o( tn" botto* %ond&t&on7 Evut&on tn" (oundt&on %ond&t&onr7 R" (&ure due to br&tte (r%ture#7 Evute te %u#e o( %orro#&on e"# %r%"# nd *e%n&% deter&ort&ont7 Evute te %ond&t&on o( n%or bot# $&$e %onne%t&on# ground %onne%t&on# nd

&n#ut&on

87 'AL';LA!IONS FOR E2AL;A!ING !


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=7 ;NDERS!ANDING OF !


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($5 Ee%tr&% I#ot&on 'e An e"ectrica" circuit where e"ectrica" current f"ows from certainareas of a meta" to other areas through a so"ution capa&"e of conducting e"ectricit9 e"ectro"9te($6 Ee%tro%e*&% 'e An e"ectrochemica" s9stem consisting of an anode and a cathodeimmersed in an e"ectro"9te so as to create an e"ectrica" circuit The anode and cathode ma9 &eseparate meta"s of dissimi"ar areas on the same meta" The ce"" inc"udes the e2terna" circuit)which permits the f"ow of e"ectrons from the anode toward the cathode($7 Ee%tro Potent& The potentia" of an e"ectrode as measured against a reference e"ectrode

The e"ectrode potentia" does not inc"ude an9 resistance "osses in potentia" in either the e"ectro"9teor the e2terna" circuit It represents the re'ersi&"e work reEuired to mo'e a unit charge from thee"ectrode surface through the e"ectro"9te to the reference e"ectrode($J Ee%tro,te A chemica" su&stance containing ions that migrate in an e"ectric fie"d Bor the

purpose of this recommended practice) e"ectro"9te refers to the soi" or "iEuid adDacent to and incontact with the &ottom of an a&o'eground petro"eum storage tank) inc"uding the moisture andother chemica"s contained therein($M Env&ron*ent 'r%"&ng: The &ritt"e fracture of a norma""9 ducti"e materia" in which thecorrosi'e effects of the en'ironment is a causati'e factor(* E)tern '&r%u&t consist of the wires) connectors) measuring de'ices) current sources) etc)that are use to &ring a&out or measure the desired e"ectrica" condition within an e"ectrochemica"ce"" It is this portion of the ce"" through which e"ectrons tra'e"(*$ Fore&gn Stru%ture An9 meta""ic structure that is not intended as a part of a s9stem undercathodic protection(** Gvn&% Anode: A meta" that) &ecause of it re"ati'e position in the ga"'anic series) pro'idessacrificia" protection to another meta" that is more no&"e) when e"ectrica""9 coup"ed in ane"ectro"9te These anodes are the source of current in one t9pe of cathodic protection(*( Gvn&% Ser&e# A "ist of meta"s and a""o9s arranged according to their re"ati'e potentia"sin a gi'en en'ironment(*8 Ground-bed %onsist in one or more anodes insta""ed &e"ow the earthQs surface for the

purpose of supp"9ing cathodic protection(*5


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((M S%r&(&%& Anode Another anode name common"9 used for a ga"'anic anode(8 S%r&(&%& Prote%t&on The reduction or pre'ention of corrosion of a meta") in an e"ectro"9te

&9 ga"'anica""9 coup"ing it to a more anodic meta"(8$ Se%ondr, 'ont&n*ent A de'ice or s9stem used to contro" the accidenta" escape of astored product so it ma9 &e proper"9 reco'ered or remo'ed from the en'ironment Bor the purposeof this recommended practice) secondar9 containment refers to an impermea&"e mem&rane(8* So Anode Groundbed A group of cathodic protection anodes insta""ed indi'idua""9)

spaced uniform"9 and t9pica""9 &uried "ess that * feet &e"ow grades(8( Sunt A conductor of a known e"ectrica" resistance through which current f"ow ma9 &edetermined &9 measurement of the 'o"tage across the conductor(88 Stt&onr, Something that is permanent"9 insta""ed on the ground or on a foundation(85 Str, 'urrent %urrent f"owing through paths other than the intended circuit(86 Str, 'urrent 'orro#&on %orrosion resu"ting from direct current f"ow through paths otherthan the intended circuit(87 Stre## 'orro#&on 'r%"&ng The fracture of a meta" &9 the com&ined action of corrosionand tensi"e stress The fracture occurs under a tensi"e stress that ma9 &e we"" &e"ow the tensi"estrength or e'en the 9ie"d strength of the materia"(8J Stru%ture-to-Ee%tro,te 2otge a"so structure-to-soi" potentia" or pipe-to-soi" potentia":the difference &etween a meta""ic structure and the e"ectro"9te which is measured with a referencee"ectrode in contact with the e"ectro"9te(8M Stru%ture-to-Stru%ture 2otge a"so structure-to-structure potentia": The difference in'o"tage &etween meta""ic structures in a common e"ectro"9te(5 !n" 'u#&on: The materia" immediate"9 adDacent to the e2terior stee" &ottom of aa&o'eground storage tank(5$ !n" Pd Another name for a tank cushion(5* !e#t Led An e"ectrica""9 conducti'e ca&"e attached to a structure and "eading to acon'enient "ocation It is used for the measurement of structure-to-e"ectro"9te potentia" and othermeasurements(5( !e#t Stt&on: A sma"" enc"osed &o2-"ike housing and usua" termination point of one or moretest "eads(58 2otge An e"ectromoti'e force) or a difference in e"ectrode potentia"s e2pressed in 'o"tsA"so known as a $otent&(55 Wter Botto* A water "a9er on the &ottom of a tank caused &9 separation of water and

product due to differences in so"u&i"it9 and specific gra'it9

A7 PRA'!I'AL ;NDERS!ANDING AND FA9ILIAR WI!< !


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the tank &ottom) whi"e water and s"udge genera""9 are the e"ectro"9tes for the interna"surfaces

8$* There are man9 forms of corrosion The two most common t9pes re"ati'e to tank &ottomsare genera" and pitting corrosion In gener %orro#&on) thousand of microscopiccorrosion ce""s occur on an area of the meta" surface resu"ting in re"ati'e"9 uniformsmeta" "oss In $&tt&ng %orro#&on) the indi'idua" corrosion ce""s are "arger and distinctanode and cathode areas can &e identified .eta" "oss in this case ma9 &e concentrated

within re"ati'e"9 sma"" areas with su&stantia" areas of the surface unaffected &9corrosion

