RP-1718-999-6300-5002-8

NATIONAL IRANIAN OIL COMPANY

SOUTH PARS GAS FIELD DEVELOPMENT

N I O C

PHASES 17 & 18

Pars Oil and Gas Company

DOCUMENT No.

DOCUMENT TITLE GENERAL REQUIREMENTS

DOC. TYPE

Doc. Class: 1

PROJECT UNIT NO. MAT. CODE

S/N

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FOR CATHODIC PROTECTION RP

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FOR CONSTRUCTION DOCUMENT TITLE GENERAL REQUIREMENTS FOR CATHODIC PROTECTION (ONSHORE FACILITIES)

8

13.Dec.10

Approved for construction

IDRO

MG

A.S

KM

MF

7

25.Apr.10

Approved for construction

IDRO

FP

KM

KM

MF

6

09.Jun.09

Issued for Approval

IDRO

FP

KM

KM

MF

5

20.Jan.09

Issued for Approval

IDRO

FP

KM

KM

MF

4

28.Oct.08

Issued for Comment

IDRO

FP

KM

KM

MF

3

30/08/2008

Approved for Design (AFD)

IDRO

FM

HM

AGH

AKH

2

13/02/2008


WP

HLM

RD

RD

MS

1

13/06/2007


WP

RD

MS

RD

MS

0

16/05/2007

Issued for Company Approval (ICA)

WP

RD

MS

RD

MS

REV.

DATE

DESCRIPTION

PRPD.

CHKD.

ORIG.

APP’D.

AUTH’D.

This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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Contents 1.

DOCUMENT SCOPE ................................................................................ 6

2.

INTRODUCTION....................................................................................... 7

3.

PROJECT OVERVIEW ............................................................................. 7 3.1

4.

Plant Description ................................................................................... 8 CODES AND STANDARDS ...................................................................... 9

4.1

General Requirements .......................................................................... 9

4.2

Codes and Standards ........................................................................... 9

5.

REFERENCE DOCUMENTS .................................................................. 11

6.

ABBREVIATIONS ................................................................................... 11

7.

DEFINITIONS.......................................................................................... 13

8.

PRECEDENCE ....................................................................................... 14

9.

USE OF LANGUAGE .............................................................................. 14

10.

CATHODIC PROTECTION GENERAL ................................................... 15

10.1 11.

Overview ............................................................................................. 15 CATHODIC PROTECTION DESIGN CRITERIA..................................... 15

11.1

Design Life .......................................................................................... 15

11.2

Current Density ................................................................................... 16

11.3

Soil/Sea Water/Water Conditions........................................................ 18

11.4

Current Drain....................................................................................... 19

11.5

CP Protection Potential Ranges.......................................................... 19

11.6

Protection Current Demand and Anode Distribution ........................... 20

12. 12.1

DESIGN CONSIDERATIONS ................................................................. 20 At Grade Storage Tank Bottoms ......................................................... 20




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12.2

Internal Tank Protection ...................................................................... 22

12.3

Reinforcement Steel and Electrical Earthing Material (Uninsulated Copper or Steel)................................................................................................... 23

12.4

Cathodic Protection Plant Piping......................................................... 24

12.5

Electrical Continuity and Isolation ....................................................... 24

12.6

Cased Crossings................................................................................. 25

12.7

Temporary Cathodic Protection System.............................................. 25

12.8

Interaction and Induced Effects........................................................... 25

13.

MATERIALS ............................................................................................ 26

13.1

Transformer Rectifier Requirements ................................................... 26

13.2

Anode Materials .................................................................................. 26

13.3

Impressed Current Anodes ................................................................. 28

13.4

Zinc Anodes ........................................................................................ 29

13.5

Magnesium Anodes ............................................................................ 29

13.6

Anode Backfill ..................................................................................... 30

13.7

Reference Electrodes.......................................................................... 31

13.8

Cables ................................................................................................. 31

13.9

Distribution Boxes ............................................................................... 32

13.10

Isolation Joints .................................................................................... 32

13.11

Over Voltage Protective Devices......................................................... 33

13.12

Polarisation Cell Replacement ............................................................ 33

13.13

Test Stations ....................................................................................... 33

14.

INSTALLATION & TESTING ................................................................... 34

14.1

Cable Connections to Buried Piping and Tank Bottom ....................... 34

14.2

Sacrificial Anodes................................................................................ 35




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Electrical Isolation ............................................................................... 35

15.

ELECTRICAL INTERFERENCE ............................................................. 35

16.

DOCUMENTATION................................................................................. 36

16.1

Detail Design Report ........................................................................... 36

16.2

CP Layout Drawings and Detail Drawings .......................................... 36

16.3

Equipment Datasheets........................................................................ 37

16.4

Cable Schedule and Test Post Schedule............................................ 37

16.5

Material Take off List........................................................................... 37

17.

PRE-COMMISSIONING .......................................................................... 37

18.

