# Pipeline Cathodic Protection Design

August 1, 2017 | Author: Nguyen Thi Thu Huong | Category: Pipeline Transport, Corrosion, Electrochemistry, Applied And Interdisciplinary Physics, Physical Chemistry

#### Short Description

Tiêu chuẩn Norsok tính toán CP...

#### Description

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3533

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN TABLE OF CONTENTS

1.0

INTRODUCTION ........................................................................................................................................................3

2.0

SUMMARY OF RESULTS .........................................................................................................................................4

3.0

DESIGN PARAMETERS............................................................................................................................................6

4.0

METHOD OF ANALYSIS ..........................................................................................................................................8

5.0

CONCLUSION...........................................................................................................................................................14

6.0

REFERENCES ...........................................................................................................................................................15

APPENDIX A COMPUTER PRINTOUTS ANODE SIZING CALCULATIONS

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN

1.0

INTRODUCTION This calculation note presents the offshore pipeline external corrosion protection design for the two of 30-inch crude oil carbon steel insulated pipeline from the Pipeline End Manifold (PLEM) system located on the seabed below the Single Point Mooring (SPM) buoy to the landfall (up to KP 3.960) as part of the Dung Quat Refinery Project. The scope of work includes:

1.1

i.

Determining the type of anti-corrosion coating required for pipeline against external corrosion throughout its design life.

ii.

Design of aluminium sacrificial bracelet anodes required for the pipeline against external corrosion for the design life of 20 years.

ABBREVIATIONS CP CPR ID KP OD 3LPP Thk. yrs

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-

Cathodic Protection Crack Propensity Ratio Inside Diameter Kilometre Point Outer Diameter 3 Layer Polypropylene Thickness years

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 2.0

SUMMARY OF RESULTS

2.1

EXTERNAL ANTI-CORROSION COATING The selected external anti-corrosion coating system for the 30-inch pipeline from the Pipeline End Manifold (PLEM) system to the landfall is presented in Table 2.1.1. Table 2.1.1

2.2

External Anti-Corrosion Coating System

Section

Type of Anti-Corrosion Coating

KP 0.0-3.200

2.5 mm thick 3LPP

CATHODIC PROTECTION The pipeline cathodic protection requirements for the 30-inch pipeline from the Pipeline End Manifold (PLEM) system to the landfall are presented in Table 2.2.1. Table 2.2.1

Description Anode Type Anode Inside Diameter Anode Outside Diameter Anode Thickness Anode Length Net Weight / Pair (Note 1) Spacing (Pipe Joint) Total Anode Quantity (for 2 lines) Total Net Weight Crack Propensity Ratio (Note 2) Anode Material Notes:

Cathodic Protection Requirements for Pipeline

Unit

KP 0.0 KP 1.390

KP 1.390 KP 2.000

KP 2.000 KP 2.610

KP 2.610 KP 3.200

-

I (Submerged)

II (Submerged)

II (Buried)

III (Buried)

832.6 (Note 4)

mm mm

942.60

982.60

1042.60

mm

60.0

80.0

110.0

mm

361.41

369.62

433.37

kg

140.0

200.0

340.0

-

12

8

9

set

20

10

14

12

kg

2800.0

2000.0

2800.0

4080.0

-

1.13

-

0.46 Aluminium-Indium Alloy Bracelet

0.20 (Half-Shell Type)

1.

One (1) pair of anode is made up of two (2) pieces of half-shell bracelet anode.

2.

Crack Propensity Ratio (CPR) is a measure of the ratio of anodes length, diameter and thickness. A CPR value of less than 5 will ensure a lesser probability for the occurrence of cracks in the anodes.

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN

2.3

3.

Vendor shall propose steel core dimensions and shall include in their calculations.

4.

Positive tolerance on OD of pipe (3mm) and 0.1mm thick coating inside the anode has been considered in anode ID calculation.

INSULATION JOINTS Monolithic insulation joints have been considered at the following location. •

One each at the shore line on 30-inch pipelines between onshore and offshore pipeline section.

One each on the 30-inch onshore pipeline at the transition of above ground to below ground at pig launcher/receiver station.

