Body of Knowledge for API-2003

8/20/2019 Body of Knowledge for API-2003

1/30

BODY OF KNOWLEDGE FOR API-653Aboveground Storge !n" In#$e%t&on 'ert&(&%t&on E)*&nt&on

+nur, re$%e# Augu#t .//01I-

Reference:API-575 Inspection of Atmospheric and Low-Pressure Storage Tanks

API- 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) Section6$) Bigure 6-$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) ;/


2/30

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

=- WELD SI>ES FOR S


3/30

7 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 &etween

sett"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 1oteStud9 ta&"e


4/30

/- E:IS!ING !ANK S


5/30

b7 Deter*&ne StH obe #tre## (or ,dro#tt&% te#t %ond&t&on API-653 813181.1b ? F&gure8-.7

%7 Deter*&ne t.H verge t&%"ne## (or %orroded re API-653 813181.1% 813181.1d F&gure8-.7

d7 Deter*&ne t *&nH (or te %orroded re


6/30

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&on# & 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 te $$&%be PR nd 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,$&% o&nt nd de(&n&t&on#b7 ed #&e#%7 re#tr&%t&on# on o&nt#d7 *)&*u* obe re&n(or%e*ente7 &n#$e%t&on reu&re*ent#

41. De(&n&t&on#In this standard) terms re"ating to we"ding sha"" &e interpreted as defined in Section I3 of theAS./ %ode Additiona" terms are defined in 7$$ and 7$*

7* An ang"e @oint is a Doint &etween two mem&ers that intersect at an ang"e &etween degrees a &ui"t Doint and M degrees a corner Doint

7$* Porosit9 refers to gas pockets or 'oid in meta"

418 u&(&%t&on o( Wed&ng Pro%edure#4181. Gener Reu&re*ent#7*$$ /ach erection manufacturer and the fa&rication manufacture) if other that the erectionmanufacturer) if other that the erection manufacture) sha"" prepare we"ding procedures specifications andsha"" perform tests documents &9 procedure Eua"ification records to support the specifications) as reEuired

&9 Section I3 of the AS./ %ode and an9 additiona" pro'ision of this standard If the manufacturer is partof an organi4ation that has) to the purchasers satisfaction) esta&"ished effecti'e operationa" contro" of the

Eua"ification of we"ding procedures and or we"der performance for two o more companies of differentnames) then separate we"ding procedures Eua"ifications are not reEuired) pro'ided a"" other reEuirementsof 7*) 7() and Section I3 of the AS./ %ode are met

7*$* The we"ding procedure used sha"" produce we"dments with the mechanica" properties reEuired &9the design

7*$( .ateria" specification "isted in Section * of this standard &ut not inc"uded in !-8** of SectionI3 if AS./ %ode sha"" &e considered P$ materia" with group num&ers assigned as fo""owsaccording to the minimum tensi"e strength specified:


7/30

a Less that 8J5 .Pa 7ksi- Froup $ & /Eua" to or greater than 8J5 .Pa 7 ksi &ut "ess or eEua" to 55 .Pa J ksi-Froup *c Freater than 5 .Pa J ksi- Froup (

Separate we"ding procedures and performance Eua"ifications sha"" &e conducted for A J8$ .AJ8$ materia"s

7*$8 !e"ding 'aria&"es inc"uding supp"ementar9 essentia" 'aria&"e when impact tests are reEuired &97**) as defined &9 !-*5 of Section I3 of the AS./ %ode) sha"" &e used to determine thewe"ding procedures specifications and the procedures Eua"ification records to &e instituted Inaddition) when impact test of the heat affected 4one are reEuired) the heat treated condition of the

&ase materia" sha"" &e a supp"ementar9 essentia" 'aria&"e If a protecti'e coating has &een app"iedto we"d edge preparations) the coating sha"" &e inc"uded as an essentia" 'aria&"e of the we"ding

procedure specification) as reEuired &9 5*$M

41818 I*$%t !e#t

7**$ Impact test for the Eua"ification of we"ding procedures sha"" comp"9 with the app"ica&"e pro'isionof **Jand sha"" &e made at or &e"ow the design meta" temperature