COMMISSIONING .................................................................................. 38

Appendices APPENDIX 1. – CATHODIC PROTECTION BASIC DESIGN CALCULATION METHODS




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DOCUMENT SCOPE

This specification defines the minimum requirements for design, supply, installation and commissioning of the Cathodic Protection Systems for the Onshore Facilities. The cathodic protection shall be applied to all external surfaces of metallic structures within the boundary limits of the Plant, which will be buried and/or in contact with the soil and shall include but not be limited to the following: · External surfaces of above ground storage tanks in contact with soil · External surfaces of buried metallic piping including metallic risers associated with firewater hydrants, monitors on non-metallic piping systems · External surfaces of buried metallic vessels · Miscellaneous parts such as steel piles, rebar of reinforced concrete and etc. which are in direct contact with the soil or electrolyte media. · The onshore portion of the offshore pipelines coming, where they are in direct contact with soil ,sea water or electrolyte media. · All equipment related to earthing system which are in direct contact with soil or electrolyte media Cathodic protection shall also be applied to the internals surfaces of the following items of equipment · Internal surfaces of hydrocarbon tanks containing discrete water phase. · Internal surfaces of above ground storage tanks containing conductive water such as fire water and potable water tanks · Internal surfaces of hydrocarbon vessels containing a discrete water phase At the detailed engineering stage, the VENDOR shall compile a complete list of all structures to be protected in accordance with the final project data and drawings and shall submit the list for approval to the CONTRACTOR.




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INTRODUCTION

The IDRO/OIEC/IOEC Consortium has been contracted by the National Iranian Oil Company (NIOC) to conduct the EPCC for South Pars Phases 17 & 18 Project. This Project includes Offshore Facilities, platform and undersea pipelines, and Onshore Facilities for the processing of the reservoir fluid. WorleyParsons Pty Ltd has in turn been contracted by the IDRO/OIEC Consortium to conduct the Basic Engineering and FEED for South Pars Phases 17 & 18 for the Onshore facilities. The South Pars Phases 17 & 18 Project offshore work-scope is being carried out by a separate Offshore Consultant. WorleyParsons will lead, identify and coordinate deliverables required to manage the physical interfaces between the Onshore and Offshore Design Consultants.

3.

PROJECT OVERVIEW

The Iranian South Pars field is the largest discovered offshore gas field in the world, located 100 km offshore in the Persian Gulf. Reservoir fluids are transported to shore via two sealines to the mainland (ASSALUYEH) at a distance of approximately 105 km for further treatment. South Pars Phases 17 & 18 are a further development of the South Pars gas field consisting of two 1000 MMSCFD phases. The facilities shall be developed on the basis of supplying treated lean gas to the domestic gas network and ethane gas to the nearby petrochemical complex at the required specifications while maximising liquid recovery as propane and butane and stabilised hydrocarbon condensate for export. A new interconnecting pipeline shall transport the lean gas produced to the domestic gas distribution network via fiscal metering facilities. The produced condensate shall be stored in dedicated storage facilities, periodically pumped through a condensate export pipeline to a SBM via fiscal metering facilities. The treated propane and butane shall be stored separately in refrigerated atmospheric double wall storage tanks, periodically pumped through a dedicated loading pipelines network to LPG carriers berthed at a jetty via fiscal metering facilities.




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Plant Description

The main functions of the Onshore processing facilities are: · Reception facilities for the HP fluids and separation of the raw gas and condensate/water/MEG mixture. · Condensate stabilisation producing stabilised condensate for storage and export. The light ends are recycled to the HP gas system. One condensate flashing unit, normally not operated, is provided as a back-up to the stabilisation facilities. · Gas treatment facilities producing sales gas, gaseous ethane and NGL’s consisting of: - H2S removal from gas / CO2 partial removal from gas. - Dehydration unit, using molecular sieves technology. - Mercury guard. - Ethane extraction unit, producing sales gas, gaseous ethane and NGL. · Ethane treatment for CO2 removal and drying for further export. · NGL fractionation facilities to produce sour liquid propane, butane and condensate. This condensate is routed to the condensate stabilisation system for treatment. · Propane and butane treatment for mercaptans removal and drying for storage and export. · Propane and butane separate atmospheric storage tanks, double wall, and full containment, refrigerated with reinforced concrete external walls. · MEG regeneration and injection unit. · Sulphur recovery producing liquid sulphur for solidification, granulation and export. · Utilities, offsites as required for operation. · Gas export compression.




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CODES AND STANDARDS

All work shall be completed in accordance with engineering codes and standards listed in document: DB-1718-999-P332-0203: List of Applicable Codes & Industry Standards.

4.1

General Requirements

The cathodic protection design for the plant shall be based on the codes, standards, documents and drawings referred to in Sections 4.2 and 5 using the last revision before February 2005.

4.2

Codes and Standards

The cathodic protection system shall meet when applicable the requirements of the following Standards and Codes in their latest edition. API RP 1632

Cathodic Protection of Underground Petroleum Storage Tanks and Piping Systems.

API RP 651

Cathodic Protection of Aboveground Petroleum Storage Tanks.

ASTM G 97

Laboratory Evaluation of Magnesium Sacrificial Anode Test Specimens for Underground Applications.

ASTM G57

Field Measurement of Soil Resistivity Using Wenner Four-Electrode Method.

BS 1377 Part 1

Methods of test for soils for civil engineering purposes. General requirements and sample preparation.

BS 1377 Part 3

Methods of test for soils for civil engineering purposes. Chemical and electrochemical tests.

BS 1377 Part 9

Methods of test for soils for civil engineering purposes. In-situ tests.

BS 7430

Code of practice for earthing.

BSI, BS 7361: Part 1 Cathodic Protection, part 1 code of practice for land and marine applications. IEC 60076

Power Transformers.

IEC 60076-11

Power Transformers –Part 11:Dry-Type Power Transformers




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IEC 60296

Insulation Oils for Transformers and Switch Gear.

IEC 60529

Degree of protection provided by Enclosure.

IEC 60726

Dry-Type Power Transformers.