This report addresses only design of Cathodic Protection System of offshore pipelines. Cathodic Protection design for onshore pipelines will be carried out by others.

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 3.0

DESIGN PARAMETERS

3.1

DESIGN DATA Unless otherwise stated, the design data are as per Crude Oil Pipeline Design Basis [Ref. 1] and the requirements of DNV RP B401 [Ref. 3] Table 3.1.1

Design Parameters for Cathodic Protection Design

Description

KP0.000– KP1.390

Unit

KP 1.390 – KP 2.000

KP 2.000 – KP 2.610

KP 2.610 – KP 3.200

Pipeline Data Pipeline OD

mm

762.0

Pipeline Wall Thickness

mm

15.9

Segment Length

m

Corrosion Coating Type Corrosion Coating Thk. Insulation Thickness (HDPU) Insulation Density Outer Case Thickness (HDPE) Outer Case Density

1390

610

-

3LPP

mm mm kg/m3 mm kg/m3

2.5

Concrete Coating Thk.

mm

Design Life

yrs

610

590

80.0

110.0

23.0 180.0 8.2 940 60.0

80.0

20 (Note 8)

Anode Data Anode Thickness (Note 2) Bracelet Gap Width Density of Anode Closed Circuit Potential Driving Potential Difference Anode Design Temperature (Note 3) Anode Current Capacity (Note 4) Anode Material Type Current Density at 25oC (Note 5) Coating Breakdown Factor (Note 6)

mm

55.0

75.0

75.0

mm kg/m3

100.0

V

-1.05 (w.r.t Ag/Ag/Cl)

volts

2730

0.25

0.15

°C

32

Ahr/kg

2176.0

-

Aluminium-Indium Alloy 2

Initial Mean

mA/m mA/m2

157.0

27.0

77.0

27.0

Final

mA/m2

97.0

27.0

Initial

%

1.00

Mean

%

5.00

Final

%

7.00

Anode Utilization Factor

-

0.80

Surrounding Resistivity Resistivity (Note 7)

Ohm-m

8474L-082-CN-3533-101-0.doc

105.0

0.21 (Seawater)

1.00 (Soil)

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN Notes: 1.

The anode shall be designed to employ the factory limitations for producing the anode.

2.

Selected anode thickness is 5mm lower than the corresponding concrete coating thickness.

3.

The design temperature is taken as maximum seabed temperature.

4.

Anode electrochemical efficiency shall be determined by the following formula as recommended by DNV RP B401: Efficiency = 2500 – 27 [Anode Temperature (°C) – 20] Ahr/kg Assuming anode efficiency is 2500 Ahr/kg at 20°C.

5.

The current density has been increased by 1 mA/m2 for each 1oC that outside steel temperature exceeds 25oC.

6.

The coating breakdown factors due to ageing of coating during design time are calculated in accordance with DNV RP B401. Since coating break down factor due to damage is very small, those are ignored.

7.

As per DNV RP B401, soil resistivity has been considered five times of seawater density (for sandy soil).

8.

Though the pipeline mechanical design life is 60 years, pipeline cathodic protection is designed to 20 years in accordance with the requirement 8474L-000-JSD-1600-008 [Ref. 5]

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 4.0

METHOD OF ANALYSIS

4.1

ANTI-CORROSION COATING SELECTION CRITERIA The selection of the external coating system for the pipeline has been made taking into considerations cost, fit for purpose, project specification requirements [Ref. 1] and at the same time satisfying the following criteria:

4.2



Maximum pipeline operating temperature



Coating impact resistance



Cathodic disbonding



Concrete coating suitability (for concrete coated pipe)



Field joint coating material and its compatibility with the proposed coating



Field experience

CATHODIC PROTECTION ANALYSIS The external corrosion coating provides passive protection to the pipeline against corrosive actions of seawater. However, this may still be subjected to breakdown due to harsh environment, incorrect pipe handling and others, exposing the surface of the pipe to corrosion. An active protection mechanism, in the form of anodes, shall be provided to supplement the FBE coatings as a corrosion protection measure. The provision of anodes is discussed in the following section. The cathodic protection (CP) analysis is performed to determine the dimensions and quantity of sacrificial bracelet anode required to protect the pipeline against external corrosion throughout its design life. The following sections describe the methodology and governing equations for the CP design. Aluminum based material have been selected for the anode. Calculations have been performed using TPGM’s in-house computer program ‘Anode-B401 Version 3’ [Ref. 4]. This program calculates the number of anode for cathodic protection in accordance with the requirements of DNV RP B401 [Ref. 3].