5 Deter*&nt&on o( need (or 'tod&% Prote%t&on#

0$ Introduction!e need (or %tod&% $rote%t&on *u#t be deter*&ned (or #torge (%&&t&e#1This section discusses parameter that must &e considered when determining whether astee" a&o'eground storage tank &ottom reEuired cathodic protection If it is determinedthat corrosion wi"" occur) adeEuate corrosion contro" procedure shou"d &e adopted toensure meta" integrit9 for safe and economica" operation o'er the ser'ices "ife of thetank The "ocation of a faci"it9 or the presence of a "eak detection s9stem a"one shou"dnot &e used to determine the need for the cathodic protection !e de%&on govern&ngte need (or %tod&% $rote%t&on #oud be b#ed on dt (ro* %orro#&on #urve,#o$ert&ng re%ord# $r&or te#t re#ut# &t #&*&r tn" #,#te*# &n #&*&renv&ron*ent# nt&on #tte nd o% %ode reu&re*ent# nd tere%o**endt&on *de &t&n t do%u*ent1

5$$ 1ew A&o'eground Storage Tanks%orrosion contro" &9 cathodic protection for new a&o'eground storage tank shou"d &e

pro'ided in the initia" design and shou"d &e maintained during the ser'ice "ife of thes9stem) un"ess detai"ed in'estigation indicate that cathodic protection is not reEuired

51.18 E)t&ng Aboveground Storge !n"#1Stud&e# #oud be *de &t&n #u&tbe t&*e (r*e &n %%ordn%e &t APIStndrd 653 %on%ern&ng te $o##&be need (or %tod&% $rote%t&on1 !hen these

studies indicate that the corrosion wi"" affect the safe or economic operation of thes9stem) adeEuate contro" measures shou"d &e used

5$( Interna" %athodic ProtectionPure h9drocar&on f"uids are usua""9 not corrosi'e and do not reEuire corrosion contro"for interna" surfaces ,owe'er) &ased upon e2perience) interna" corrosion ma9 occur ina&o'eground storage tanks that ha'e interna" surfaces e2posed to water) sediments) orother contaminants Fenera""9) coatings are used to reduce or e"iminate corrosion oninterna" surfaces Bor tanks in petro"eum ser'ice) interna" cathodic protection inconDunction with coating has not gained widespread use) &ut under certain conditions itcan &e effecti'e in protecting against corrosion at ho"ida9s in the coating Bor moredetai"ed information on interna" cathodic protection) see 1A%/ RP575 and RP(JJ

51.1= L&*&tt&on# o( E)tern 'tod&% Prote%t&on

'tod&% $rote%t&on n e((e%t&ve *en# o( %orro#&on %ontro on, &( &t $o##&be to$## ee%tr&% %urrent beteen te node nd %tode tn" botto*71 .an9 factorscan either reduce or e"iminate the f"ow of e"ectrica" current and) therefore) *, &*&t tee((e%t&vene## o( %tod&% $rote%t&on &n #o*e %#e# or $re%ude &t# u#e &n oter1 Su% factors inc"ude:7 Foundt&on# #u% # %on%rete #$t or o&ed #nd1b7 An &*$erv&ou# &n&ng beteen te tn" botto* nd node# #u% # &n #e%ondr,

%ont&n*ent #,#te*#1%7


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These and other re"ated factors are discussed in more detai"s in 5( and 58 It shou"d &erecogni4ed that e2terna" cathodic protection has no effect on interna" corrosion

5* !n"


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513 Foundt&on nd So& 'ond&t&on#

5($ IntroductionCue to a wide 'ariet9 of surfaces) su&-surface) and c"imatic conditions) different t9pes offoundations are constructed for a&o'eground storage tank The cushion materia" underthe tank has a significant effect on e2terna" corrosion of the tank &ottom and caninf"uence the effecti'eness and app"ica&i"it9 of e2terna" cathodic protection

It ver, &*$ortnt to en#ure tt tere not debr #u% # #t&%" u#ed ed&ngrod# ro%"# or %, &n te %u#&on *ter&1 !e %u#&on *ter& $rt&%e# #oudbe (&ne nd un&(or*1 Thanks shou"d &e &ui"t on an e"e'ated &erm to a""ow adeEuatedrainage awa9 from the tank &ottom) !e u#e o( (&ne $rt&%e# & $rov&de *oreden#e %u#&on to e$ redu%e te &n(u) nd out(o o( o),gen (ro* te $er&*eter o(te tn" # &t e*$t&ed nd (&ed1 I( rge $rt&%e #&e# re u#ed d&((erent&ert&on %orro#&on *, re#ut t $o&nt# ere te rge $rt&%e# or debr %ont%tte #tee tn" botto* In this case) cathodic protection wi"" not &e effecti'e ine"iminating the pitting There are a wide 'ariet9 of cushion materia"s a'ai"a&"e) some ofwhich actua""9 pre'ent &eneficia" effects of cathodic protection %on'erse"9) there aresituations where some of these materia"s) when proper"9 se"ected and insta""ed) can &e

&eneficia" in reducing corrosion to the e2tent that cathodic protection ma9 not &eneeded

5($* So& re#t&v&t, $rov&de# vube &n(or*t&on bout te 'orro#&v&t, o( te *ter&u#ed under nd round tn"1 A gener re#t&v&t, %##&(&%t&on g&ven &n tbe-.1!ere re #ever te%n&ue# (or *e#ur&ng #o& re#t&v&t, A common method isdescri&ed in AST. F 57

Ta&"e $ Gener '##&(&%t&on o( Re#t&v&t, Resisti'it9 Range#,.-%. Potentia" %orrosion Acti'it9


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5(* 'ont&nuo# 'on%rete 'u#&on5(*$ A $ro$er, de#&gned %on%rete tn" %u#&on %on#tru%ted on #tbe $ro$er,

$re$red #ub#o& *, be e((e%t&ve &n e&*&nt&ng &ntru#&on o( groundter #o&-#&de%orro#&on nd te need (or %tod&% $rote%t&on Preparation of a sta&"e soi" to supportthe concrete s"a& is 'er9 important to ensure the continued integrit9 of the pad Nnsta&"esoi" ma9 induce crack in the s"a& through which water and contaminants can permeateto the stee" tank &ottom and pro'ide a corrosi'e en'ironment The portion of the tank

&ottom in contact with a concrete ring-wa"" wi"" pro&a&"9 &ot &e cathodica""9 protected%orrosion protection for this portion of the tank &ottom can &e enhanced &9 e"iminatingthe ingress of water and other corrosi'e contaminants from the tank peripher9

