Corrosion Management on Corrosion Management on Pipeline with Cathodic Pipeline with Cathodic

ProtectionProtection

Ilmu Bahan dan KorosiIlmu Bahan dan Korosi

OutlineOutline• Pipeline Risks and CorrosionPipeline Risks and Corrosion

• Cp Technique : Cp Technique : Galvanic Sacrificial Galvanic Sacrificial Anode (Anode (PrinciplePrinciple, , InstallationInstallation))

• Cp Technique : Cp Technique : Impressed Current (Impressed Current (PrinciplePrinciple, , InstallationInstallation))

• Case StudyCase Study : : Sacrificial AnodeSacrificial Anode

• Case StudyCase Study : : Impressed Current Impressed Current

The product of the frequency with which an event is anticipated to occur and the consequence of the event outcome.

Risks on PipelineRisks on Pipeline

RISK = PROBABILITY x SEVERITY

LEAKAGE

CORROSION

PRESSURE DROP

Risks on PipelineRisks on Pipeline

Corrosion ControlCorrosion Control• CoatingCoating : insulation : insulation

• Cathodic Protection: DC current Cathodic Protection: DC current injection towards pipeline, result: injection towards pipeline, result: pipeline is “shifted” as cathode. pipeline is “shifted” as cathode.

Sacrificial anodeSacrificial anode

Impressed currentImpressed current

Galvanic Sacrificial Anode Galvanic Sacrificial Anode - Principle- Principle

• Metal Driving voltage (Metal Driving voltage (VdVd))

• Negative Negative VdVd = active metal = active metal =tendency to corrode=tendency to corrode

• Pipeline: connected with active Pipeline: connected with active metalmetal

• Anode: Mg, Zn Cathode: pipelineAnode: Mg, Zn Cathode: pipeline

• Corrosion on Mg, Zn hence Corrosion on Mg, Zn hence “sacrificial”“sacrificial”

Galvanic Sacrificial Galvanic Sacrificial Anode-PrincipleAnode-Principle

Material Driving Voltage (V)

Silver (Ag/Ag+) +0.8 (cathodic)

Copper (Cu/Cu2+) +0.34

Water (O2+H20+4e- = 4OH-) +0.401

Hydrogen (H2) 0 (reference)

Iron (Fe/Fe2+) -0.44

Zinc (Zn/Zn2+) -0.76

Magnesium (Mg2+) -2.36 (anodic)

Galvanic Sacrificial Galvanic Sacrificial Anode-InstallationAnode-Installation

(Source: Peabody’s Control of Pipeline Corrosion)

Galvanic Sacrificial Galvanic Sacrificial Anode-InstallationAnode-Installation

(Source: Peabody’s Control of Pipeline Corrosion)

Impressed CurrentImpressed Current

• Minimum potential: -0.85VMinimum potential: -0.85V• Reference electrode: Copper Sulfate Reference electrode: Copper Sulfate

(Source: Peabody’s Control of Pipeline Corrosion)

Galvanic Sacrificial Galvanic Sacrificial Anode-DesignAnode-Design

• Calculate total area to be protected (Ap)Calculate total area to be protected (Ap)• Determine the current density (Determine the current density (ρρ))• Calculate total protection current (Itot = Calculate total protection current (Itot =

ρρ .Ap) .Ap)• Calculate R per anode : R = f(d,l,Calculate R per anode : R = f(d,l,ρρ)) • Calculate Ia per anode : (Vd-0.85/R)Calculate Ia per anode : (Vd-0.85/R)• Calculate total anode needed : Calculate total anode needed :

Initial : N=Itot/InInitial : N=Itot/InLifetime: N = f(mass,lifetime,A/poundyear)Lifetime: N = f(mass,lifetime,A/poundyear)

Impressed Current-PrincipleImpressed Current-Principle

• RectifierRectifier

• Variable voltage, variable Variable voltage, variable currentcurrent

• Higher current density (> 1 A)Higher current density (> 1 A)

• Higher soil resistivity (> 10Higher soil resistivity (> 104 4

Ωcm)Ωcm)

Impressed Current-Impressed Current-InstallationInstallation

• Types of anode:Types of anode: Graphite : big CR (pound/A/year)Graphite : big CR (pound/A/year) High Silicon Cast Iron : medium CRHigh Silicon Cast Iron : medium CR Platinum & niobium : small CRPlatinum & niobium : small CR

• Rectifier rating:Rectifier rating: Voltage, Amperes, Watt, Freq.Voltage, Amperes, Watt, Freq. Cooling System : Air, OilCooling System : Air, Oil EfficiencyEfficiency

CR: Consumption Rate

Impressed Current - Impressed Current - InstallationInstallation

(Source: Peabody’s Control of Pipeline Corrosion)

Impressed Current - Impressed Current - DesignDesign

• Calculate total area to be protected (Ap) Calculate total area to be protected (Ap) • Determine curent density (Determine curent density (ρρ))• Calculate total protection current (Ip)Calculate total protection current (Ip)• Calculate total anode needed (N)Calculate total anode needed (N)

InitialInitial LifetimeLifetime

• Calculate total anode resistance (Rtot = Calculate total anode resistance (Rtot = f(N,f(N,ρρ,d,L,spacing)),d,L,spacing))

• Calculate rectifier specification (Vdc, Idc, Pdc Calculate rectifier specification (Vdc, Idc, Pdc = f(Rtot,Ip)= f(Rtot,Ip)