IEC 60947

Low voltage Switch Gear and Control Gear.

Page 10 of 46

. NACE RP 0169

Control of External Corrosion on Underground or Submerged Metallic Piping Systems.

NACE RP 0575

Internal Cathodic Protection Systems in oil-Treating Vessels.

NACE RP 0675

Control of external corrosion on offshore steel pipelines.

NACE RP0388

Impressed current protection of internal submerged surfaces of carbon steel water storage tanks

NACE RP0177

Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems.

NACE RP0193

External Cathodic Protection of on Grade Metallic Storage Tank Bottoms.

NACE RP0196

Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks.

NACE RP0285

Corrosion Control of Underground Storage Tank Systems by Cathodic Protection.

NACE RP0387

Metallurgical and Inspection Requirements for Cast Sacrificial Anodes for Offshore Applications.

NACE RP0388

Impressed Current Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks.

NACE-RP-0286

The Electrical Isolation of Cathodically Protected Pipelines.




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REFERENCE DOCUMENTS

This document is complemented by the following documents: ·

RP-1718-999-1300-0001

Piping Material Classes.

·

RP-1718- 999-1630-0017

Specification for Transformer-Rectifier Units for Cathodic Protection.

·

RP-1718-999-6600-0001

Specification for Shop and Field Painting.

·

DB-1718-999-P332-0204

Basic Engineering Design Data for Onshore Facilities.

·

To be issued during detail design Cathodic Protection Isolating Joints.

·

RP-1718-999-2500-0001

Cylindrical Storage Tanks Small and Medium Size.

·

RP-1718-999-1630-0007

Onshore Electrical Design Criteria.

·

RP-1718-999-1630-0029

Electrical Cables Specification.

·

SP-1718-999-1630-0008

Electrical Installation Specification.

·

RP-1718-999-1630-5012

Specification for Electrical Junction Boxes

6.

ABBREVIATIONS IDRO

Industrial Development and Renovation Organisation

IOEC

Iranian Offshore Engineering and Construction Company

NIOC

National Iranian Oil Company

OIEC

Oil Industries Engineering and Construction Company

POGC


AC

Alternating Current

AFC

Approved for Construction

AFD

Approved for Design

Ag/AgCl

Silver/Sliver chloride Reference Electrode




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ASA

Advanced Safety Audit

bbl

Barrels

CP

Cathodic Protection

EPCC

Engineering, Procurement, Construction and Commissioning

FEED

Front End Engineering Design

HMWPE

High Molecular Weight Polyethylene

HSE

Health, Safety & Environment

ICCP

Impressed Current Cathodic Protection

IR

Soil Voltage Drop

ISO

International Organisation for Standardisation

MFD

Material Flow Diagram

Mg

Magnesium

MMO

Mixed Metal Oxide

MMSCFD

Million standard cubic feet per day

NaCl

Sodium chloride

OVP

Over Voltage Protection

PCR

Polarisation Cell Replacement

PDB

Positive Distribution Box

PVC

Polyvinyl chloride

PVDF

Polyvinylidene Fluoride

SBM

Single Buoy Mooring

SCADA

Supervisory Control and Data Acquisition

SRB

Sulphate Reducing Bacteria

STBPD

Stock tank barrels per day

Page 12 of 46




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TDS

Total Dissolved Solids

TR

Transformer Rectifier

WP

WorleyParsons Services Pty Ltd

XLPE

Cross Linked Polyethylene

6300

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DEFINITIONS

Within this specification the following definitions shall apply: COMPANY: Shall mean NATIONAL IRANIAN OIL COMPANY (NIOC-POGC) CONTRACTOR: Shall mean the Consortium of IDRO, OIEC and IOEC (IOIC) in charge of EPCC realisation of SOUTH PARS Phases 17 & 18 in the CONTRACT with COMPANY, or his representative. CONSTRUCTION CONTRACTOR: Shall mean the party sub-contracted by CONTRACTOR for Construction WORK, or his representative. INSPECTION AGENCY: This term designates the inspection bodies as third party agencies which will be nominated by CONTRACTOR and approved by COMPANY to carry out the inspection and certification tasks independently based on the approved Inspection & Test Plans. SUB-CONTRACTOR: Shall mean the party sub-contracted by the CONTRACTOR for Engineering, Construction WORK. SITE: Shall mean the premises and places on, under, in, over or through which the WORK is to be executed or carried out including CONTRACTOR’s engineering office and the PLANT. SUPPLIER or VENDOR: Shall mean any person, firm or business which manufacture or supply material, equipment or services for the performance of any item of WORK. SUB-SUPPLIER or SUB-VENDOR: Shall mean any person, firm or business which is in CONTRACT with SUPPLIER/VENDOR to manufacture or supply material, equipment or services for the performance of any item of WORK. WORK: Shall mean all and any of the works and / or services and/or materials required to be provided by the CONTRACTOR or CONSTRUCTION CONTRACTOR.

QUALITY: Shall mean the degree to which a set of inherent characteristics fulfil requirements. This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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QUALITY MANAGEMENT SYSTEM: Shall mean the management system that directs and controls an organisation with regard to quality. CONTINUED IMPROVEMENT: Shall mean a culture that encourages each team member to try to increase Project quality at every opportunity. PREVENTATIVE ACTION: Shall mean an action taken to eliminate the cause of a potential nonconformity or other potentially undesirable situation. CORRECTIVE ACTION: Shall mean an action taken to eliminate the cause of a detected non-conformity or other undesirable situation. VERIFICATION: Shall mean confirmation, by the provision of objective evidence, that specified requirements have been fulfilled. VALIDATION: Shall mean confirmation, by the provision of objective evidence, that the requirements for an intended use have been fulfilled.

