Cathodic Protection Report

NIGER DELTA PETROLEUM RESOURCES

ENGINEERING DESIGN OF 12” x 20 KM OGBELE – RUMUJI PIPELINE PROJECT

CATHODIC PROTECTION REPORT OG0108-OGB-SR-C-001

Rev. No.

Date

0

0 Oct.! "00#

Description Approved $or Construction

Author %. Ebesunun

Reviewed by

Approved by

I. &bonu

'. O(ani)be

POINT

POINT ENGINEERING LIMITED

This document is controlled electronically and is uncontrolled when uncontrolled when printed.

Approved by NDPR

Cathodic Protection Report ,"-  "0 '/ O)bee 1 Ru/u2i Pipeine Pro2ect

POINT EN*INEERIN* +I&ITED O*0,034O*546R4C400,

TA5+E O7 CONTENT

,.0 INTROD8CTION ,., PRO:ECT 5AC'*RO8ND ,." 6COPE

9 9 9

".0 CATHODIC PROTECTION REPORT "., *ENERA+ "." TRAN67OR&ER IN6PECTION AND TE6TIN* ".@ CA+C8+ATION ".3 C8RRENT RE8IRE&ENT 7OR THE NE= 7+O=+INE ".#DEEP=E++ *RO8ND 5ED 6IBIN* ".#., ANODE RE8IRE&ENT ".#." *RO8ND5ED RE6I6TANCE ".#. 8ANTIT O7 5AC'7I++ .0 CONC+86ION

; ; ; ; > > > @ @ 3 3 # ,0 ,"

9.0 RE7ERENCE6

,

Cathodic Protection Report

Oct! "00# Pa)e " o$ ,



Abbre!"#!$%&

AC

Aternatin) Current

CP

Cathodic Protection

DC

Direct Current

H&=4PE

Hi)h &oecuar =ei)ht poyethyene

'& '/

'io/eter

NDEP

Ni)er Deta Eporation and Production

NDPR

Ni)er Deta Petroeu/ Resources +i/ited

N+N*

Ni)erian +iFue$ied Natura *as

PE76

Process En)ineerin) 7ow 6che/e

P76

Process 7ow 6che/e

POINT

Point En)ineerin) +i/ited

RO=

Ri)ht o$ =ay

6=A

6in)e =ire Ar/oured

6O=

6cope o$ =or(

6PDC

6he Petroeu/ Deveop/ent Co/pany


Oct! "00# Pa)e  o$ ,



1'0 INTRODUCTION

,.,

PRO:ECT 5AC'*RO8ND The cient! Ni)er Deta Petroeu/ Resources NDPR +i/ited desires to deiver +ean *as via a ,"-  "0(/ pipeine $ro/ its $ied in O)bee
,."

6COPE The overa purpose o$ this report is to evauate the adeFuacy o$ the eistin) Cathodic Protection syste/ on the site $or the new "0(/ O)bee 1 Ru/u2i pipeine usin) the eistin) recti$ier< trans$or/er.


Oct! "00# Pa)e 9 o$ ,



2'0 CAT(ODIC PROTECTION REPORT

".,

*ENERA+ The Cathodic protection syste/ that wi operate in ,"-  "0 '/ O)bee 1 Ru/u2i pipeine pro2ect is the eistin) i/pressed current type. The eistin) cathodic protection syste/ is suppied power $ro/ Obee diese )eneratin) sets and suppy "0% AC vota)e! ">.@A! ;0HG $reFuency at the input and ;0% DC! ;0A at the output. The syste/ has an operatin) te/p o$ 9; 0C! oi cooed case. There are three cabe routes $ro/ the trans$or/er //" H&=4PE cabe to the ,"- new pipeine as shown on drawin) O*0,034O*54ED4C400, throu)h the spare rheostat. The new pipeine wi be connected to :54 spare rheostat as shown on drawin) O*0,034O*54ED4C4009.

"."

TRAN67OR&ER
".

DEEP=E++ *RO8ND 5ED This section provides a )uideine $or desi)n o$ i/pressed current )round bed. 7or this pro2ect! one vertica deep we )round bed is proposed to boost the per$or/ance o$ the eistin) cathodic protection syste/ in order to acco//odate the new ,"-  "0 '/ pipeine. However! this proposition is to /aintain the initia desi)n o$ two )round beds $or the syste/ $or which one o$ the )round beds was not in use presenty. The )round bed sha be instaed as shown on drawin) O*0,034O*54ED4C400. Durin) the )round bed instaation! the $oowin) shoud be ta(en into consideration •

The )round bed shoud be sited at east ,00/ $ro/ a buried /etaic structures within the area o$ in$uence surroundin) the )round bed. This is to prevent the /etaic structures $ro/ pic(in) up current $ro/ the )round bed and create a stray current inter$erence probe/ that wi reFuire corrective /easures when usin) the site.