Pipeline Cathodic Pipeline Cathodic Protection– Case StudyProtection– Case Study

Galvanic Sacrificial Anode Galvanic Sacrificial Anode – Case Study– Case Study

Variabel Nilai

Pipe Diameter (d) a. 2 inch = 0.0508mb. 1 inch = 0.0254m

Pipe Length (l) a. 2 inch pipe: 300mb. 1 inch pipe: 1300m

Soil Resistivity (average) 4500 Ωcm

Current Density (ρ) 9mA/sqmm

Type of Anode Magnesium, weight 9 pon, r = 8.89cm, l = 53.54cm

Coating efficiency (n) 50%

Lifetime 20 years

Galvanic Sacrificial Anode Galvanic Sacrificial Anode – Case Study– Case Study

• Step 1: Step 1: surface area of pipelinesurface area of pipeline

• Step 2: Step 2: total protection areatotal protection area

• Step 3: Step 3: total protection currenttotal protection current

22 806,75613,151%50 mmApnAc

AmAmsqmmAAcIp 682,0254,682806,75/9 2

Galvanic Sacrificial Anode Galvanic Sacrificial Anode – Case Study– Case Study

• Step 4: Step 4: Anode resistance (Dwight’s Equation)Anode resistance (Dwight’s Equation)

• Step 5: Step 5: Current per AnodeCurrent per Anode

15,291

89,8

54,534ln

54,53

159,045001

4ln

159,0

r

L

LR

mARae

E

ctrolyteceAnodeElesis

eteelVoltagPolarisedstageDrivingVolIa 024,0

15,29

85,055,1

tanRe

Galvanic Sacrificial Anode Galvanic Sacrificial Anode – Case Study– Case Study

• Step 6: Step 6: Total Number of AnodeTotal Number of Anode

InitialInitial

LifetimeLifetime

Selected number of anodes: Selected number of anodes: 3131. .

anodesmA

A

Ia

IpN 41.28

024,0

682,0

anodestAnodeWeigh

IpLifetimeN 75.30

93,49

254,68220

3,49

Galvanic Sacrificial Anode Galvanic Sacrificial Anode – Case Study– Case Study

• Step 7: Step 7: Distribution and LayoutDistribution and Layout

DistributionDistribution

LayoutLayout

2445.231

806.75m

N

AcA

2935.233000508,05.0 m 10445,2:93,23

287.5113000254,05,0 m 21445,2:87.51

Type of Pipe Effective Surface (Ac) Number of Anode (Ac/A)

Diameter 2inch (0.0508m)

Diameter 1inch (0.0254m)

Total 31

Impressed Current Impressed Current Case StudyCase Study

Variabel Value

Pipe Diameter (d) 6 inch = 0,1524 m

Pipe Lengyth (l) 6800 feet = 2072 m = 2,072 km

Soil Resistivity (average) 2000 Ωcm

Current Density (ρ) 30mA/sqmm

Type of Anode Stated in next section

Coating Efficiency (n) 50%

Coating Impedance 25000Ω/m2

Maximum Groundbed Resistance

2Ω

Lifetime 15years

Impressed Current Impressed Current Case StudyCase Study

• Step 1: Step 1: surface area of pipelinesurface area of pipeline

• Step 2: total protection area

• Step 3: Step 3: total protection currenttotal protection current

• Step 4: Step 4: determine type of anodesdetermine type of anodesIron Silicon Chromium. Weight: 110 pon, cross section 4 sqft (0,371m2), Iron Silicon Chromium. Weight: 110 pon, cross section 4 sqft (0,371m2),

diameter 10 inch (0,833 feet = 2,54cm), length 84 inchi (7 feet = diameter 10 inch (0,833 feet = 2,54cm), length 84 inchi (7 feet = 20,32cm)20,32cm)

203,99220721524,0 mdlAp

22 015,49603,992%50 mmApnAc

AmAmsqmmAAcIp 88,1445,14880015,496/30 2

Impressed Current Impressed Current Case StudyCase Study

• Step 5: Step 5: total number of anodestotal number of anodes

• Current limit (silicon: 10.76 Current limit (silicon: 10.76 A/mA/m22))

• LifetimeLifetime

Total anodes: Total anodes: 44..

anode

mAm

A

IcAi

IpN 72,3

76,10371,0

88,14

22

anodepon

mA

tAnodeWeigh

IpLifetimeN 02,2

1101000

1488015

1000

Impressed Current –Case Impressed Current –Case StudyStudy

• Step 6: Step 6: groundbed resistance calculationgroundbed resistance calculation

Resistance limit: 2Ω (to limit rectifier’s spec)Resistance limit: 2Ω (to limit rectifier’s spec)

Spacing: Spacing: SS = 30 = 30 feetfeet , Anode Length: , Anode Length: LL = 7 = 7 feetfeet

Anode Diameter: Anode Diameter: DD = 0.8333 = 0.8333 feetfeet

Groundbed resistance is Groundbed resistance is below limitbelow limit. .

If not, If not, choose longer spacingchoose longer spacing..

36.1

4656.0ln30

721

833.0

78ln

47

200000521.0

)656.0ln2

18

(ln00521.0

NS

L

d

L

NLRg

Impressed Current - Impressed Current - PrinciplePrinciple

• Step 7: Step 7: rectifier specificationrectifier specification

Specification: Specification: 2121VDCVDC, 302, 302WW . .

Final ResultsFinal Results::

• Anodes : Anodes : Iron Silicon ChromiumIron Silicon Chromium, , 44 anodes. anodes.

• Rectifier : Rectifier : 21VDC, 302W21VDC, 302W..

WIpVrecSrec

VRgIpVrec

123,301

.237,2036.188,14