5131818 A"though corrosion from the soi" ma9 &e pre'ented &9 a concrete pad) there ma9 sti"" &e %oe%t&on o( *oture beteen te tn" botto* nd te $d due to %onden#t&onbo&ng r&n or #no or (ood&ng due to &ndeute dr&nge1 'orro#&on *, o%%urdue to te *oture %%u*ut&on1 'tod&% $rote%t&on gener, not %on#&deredn e((e%t&ve , to %o*bt t %orro#&on A free-draining concrete pad or ring-wa""and sea" around the peripher9 of the tank ma9 &e effecti'e and e"iminating theaccumu"ation of moisture &etween the pad and the tank &ottom where f"ooding in thedike area a&o'e the tank &ottom not occurs No-%ont&nuo# %on%rete tn" (oundt&onde#&gn# (or e)*$e #otted $d#7 do not re#tr&%t te entr, o( o),gen1 In #&tut&on#ere ter *, %onden#e on te tn" botto* or ter ret&ned bove te%on%rete $d %%eerted t*o#$er&% %orro#&on *, o%%ur1

5131813 Cue to numerous comp"e2 factor that can &e affect the corrosion of a tank &ottomunderside in the present of concrete $red&%t&on o( te $ro$en#&t, &n t %#e e)tre*e, d&((&%ut Thus) care shou"d &e o&ser'ed with tanks on concrete pads sincecathodic protection most &"e, & not e$ redu%e n, %orro#&on tt *&gt beo%%ur1

5(( 'ont&nuo# A#$t 'u#&on

5(($ A %u#&on o( te ne #$t *, $rov&de *n, o( te #*e dvntge# nd

ddvntge# # %on%rete %u#&on (or redu%&ng %orro#&on nd e&*&nt&ng te need(or %tod&% $rote%t&on1 The importance of proper support to pre'ent cracks and to pre'ent accumu"ation of water &etween the cushion and the tank &ottom is possi&"9 e'enmore important for aspha"t than for concrete be%u#e #$t not &nerent, "&nend tere(ore doe# not ve te $otent& o( $revent&ng %orro#&on &n te event o(%r%"#1

5((* Aspha"t degrades with the time and can pro'ide a path for water and disso"'ed chemica"to come into contact with the stee" tank &ottom) a""owing corrosion to occur 'tod&%$rote%t&on &( $$&ed *, or *, not &d &n #to$$&ng %orro#&on en te #$tbe%o*e deter&orted In fact) deteriorated aspha"t ma9 shie"d cathodic protectioncurrent in a manner simi"ar to a dis&onded coating on a pipe"ine The condition of thee2terna" of the surface of the tank &ottom as we"" as the aspha"t can &e determined if

coupons are cut from the tank &ottom

5(8 Nt&ve So& 'u#&on

5(8$ So& n,# o(ten u#e(u te#t (or e$&ng to deter*&ne eter te $otent&%orro#&on %t&v&t, & be &g enoug to *"e %tod&% $rote%t&on ne%e##r, ndeter %tod&% $rote%t&on & be $r%t&% $$&%t&on to $revent %orro#&on1 Cetermination of aggressi'e ions such as ch"orine and su"fates a"ong with measurementsof p, and resisti'it9 are he"pfu" for further corrosion ana"9sis Ta&"e * pro'ides a

$5


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guide"ine for re'iewing soi" ana"9sis data The 'ariet9 of partic"e si4es and chemica"differences as discussed in 5($ Shou"d a"so &e considered

5(8* %athodic protection or other corrosion contro" measures shou"d &e considered when soi"ana"9sis data indicates that soi" is corrosi'e

5(5 'en or O&ed-Snd 'u#&on

'en #nd te *o#t %o**on *ter& u#ed # %u#&on benet #torge tn"botto*# The use of c"ean sand a"one norma""9 does not e"iminate the need for cathodic

protection since corrosion ma9 occur due to intrusion of water from rain) snow) orsha""ow water ta&"e Fuide"ines for the materia" ana"9sis of the sand for corrosi'econtaminants are discussed in 5(8$ In some cases oi" has &een added to the sand for'arious reasons) inc"uding compaction and corrosion contro"

!be 8-------Gu&de&ne# (orRev&e&ng So& An,# Dt

%onstituent %orrosi'e 0er9 %orrosi'e

p, 5-65 H 5%h"orides (-$ PP. $ PP.Su"fates $- 5 PP. 5 PP.

/2perience in the industr9 is 'aried as to the effecti'eness of oi"ed sand for corrosioncontro" !e $re#ent o( o&ed #nd benet tn" botto*# not been $roven # ne((e%t&ve %orro#&on %ontro *e#ure nd tu# doe# not e&*&nted te need (or%tod&% $rote%t&on to be e## e((e%t&ve be%u#e o( te &ger re#t&v&t, o( te o&ed#nd1

5(6 'ont*&nted So& 'u#&on

5(6$ In %o#t re# #t #$r, on tn" #ur(%e# wi"" &e washed down the side of the tank &9 rain and wi"" f"ow &eneath the tank to %ont*&nte te tn" %u#&on This a"so canoccur in areas ere (ert&&er# or %e*&%# *, be &n te t*o#$ere e&ter (ro*spra9ing or industria" operations !e tn" %u#&on #o %n be%o*e %ont*&nted b,&%"&ng %t&on tt %n dr %ont*&nte# #u% # %or&de# u$ (ro* te ter

tbe1 'tod&% $rote%t&on u#u, ne%e##r, (or %orro#&on $revent&on &n te#e#&tut&on#1

5(6* If a "eak occurs in a tank &ottom) the e"&ng *ter& #o %n &n(uen%e %orro#&on onte e)tern #&de I water "eaks from the tank) the en'ironment under the tank ma9

&ecome corrosi'e I( $rodu%t e"# (or* te tn" &t %oud %rete %orro#&on %e# ttd&d not $rev&ou#, e)t or dver#e, ((e%t te e((e%t&vene## o( te %tod&%$rote%t&on1 A e" *, # $rt o( te (oundt&on *ter& nd e&*&nte te%ont%t o( te tn" botto* &t te ground &n #o*e re# %athodic protection wi""not &e effecti'e in such areas Additiona""9) the drainage properties of the foundationmateria"s ma9 &e deteriorated &9 a "eak and a""ow water and contaminates to remain incontact with the tank &ottom

5(7 %rushed-Limestone or %"am-She"" %ushion

In #o*e $rt# o( te ;n&te# Stte# te tn" %u#&on %on#t# o( ,er o( %ru#ed&*e#tone or %*#e# Such tank cushions without the use of cathodic protection ha'e

produced mi2es resu"ts The tank cushion shou"d &e fine and uniform) since differentia"aeration corrosion ce""s wi"" cause pitting at contact areas &etween the "arge partic"es andthe meta" The intrusion of water from rain or groundwater makes the en'ironmentunder the tank a"ka"ine) which ma9 reduce corrosion if contaminants are present in thecushion) or with time infi"trate the cushion) corrosion ma9 acce"erate !u# te u#e o(

$6


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%ru#ed &*e#tone or %*#e# doe# not %er, e&*&nte te need (or %tod&%$rote%t&on1

