112238-02-CAL-203 REV 03 CP Calculation

PVGASPROJECT MANAGEMENT COMPANY

CALCULATION DOC.NO. 112238-02-CAL-203PAGE 1 of 6

CATHODIC PROTECTION SYSTEM CALCULATION

TIEN HAI THAI BINH LOW PRESSURE GAS DISTRIBUTION PIPELINESYSTEM PROJECT

3 10/Dec/13 Issue For Approval P.H.T P.T.H.G L.P.K

2 17/Sep/13 Issue For Approval P.H.T P..H L.P.K

1 15/Nov/11 Issue For Approval P.H.T P..H L.P.K

0 20/Oct/11 Issue For Approval P.H.T P..H L.P.K

REV. NO. DATE DESCRIPTION PREP'N REVIEW PMCs APPR APPROVAL

This DOCUMENT is the property of Petrovietnam Gas Joint Stock Corporation. Therefore, it shall not be released toany third party without permission of an authorized personnel of the PVGas.

PETROVIETNAM GAS JOINT STOCK CORPORATIONPVGAS PROJECT MANAGEMENT COMPANY

TIEN HAI THAI BINH LOW PRESSURE GAS PIPELINE PROJECTCATHODIC PROTECTION SYSTEM CALCULATION

Cathodic Protection System Calculation Document No. 112238-02-CAL-203Page 2/6 Rev.3

CONTENTS

1.0 SCOPE OF WORK..................................................................................32.0 REFERENCE ..........................................................................................33.0 CODES, STANDARD ..............................................................................34.0 SUMMARY ............................................................................................35.0 CALCULATION BASIS...........................................................................45.1 Parameters...........................................................................................45.2 CP current density: ..............................................................................46.0 Cathodic protection calculation and consideration.............................56.1 Pipeline Total Surface Area .................................................................56.2 Cathodic protection system at Thai Binh GDC.....................................66.3 Anodes Ground bed and DC cables......................................................66.4 Conclusion............................................................................................6




1.0 SCOPE OF WORKThis document defines the calculations of Cathodic Protection Systemby Impressed current for underground 10, 6, 4, 3, and 2 Gaspipelines from Low Gas Distribution Station (LGDS) at Tien Hai - ThaiBinh to customers stations in Tien Hai IZ.The Tien Hai Thai Binh low pressure gas pipeline shall be protectedby ICCP system which is located at Thai Binh GDC.

2.0 REFERENCE Cathodic protection calculation Doc No. 111237-02-CAL-02-201

(Thai Binh - Ham Rong Gas Distribution and Gathering systemProject).

Specification for Cathodic Protection System Doc No. 112238-02-SPE-202.

3.0 CODES, STANDARDAS 2832.3 -1992 Guide to the cathodic Protection of metalsBS-7361 Cathodic Protection Code of Practice for Land

and marine applicationsNACE RP-0169-2002 Control of External Corrosion on Underground

or Submerged Metallic Piping Systems4.0 SUMMARY

The design parameters are listed in section 5.1 of this document. Animpressed current Cathodic Protection (ICCP) system to be installed toprotect the underground Tien Hai - Thai Binh low pressure distributiongas pipeline.Approximately 2.216 km long of the 10 Pipeline shall be buried fromTien Hai LGDS station to tie in point TIP04 and TIP05. Approximately0.735 km long of the 6 pipeline shall be buried along road no 5 to tiein point TIP06 and TIP07. Approximately 2.7 km long of the 4, 3, 2branch pipeline shall be buried from main pipeline to customersstations. The most appropriate cathodic protection is to use CP systemthat is located in Thai Binh GDC Station. All consideration/calculationbelow to demonstrate whether it is possible.




5.0 CALCULATION BASIS5.1 Parameters

The following sub-sections include parameters which have been usedfor calculation of the proposed cathodic protection system.Design life : 30 yearsCP current density: 30mA/m2 Tien Hai Thai Binh low pressure Gas pipeline:

Outside Diameter of Pipe (m) Length of pipe (m)(10)= 0.2731m 2400(6)= 0.1683m 500(4) = 0.1143 m 200(3) = 0.0889 m 1421(2) = 0.0603 m 700

Coating: Polyethylene Calculated demand of Thai Binh Ham Rong pipelines:Table below is extracted from the Thai Binh - Ham Rong pipelineProject Calculation Document No: 111237-02-CAL-02-201

Pipelinesection/Dia.

Length (m) Suface area(m2)

Currentdensity(mA/m2)

Currentrequired(A)

Thai Binh HamRong 12 pipeline

6000 6102.28 30

Thai Binh lowpressure gasdistribution 10pipeline project

5000 4286.1 30

CP System current Idcr 1 = 17 A5.2 CP current density:

Current density for pipeline with Polyethylene coating will be 30mA/m2as per the above parameters. Safety factor shall be of 10%.




6.0 Cathodic protection calculation and consideration6.1 Pipeline Total Surface Area

Pipeline area:Sa = ld

Where: Sa = Surface area (m2)Pi = 3.1416l = Length of pipeline (m)d = Diameter of pipeline (m)

The required current of cathodic protection system as follow:Idcr = SFCbIdSa 1000

Where: Sa = Total surface area (m2)Id = CP current density (mA/m2)Cb = Coating breakdown factor (5%=0.05)SF = Safety factor (10%=1.1)Idcr = Required Current of CPS

Remaining pipelines 10, 6, 4, 3 and 2 pipelines will be protected byICCP. Calculation detail as table below:

PipesDiameter length Coating

Surfacearea

Currentdensity

Coatingbreakdown factor

Safetyfactor

Requiredcurrent

(m) (m) Sa (m2) Id(mA/m2) Cb = 5% Idcr (A)0.3239 6000 Polyethylene 6102.28 30.00 0.05 1.1 100.2731 2400 Polyethylene 2058.08 30.00 0.05 1.1 3.40.1683 500 Polyethylene 264.23 30.00 0.05 1.1 0.440.1143 200 Polyethylene 71.78 30.00 0.05 1.1 0.120.0889 1421 Polyethylene 396.67 30.00 0.05 1.1 0.650.0603 700 Polyethylene 132.54 30.00 0.05 1.1 0.22Total 11221 9025.58 14.83IDCR = 14.83 AIDCR < Idcr 1 : Acceptable




6.2 Cathodic protection system at Thai Binh GDCThe CP system is located at Thai Binh GDC station shall install duringThai Binh Ham Rong pipeline construction.The Thai Binh GDC Transformer Rectifiers rating is 20 Adc and 20 Vdchas sufficient current and voltage capacity for the intergrated CPS with14.83 A demand.

6.3 Anodes Ground bed and DC cablesThe anode groundbed and DC cable are calculated to accommodatethe 20 Adc output. That is sufficient capacity for 14.48 A demand withTien Hai Thai Binh low pressure distribution gas pipeline added.

6.4 ConclusionThai Binh Ham Rong 12 pipeline and Tien Hai Thai Binh lowpressure distribution gas pipeline external corrosion protection usingan integrated CPS system.The CPS at Thai Binh GDC is sufficient capacity for the integrated CPS.

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112238-02-CAL-203 REV 03 CP Calculation