8. PRECEDENCE In case of conflict between requirements specified herein and the requirements of any other referenced document, the order of precedence shall be:

9.

-

This specification

-

Particular specification

-

Applicable technical codes industrial standards

-

Data sheet

-

Material requisition

USE OF LANGUAGE

Throughout this specification, the words "will", "may", "shall" and "should” when used, have meaning as follows: · "Will" is used normally in conjunction with a request from CONTRACTOR; This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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· "May" is used where alternatives are equally acceptable; · "Shall” is used where a provision is mandatory; · "Should" is used where a solution is preferred.

10.

CATHODIC PROTECTION GENERAL

10.1 Overview The sacrificial anode/impressed current cathodic protection systems for the onshore facilities of the SOUTH PARS Phase 17/18 project will be generally applied to structures and surfaces which have been coated with a high quality coating. The items to be protected are indicated in Section 1 of this specification. All coating shall be in accordance with document RP-1718-999-6600-0001. All coatings used will have their suitability for use in conjunction with cathodic protection confirmed by documented cathodic disbondment testing and a demonstrated track record in the proposed environment whilst under cathodic protection. The cathodic protection system for the different areas shall be in accordance with the design criteria given in the following sections.

11.

CATHODIC PROTECTION DESIGN CRITERIA

11.1 Design Life The design life for the cathodic protection systems shall be as follows: · Permanent impressed current CP systems shall be 25 years. · Permanent sacrificial anodes buried in the ground shall be 5 years minimum, see note below. · Sacrificial anodes used in tank internals shall be 5 years minimum. · Temporary Sacrificial anode system shall be 2 years or the same as the time delay between installing the pipe and power on the transformer rectifiers Note: Normally packed sacrificial anodes for use in the ground will only have a life span of 10 – 12 years maximum. This is often due to self corrosion due to low resistivity of backfill.




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Note: The Sacrificial Anodes shall be designed for minimum 5 years life span and the relevant calculations shall be carried out during detail stage.

11.2 Current Density The current density values for cathodic design shall be based on the following table. Table 1 Current Density Values




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Design Current Density

Design Current Density

Uncoated Steel, (mA/m2)

Coated Steel, (mA/m2)

At grade tank bottoms

20

4

Plant piping bare steel

30

Structure

Coated plant pipeline: 3 Layer Polyethylene

0.01

3 Layer Polypropylene Fusion Bonded Epoxy Liquid applied Coatings

0.01

Coal Tar Enamel Bitumen

0.3

Tape Wrap system Water tank internal

20 (fresh water)

2

40 (seawater/produced water)

4

10

N/A

150 (galvanised steel)

N/A

500 (copper)

N/A

Concrete rebar (where applicable) Electrical earthing

For structures and tanks operating at elevated temperatures the current density values shall be increased by 25% for each 10 deg. C rise in operating temperature above 30 deg. C.

The current densities given in Table 1 are indicative and valid for moderately corrosive soils. Should the soil survey indicate a very corrosive or non corrosive soil, then the above current densities should be adjusted accordingly during detail design. This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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The expected coating breakdown in water tank internals will be typically in the range 5-10% and it is assumed that the coating will be regularly inspected and maintained in order to ensure that the exposed steel in these tanks is always less than 10% of the overall wetted tank area. Detail design of the CP system for the tanks shall take into consideration the specific operating conditions, coating system and estimate coating breakdown factors for each individual tank.

11.3 Soil/Sea Water/Water Conditions Preliminary geotechnical survey data, including soil and water resistivity data will be provided by CONTRACTOR/COMPANY. During the early stages of CP design VENDOR shall perform a soil survey establish soil corrosivity. The survey shall include soil resistivity measurements and chemical analysis of the soil for the actual sites where piping, structure and/or vessels are proposed to be installed. The survey shall also take into consideration the presence of any oil contaminated soil. The soil resistivity shall be measured by the 4-pin Wenner method using 4 pins of equal separation in accordance with ASTM G57. The survey frequency and survey depths shall be established during detail design but as minimum resistivities shall be recorded at depths of 1, 2 and 3 meters, resistivities at greater depths shall be required if deep groundbeds are selected. Soil analysis is required for each of the soil resistivity locations as follows: · pH – by indicator papers in the field and by glass electrode in conjunction with a high impedance milli-voltmeter in the laboratory · Bacteria – the level of sulphate reducing bacteria in the soil assessed by a field test such as “RapidChek II SRB Detection System” or equivalent and reported as SRB per ml. As an alternative an incubation technique in a culture media may be used (refer NACE/CEA document 0288). · NaCl content - Water soluble and acid soluble chloride salts in the soil in accordance with BS 1377 Part 3. In addition, VENDOR shall review at site all CP interfaces with existing systems not only on this plant but also on adjacent pants, if in close proximity, to ensure the CP design has no interaction effects. Additionally the conductivity ,temperature and make up of waters to be contained within all tankage and other pertinent information including age and history of the tank ,and whether the tank is of welded ,bolted or etc. construction will also be required for design purposes and will be provided by CONTRACTOR. The water make up data required should as a minimum contain details of TDS, Conductivity, pH and chloride content This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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Where tanks are constructed on ring beams the infill shall be selected washed sand and crushed rock. The resistivity of this material shall be taken in the range 250 to 500 ohm m for design purposes. Bituminous sand or asphaltic layers shall not be used and the tank floor will rest directly on the sand or crushed rock infill. In this manner the CP system will be able to more effectively protect the floor plates.