58 Oter F%tor A((e%t&ng 'tod&% Prote%t&on

51=1. The contents Tanks the contents of a storage tank can inf"uence corrosion on tank &ottoms A%%eerted %orro#&on %n o%%ur on te e)tern #ur(%e o( te botto* o(

eted tn"# due to te eevted te*$erture# &( te re et1 Storge tn"#%ont&n&ng ot $rodu%t *, reu&re n &n%re#e &n %urrent den#&t, to %&evedeute $rote%t&on on te e)tern #ur(%e o( te botto*1 'onver#e, #u((&%&entet %oud dr, out e-dr&ned tn" $d tu# &n%re#&ng &t# re#t&v&t, ndredu%&ng te need (or %tod&% $rote%t&on1


18/29

Thick-fi"m) "aminated) and corrosion- and chemica"-resistant "inings are insta""ed intanks primari"9 to pre'ent interna" corrosion and are freEuent"9 used as an a"ternati'e torep"acing the stee" &ottomAs "ong as a corrosi'e condition e2ists under the tank) the "ining) which is not designedfor structura" strength) cou"d fai" due to inadeEuate structura" support !e u#e o( t&%"-(&* *&nte or oter t,$e o( &ntern &n&ng #oud not be %on#&dered ##u((&%&ent u#t&(&%t&on to e&*&nte te nee (or e)tern %tod&% $rote%t&on o( tn"

botto*

Stud, te oe %$ter (or te e)* $ur$o#e1

6 9etod o( 'tod&% Prote%t&on (or 'orro#&on 'ontro

6$ %athodic protection is a wide"9 accepted method of corrosion contro" %orrosion ofa&o'eground stee" storage tank &ottoms ma9 &e reduced or e"iminated with properapp"ication of cathodic protection %athodic protection is a techniEue for pre'entingcorrosion &9 making the entire surface of the meta" to &e protected act as the cathode ofan e"ectrochemica" ce"" !ere re to #,#te*# o( %tod&% $rote%t&on7 gvn&%b7 I*$re##ed 'urrent

6* Fa"'anic S9stemGvn&% S,#te*# u#e *et *ore %t&ve tn #tru%ture to de $rote%ted to #u$$,te %urrent reu&red to #to$ %orro#&on #ee tbe-3 (or $rt& gvn&% #er&e#7 !e*ore %t&ve *et %ed n node %o**on, re(erred to # gvn&% node or #%r&(&%& node The anode is e"ectrica""9 connected to the structure to &e protectedand &uried in the soi" A ga"'anic corrosion ce"" de'e"ops and the acti'e meta" anodecorrodes is sacrificed whi"e the meta" structure cathode is protected As the protecti'ecurrent enters the structure) it pre'ents the f"ow of corrosion current from the meta"surface %urrent them returns to the ga"'anic anode through a meta""ic conductor seefig 5 9et# %o**on, u#ed # gvn&% node# &n #o& re 9gne#&u* nd >&n% &ne&ter %#t or r&bbon (or*1 The anodes are usua""9 distri&uted around the perimeter ofthe tank or &uried &eneath the tank &ottom Gvn&% S,#te*# re nor*, $$&ed

on, to #*-d&*eter tn"16** Advntge# o( Gvn&% S,#te*#There are se'era" ad'antages of ga"'anic s9stemsa 1o e2terna" power supp"9 is reEuired

& Insta""ation is re"ati'e"9 eas9c %apita" in'estment I "ow for sma""-diameter tankd .aintenance coast is minima"e Interference pro&"ems stra9 currents are raref Less freEuent monitoring is reEuired

61813 Ddvntge# o( Gvn&% S,#te*#There are se'era" disad'antages of ga"'anic s9stemsa Cri'ing potentia" is "imited

& %urrent outputs is "ow

%7 9etod &*&ted to u#e &n o-re#t&v&t, #o&1d7 9etod not $r%t&% (or $rote%t&on o( rge bre #tru%ture1

6( I*$re##ed 'urrent S,#te*#

6($ Fenera"The second method of app"9ing cathodic protection to an a&o'eground storage tank

&ottoms is to used impressed current from an e2terna" source I*$re##ed %urrent#,#te*# u#e d&re%t %urrent u#u, $rov&ded b, re%t&(&er tt%ed to n A' $oer

#our%e1 D&re%t %urrent (ro* te re%t&(&er (o# to te bur&ed &*$re##ed %urrent

$J


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node 8 (ro* te node troug te #o& ee%tro,te 3 nd onto te tn" botto* ##o &n (&g1 61

61318 Advntge# o( I*$re##ed 'urrent S,#te*#

The ad'antages of impressed current s9stems inc"udes:a A'ai"a&i"it9 of "arge dri'ing potentia"

& ,igh current output capa&"e of protecting "arge structuresc %apa&i"it9 of 'aria&"es current outputd App"ica&i"it9 to a"most an9 soi" resisti'it9

61313 Ddvntge# o( I*$re##ed 'urrent S,#te*#The disad'antages of impressed current s9stems inc"ude:a Possi&"e interference pro&"ems stra9 currents on foreign structures

& Loss of A% power causes "oss protectionc ,igher maintenance and operating costd ,igher capita" cost for sma"" insta""atione Safet9 aspects of negati'e "ead connectionf .ore freEuent monitoring

6131= 'tod&% Prote%t&on Re%t&(&er#

A t,$&%, %tod&% $rote%t&on re%t&(&er# # to *or %o*$onent#7 #te$ Jdon trn#(or*er to redu%e te A' #u$$, votge ndb7 Re%t&(,&ng ee*ent# to %onvert A' &n$ut to D' out$ut1 ;n&t# *, be obt&ned &t e&ter #een&u* or #&&%on re%t&(&er ee*ent#1 S&&%onre%t&(&er# re gener, *ore e((&%&ent oever te, re *ore #u#%e$t&be tod*ge (ro* $oer #urge#1Therefore) protecti'e de'ices shou"d considered for these units to pre'ent "ighting

damage +ecause of decreased "ife at higher temperatures are e2pected to e2ceed $(°B

55°%

6(5 Impressed %urrent Anodes

I*$re##ed %urrent node# u#ed &n #o& re *de o( *ter&# #u% # gr$&te #tee&g #&&%on %#t &ron or *&)ed *et o)&de# on t&tn&u*1 Anode# re u#u, bur&ed&n %o"e breee b%"(& to e)tend te&r &(e nd redu%e %&r%u&t re#tn%e The9 ma9

&e "ocated in remote ground&eds) distri&uted around the tank) insta""ed underneath thetank) or insta""ed in deep ground&eds