4.2.2

CALCULATION OF REQUIRED NUMBER OF ANODES Calculation of the number of anodes shall satisfy four criteria: a) The number of anodes required to initially polarize the pipeline. b) The number of anodes required to provide the maintenance current throughout the life of the design. c)

The number of anodes required to provide adequate protection on the final day of the design life.

d) Maximum allowable anode spacing.

4.2.2.1 Total Surface Area of Pipeline (Ac) Ac

=

π x D x Ltot

= =

Pipeline outside diameter Pipeline segment length

Where, D Ltot

8474L-082-CN-3533-101-0.doc

(Eq. 4.2.2.1.1)

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 4.2.2.2 Anode Inside Diameter (Dia) Dia

=

D + 2 tC

(Eq. 4.2.2.2.1)

= =

Pipeline outside diameter Pipe corrosion coating thickness

Where, D tC

4.2.2.3 Anode Outside Diameter (Doa) Doa

=

Dia + 2 ta

(Eq. 4.2.2.3.1)

= =

Anode inside diameter Anode thickness

Where, Dia ta

4.2.2.4 Anode Length (La) Required anode length based on the weight and diameter of the anode specified in design, La

=

Ma   Da  π Dia t a + t a2  − 2b t a    

    cos  sin− 1    



(Eq. 4.2.2.4.1)

b/2     Dia /2    

Where, Ma ta

= =

Assumed mass of each anode (net) Anode thickness

b

=

Side gap width of anode

Da Dia

= =

Anode material density Anode inside diameter

4.2.2.5 Anode Surface Area at Initial Life (Aai) With the defined dimensions, anode surface area at the start of design life, Aai can be found by:

Aai

=

D  −1  b/2  π   π DoaLa – 2 La  oa ×  2 sin  ×   2   D oa /2  180    

= = =

Anode outside diameter Anode length Side gap width of anode

Where, Doa La b

8474L-082-CN-3533-101-0.doc

(Eq. 4.2.2.5.1)

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 4.2.2.6 Anode Surface Area at End of Life (Aaf) With the defined dimensions, anode surface area at the end of design life, Aaf can be found by:          D + 2t (1 − u )  π b / 2 − 1 ia a  . A af = π[Dia + 2t a (1 − u)]L a − 2L a  . 2 sin    D ia + 2t a (1 − u)  180  2       2      (Eq. 4.2.2.6.1) Where, Dia

=

Anode inside diameter

U

=

Anode utilization factor

La

=

Anode length

b

=

Side gap width of anode

ta

=

Anode thickness

4.2.2.7 Anodes Required To Initially Polarize The Pipeline Initial anode current output =

E

(Eq. 4.2.2.7.1)

0.315xρ

A ai Where, E ρ Aai

= = =

Potential difference between anode and the linepipe protection Resistivity of surrounding Anode surface area at initial of life

4.2.2.8 Anodes Required To Protect The Pipeline At The End Of Life Final anode current output

=

E 0.315X ρ

(Eq. 4.2.2.8.1)

A af

Where, E ρ Aaf

= = =

Potential differences between anode and the linepipe protection Resistivity of surrounding Anode surface area at end of life

4.2.2.9 Total Number of Anodes Required To Polarize The Pipeline

Number of anodes (N)

8474L-082-CN-3533-101-0.doc

=

i ci × A c × fci Iai × 1000

(Eq. 4.2.2.9.1)

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN Where, ici = Ac =

Initial current density; Current required to polarize an unprotected pipeline located on sea bottom Total surface area of pipeline segment

fci

=

Initial coating breakdown factor

Iai

=

Initial anode current output

4.2.2.10 Anodes Required To Provide The Maintenance Current Number of anodes (N) =

icm × A c × fcm × t f × 8760 ε ×1000 ×u×Ma

(Eq. 4.2.2.10.1)

Where, icm

=

Maintenance current density; The current density required maintaining protection on the pipeline.