7*** !hen impact testing of a materia" is reEuired &9 **J or **M impact test of the heat affected4one sha"" &e made for a"" automatic and semiautomatic procedures

7**( Bor a"" materia" to &e used at a design meta" temperature &e"ow $Q % 5QB the Eua"ification ofthe we"ding procedure Doints sha"" inc"ude impact test of the we"d meta" If 'ertica" Doints are to &emade &9 an automatic or semiautomatic process) impact tests of the heat affected 4one sha"" &ea"so made

7**8 Impact test of the we"d meta" sha"" &e made for a"" procedures used for we"ding the components"isted in **M$ and attachments to these components when the design meta" temperature is

&e"ow -7Q% *QB7**5 Impact test sha"" show minimum 'a"ues for acceptance in accordance with **J( and the

fo""owing:a Bor P$) Froup $) materia"s- * @ $5 ft-"&f) a'erage of three specimens

& Bor P$) Froup *) materia"s- *7 @ * ft-"&f) a'erage of three specimensc Bor P$) Froup () materia"s- (8 @ *5 ft-"&f) a'erage of three specimensBor she"" p"ates thicker than 8 mm $ G in) these 'a"ues sha"" &e increased &9 7 @ 5 ft-"&f for

each $*5 mm $* inch o'er 8 mm $ G inch Interpo"ation is permitted

7**6 !e"d-meta" impact specimens sha"" &e taken across the we"d with one face su&stantia""9 para""e"to and within $5 mm $$6 inch of the surface of the materia" The notch sha"" &e cut norma" tothe origina" materia" surface and with the we"d meta" entire"9 within the fracture 4one

7**7 ,eat affected 4one impact specimens sha"" &e taken across the we"d and as near the surface of themateria" as is practica&"e /ach specimen sha"" &e etched to "ocate the heat affected 4one) and thenotch sha"" &e cut appro2imate"9 norma" to the origina" materia" surface and with as much heataffected 4one materia" possi&"e inc"uded in the fracture 4one

7**J Production we"ding sha"" conform to the Eua"ified we"ding procedure) &ut production-we"d test p"ates need to &e made

413 u&(&%t&on o( Weder#

7($ The erection manufacture and the fa&rication manufacturer) if other that the erectionmanufactures) sha"" conduct test for a"" the we"ders assigned to manua" and semiautomaticwe"ding and a"" operators assigned to automatic we"ding to demonstrate the we"ders andoperators a&i"it9 to make accepta&"e we"ds Test conducted &9 one manufacturer sha"" not Eua"if9a we"der or we"ding operator to do work for another manufacturer


8/30

7(* The we"ders and we"ding operators who we"d pressure parts and Doint non-pressure part) such asa"" permanent and temporar9 c"ips and "ugs) to pressure parts sha"" &e Eua"ified in accordancewith Section I3 of the AS./ %ode

7(( The records of the test for Eua"if9ing we"ders and we"ding operators sha"" inc"ude the fo""owing:

a /ach we"der or we"ding operator sha"" &e assigned a identif9ing num&er) "etter or s9m&o"

&9 the fa&rication erection manufacturer & The fa&rication erection manufacture sha"" maintain a record of the we"ders or we"ding

operators emp"o9ed that shows the date and resu"ts of the test for each we"der oroperator and the identif9ing mark assigned to each we"der or operator This record sha""

&e certified &9 the fa&rication or erection manufacturer and sha"" &e accessi&"e to theinspector

78 Identification of !e"ded @ointThe we"der or the we"der operators identification marks sha"" &e hand-or machine stampedadDacent to and at inter'a"s not e2ceeding $ meter ( ft a"ong the comp"eted we"ds In "ieu ofstamping) a record ma9 &e kept that identifies the we"der or we"ding operator emp"o9ed for eachwe"ded Doint these records sha"" &e accessi&"e to the inspector Roof p"ates we"ds and f"anges tono44"e neck we"ds do not reEuired identification

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 generrue# (or NDE &n API-653 Se%t&on .@