.. O$ert&on nd 9&ntenn%e o( 'tod&% Prote%t&on S,#te*#

$$$$ The purpose of this section is to recommend procedures and practices for energi4ing andmaintaining continuous effecti'e and efficient operation of cathodic protection s9stems

$$$* Ee%tr&% *e#ure*ent# nd &n#$e%t&on# re ne%e##r, to deter*&ne tt $rote%t&on# been e#tbed %%ord&ng to $$&%be %r&ter& nd tt e% $rt o( te%tod&% $rote%t&on #,#te* o$ert&ng $ro$er, %onditions that affect protection are

su&Dect to change with time %orresponding changes ma9 &e reEuired in the cathodic protection s9stems 'ond&t&on# *, e)t ere o$ert&ng e)$er&en%e &nd&%te# ttte#t&ng nd &n#$e%t&on #oud be *de *ore (reuent, tn re%o**ended ere&n1

$$$( %are shou"d &e e2ercised in se"ecting the "ocation) num&er) and t9pe of e"ectrica"measurements used to determine the adeEuac9 of cathodic protection If tanks are empt9there ma9 &e "arge areas if the &ottoms) which are not in contact with the under"9ing)soi" Potentia" sur'e9) in this case) ma9 gi'e mis"eading informationBotto*-to-ee%tro,te $otent& red&ng# *, &nd&%te deute %tod&% $rote%t&on(or te $ort&on o( te tn" botto* &n %ont%t &t te #o& but en te tn" (u

$M


20/29

nd o( te tn" botto* &n %ont%t &t te #o& $rote%t&on *, be &n#u((&%&ent1 Therefore) potentia" sur'e9 shou"d &e conducted with an adeEuate "e'e" in the tank toma2imi4e contact of the tank &ottom with the cushion materia"

$$$8 The cathodic protection de'ices are shut off whi"e working on storage tanks) the s9stemshou"d &e re-energi4ed as soon as possi&"e to a'oid corrosion damage during e2tensi'emaintenance period

$$* Safet9

$$*$ A"" impressed current s9stems must &e designed with safet9 in mind 're *u#t bet"en o ##ure tt %be# re $rote%ted (or* $,#&% d*ge nd te$o##&b&&t, o( r%&ng1

$$** Re%t&(&er# nd un%t&on bo)e# *u#t *eet regutor, reu&re*ent# (or te #$e%&(&%o%t&on# nd env&ron*ent &n &% te, re &n#ted1 Su% o%t&on# # bedeter*&ned b, rev&e&ng o% #tte (eder nd $rev&&ng &ndu#tr& %ode#1'on#&dert&on #oud be g&ven to o%t&on ot&ng dev&%e# un%t&on bo)e# ndre%t&(&er# out#&de o( rdou# re# &n %#e #$r"# o( r%# o%%ur dur&ng te#t&ng1

..18131 In order to $revent r%&ng %re *u#t be e)er%ed en or"&ng on bre"out$&$&ng tt%ed to tn"# &t %tod&% $rote%t&on $$&ed1 Wen %tod&%$rote%t&on #,#te*# re turned o(( #u((&%&ent t&*e *u#t be oed (or de$or&t&onbe(ore o$en&ng %onne%t&on#1 Bond&ng %be# *u#t be u#ed en $rt&ng bre"out-$&$&ng o&nt#1

$$*($ Additiona" guidance regarding arcing due to static e"ectricit9) stra9 current or "ighteningcan &e o&tained from API RP *( ;Protection against Ignition Arising #ut of Static)Lightning) and Stra9 %urrent


21/29

$$(($ A"" sources of impressed current shou"d &e checked at inter'a"s not e2ceeding twomonths /'idence of proper function ma9 &e current output) norma" power consumption)a signa" indicating norma" operation) or satisfactor9 e"ectrica" state of the protectedstructure A satisfactor9 comparison &etween the rectifier operation on a &imonth"9 &asicand the rectifier operation during the annua" sur'e9 imp"ies the protected status ofaffected structures is simi"ar

This does not take into account possi&"e effects of foreign current sources

$$((* A"" impressed current protecti'e faci"ities shou"d &e inspected annua""9 as part of a pre'enting maintenance program to minimi4e in-ser'ice fai"ure Inspections shou"dinc"ude a check for e"ectrica" shorts) ground connections) meter accurac9) efficienc9) andcircuit resistance

$$((( The effecti'eness of iso"ation de'ices) continuit9 &onds and insu"ator shou"d &ee'a"uated during the periodic sur'e9 This can &e accomp"ished &9 on-site inspection or

&9 e'a"uating corrosion test data..13131= !e tn" botto* #oud be e)*&ned (or ev&den%e o( %orro#&on tever %%e## to

te botto* $o##&be This ma9 &e during repairs or modifications or in conDunctionwith the inspections reEuired &9 API Standard 65( E)*&nt&on (or botto*-#&de%orro#&on *, be done b, %ou$on %utout# or b, nonde#tru%t&ve *etod# #u% #utr#on&% &n#$e%t&on or ee%tro*gnet&% (u) e"ge1

$$((5 Remedia" measurements shou"d &e taken where periodic test and inspection indicate that protection is no "onger adeEuate according to app"ica&"e criteria These measures ma9inc"ude the fo""owing:a Repair) rep"acement) or adDustment of cathodic protection s9stem components

& Pro'ide supp"ementar9 faci"ities where additiona" protection is necessar9c Repair) rep"acement) or adDustment of continuit9 and interference &ondsd /"imination of accidenta" meta""ic contactse Repair of defecti'e insu"ating de'icesf Reso"ution of interference current

$$8 %athodic Protection Record

$$8$ !e $ur$o#e o( t #e%t&on to de#%r&be %orro#&on %ontro re%ord# tt &do%u*ent &n %er %on%e or"be *nner te dt $ert&nent to te de#&gn&n#tt&on o$ert&on *&ntenn%e nd e((e%t&vene## o( %orro#&on %ontro*e#ure#1

$$8* In Cetermining of the need for cathodic protection) items "isted in 5* shou"d &e recorder go to page 6

$$8( In de#&gn&ng %tod&% $rote%t&on #,#te*# te (oo&ng #oud be re%ordeda Cesign the "ocation of insu"ation de'ices) test "eads and other test faci"ities) and

detai"s of other specia" corrosion contro" measures taken & Resu"ts of current reEuirement test) where made) and procedures usedc 1ati'e structure-to soi"s potentia"s &efore current is app"iedd Resu"ts of soi" resisti'it9 test at the site) where the9 were made) and procedures

usede 1ame of the person conducting sur'e9s

$$88 In &n#t&ng %orro#&on %ontro (%&&t&e# te (oo&ng #oud be re%orded1a Impressed %urrent S9stem$- Location and date p"aced in ser'ice*- 1um&er) t9pe) si4e) depth) &ackfi"") and spacing of anodes(- Specification of rectifiers or other energ9 sources8- Interference tests and the parties participating in reso"ution of an9 interference