11.4 Current Drain CP of steel reinforcement within concrete is not considered here as concrete quality and below grade coating should negate its requirement. However, the effect of current drain to steel reinforcement on the CP system shall be considered at detail design along with the effect of stray current corrosion on the steel reinforcement and other structures and in particular in areas where steel or concrete pile foundations are to be used. All parts of steel reinforced which are in contact with soil or electrolyte media shall be considered in scope of cathodic protection system. Current drainage to coated and buried onshore piping, which are not included in the CP design, and un insulated buried electrical earthing should also be addressed in the detailed design. Particular attention should be taken to the high current drain of copper in low resistivity soils. It is preferred that copper earthing rods and un insulated buried copper earthing cables not to be used, if not, all parts of earthing network which are in direct contact with soil or electrolyte media shall be considered in cathodic protection system scope. Earthing rods shall be galvanised steel.

11.5 CP Protection Potential Ranges The target IR free potential value for protection shall be: Steel in soil

-0.850 to -1.200 Volts versus copper/copper sulphate half-cell

Steel in soil/water

-0.800 to -1.150 Volts versus silver /silver chloride half cell

In cases where silver /silver chloride half-cells are used these shall be of the sealed low ion type. IR free potentials onshore shall be measured after disconnection of all bonds and sacrificial anodes (if practical) and instantaneously following the switching off all transformer rectifiers. Other methods of recording IR free potentials may also be used if approved by COMPANY e.g. waveform analyser or CP analyser.

[Deleted]




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For in-plant areas the complicated nature, which often exists in conjunction with the combination of materials used in some locations, can influence the potential levels. It may therefore be necessary to allow some flexibility in the protection potential criteria required. For example the 100mV polarisation decay test method (ref. NACE RP0169) may be used in congested areas, subject toCOMPANY approval, or in areas subject to cathodic shielding to determine that adequate protection has been achieved.

11.6 Protection Current Demand and Anode Distribution The protection current for all structures will be determined taking into account the applicable applied current density, the surface area and geometry of the structure and any allowances for current drainage to other metallic items in the vicinity of the structure intended to be protected. In the case of at grade storage tanks, due consideration shall be given to uncoated surfaces of the floor plates at the welding junctions. The use of the coating systems on the structures will result in a lower protection current demand at cathode surfaces in the initial phases of the life of the structure and this will facilitate polarisation of the structure. Towards the latter stages of the structures’ life the current demand will increase due to coating breakdown, anode distribution shall take this condition into account. When the total current requirement is calculated, a 50% safety margin shall be added.

12.

DESIGN CONSIDERATIONS

12.1 At Grade Storage Tank Bottoms Where the external surfaces of the bases of at grade storage tanks will be constructed on a ring beam the external tank bottom plate shall be protected from corrosion by means of coating in combination with cathodic protection. The coating system will improve current distribution and decrease current demand initially. The coating system shall be an immersion grade epoxy coating material applied directly over a prepared substrate without primer prior to installation. Appropriate provision shall be considered for welding works which may come in future. Bituminous sand or asphaltic layers between the tank floor and the foundation surface shall not be used as this interferes with the application of cathodic protection. Where the tank base will be constructed on thermal insulation material or full concrete pad foundations the need for CP is to be reviewed in each case. CP system design for the external coated surfaces of at grade storage tanks bases shall be by impressed current MMO anodes using closely distributed linear anode or grid system installed within the tank This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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foundation. The calculation of current requirements, anode type, final siting of anodes, interconnection of tanks by bond cables and use of electrical isolation devices shall be addressed within the detailed design taking into account of the referenced codes and standards and due recognition of the service conditions likely to be encountered. Monitoring of the effectiveness of the CP systems shall be by potential measurement using permanent reference electrodes installed at time of construction beneath the tank floor. Electrodes shall be placed as close as possible to the tank floor to minimise the IR drop in the soil path. Numbers and distribution of reference electrodes for various tank diameters are given below:

Tank Diameter(D/m)

Number of Reference Electrodes

Reference Electrode Location

30
1

Central

3

1/3D at 120 Degree

4

2/3D at 90 degree

1

Central

2

1/3D opposite

3

2/3D at 120 degree

1

Central

2

1/3D opposite

2

2/3D opposite

1

Central

2

1/2D opposite

5
1

Central

D≤5

None

--

18
10
8
D = Tank diameter Further monitoring facilities shall be provided at the tank periphery in the form of test cell access tubes penetrating the tank foundation. The access tubes shall be installed under the tank base and shall be in This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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the form of slotted plastic tubes. These access points will be used in conjunction with portable monitoring equipment. This is particularly important where a secondary containment liner is used under the tank base as it allows a cross check of permanent electrodes with field measurements.