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#


9/30

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


10/30

=1818 ;#e o( At*o#$er&% Storge !n"#=1813 !,$e# o( At*o#$er&% Storge !n"#

=13 Lo-Pre##ure Storge !n"#=131. De#%r&$t&on nd De#&gn o( Lo-Pre##ure Storge !n"#=1318 ;#e o( Lo-Pre##ure Storge !n"#=1313 !,$e# o( Lo-Pre##ure Storge !n"#

Tanks that ha'e c9"indrica" she"" and cone or dome roofs are t9pica""9 used for pressures "ess thana&out 5 pounds per sEuare inch gauge Tanks &ottoms ma9 &e f"at or ha'e a shape simi"ar to theroof ,o"d down anchorage of the she"" is genera""9 reEuired Bor pressure a&o'e a&out 5 pounds

per sEuare inch gauge) the hemispheroida") spheroida") and nodded spheroida" tank t9pes arecommon"9 used for "ow-pressure storage tanks Such tanks are designed to withstand the 'apor

pressure that ma9 &e de'e"oped within a tank ha'ing no de'ice or means to change the interna"'o"ume As with atmospheric storage tanks) these tanks are pro'ided with re"ief 'a"'es to pre'ent

pressures from rising a&o'e safe 'a"ues

87 Pro%edure# to $er(or* e)tern nd &ntern &n#$e%t&on

37 !e t,$e# o( e)tern nd &ntern &n#$e%t&on=7 Pro%edure# to deter*&ne #u&tb&&t, (or %ont&nued #erv&%e57 Evut&on %nge-o(-#erv&%e# on #u&tb&&t, (or %ont&nued #erv&%e#67 Evut&on nd gener %ond&t&on o(

7 Dtort&on (#b7 !n" (oundt&on#%7 'u#e# o( %orro#&on e"# %r%"# nd *e%n&% deter&ort&ond7 Au)&&r, eu&$*ente7 An%or bot# $&$e %onne%t&on# ground %onne%t&on#(7 In#ut&ong7 Se nd roo(#

API-653 !n" In#$e%t&on Re$&r# Atert&on nd Re%on#tru%t&on nd te reted $ort&on# o( API-

65@ Weded Stee !n"# (or O& Storge API-653 $$&%be to te e)*&nt&on une## #$e%&(&%, e)%uded7

A7 !n" In#$e%t&on NDE nd !e#t&ng

.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&on

g7 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&on


11/30

7 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 !


12/30

API-65.

API- 65. 'tod&% Prote%t&on o( Aboveground Petroeu* Storge !n"#Note on, #e%t&on# .83=560 nd .. & be %overed on te e)*&nt&on

Specia" note:Boreword:Scope:The purpose of this recommended practice is to present procedures and practices for achie'ingeffecti'e corrosion contro" on a&o'eground storage tank &ottom through the use of cathodic

protection

API-65.

C/BI1ITI#1S($ Aboveground #torge tn" A stationar9 container) of grater than 5 &arre" capacit9 usua""9c9"indrica" in shape) consisting of a meta""ic roof) she"") &ottom) and support structure wheremore than M of the tank 'o"ume is a&o'e surface grade(* Anode The e"ectrode of an e"ectrochemica" ce"" at which o2idation corrosion occurs)Anton9m: cathode(( B%"(& .ateria" p"aced in a ho"e to fi"" the space around anodes) 'ent pipes) and &uriedcomponents of a cathodic protection s9stem Anodes can &e prepackaged with &ackfi"" materia"for ease of insta""ation(8 Bre"out P&$&ng A"" piping associated with the transfer of product in and out of storagetanks