pro&"ems

*$


22/29

& Fa"'anic Anode S9stems$- Location and date p"aced in ser'ice*- 1um&er) T9pe) Si4e) depth) &ackfi"") and spacing of the anodes un"ess part of

factor9-insta""ed s9stem

$$85 A record of sur'e9s) inspection) and tests descri&ed in $$* and $$( shou"d &emaintained to demonstrate that app"ica&"e criteria for cathodic protection ha'e &een

satisfied

$$86 In *&nt&n&ng %orro#&on %ontro (%&&t&e# te (oo&ng &n(or*t&on #oud bere%orded

a Repair of rectifier and other C% power sources & Repair or rep"acement of anodes) connections) and ca&"esc .aintenance) repair) and rep"acement of coating) iso"ation de'ices) test "eads) and

other test faci"ities

$$87 Re%ord# #u((&%&ent to de*on#trte te need (or %orro#&on %ontro *e#ure# #oud beret&ned # ong # te e((e%t&vene## o( %tod&% $rote%t&on #oud be ret&ned (or $er&od o( 5 ,er# une## #ort $er&od #$e%&(&%, oed b, regut&on

B7 &n(or*t&on %ont&ned &n RP-65. &% te &n#$e%tor & not be e)*&ned on

API-658LINING OF ABO2EGRO;ND PE!ROLE;9 S!ORAGE !ANK BO!!O9

API Re%o**ended Pr%t&%e Se%ond Ed&t&on DE'E9BER .//4

**


23/29

A7 Pr%t&% under#tnd&ng nd be (*&&r &t te &n(or*t&on %ont&ned &n RP-658 retedtoS%o$e This recommended practice present procedures and practices for achie'ing acti'ecorrosion contro" in a&o'eground storage tanks &9 app"ication of tank &ottom "iningIt contains pro'ision for the app"ication of tank &ottom "inings to &oth e2isting and new tanks Inman9 cases) tank &ottom "ining ha'e pro'en to &e an effecti'e method of pre'enting interna"corrosion of stee" tank &ottom

The intent of this recommendation practice is to pro'ide information and guidance specific toa&o'eground stee" storage tanks in h9drocar&on ser'ices %ertain practice recommended hereinma9 a"so &e app"ica&"e to tanks in other ser'ices This recommended practice is intended to ser'eon"9 as a guide Cetai"ed tank &ottom specifications are not inc"udedThis recommended practice does not designated specific tank &ottom "ining for e'er9 situation

&ecause of the wide 'ariet9 of ser'ices en'ironments

31 DEFINI!IONS

($ A&o'eground Storage tank: A stationar9 container) usua""9 c9"indrica" in shape) consisting of a meta""ic roof) she"") &ottom and support structure where more than M percent of the tank'o"ume is a&o'e surface grade

(* Adduct : A curing agent) genera""9 an amine that has &een com&ined with a portion of resin)usua""9 an epo29

(( Amine: An organic) compound ha'ing amino functiona" groups which pro'ide chemica"reacti'it9 and uti"it9 as a curati'e for epo29 and other resins

(8 Anchor Pattern: Surface profi"e or roughness(5 Anode(6 Aromatics: strong h9drocar&on so"'ents whose chemica" structure has an unsaturated ring

with de-"oca"i4ed pi-e"ectrons +en4ene) to"uene) and 29"ene are common e2amp"es ofaromatic so"'ents

(7 +ispheno"-A Po"9ester: A po"9ester whose chemica" structure incorporates +ispheno"-A intothe resin mo"ecu"e in p"ace of some or a"" of the g"9co" The so"id resin is genera""9 pro'idedas a so"ution in St9rene) which acts as a so"'ent and as a cross-"inking agent for the resin

($ %oa" Tar: A &"ack h9drocar&on residua" remaining after coa" is disti""ed($$ %oa" Tar /po29: A coating in which the &inder is a com&ination of coa" tar and epo29 resin

($* %opo"9mer: A "arge mo"ecu"e whose chemica" structure consists of at "east two differentmonomers($8 %uring: The setting up of hardening) genera""9 due to a po"9meri4ation reaction &etween two

o more chemica"s resin and curati'e($5 Cue Point: The temperature at which moisture condenses from the atmosphere($J /"ectro"9te: A chemica" su&stance coating ions that migrate in an e"ectric fie"d($M /po29: Resin containing epo2ide o2irane functiona" groups that a""ow for curing &9

po"9meri4ation with a 'ariet9 of curati'es /po29 resins are usua""9 made from +ispheno"-Aand epich"oroh9drin

(* Borce-%uring: Acce"eration of curing &9 increasing the temperature a&o'e am&ient)accompanied &9 force air circu"ation

(*( Lining: A coating &onded to the interna" surfaces of a tank to ser'e as a &arrier to corrosion &9 the contained f"uids

(*8 .i": #ne one-thousandth of a n inch $


24/29

(( 0in9" ester: A po"9ester that usua""9 contains +ispheno"-A in the resin &ack&one and two'in9" groups for reacti'it9 The so"id resin in genera""9 pro'ided as a so"ution in st9rene)which acts as a so"'ent and as a cross-"inking agent for the resin

(($ 0in9" group: A functiona" group on a resin mo"ecu"e that consists of a car&on-to-car&ondou&"e &ond at the end of the mo"ecu"e

.7 t,$e# o( tn" botto* &n&ng nd dvntge# nd ddvntge# o( e%

6 !n" Botto* L&n&ng See%t&on61. Fenera"

Tank &ottom "inings can genera""9 &9 di'ide into two c"asses: thin fi"ms * mi"s or "essand thick fi"ms greater than * mi"s Lining ma9 &e app"ied to the &ottoms of storagetanks when the9 are first constructed or the9 ma9 &e insta""ed after some period ofser'ice Fenera""9) thin-fi"m "inings ma9 &e app"ied to the new tanks and &ottoms ofstorage than ha'e e2perienced minima" corrosion The ad'antages and disad'antages ofthin and thick-fi"m tank &ottom "ining s9stems are discussed in this section

618 Thin-fi"m tank &ottom "ining s9stems are freEuent"9 &ased on epo29 or epo29-copo"9mer resin) Ta&"e $ "ist se'era" generic t9pes of thin-fi"ms and "inings and their suita&i"it9 for'arious store h9drocar&on and petrochemica" products A"" "inings that are emp"o9ed to

protect tank &ottoms a"so must &e resistant to water) since water must &e present at thetank &ottom for e"ectrochemica" corrosion to occur