Ac

=

Surface area

tf

=

Design life

fcm

=

Mean coating breakdown factor

ε

=

Anode electrochemical capacity

u

= =

Utilization factor

Ma

Assumed mass of each anode (net)

4.2.2.11 Anodes Required To Protect The Pipeline At The End Of Life

Number of anodes (N)

=

i cf × A c × fcf Iaf × 1000

(Eq. 4.2.2.11.1)

Where, icf

8474L-082-CN-3533-101-0.doc

=

Final current density. The current density required maintaining protection on the pipeline under end of life operating conditions.

Ac

=

Surface area

fcf Iaf

=

Final coating breakdown factor

=

Initial current output per anode

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 4.2.3

ANODES SPACING The anodes shall be evenly spaced along the pipeline. For pipelines with inlet product temperatures in excess of 45°C, closer spacing of the anodes until the product has cooled to less than 45°C is acceptable. The spacing shall not exceed the minimum allowable spacing. The anode spacing, Sm (in meters) can be found by:

Sm

L tot

=

Max (Nmean , N final )

(Eq. 4.2.3.1)

Where, Ltot Nmean Nfinal

= = =

Pipeline segment length Number of anodes to meet mean current demand Number of anodes at final design life

The number of spacing in pipe joints is given by:

S jo int s =

Sm SLL

(Eq. 4.2.3.2)

Where, Sm SLL

= =

Anode spacing Standard linepipe length per joint

The recommended anode spacing, SR, is the calculated number of spacing in pipe joint, Sjoints rounded down to an integer. To obtain the recommended anode quantity, NR, the following equation is used:

NR

=

L tot SLL × S R

(Eq. 4.2.3.3)

Where, Ltot SLL SR

= = =

Pipeline segment length Standard linepipe length per joint Recommended anode spacing

The recommended anode quantity is rounded up to the next integer to get a whole number.

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 4.2.4

CRACK PROPENSITY RATIO (CPR) Crack Propensity Ratio (CPR) is used to adjust the ratio of anode length, diameter and thickness so that the anode will be manufactured with lesser probability of cracks. It is advised to design anode of which CPR value is 5 or less.

CPR

=

π x L a x D ia 5 x ta

3

(Eq. 4.2.3.4)

Where, La Dia ta 4.2.5

= = =

Anode length Anode inner diameter Anode thickness

COATING BREAKDOWN FACTORS The coating breakdown factor specified the amount of damage that is expected to occur to the pipeline’s corrosion coating at various stages of the pipeline’s life. The breakdown factor is determined by the type of coating, predicted operating temperature of the pipeline, whether the pipeline is concrete coated and an estimation of the amount of physical damage that will occur to the pipeline.

4.2.6

ANODE ELECTROCHEMICAL EFFICIENCY The performance of a sacrificial anode material is dependent on its actual chemical composition. At increased temperatures, the self-corrosion of the anodes is greater and therefore their efficiency decreases. In practice, the theoretical capacity of sacrificial anodes is not fully available for cathodic protection. Refer to Section 6.6 of DNV RP B401 [Ref. 3] for further details.

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 5.0

CONCLUSION The selection of external anti-corrosion coating system is made in view of the following criteria: Subsea Pipeline

The 3LPP coating is selected for the subsea section of this concrete coated 30-inch pipeline. The requirements of sacrificial bracelet anode are determined to satisfy the following criteria: i)

The number of anodes required to initially polarize the pipeline.

ii)

The number of anodes required to provide the maintenance current throughout the design life of the pipeline.

iii)

The number of anodes required to re-polarize the pipeline if such layers are partly and periodically damaged at final of design life.

i)

The maximum allowable anode spacing.

ii)

Ease of installation. As a conclusion, the pipeline external corrosion protection design consists of passive corrosion protection system via the coating of the pipeline and active corrosion protection in form of cathodic protection system, as presented in Table 2.2.1, can sufficiently protect the pipeline for the design life of 20 years.

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN 6.0

REFERENCES 1.