(5 'tode The e"ectrode of an e"ectrochemica" ce"" at which a reduction reaction occursAnton9m: anode(6 'tod&% Prote%t&on A techniEue to reduce corrosion of a meta" surface &9 making theentire surface the cathode of an e"ectrochemica" ce""(7 'o"e Breee A car&onaceous &ackfi"" materia"(J 'ont&nu&t, Bond A meta""ic connection that pro'ides e"ectrica" continuit9(M 'orro#&on The deterioration of a materia") usua""9 a meta" that resu"ts from a reaction withits en'ironment($ 'urrent Den#&t, The current per unit area f"owing to or from a meta""ic surface($$ 'urrent reu&re*ent te#t %reates direct current f"ow from a temporar9 ground to thestructure to &e protected to determine the amount of current necessar9 to protect the structure($* Dee$ Grounded #ne or more anodes insta""ed 'ertica""9 at a nomina" depth of $5 m 5 ftor more &e"ow the earths surface in a sing"e dri""ed ho"e for the purpose of supp"9ing cathodic

protection

($( D&((erent& Aert&on 'e An e"ectrochemica" ce"" the e"ectromoti'e force of which is dueto a different in air o29gen concentration at one e"ectrode as compared with that at anothere"ectrode if the same materia"($8 Ee%tr&% I#ot&on The condition of &eing e"ectrica""9 separated from other meta""icstructures or the en'ironment($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 &e


13/30

separate 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($7 Ee%tro Potent& The potentia" of an e"ectrode as measured against a reference e"ectrodeThe e"ectrode potentia" does not inc"ude an9 resistance "osses in potentia" in either the e"ectro"9teor the e2terna" circuit It represents the re'ersi&"e work reEuired to mo'e a unit charge from thee"ectrode surface through the e"ectro"9te to the reference e"ectrode($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 earths surface for the

purpose of supp"9ing cathodic protection(*5


14/30

(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!< !


15/30

8$* There are man9 forms of corrosion The two most common t9pes re"ati'e to tank &ottoms

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

corrosion

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 thesestudies indicate that the corrosion wi"" affect the safe or economic operation of the

s9stem) 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

5$8 Limitations of /2terna" %athodic Protection

%athodic protection is an effecti'e means of corrosion contro" on"9 if it is possi&"e to pass e"ectrica" current &etween the anode and cathode tank &ottom .an9 factors caneither reduce or e"iminate the f"ow of e"ectrica" current and) therefore) ma9 "imit theeffecti'eness of cathodic protection in some cases or prec"ude its use in other Suchfactors inc"ude:a Boundations such as concrete) aspha"t) or oi"ed sand

& An imper'ious "ining &etween the tank &ottom and anodes such as in secondar9containment s9stems

c ,igh resistance soi"s or rock foundationsd #"d storage tank &ottoms "eft in p"ace when &ottom is insta""ed


16/30

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"


17/30

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 can

inf"uence the effecti'eness and app"ica&i"it9 of e2terna" cathodic protectionIt is 'er9 important to ensure that there is not de&ris such as stick) used we"ding rods)rocks) or c"a9 in the cushion materia" The cushion materia" partic"es shou"d &e fine anduniform Thanks shou"d &e &ui"t on an e"e'ated &erm to a""ow adeEuate drainage awa9from the tank &ottom) The use of fine partic"es wi"" pro'ide a more dense cushion to he"preduce the inf"u2 and outf"ow of o29gen from the perimeter of the tank as it is emptiedand fi""ed If "arge partic"e si4es are used) differentia" aeration corrosion ma9 resu"t at

points where the "arge partic"es or de&ris contact the stee" tank &ottom In this case)cathodic protection wi"" not &e effecti'e in e"iminating the pitting There are a wide'ariet9 of cushion materia"s a'ai"a&"e) some of which actua""9 pre'ent &eneficia" effectsof cathodic protection %on'erse"9) there are situations where some of these materia"s)when proper"9 se"ected and insta""ed) can &e &eneficia" in reducing corrosion to thee2tent that cathodic protection ma9 not &e needed

5($* Soi" resisti'it9 pro'ides 'a"ua&"e information a&out the %orrosi'it9 of the materia" usedunder and around a tank A genera" resisti'it9 c"assification is gi'en in ta&"e-$ Thereare se'era" techniEues for measuring soi" resisti'it9 A common method is descri&ed inAST. F 57

Ta&"e $ Fenera" %"assification of Resisti'it9 Resisti'it9 Range#,.-%. Potentia" %orrosion Acti'it9