12.2 Internal Tank Protection 12.2.1

Internal Sacrificial Anodes for Aboveground Storage Tanks and Vessels

Internal corrosion protection of the tanks and vessels shall be achieved by lining (coating) of the tanks in conjunction with a cathodic protection system. Internal cathodic protection shall be provided for all submerged surfaces exposed to natural waters or contaminated waters (brines). The water resistivity shall determine the type of CP system to be installed. For water resistivities less than 10 ohm.m (i.e. water phase in the bottom of hydrocarbon tanks) zinc anodes shall be used. In general, aluminium anodes shall only be used in brines with resistivities of 1 ohm.m or less. Conventional zinc anodes as detailed in section 13.4 shall be used in the water phase of condensate tanks for temperatures <60°C. Permanent monitoring within tanks shall be accomplished by provision of special connections on the side of the tank which allows insertion and retrieval of reference electrodes into the tank. The design of this connection shall be developed during detailed design. Proprietary “Noranode” zinc anodes, or approved equivalent, shall be used in vessels where the temperature is less than 80oC. Zinc anodes shall not be used in water systems providing water for human or animal consumption. The coating system shall be inspected and repaired at regular intervals. Coating breakdown shall not exceed 5 – 10% in the wetted areas. The anodes shall be located to ensure even current distribution over the whole water wetted area. Bolted or screwed connections shall be used to permit anode replacement at future inspections. The anodes shall be attached to plates or bosses that are pre-welded to the tank floor. Bolted and screwed connections, pads or mounting brackets shall be coated but shall not interfere with the electrical connection between the tank and the anode insert. Electrical continuity between the tank/vessel and the anode shall be checked and the resistance shall be less than 0.01 ohms.




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Internal Impressed Current Cathodic Protection for Aboveground Water Storage Tanks

For aboveground water storage tanks where the water resistivity is greater than 10 ohm.m, this may include the potable water and firewater storage tanks, sacrificial anodes will not be able to provide a practical CP system and an ICCP system shall be used. MMO anode wire strings shall be used for the impressed current system. The anode wires shall be suspended from the tank roof as an anode string through access hatches. The impressed current anodes shall be MMO coated titanium anode/copper wire strings. The quantity of anode wire strings and anode loop-to-tank and anode loop-to anode loop spacing will be dependent upon the tank diameter and water level. The anode wires shall be suspended from the hatch cover on a polypropylene rope wire with a cable connection to each anode. The cable shall be routed back to a junction box on the tank roof containing a suitably sized shunt. The anode strings shall be cabled back to a positive distribution box and this box shall be fed via a dedicated transformer rectifier unit. For tanks with internal and external impressed current the transformer rectifier unit for the internal CP and external CP systems shall be totally separate. Provision shall be made within the transformer rectifier unit for monitoring the DC current output and tankto-water potential via the SCADA system. Signal converters (4-20mA) shall be used for this purpose. Facilities shall be provided for each above ground water tank to enable internal monitoring of the structure-to-electrolyte potentials. Permanent monitoring within tanks with impressed current system installed shall be accomplished by permanent CU/CUSO4 reference electrodes in accordance with NACE RP0196 installed within each tank. In addition to these permanent devices, access ports around the roof periphery shall be provided to allow the insertion of portable reference electrodes for measuring tank shell potentials. All below and above cable runs shall be in accordance with SP-1718-999-1630-0008 Electrical Installation Specification.

12.3 Reinforcement Steel and Electrical Earthing Material (Uninsulated Copper or Steel) Where ICCP is used the effect of CP on the corrosion rates of steel within concrete foundations and other structures shall be considered and allowances made for current losses. Generally in the case of in-plant, it is advantageous to use uncoated reinforcing steel so that interaction between individual sections is kept This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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to a minimum. Depending upon the anode type and distribution used the reinforcing steel and electrical grounding shall be made deliberately continuous with the tank to ensure interaction and accelerated corrosion of either one is avoided. To minimise current drainage and cathodic shielding galvanised steel or stainless steel earthing rods shall be used rather than copper rods or copper earthing grids. Wherever possible, a proximity distance of at least 6 metres shall be maintained between earthing rods and protected steel structures and earthing rods and anodes. Under no circumstances shall earthing electrodes be installed between anodes and the structures they are intended to protect.

12.4 Cathodic Protection Plant Piping Buried plant piping shall be cathodically protected using a distributed impressed current cathodic protection arrangement utilising MMO anodes. The anodes shall be placed locally to the buried piping. The CP design shall be based on a distributed anode arrangement, within close proximity to any buried piping. The actual anode placement shall be determined by calculation in detailed design. To ensure that a fully functional cathodic protection system is installed and that shorting does not occur, electrical isolation in plant will not be applied. Electrical continuity between all buried items shall ensure that there are no locations, where under-protection occurs. However, a fully bonded cathodic protection system shall result in current drain to earthing, rebar, foundations etc, which will be accounted for in the detailed design. Steel risers associated with hydrants etc on buried non-metallic piping systems (e.g. HDPE or GRE) shall be protected using magnesium sacrificial anodes. The anodes shall be in accordance with section 13.5.

12.5 Electrical Continuity and Isolation To ensure that the buried plant facilities are fully electrical continuous, and that stray current interaction is minimised the plant CP system will be based on a fully bonded CP system. Flange insulation kits, such as Pikotek, shall not be installed anywhere within the plant. Monobloc isolation joint shall be installed on all pipelines and piping entering or exiting the plant. This will ensure that all buried steel structures inside the plant area are isolated from pipelines/steelwork outside the plant boundary. The monobloc isolation joints shall be in accordance with section 13.10.




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12.6 Cased Crossings Steel cased crossings shall not be used, however where required due to loading, concrete casings or pipe with extra wall thickness shall be used. Should cased crossings be required the concrete shall be conductive and suitable non-metallic spacers shall be attached to the casing pipe at regular intervals within the annular space to electrically isolate the pipeline from the rebar in the casing. The anode wire shall follow the pipeline inside the casing. Test posts shall be installed at each end of the casing.