Oct! "00# Pa)e ; o$ ,


•


The current source shoud be ta(en $ro/ the eistin) recti$ier4powered i/pressed current on the site.

•

The )round bed site shoud be reasonaby accessibe $or construction and /aintenance purposes.

•

The )round bed /ust be $ree $ro/ $urther buidin) construction new pipeines! hi)hway deveop/ent! or other si/iar wor( that wi /a(e the site untenabe in the near $uture.

".9

CA5+E6 AND ACCE66ORIE6 •

Cabes sha be sin)e core /uti4stranded copper conductors! H&=4PE insuated! 6=A! and over sheathed! with the coor indicated on construction drawin)s.

•

The cabe cross4sections and routes are shown on the drawin)s O*0,034 O*54ED4C400.

•

The cabe ayin) shoud be done with opti/u/ care to avoid (in(.

•

The cabe shoud be aid to ensure that their aowabe bendin) radius is not eceeded.

•

Test point cabes connection to the pipeines sha be by ther/ite wedin) accordin) to 6tandard Construction 6peci$ication 6,@ o$ 6he Dep. 0.,0.@.,04 *en. Nov "00 p) @#.

•

Eectrica connections between anode and eads and header cabe are critica part o$ i/pressed current )round bed construction. Anode eads /ust be connected to the header cabe by a /ethod that wi have per/anenty ow resistance.

•

The connection! once /ade! /ust be insuated so that it wi be waterproo$ to present current ea(a)e and cabe corrosion.

".;

:8NCTION 5O? •

The proposed :unction bo :549 sha be desi)ned to provide eectrica continuity! vota)e re)uation via rheostats and potentia baancin) $or the cathodic protection syste/ as shown on the drawin) O*0,034O*54ED4C400.

•

:549 sha be instaed such that o$$er ease o$ /aintenance! and aso provide with specia oo(in) syste/.

•

The instaed 2unction bo sha be co/pete with resistors and current shunts.


Oct! "00# Pa)e > o$ ,


".>


IN6PECTION AND TE6TIN* A$ter co/pete instaation o$ the cathodic protection syste/! it is necessary to carry out tests to ensure and con$ir/ satis$actory instaation and operation o$ a parts o$ the syste/.

".@

CA+C8+ATION The soi data used beow $or the anaysis are based on the 7ina Report on 6ubsoi Investi)ation $or the proposed NDPR *as Pant- dated :uy "00@ +en)th o$ eistin) pipe ine

J

@.; '/

Dia/eter o$ eistin) pipe

J

>- ,;."9 c/

+en)th o$ new $ow ine

J

"0 '/

Tota en)th o$ distribution 

J

"@.; '/

Dia/eter o$ new pipe d

J

,"- 0.; c/

Tota dia/eter o$ pipe D

J

,3- 9;.@9 c/

Avera)e soi resistivity

J

,;00 Kc/

Corrosion Coatin) Thic(ness tc

J

 //

Avera)e ea(a)e conductance *

J

".,9  ,0 4s
Avera)e potentia shi$t to re/ote earth

J

40.";0%

Tota sur$ace area o$ the instaation pipe A

J

Ld L J .,9"

.,9"  9;.@9<,00  "@.;

J

#.;""/M

Esti/ated ea(a)e conductance o$ new pipe in ,00 Kc/ ) J

*A

J

".,9  ,0 4  #.;""

J

0.039> sie/ens

Resistance to re/ote earth

J

,
,<0.039>

J

,,.3"9K

Esti/ated resistance to re/ote earth in ,;00 Kc/ soi J

,,.3"9  ,.;

J

,@.@>K

Esti/ated current to shi$t pipe potentia to re/ote earth 40.";0% =

I


E/R

=

0.250/17.736

J

0.0,9,A

Oct! "00# Pa)e @ o$ ,


".3


C8RRENT RE8IRE&ENT 7OR THE NE= 7+O=+INE Pipeine sur$ace Area

A

J J J

A

D  "tc+ π,"  ";.9  ",0  "0 ".09"  ,0 4 /2 

The /ini/u/ desi)n current density $or PE coatin) $or up to 0 4 year i$e is 0.0,/A
".#

J

A  : < ,000

J

0.;  ".09"  ,0 < ,000

J

,0."," A

9

DEEP=E++ *RO8ND 5ED 6IBIN* In the $oowin) section! )round bed siGin) cacuations are detaied. Note that the siGin) is based on Dwi)hts $or/ua. In addition! due to the unavaiabiity o$ soi resistivity data! the )round bed resistance cacuation is based on assu/ed vaue o$ ,;00 oh/.c/! which is reasonabe at the )reat depth considered in this desi)n.