Crude Oil Pipeline Design Basis Doc. No.: 8474L-082-JSD-3500-001

2.

Concrete Coating Thickness Doc. No.: 8474L-082-CN-3531-002

3.

DNV RP B401 Cathodic Protection Design (1993)

4.

Technical User Manual and Validation Report ANODE-B401 Computer Program for Cathodic Protection of Submarine Pipeline Doc. No.: PL/TM/VR/07

5.

Internal and External Cathodic Protection. Doc. No.: 8474L-000-JSD-1600-008

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VIETNAM OIL AND GAS CORPORATION ( PETROVIETNAM ) DUNG QUAT REFINERY (DQR) PROJECT PIPELINE CP DESIGN

APPENDIX A COMPUTER PRINTOUTS ANODE SIZING CALCULATIONS

ANODE_DUNGQUAT

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A

E-ANODE Version 3.0 (04/03/2005) 1 2 3 4

PIPELINE CATHODIC PROTECTION REQUIREMENT PROJECT : DUNG QUAT REFINERY PROJECT LINE : 30" PIPE (60mm THK CONCRETE COATING) KP 0.000-1.390(On the seabed) BASIS OF DESIGN : The calculation is as per DnV-RP-B401(1993) with spacing requirement.

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

DESCRIPTIONS INPUT: Pipeline Outside Diameter Pipeline Wall Thickness Pipeline Segment Length Corrosion Coating Thickness + Insulation Thickness Resistivity of Linepipe Material Anode Thickness Anode Material Anode Material Density Assumed Anode Mass (Net) Resistivity of Surrounding Side Gap Width of Anode Potential Difference Between Anode And Linepipe Standard Linepipe Length per Joint Design Life

SYMBOLS

DATA

D d Ltot tc ρMe ta

UNIT

762.00 mm 15.9 mm 1390.00 m 33.7 mm 2.00E-07 Ohm-m 55.00 mm Aluminium-Indium Alloy 3 2730.00 kg/m

Da Ma ρ b E = Eco - Eao SLL tf

140.00 0.21 100.00 0.25 12.20 20

kg Ohm-m mm volts m Years

23 24

Current Density :

Initial o

At 32 C

Mean

25

o

At 32 C

Final

26

ici

2 157.00 mA/m

icm

2 77.00 mA/m

icf

97.00 mA/m

2

27 28

Coating Breakdown Factor :

29 30

Initial Mean Final

0.01 0.05 0.07

fci fcm fcf

31 32 33 34

Anode Electrochemical Efficiency Anode Utilization Factor

2176.00 A-hr/kg 0.80

ε u

35

40

OUTPUT: Surface Area of Pipeline Segment Anode Inside Diameter Anode Outside Diameter Anode Length (Based on Net Mass)

Ac Dia Doa La

41

Anode Surface Area at Initial of Life

Aai

2 0.9942 m

42

Anode Surface Area at End of Life Initial Current Output per Anode Final Current Output per Anode Initial Current Demand Mean Current Demand Final Current Demand Maximum Allowable Anode Spacing

Aaf Iai Iaf Ici Icm Icf s

0.8942 3.77 3.57 5.22 12.81 22.59 12.00

36 37 38 39

43 44 45 46 47 48

3327.51 829.40 939.40 361.41

m

2

mm mm mm m2 Amps Amps Amps Amps Amps joints

49 50 51

Number of Anodes Required (N) Initial Maintenance Final

Calculated Anode Spacing (S) (m) Joints

Recommended Anode Spacing (Joints) Quantity (Nos.)

52 53

1.39

9.21

6.32

150.93

12.37

12.00

54 55

CRACK PROPENSITY RATIO, CPR =

56 57

REMARKS:

1.13

< 5

OK

10

E-ANODE Version 3.0 (04/03/2005) 1 2 3 4

PIPELINE CATHODIC PROTECTION REQUIREMENT PROJECT : DUNG QUAT REFINERY PROJECT LINE : 30" PIPE (80mm THK CONCRETE COATING) KP 1.390-2.000(On the seabed) BASIS OF DESIGN : The calculation is as per DnV-RP-B401(1993) with spacing requirement.