12.7 Temporary Cathodic Protection System If there is a time delay between installing the pipe and switching on the ICCP system then a temporary cathodic protection system consisting of magnesium anodes shall be installed at all test posts. All temporary anodes shall be disconnected immediately prior to installing the permanent ICCP system.

12.8 Interaction and Induced Effects 12.8.1

Foreign Service Crossings

At all locations where a buried line crosses existing metallic and buried foreign services, facilities shall be installed to allow testing to determine whether resistive bonding is required. Bonding facilities, if necessary, shall include resistors or diodes and current measuring shunts. Given the high integrity of the coating system to be applied on the pipelines, bonding to foreign pipelines should only be undertaken if all other mitigation measures are found to be ineffective. If such bonding is carried out consideration should be given to the possibility of over protection from existing CP systems that may be providing high current outputs to old or poorly coated pipeline systems.

12.8.2

Parallelisms with High Voltage AC

Interaction at points where pipelines run parallel with other services such as high voltage overhead power transmission lines (>11kV) shall also be addressed. This interaction due to induced AC or short term interference effects (e.g. grounding fault) can lead to safety concerns with regards to personnel subject to electric shocks, accelerated corrosion of the pipeline and damage to the coating. As the pipeline coatings will be of high integrity it should be anticipated that induced AC may be problematic. AC interference effects should be investigated by survey to estimate the magnitude of the effects. If such surveys in conjunction with calculations demonstrate that there is a possibility of harmful This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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voltages then mitigation measures should be provided. These mitigation measures may consist of one or a combination of the following: · Dedicated pipeline earthing such as zinc ribbon · Installation of solid state polarisation cells to allow AC current to flow (low impedance to AC) to earthing devices but to prevent flow from DC current (high resistance) from CP systems · Installation of buried steel coupons in the affected section · Installation of monobloc isolating joints at each end of the parallelism

13.

MATERIALS

13.1 Transformer Rectifier Requirements Transformer Rectifiers shall comply with the specification for Transformer-Rectifier Units for Cathodic Protection RP-1718- 999-1630-0017 and latest standards. Measuring unit shall provide facility as data logger for minimum 5 days.

13.2 Anode Materials Cathodic protection for surfaces in contact with soil or corrosive water shall generally be based on the following:




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ANODE CONFIGURATION

BACKFILL

Plant piping

MMO

Wire type Horizontal

Calcined petroleum coke or approved equivalent

At grade storage tank bottoms

MMO

Loops or grid

Washed sand

Mg

Vertical

Mg anodes only: Bentonite clay + Gypsum + Sodium sulphate

Water storage tanks resistivity ≤ 1 ohm.m)

Al

Stand-off or flush

N/A

Water storage tanks 1ohm.m
Zn

Stand-off or flush

N/A

Water storage tanks (resistivity ≥ 10 ohm.m)

MMO

Suspended single anodes or anode loops

N/A

Zn

Flush mounted

N/A

Firewater Hydrants

Internal tanks:

Hydrocarbon tanks (With discrete water phase)




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13.3 Impressed Current Anodes Impressed current anodes shall be of the Mixed Metal Oxide type (MMO) on a titanium or titanium copper core substrate. The anodes type shall be as follows: · Centre connected and sealed tubular type for Pipeline · Wire or tubular for Piping · Ribbon Type for Tanks

13.3.1

Wire Anodes

Wire anodes shall be of the MMO titanium type. Copper cored MMO titanium anodes shall be used where there are long anode runs and where current attenuation along the wire is of a concern. The wire anodes shall comply with the following:

Substrate

Titanium or Titanium/copper

Anode coating type

MMO

Anode coating thickness

Rated for maximum current output for full design life

Wire diameter

3mm (min)

Maximum anode current density (to be verified by MMO anode VENDOR)

3 A/m2 in soil 50 A/m2 in petroleum coke 50 A/m2 in fresh water

13.3.2

Tubular Anodes

Tubular anodes shall be MMO/Titanium type in a “LIDA” type arrangement and comply with the following: Substrate

Titanium

Anode coating type

MMO

Anode coating thickness

Rated for maximum current output for full design life




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Tube diameter

25mm (min)

Tube length

1000mm (min)

Maximum anode current density

3 A/m2 in soil

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(to be verified by MMO anode VENDOR) 50 A/m2 in petroleum coke

13.4 Zinc Anodes Zinc anodes shall be a high purity grade. Composition shall comply with ISO 15589 – 1 as follows: Element

Min %

Max %

Cu

-

0,005

Al

0,10

0,50

Fe

-

0,005

Cd

0,025

0,07

Pb

-

0,006 Remainder

Zn

The maximum amount of other elements shall be 0.02 % each. Alloy Potential

-1.050 Volts (vs Cu/CuSO4 ref cell)

Alloy Capacity

780 Amp.hour / kg

Zinc anodes should not be used if the resistivity of the electrolyte is higher than 30 Ωm unless the engineering evaluation or field test confirm that the design requirements can be met.

13.5 Magnesium Anodes Magnesium anodes shall be performance tested in accordance with ASTM G 97 – 89. The values obtained from the testing shall be the basis for the design of the system. Composition shall comply with ASTM B843 as follows: This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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Element

Min %

Max %

Cu

-

0,02

Al

5,3

6,7

Si

-

0,1

Fe

-

0,003

Mn

0,15

-

Ni

-

0,002

Zn

2,5

3,5

Mg

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Remainder

The maximum amount of other elements shall be 0,005 % each.