18/30

&"owing rain or snow) or f"ooding due to inadeEuate drainage %orrosion ma9 occur dueto the moisture accumu"ation %athodic protection is genera""9 not considered aneffecti'e wa9 to com&at this corrosion A free-draining concrete pad or ring-wa"" andsea" around the peripher9 of the tank ma9 &e effecti'e and e"iminating the accumu"ationof moisture &etween the pad and the tank &ottom where f"ooding in the dike area a&o'ethe tank &ottom not occurs 1o-continuos concrete tank foundation designs fore2amp"e) s"otted pads do not restrict the entr9 of o29gen In situations where water ma9

condense on the tank &ottom or water is retained a&o'e the concrete pad) acce"eratedatmospheric corrosion ma9 occur

5(*( Cue to numerous comp"e2 factor that can &e affect the corrosion of a tank &ottomunderside in the present of concrete) prediction of the propensit9 in this case ise2treme"9 difficu"t Thus) care shou"d &e o&ser'ed with tanks on concrete pads sincecathodic protection most "ike"9 wi"" not he"p reduce an9 corrosion that might &e occur

51313 'ont&nuo# A#$t 'u#&on

5(($ A cushion of new aspha"t ma9 pro'ide man9 of the same ad'antages and disad'antagesas a concrete cushion for reducing corrosion and e"iminating the need for cathodic

proDection The importance of proper support to pre'ent cracks and to pre'entaccumu"ation of water &etween the cushion and the tank &ottom is possi&"9 e'en moreimportant for aspha"t than for concrete &ecause aspha"t is not inherent"9 a"ka"ine and)therefore) does not ha'e the potentia" of pre'enting corrosion in the e'ent of cracks

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 %athodic

protection) if app"ied) ma9 or ma9 not aid in stopping corrosion when the aspha"t &ecome deteriorated In fact) deteriorated aspha"t ma9 shie"d cathodic protection currentin a manner simi"ar to a dis&anded coating on a pipe"ine The condition of the e2terna"surface of the tank &ottom as we"" as the aspha"t can &e determined if coupons are cutfrom the tank &ottom

5(8 1ati'e Soi" %ushion5(8$ Soi" ana"9sis is often a usefu" test for he"ping to determine whether the potentia"

corrosion acti'it9 wi"" &e high enough to make cathodic protection necessar9 andwhether cathodic protection wi"" &e a practica" app"ication to pre'ent corrosionCetermination of aggressi'e ions such as su"fates a"ong with measurement of p, andresisti'it9 are he"pfu" for further corrosion ana"9sis Ta&"e * pro'ides a guide"ine forre'iewing soi" ana"9sis data The 'ariet9 of partic"es si4es and chemica" differences asdiscussed in 5($ shou"d a"so &e considered

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

5(5 %"ean or #i"ed-Sand %ushion%"ean is the most common materia" used as a cushion &eneath storage tank &ottoms Theuse of c"ean sand a"one norma""9 does not e"iminate the need for cathodic protectionsince corrosion ma9 occur due to intrusion of water from rain) snow) or a sha""ow waterta&"e Fuide"ines for the chemica" ana"9sis of the sand for corrosi'e contaminants are

discussed in 5(8$ In some cases oi" has &een added to the sand for 'arious reason)inc"uding compaction and corrosion contro"

Ta&"e-*- Fuide"ine for Re'iewing Soi" Ana"9sis Cata

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

p, 5-65 H 5%h"orides (-$ PP. U $PP.Su"fates $-5 PP. U5 PP.


19/30

/2perience in the industr9 is 'aried as to the effecti'eness of oi"ed sand for corrosioncontro" The present of oi"ed sand &eneath tank &ottoms has not &een pro'en as aneffecti'e corrosion contro" measure and thus does not e"iminate the need for cathodic

protection and ma9 cause cathodic protection to &e "ess effecti'e &ecause of the higherresisti'it9 of the oi"ed sand