!be . !&n F&* !n" Botto* L&n&ng S,#te*# MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM L&n&ng S,#te* re#&n%urt&ve7 !,$&% Serv&%e# 9)1 !e*$1

Rnge F

MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM %oa" tar epo29amine Bou" water ser'ices and crude oi" $*-$7

Light products) disti""ates) aromatic) high purit9/po29 pheno"icamine

!ater) sour product) crude) and gaso"ine $J-**

/po29Amine !ater) Light product) disti""ates) aromatics) crude

And gaso"ine $6-**/po29Po"9amide !ater) disti""ates) crude) and gaso"ine $6-$J/po29Po"9amidoamine !ater) disti""ates) crude and gaso"ine $6-$J

1ote:Gener, app"ied o'er a white or near-white a&rasi'e &"ast c"eaning in *-( coats 1o primer isreEuired Information re"ated to the $er(or*n%e "imitations if specific products with regards tochemica" immersion and e"e'ated temperatures ma9 &e o&tained from the "ining manufacturerFor tn"# containing a water "a9er on the &ottom) the ma2imum temperature wi"" &e at the "ower end of this range for this water immersion #erv&%e1

!be 8 !&%"-F&* !n" Botto* L&n&ng S,#te*#

G##-Re&n(or%ed L&n&ng S,#te*# !,$&% Serv&%e# 9)1 !e*$

Rnge F

MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM I#o$t&% Po,e#ter Wter %rude o& dt&te#

And G#o&ne [email protected]@B$eno-A Po,e#ter Wter 'rude o& dt&te#

And g#o&ne [email protected]@2&n, E#ter Wter %rude o& ro*t&%#

Sovent# %oo g#ooO& nd %e*&% .0@-88@

E$o), Wter %rude o& ro*t&%#Dt&te# nd g#o&ne .0@

*8


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Note#F"ass reinforcements inc"ude f"akes) chopped strand) mat and ro'ing A"" app"ied o'er a white1A%/ 1# $sspc-sp-5 or near-white 1A%/ 1o *SSP%-SP $ &rasi'e &"ast c"eaning in $-8coats Primer freEuent"9 reEuired Cependent upon thickness) one or two &od9 coats specifiedRein-rich topcoat or f"ood coat needed Po"9ester reEuired wa2 addition to topcoats to ensuretime"9 cure Information re"ated to the performance "imitation of specific products with regards tochemica" immersion and e"e'ated temperatures ma9 &e o&tained from "ining manufacture

Bor tanks containing a water "a9er on the &ottom) the ma2imum temperature wi"" &e at the "owerend of this range for this water immersion ser'ice

61 %on#&dert&on# (or re%o**end&ng tn" botto* &n&ng#41 %u#e# o( tn" botto* &n&ng (&ure#01 t,$e# o( tn" botto* &n&ng *ter&#/1 #ur(%e $re$rt&on reu&re*ent# (or te &n#tt&on o( tn" botto* &n&ng.@1 #ue# ((e%t&ng te $$&%t&on o( tn" botto* &n&ng

[email protected] 'LEANING PE!ROLE;9 S!ORAGE !ANKS

A7 $r%t&% under#tnd&ng nd be (*&&r &t te &n(or*t&on %ont&ned &n [email protected] retedto

.7 d*&ntrt&ve #(e, $rogr*# nd re#$on#&b&&t&e#87 #te$ b, #te$ $ro%edur reu&re*ent# (or ##ur&ng #(e entr,37 entr, %##&(&%t&on=7 t,$e o( te#t nd eu&$*ent u#ed to ver&(, #(et,57 rd &nerent &n &n#$e%t&on o( tn"#67 ver&(,&ng te tn" #(e to return #erv&%e47 roe nd re#$on#&b&&t&e#

API-88@4

*5


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PREPARING !ANK BO!!O9S FOR


27/29

As an a"ternati'e to scraping down to &are meta") we"ders shou"d use air-supp"iedrespirators eEuipment If the area descri&ed a&o'e is not scraped down to &are meta" andas "ong as freEuent air-Eua"it9 tests during the hot work indicate a safe atmosphere) itma9 &e unnecessar9 for other personne" in the tank to wear air-supp"ied respirator9eEuipment see API- Pu&"ication *$5

(*5 Frounding "eads from the we"ding machine shou"d &e attached direct"9 to a &are surface

on the tank she"" on which hot work is to &e performed !e"ding "eads shou"d &ecarefu""9 inspected for insu"ation a&rasion) cuts) scuffs) or &reaks an9 of these can causeshorting

(*6 %ompressed-gas c9"inders used for cutting operations shou"d &e secure"9 fastened in anupright position and kept outside the tank at a safe distance from the open manho"es!hen not in use) cutting torches and hoses must &e shut odd at the c9"inder 'a"'es andkept outside the tank %ompressed-gas supp"9 hoses and hose connection shou"d &einspected for "eaks prior to &eing taken inside tankTo pre'ent a possi&"e f"amma&"e mi2ture with air from forming in the tank) compressed-gas supp"9 hoses must &e protected from damage outside the tank and from &urns) cuts)

&reaks) or other damage inside the tank

(*7 !hi"e work is in progress) a"" work areas must &e monitored for o29gen deficienc9 andcom&usti&"e and to2ic atmospheres

8 In#$e%t&on Pro%edure#8

8$ Fenera" ProceduresThe tank &ottom must &e inspected) when repairs are p"anned) regard"ess of its suspectedcondition

8* Appropriate"9 si4ed sma"" opening are sometimes made in the tank &ottom &9 co"dcutting or &9 dri""ing ho"es in each area where hot work is to &e performed Theseopenings faci"itate 'isua" inspection and freeing the interior from gas !hen suchopenings are made) care must &e taken to a'oid a source of ignition that cou"d resu"t in afire e2p"osion arising from f"amma&"e 'apors or "iEuid that might &e re"eased fromunder the tank &ottom A coo"ant shou"d &e app"ied to the cutting edge or too" to reduce

friction heat The used of open-t9pe e"ectric dri"" machines is not recommendedIf tank-&ottom-to-she"" repair are to &e made) care must &e taken to remo'e an9 e2teriorinsu"ation on the &ottom of the tank she"" that cou"d &e oi" soaked hot work conductedinterna""9 cou"d cause oi"-soaked insu"ation to ignite +efore the insu"ation is remo'ed)its t9pe shou"d &e determined so that it can &e remo'ed proper"9