".#., ANODE RE8IRE&ENT Anode Type

&ied &eta Oide

Anode Di/ensions

,00 c/  ".; c/

Net =ei)ht

0.> ()

No/ina Consu/ption Rate

0.00"@()
&ai/u/ Output per Anode at ,/A
3.0 A

8tiisation 7actor

@0

ReFuired +i$eti/e

"; years


Oct! "00# Pa)e 3 o$ ,


ReFuired Nu/ber o$ Anodes n


J Current ReFuired $or Protection

Current output
6ay Anodes *roup =ei)ht

J

"0  0.>

,00  ,00 3  @0 J

,@.3;@

J

"0 Anodes.

J

@." ()

Anodes consu/ption at /ai/u/ )round bed current output $or the entire "; years is J

";  ,00  0.00"@

J

>.@; ()

This is ess than the anodes )roup wei)ht and hence /eets the anodes reFuire/ents $or the speci$ied i$e o$ the pipeines. The resistance to earth o$ the )round bed /ust aow the /ai/u/ predicted current de/and to be /et at 30 or ess o$ the vota)e capacity o$ the DC source. This /inus the " % bac( vota)e o$ the co(e bac($i divided by the current output $ro/ the recti$ier )ives a /ai/u/ circuit resistance! R/a! o$ R/a

J

Idc

,00

%dc  30 4 "

J

;0  0.3 1 "

J 0.3.K

=here %dc and I dc are the DC output ratin)s o$ vota)e and current respectivey o$ the trans$or/er recti$ier. ".#."

*RO8ND5ED RE6I6TANCE

7or a sin)e anode paced verticay in soi! its resistance to the bac($i /ediu/ in this case o$ ; oh/ resistance is Ra

=

ρ

2 π L

 8 L − 1   d 

ln

=here! RaJ anode resistance in oh/ ρ

J /ediu/ resistivity in oh/.c/

+J anode en)th in c/ dJ anode dia/eter in c/


Oct! "00# Pa)e # o$ ,



 8 × 100   ×  ln   − 1  = 2 × π × 100   2.5   5

0.038

Ω

7or an anode surrounded by co(e bac($i cou/n o$ >00 c/ en)th and "0 c/ dia/eter! the resistance o$ the bac($i cou/n to earth beco/es

 8 × 600   ×  ln   − 1 = 2 × π × 600   20    5

0.006

Ω

Hence anode interna resistance is 0.03

0.00>

0.0"

=

Ω

Resistance o$ one anode instaation in bac($i o$ the )iven di/ensions and soi o$ ,;00 oh/.c/ resistivity beco/es

R

=

 8 × 600   ×  ln   − 1  + 2 × π × 600   20   1500

0.032

=

1.815

Ω

The co/bined resistance o$ the anodes and hence the anode )round bed resistance! R)b! ta(in) into consideration the /utua inter$erence is obtained $ro/

Rgb

=

R n

+

ρ π nS

ln( 0.66 n )

Ω

=here n J nu/ber o$ anodes 6

J anode spacin) ;00c/

R

J sin)e anode resistance

Rgb

=

1.221 20

+

1500 π

× 20 × 500

ln ( 0.66 × 20)

=

0.184

Ω

Hence the )round bed con$i)uration wi be "0 no. anodes surrounded by carbonaceous bac($i /ateria in a "00// casin) with anodes at 0.; / spacin)! the tota active en)th o$ the )round bed wi be 0.;,  "0 J 0 / Cathodic Protection Report

Oct! "00# Pa)e ,0 o$ ,



*ivin) a tota deep we )round bed depth o$ "0  0 J ;0 /

".#. 8ANTIT O7 5AC'7I++ The /ai/u/ vou/e occupied by the bac($i in the we bore is ta(en! $or ease o$ cacuation! to be the vou/e o$ the active en)th o$ the we bore ne)ectin) the vou/e occupied by anodes! cabes etc.This vou/e is cacuated $ro/

Vb

=

π

× D × L 2

m

3

4

=here + J en)th o$ active section D

J

dia/eter o$ bore hoe

8sin) the )round bed active section en)th o$ 0/ and we bore o$ "0c/ interna dia/eterQ the bac($i vou/e is obtained $ro/

Vb =

π

× 30 × 0.2 2 4

m

3

%b

J

0.#9 /

There$ore vou/e o$ bac($i wi be %b

J

0.#9 /


Oct! "00# Pa)e ,, o$ ,



)'0 CONCLUSION

The eistin) recti$ier

Oct! "00# Pa)e ," o$ ,



*'0 REFERENCES

,. Cathodic Protection syste/ siGin) report $or Ginc anodes o$ )as trans/ission syste/ Ndee45onny pipeine T4,0.,,.","4A ". Cathodic protection syste/ instaation detai $or deep we )round bed T4 ,0.,,.,0043 . Cathodic protection EPT 034T40" Nove/ber ,##" Dra$t 9. Contro o$ pipeine corrosion by A.=. Peabody second edition edited by Ronad +. 5ianchetti ;. 6tandard Construction 6peci$ication 6,@ o$ 6PDC.


Oct! "00# Pa)e , o$ ,

Cathodic Protection Report

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