5(6 %ontaminated Soi" %ushion5(6$ In coasta" areas) sa"t spra9 on tank surfaces wi"" &e washed down the sides of the tank &9

rain and wi"" f"ow &eneath the tank cushion This a"so can occur in areas whereferti"i4ers or chemica"s ma9 &e in the atmosphere either from spra9ing or industria"operations The tank cushion a"so can &ecome contaminated &9 wicking action that candraw contaminates such as ch"orides up from the water ta&"e %athodic protection isusua""9 necessar9 for corrosion pre'ention in these situations

5(6* If a "eak occurs in a tank &ottom) the "eaking materia" a"so can inf"uence corrosion onthe e2terna" side If water "eaks from the tank) the en'ironment under the tank ma9

&ecome more corrosi'e If the product "eaks from the tank) it cou"d create corrosion ce""sthat did not pre'ious"9 e2ist or ad'erse"9 affect the effecti'eness of the cathodic

protection A "eak ma9 wash awa9 part of the foundation materia" and e"iminate thecontact of the tank &ottom with the ground in some areas %athodic protection wi"" not

&e effecti'e in such areas Additiona""9) drainage properties of the foundation materia"ma9 &e deteriorated &9 a "eak and a""ow water and contaminates to remain in contactwith the tank &ottom

5(7 %rushed-Limestone or %"am-She"" %ushionIn some parts of the Nnited State) the tank cushion consists of a "a9er of crushed"imestone or c"am she""s Such tank cushion without the use of cathodic protection ha'e

produce 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 the

cushion) or with time infi"trate the cushion) corrosion ma9 &e acce"erated Thus the useof crushed "imestone or c"am she""s does not c"ear"9 e"iminate the need for cathodic protection

58 #ther Bactor Affecting %athodic Protection

58$ %ontents TanksThe contents of a storage tank can inf"uence corrosion on tank &ottoms Acce"eratedcorrosion can occur on the e2terna" surface of the &ottom of heated tank due to e"e'atedtemperatures if the area is wet Storage tanks containing a hot product ma9 reEuired anincrease of current densit9 to achie'e adeEuate on the e2terna" surface of the &ottom%on'erse"9) sufficient heat cou"d dr9 out a we""-drained tank pad) thus increasing itsresisti'it9 and reducing the need for cathodic protection,owe'er) tank operators shou"d &e aware that if water penetrates the pre'ious"9 dr9 out

tank pad such as cou"d &e caused &9 a&o'e-a'erage rainfa"") the resisti'it9 of the tank pad decrease) de'e"oping a more corrosi'e condition Bor this situation) the insta""ationof a cathodic protection s9stem shou"d &e considered

58* +ottom Rep"acementRep"acement of tank &ottoms is an accepted practice%athodic protection s9stem can &e used to ensure "ong-term integrit9 of e2isting andrep"acement &ottoms The methods of insta""ing rep"acement &ottoms) secondar9containment s9stems) and interna" "ining must &e considered when determining the needfor and the method of insta""ation of a cathodic protection s9stem These factors re"ate to


20/30

&oth e2isting and new cathodic protection s9stems and ha'e a significant impact on thefeasi&i"it9 and effecti'eness of the cathodic protection The effect of rep"acement &ottomsand secondar9 containment on cathodic protection s9stem design is discussed in 7*

58( Secondar9 %ontainment

58($ There are a 'ariet9 of methods a'ai"a&"e for secondar9 containment These inc"ude) &ut

are not "imited to:a Nsed of imper'ious c"a9 pad in the tank dike

& Cua" &ottom tank designc Imper'ious nonmeta""ic mem&rane

58(* The use of secondar9 containment wi"" reduce the en'ironmenta" risk in the e'ent of a"eak ,owe'er) the use of certain secondar9 containment techniEues ma9 prec"ude theuse of cathodic protection and in some cases ma9 cause acce"erated corrosion of the tank

&ottom An e2amp"e of a dou&"e &ottom secondar9 containment s9stem is the insta""ationof a new stee" &ottom o'er an e2isting stee" &ottom which has &een repaired If water orother e"ectro"9te intrudes into the annu"us) a ga"'anic ce"" ma9 &e formed which wi""cause the new stee" tank to corrode at an acce"erated rate In order to app"9 cathodic

protection to a new &ottom if sand or other su&stances that are conducti'e or that ma9 &ecome wet are uses as fi"" materia"