5 S(et, $r%t&%e# nd $ro%edure# nd $o##&be rd#5$ Fenera"

The work procedures adopted wi"" depend on the condition of the tank &ottom) the t9pe

and e2tent of the hot work repairs to &e performed) and the resu"ts of the inspection Thesafe work procedures descri&ed in 5* through 56 app"9 on"9 to those situations inwhich f"amma&"e "iEuids or 'apors are known or suspected to &e present These

procedures are not intended to co'er a"" the different t9pes of tank-&ottom or hot workrepairs that ma9 &e encountered the9 do) howe'er) descri&e a 'ariet9 of situations inwhich these safet9 princip"es can &e app"ied Safe work procedures shou"d &e writtenand appro'ed &9 a competent) trained or e2perienced person

5* .inor Repairs

*7


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.inor repairs usua""9 in'o"'e we"ding corrosion pits and patches or other "oca"i4ed Do&s)such as we"ding support or &races If the &ottom is not in good condition) the fo""owing

procedure ma9 &e used:a Cri"" and tap ho"e for a $(mm $*inch pipe adDacent co the repair area

& %onnect a supp"9 if car&on dio2ide or other inert gas to the $(mm $*inch tap)using meta" tu&ing A pressure contro" 'a"'e with a f"ow indicator shou"d &e used to

pre'ent o'er-pressuring of the tank &ottom

c Prior to &eginning the hot work) esta&"ish a f"ow of inert gas under the tank &ottomin the 'icinit9 of an9 proposed we"ding to ensure that na9 f"amma&"e 'apor &eenswept awa9 or di"uted so that the9 cannot support com&ustion

d !hen using inert gas) continuous"9 monitor the area to assure that the o29gencontent remains &etween $M5 and **5 percent

e !hen the we"ding has &een finished in a "oca"i4ed area) stop the f"oe of inner gas)remo'e the tu&ing) p"ug the ho"e with a tapered pin or other de'ice) and &ack we"d

prompt"9 &efore mo'ing to another area

5( !hen repairs in'o"'e most of the tank &ottom) it ma9 &e desira&"e to disp"ace thef"amma&"e "iEuids &eneath the tank &9 water f"ooding This ma9 &e done as fo""ows:a Around the tankQs outer she"") construct an earthen dike higher that the highest

f"oor p"ate in the tank see fig $ & At the highest points in the tank &ottom) dri"" a tap ho"es for $(mm $*inch pipe

These ho"es shou"d &e "ocated to ensure that a""-f"amma&"e "iEuids or 'apors underthat tank wi"" &e disp"aced with water

Errt dd te (oo&ng t te end o( te te)t &n te (&(t ed&t&on o( Pub&%t&on88@4c Insta"" pipe nipp"es to &e used as 'ents and checkpoints The higher of the nipp"es

shou"d e2ceed that of the temporar9 earthen diked Bi"" the space under the tank with water unti" seepage occurs at each nipp"e

%ontinue the f"ow of water to maintain a constant "e'e" within the dike to ensurethat no 'oids de'e"op under the tank

e !atch for "eaks inside the tank and p"ug them as necessar9 to keep the tank &ottomdr9

f !hen repairs are comp"eted) empt9 the water from the dike to Dust &e"ow the

nipp"es) remo'e the nipp"es) p"ug the ho"es with a tapered pin or other de'ices) and &ack we"d

58 Per&*eter Re$&r#Re$&r# round te $er&*eter o( tn" botto* *, be *de #(e, (ter te(oo&ng $re$rt&on#7 E)%vte under te edge o( tn" (or *&n&*u* o( 3@%* .8&n%e#7 be,ond

te $o&nt o( n, ot or" re1 !e e)%vt&on #oud be rge enoug (or $er#on to or" &n #(e, nd %o*(ort &e e)%vt&ng nd $$,&ng &u&d orv$or brr&er1 !e re #oud be %ont&nuou#, *on&tored to ##ure te o),gen%ontent beteen ./15 nd 8815 $er%ent1

b7 Se o(( o$en&ng beteen te (oor $te# nd te tn" (oundt&on b,$%"&ng te* &t *ud or #o*e oter #u&tbe non-%orro#&ve *ter&1 !e$%"&ng #oud be %e%"ed $er&od&%, nd "&ng on te tn" botto* #oudbe re#tr&%ted to en#ure tt te #e re*&n# &nt%t #ee (&g1.71

%7 ;#e v$or &nd&%tor to %e%" te e)%vt&on nd te #e beteen te (oor$te# nd te (oundt&on1

d7 Be(ore #trt&ng ot or" nd &e or" &n $rogre## *on&tor te#urround&ng re &n%ud&ng te e)%vt&on nd te tn" &nter&or (or te$re#en%e o( &rborne %on%entrt&on# o( %e*&% %ont*&nnt#1

*J


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e7 2ent&te te e)%vt&on &( ne%e##r, &t $ortbe &r boer rted (or te$$ro$r&te ee%tr&% %##&(&%t&on1

Note when the repairs are comp"eted) e2ca'ations shou"d &e prompt"9 and carefu""9 refi""ed to pre'ent the possi&"e fai"ure of the tank foundations

515 Doube-Botto* In#ut&onWen tn" doube botto* %on#tru%ted te (oo&ng $ro%edure# *, be u#ed

7 P"ace appro2imate"9 $cm 8 inches of sand or other sea"ing materia" o'er thee2isting f"oor

b7 Insta"" a new &ottom &9 we"ding

Note If 'apors in the f"amma&"e range are not present under the origina" tank &ottom) hotwork can &e performed safe"9 on the new tank &ottom) e'en though the origina" tank &ottom isresting on a foundation saturated wit oi" In addition) hot work ma9 &e performed if there is not

possi&i"it9 of oi" penetrating the sand &arrier and coming in contact with the new &ottom &eingwe"ded

56 Se%t&on Re$&r#!hen sectiona" repairs are made on tank &ottoms) the fo""owing methods ma9 &e used:a !hen sectiona" a hand or air-operated too") co"d cut the tank &ottom to &e rep"aced

and remo'e it A coo"ant shou"d &e app"ied continuous"9 to the cutting edge of thetoo" to reduce the heat of friction

& Remo'e the earth from under the section to &e rep"aced Bi"" it with tamped sand)and sea" the perimeter of the patch area with mud or some other suita&"e) non-corrosi'e materia"

c %ontinuous"9 monitor the area for o29gen deficienc9 and com&usti&"e or to2icatmospheres

d !hen "arge section of the &ottom must &e rep"aced and it is Euestiona&"e whetherthe sea" wi"" remain effecti'e) maintain an inert area under the patch area whi"e hotwork is &eing performed !hi"e work is &eing performed in and around an areawith an inert atmosphere) the area shou"d &e continuous"9 monitored with ano29gen ana"94er

$ Precaution reEuired to assure safet9 and a'oid e2p"osion and fai"ure* ,a4ard re"ated to hot work on tanks

( /ntr9 c"assifications

Body of Knowledge for API.

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