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

DESCRIPTIONS INPUT: Pipeline Outside Diameter Pipeline Wall Thickness Pipeline Segment Length Corrosion Coating Thickness + Insulation Thickness Resistivity of Linepipe Material Anode Thickness Anode Material Anode Material Density Assumed Anode Mass (Net) Resistivity of Surrounding Side Gap Width of Anode Potential Difference Between Anode And Linepipe Standard Linepipe Length per Joint Design Life

SYMBOLS

DATA

D d Ltot tc ρMe ta

UNIT

762.00 mm 15.9 mm 610.00 m 33.7 mm 2.00E-07 Ohm-m 75.00 mm Aluminium-Indium Alloy 3 2730.00 kg/m

Da Ma ρ b E = Eco - Eao SLL tf

200.00 0.21 100.00 0.25 12.20 20

kg Ohm-m mm volts m Years

23 24

Current Density :

Initial o

At 32 C

Mean

25

o

At 32 C

Final

26

ici

2 157.00 mA/m

icm

2 77.00 mA/m

icf

97.00 mA/m

2

27 28

Coating Breakdown Factor :

29 30

Initial Mean Final

0.01 0.05 0.07

fci fcm fcf

31 32 33 34

Anode Electrochemical Efficiency Anode Utilization Factor

2176.00 A-hr/kg 0.80

ε u

35

40

OUTPUT: Surface Area of Pipeline Segment Anode Inside Diameter Anode Outside Diameter Anode Length (Based on Net Mass)

Ac Dia Doa La

41

Anode Surface Area at Initial of Life

Aai

2 1.0632 m

42

Anode Surface Area at End of Life Initial Current Output per Anode Final Current Output per Anode Initial Current Demand Mean Current Demand Final Current Demand Maximum Allowable Anode Spacing

Aaf Iai Iaf Ici Icm Icf s

0.9238 3.90 3.63 2.29 5.62 9.92 12.00

36 37 38 39

43 44 45 46 47 48

1460.28 829.40 979.40 369.62

m

2

mm mm mm m2 Amps Amps Amps Amps Amps joints

49 50 51

Number of Anodes Required (N) Initial Maintenance Final

Calculated Anode Spacing (S) (m) Joints

Recommended Anode Spacing (Joints) Quantity (Nos.)

52 53

0.59

2.83

2.73

215.62

17.67

17.00

54 55

CRACK PROPENSITY RATIO, CPR =

0.46

< 5

OK

56 57

REMARKS:

RECOMMENDED ANODE SPACING HAS EXCEEDED THE ALLOWABLE ANODE SPACING

3

E-ANODE Version 3.0 (04/03/2005) 1 2 3 4

PIPELINE CATHODIC PROTECTION REQUIREMENT PROJECT : DUNG QUAT REFINERY PROJECT LINE : 30" PIPE (80mm THK CONCRETE COATING) KP 2.000-2.610(Buried in seabed) BASIS OF DESIGN : The calculation is as per DnV-RP-B401(1993) with spacing requirement.

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

DESCRIPTIONS INPUT: Pipeline Outside Diameter Pipeline Wall Thickness Pipeline Segment Length Corrosion Coating Thickness + Insulation Thickness Resistivity of Linepipe Material Anode Thickness Anode Material Anode Material Density Assumed Anode Mass (Net) Resistivity of Surrounding Side Gap Width of Anode Potential Difference Between Anode And Linepipe Standard Linepipe Length per Joint Design Life

SYMBOLS

DATA

D d Ltot tc ρMe ta

UNIT

762.00 mm 15.9 mm 610.00 m 33.7 mm 2.00E-07 Ohm-m 75.00 mm Aluminium-Indium Alloy 3 2730.00 kg/m

Da Ma ρ b E = Eco - Eao SLL tf

200.00 1.00 100.00 0.15 12.20 20

kg Ohm-m mm volts m Years

23 24

Current Density :

Initial o

At 32 C

Mean

25

o

At 32 C

Final

26

ici

2 27.00 mA/m

icm

2 27.00 mA/m

icf

27.00 mA/m

2

27 28

Coating Breakdown Factor :