58(( If a secondar9 containment s9stem uti"i4ing an imper'ious mem&rane "ining is in p"ace

or is insta""ed in a diked area prior to new tank construction) the option of cathodic protection &ecome se'ere"9 "imited .ost cathodic protection s9stems are renderedineffecti'e &ecause the "iner acts as a &arrier to the f"ow of e"ectrica" current necessar9for protection Another conseEuence of secondar9 containment in'o"'es the use of animper'ious "iner which ma9 trap corrosi'e "iEuid) resu"ting in more se'ere corrosion ofthe tank &ottom There are ad'antages and disad'antages to using secondar9containment "ining Bor a further discussion of the effects of secondar9 containment oncathodic protection design) refer to 7*

588 Thick-Bi"m Interna" Linings

Thick-fi"m) "aminated) and corrosion- and chemica"-resistant "inings are insta""ed in

tanks 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"" There are two s9stems of cathodic protection:a ga"'anic

& Impressed %urrent

6* Fa"'anic S9stem


21/30

6*$ Fenera"Gvn&% 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'e

current 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*, $$&edon, to #*-d&*eter tn"1

6** 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

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


22/30

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 to

d*ge (ro* $oer #urge#1Therefore) protecti'e de'ices shou"d &e 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 AnodesI*$re##ed %urrent node# u#ed &n #o& re *de o( *ter&# #u% # gr$&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 aresu&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" (und 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 be

t"en o ##ure tt %be# re $rote%ted (or* $,#&% d*ge nd te$o##&b&&t, o( r%&ng1

..1818 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&on


23/30

be(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


24/30

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 Records

$$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 & 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 offactor9-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 &eensatisfied

$$86 In *&nt&n&ng %orro#&on %ontro (%&&t&e# te (oo&ng &n(or*t&on #oud bere%ordeda 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 In(or*t&on %ont&ned &n RP-65. &% te &n#$e%tor & not be e)*&ned on

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


25/30

A7 Pr%t&% under#tnd&ng nd be (*&&r &t te &n(or*t&on %ont&ned &n RP-658 retedto

.7 t,$e# o( tn" botto* &n&ng nd dvntge# nd ddvntge# o( e%87 %on#&dert&on# (or re%o**end&ng tn" botto* &n&ng#37 %u#e# o( tn" botto* &n&ng (&ure#=7 t,$e# o( tn" botto* &n&ng *ter&#

57 #ur(%e $re$rt&on reu&re*ent# (or te &n#tt&on o( tn" botto* &n&ng67 #ue# ((e%t&ng te $$&%t&on o( tn" botto* &n&gn

[email protected]

SAFE EN!RY nd 'LEANING o( APE!ROLE;9 S!ORAGE !ANKS

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


26/30

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

.7 Ad*&ntrt&ve #(e, $rogr*# nd re#$on#&b&&t&e#87 Ste$ b, #te$ $ro%edur reu&re*ent# (or ##ur&ng #(e entr,37 Entr, %##&(&%t&on=7 !,$e o( te#t nd eu&$*ent u#ed to ver&(, #(et,

57


27/30

API-88@4 PREPARING !ANK BO!!O9S FOR


28/30

(*6 %ompressed gas c9"inders used for cutting operations shou"d &e secure"9 fastened in an upright position and kept outside the tank at a safe distance from the manho"es !hen not in use) cuttingtorches and hoses must &e shut off at the c9"inder 'a"'es and kept outside the tank %ompressed-gas supp"9 hoses and hose connections shou"d &e inspected for "eaks prior to &eing taken insidethe tank

To pre'ent a possi&"e f"amma&"e mi2ture with air from forming in the tank) compressed-gassupp"9 hoses must &e protected from damage outside the tank and from &urns) cuts) &reaks) orother damage inside the tank

(*7 !hi"e work in progress) a"" work areas must &e monitored for o29gen deficienc9 and com&usti&"eand to2ic atmosphere


29/30

e !hen the we"ding has &een finished in a "oca"i4ed area) stop the f"ow 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 area5( !hen repairs in'o"'e most of the tank &ottom) it ma9 &e desira&"e to disp"ace the f"amma&"e