29 30

Initial Mean Final

0.01 0.05 0.07

fci fcm fcf

31 32 33 34

Anode Electrochemical Efficiency Anode Utilization Factor

2176.00 A-hr/kg 0.80

ε u

35

40

OUTPUT: Surface Area of Pipeline Segment Anode Inside Diameter Anode Outside Diameter Anode Length (Based on Net Mass)

Ac Dia Doa La

41

Anode Surface Area at Initial of Life

Aai

2 1.0632 m

42

Anode Surface Area at End of Life Initial Current Output per Anode Final Current Output per Anode Initial Current Demand Mean Current Demand Final Current Demand Maximum Allowable Anode Spacing

Aaf Iai Iaf Ici Icm Icf s

0.9238 0.49 0.46 0.39 1.97 2.76 12.00

36 37 38 39

43 44 45 46 47 48

1460.28 829.40 979.40 369.62

m

2

mm mm mm m2 Amps Amps Amps Amps Amps joints

49 50 51

Number of Anodes Required (N) Initial Maintenance Final

Calculated Anode Spacing (S) (m) Joints

Recommended Anode Spacing (Joints) Quantity (Nos.)

52 53

0.80

0.99

6.03

101.16

8.29

8.00

54 55

CRACK PROPENSITY RATIO, CPR =

56 57

REMARKS:

0.46

< 5

OK

7

E-ANODE Version 3.0 (04/03/2005) 1 2 3 4

PIPELINE CATHODIC PROTECTION REQUIREMENT PROJECT : DUNG QUAT REFINERY PROJECT LINE : 30" PIPE (110mm THK CONCRETE COATING) KP 2.610-3.200(Buried in seabed) BASIS OF DESIGN : The calculation is as per DnV-RP-B401(1993) with spacing requirement.

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

DESCRIPTIONS INPUT: Pipeline Outside Diameter Pipeline Wall Thickness Pipeline Segment Length Corrosion Coating Thickness + Insulation Thickness Resistivity of Linepipe Material Anode Thickness Anode Material Anode Material Density Assumed Anode Mass (Net) Resistivity of Surrounding Side Gap Width of Anode Potential Difference Between Anode And Linepipe Standard Linepipe Length per Joint Design Life

SYMBOLS

DATA

D d Ltot tc ρMe ta

UNIT

762.00 mm 15.9 mm 590.00 m 33.7 mm 2.00E-07 Ohm-m 105.00 mm Aluminium-Indium Alloy 3 2730.00 kg/m

Da Ma ρ b E = Eco - Eao SLL tf

340.00 1.00 100.00 0.15 12.20 20

kg Ohm-m mm volts m Years

23 24

Current Density :

Initial o

At 32 C

Mean

25

o

At 32 C

Final

26

ici

2 27.00 mA/m

icm

2 27.00 mA/m

icf

27.00 mA/m

2

27 28

Coating Breakdown Factor :

29 30

Initial Mean Final

0.01 0.05 0.07

fci fcm fcf

31 32 33 34

Anode Electrochemical Efficiency Anode Utilization Factor

2176.00 A-hr/kg 0.80

ε u

35

40

OUTPUT: Surface Area of Pipeline Segment Anode Inside Diameter Anode Outside Diameter Anode Length (Based on Net Mass)

Ac Dia Doa La

41

Anode Surface Area at Initial of Life

Aai

2 1.3283 m

42

Anode Surface Area at End of Life Initial Current Output per Anode Final Current Output per Anode Initial Current Demand Mean Current Demand Final Current Demand Maximum Allowable Anode Spacing

Aaf Iai Iaf Ici Icm Icf s

1.0995 0.55 0.50 0.38 1.91 2.67 12.00

36 37 38 39

43 44 45 46 47 48

1412.40 829.40 1039.40 433.37

m

2

mm mm mm m2 Amps Amps Amps Amps Amps joints

49 50 51

Number of Anodes Required (N) Initial Maintenance Final

Calculated Anode Spacing (S) (m) Joints

Recommended Anode Spacing (Joints) Quantity (Nos.)

52 53

0.69

0.56

5.35

110.36

9.05

9.00

54 55

CRACK PROPENSITY RATIO, CPR =

56 57

REMARKS:

0.20

< 5

OK

6