"iEuids &eneath the tank &9 water f"ooding This ma9 &e done as fo""ow:a Around the tanks outer she"") construct an earth dike higher that the highest f"oor p"ate

in the tank see Big $

& At the highest point in the tank &ottom) dri"" and tap ho"es $( mm pipe These ho"esshou"d &e "ocated to ensure that a"" f"amma&"e "iEuids or 'apors under the tank wi"" &edisp"aced with water

Cate of issue: @une $MMMAffected Pu&"ication: Pu&" **7 Bifth /dition

/RRATAP"ease add the fo""owing at the end of the te2t in the fifth edition of **7

c Insta"" pipe nipp"es to &e used as 'ents and checkpoints The height of the nipp"es shou"dthat of the temporar9 earthen dike

d Bi"" the space under the tank with water unti" seepage occurs at each nipp"e %ontinuethe f"ow of water to maintain a constant "e'e" within the dike to ensure that no 'oidsde'e"op under the tank

e !atch for "eaks inside the tank and p"ug them as necessar9 to keep the tank &ottom dr9f !hen repairs are comp"eted) empt9 the water from the dike to Dust &e"ow the nipp"e)

remo'e the nipp"e) p"ug the ho"es with a tapered pin or other de'ice) and &ack we"d58 Perimeter Repairs

Repairs around the perimeter of a tank &ottom ma9 &e made safe"9 the fo""owing preparations:

a /2ca'ate under the edge of the tank for a minimum of ( centimeter $* inches &e9ondthe point of an9 hot work area The e2ca'ation shou"d &e "arge enough for a person towork in safet9 and comfort whi"e e2ca'ating and app"9ing a "iEuid or 'apor &arrier Thearea shou"d &e continuous"9 monitored to assure the o29gen content is &etween $M5 and**5 percent

& Sea" off a"" openings &etween the f"oor p"ates and the tank foundation &9 packing themwith mud or some other suita&"e) non-corrosi'e materia" The packing shou"d &e checked

periodica""9) and wa"king on the tank &ottom shou"d &e restricted to assure that the sea"remains intact see Big $c Nse a 'apor indicator to check the e2ca'ation and the sea" &etween the f"oor p"ates and

the foundationd +efore starting hot work and whi"e work is in progress) monitor the surrounding areas)

inc"uding the e2ca'ations and the tank interior) for the present of air&orneconcentrations of chemica" contaminants

e 0enti"ate the e2ca'ation) if necessar9) with a porta&"e air &"ower rated for the appropriatee"ectrica" c"assification

1ote: !hen 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 foundation

55 Cou&"e-+ottom Insta""ation

!hen a tank dou&"e is constructed) the fo""owing procedures ma9 &e used:a P"ace appro2imate"9 $ centimeter 8 inches of sand or other sea"ing materia" o'er thee2isting f"oor

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

1ote: If 'apor in the f"amma&"e range are not present under the origina" tank &ottom) hot work can &e performed safe"9 on the new tank &ottom) e'en though the origina" tank &ottom is resting on a foundationsaturated with oi" In addition) hot work ma9 &e performed if there is not possi&"e of oi" penetrating thesand &arrier and coming in contact with the new &ottom &eing we"ded


30/30

56 Section Repairs

!hen sectiona" repairs are made on tank &ottoms) the fo""owing methods ma9 &e used:a !hen using a hand or air operated too") co"d cut the tank &ottom to &e rep"aced and remo'ed

it A coo"ant shou"d &e app"ied continuous"9 to the cutting edge of the too" to reduce the heatof 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 to2ic atmospheresd !hen "arge sections of the &ottom must &e rep"aced and it is Euestiona&"e whether the sea"

wi"" remain effecti'e) maintain the inert area under the patch area whi"e hot work is &eing performed !hi"e work is &eing performed in and around an area with an inert atmosphere)the area shou"d &e continuous"9 monitored with o29gen ana"94er

Body of Knowledge for API-2003

Documents

Transcript of Body of Knowledge for API-2003