Magnesium anode shall be selected as grade B. Alloy Potential

-1.75 Volts (vs Cu/CuSO4 ref cell)

Alloy Capacity

1230 Amp.hour / kg

Magnesium should not be used if the resistivity of the electrolyte is higher than 150 Ω.m unless the engineering evaluation or field test confirm that the design requirements can be met.

13.6 Anode Backfill 13.6.1

Calcined Petroleum Coke

Calcined petroleum coke (only for tubular anodes) for use with impressed current anodes shall comply with the following requirements: Resistivity

0.001 ohm.m

Fixed carbon

99.1% min

Ash content

0.1% max

Moisture content

0.2% max

Volatile content

0.6% max

Particle size

100% passing 1mm <10% retained 0.1mm




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Chemical Backfill

Chemical backfill for use with sacrificial anodes shall comply with the following composition: Hydrated gypsum

75%

Bentonite

20%

Sodium sulphate

5%

13.7 Reference Electrodes Permanent reference electrodes shall be of the sealed silver/silver chloride or copper/copper sulphate type. The electrode shall provide +/- 10mV stability with a 3 microampere load and shall be suitable for a minimum period of 20 years. The electrodes shall be supplied by a specialist VENDOR who has a proven track record of supplying quality electrodes, which can meet the service conditions and life expectancy.

13.8 Cables Impressed current anode cables shall be tin-coated, stranded single core copper with HMWPE/PVDF primary insulation and high molecular weight black polyethylene. All other cables shall be tin-coated, stranded single core copper with XLPE/PVC insulation. The minimum rating for all cables and wires shall be 600/1000 Volt grade. The minimum cable sizes shall be as follows: · Positive and negative cathodic protection station cables: 35 mm2. · Equi-potential bonding cables: 16 mm2. · Monitoring cables:10 mm2. · Impressed current anode cable tails: 10 mm2. · Magnesium/Zinc anode cable tail: 10 mm2. · Bonding cable: 10 mm2. · Reference electrode cable tails: 6 mm2. · Surge diverter (Over Voltage Protection) cable tails: 25 mm2. Negative cable shall be black and positive cables shall be red. Direct buried negative and positive cables shall be armoured.




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All above ground cables shall be suitably identified with stainless steel tags to show their origin and function. All below ground cables shall be suitably identified with concrete cable markers. Individual cable sizes shall be calculated at detailed design and a schedule included in the calculation package for each run.

13.9 Distribution Boxes Distribution boxes including positive, negative and bonding boxes shall be in accordance with the Specification for Electrical Junction Boxes RP-1718-999-1630-5012. Positive distribution boxes shall be fitted with coil type resistors and shunts on each anode circuit rated to the full anode current output. The box shall be sized to allow dissipation of maximum heat from resistors.

13.10 Isolation Joints Isolation joints shall be of the monobloc type. They shall be supplied with pup-pieces of same material as the mother pipe. The isolating joints shall be installed above ground or in non-floodable manholes on a straight section of the pipe and should be in an inclined plan to avoid settling of deposits which may short circuit the joints. When the pipeline/piping contains a conductive fluid the isolation joint shall be coated internally over a sufficient length to minimise the risk of short circuiting the cathodic protection current. The coating length depends on the electrolyte resistivity and on the pipe diameter and shall be calculated in accordance with the formula given below:

L = 400

D (cm) r

Where: L

=

Internal coated length

cm

D

=

Nominal diameter of pipe

cm

ρ

=

Electrolyte resistivity

Ohm.cm

Isolation joints shall be installed at the following locations: This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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· Condensate and LPG pipelines. · Lean gas export pipelines. · Ethane export pipelines. · Propane and butane circulation/vapour return lines. · Between offshore pipe lines and on shore pipe lines in battery limits The isolation joints shall be positioned with particular attention to avoid short circuiting that might be caused by a support, walkway fittings, valves and actuators or any other metallic structures whether permanently or temporarily installed. All isolation joints shall be in accordance with project specification to be developed during detail design and shall have over voltage protective devices installed in accordance with section 13.11 below.

13.11 Over Voltage Protective Devices Over voltage protective (OVP) devices should be installed across all isolating joints. They shall be suitable for hazardous area classifications Zone 0, 1 or 2 as required. The OVP shall have independent design type approval by an official test laboratory of the supplier’s country (CESI for Italy, PTB for Germany, BASEEFA for UK, lCIE or INERIS for France). Certificates shall be in English or be accompanied with an exact English translation. The Vendor shall ensure that OVPs meet all the applicable requirements, symbol clearly fixed to indicate preferably of the ATEX Directive (94/9/EC), and preferably have the compliance. Certification to IEC Standards, either under the IECEx scheme, or by way of current certificates of conformance issued by a recognised national testing authority acceptable to CONTRACTOR is an acceptable alternative certification to ATEX certification. Other certifications shall be subject to approval by CONTRACTOR.

13.12 Polarisation Cell Replacement Polarisation cell replacements (PCR) devices shall be of the solid state type. PCR shall not be used wherein the isolating joints are principally used for isolating duties [Deleted. The PCR shall have independent design type approval by CENELEC, BASEEFA, and to European standard and shall be CE stamped.

13.13 Test Stations Test stations shall be a polycarbonate (proprietary test station) or equivalent. The test post shall comprise of a 75mm thick test post to a minimum thickness of 3mm. All test posts shall have a permanent reference This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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electrode installed. In complex area where shielding of the cathodic protection system may occur, the test stations shall also have a coupon installed for local ON/OFF potential measurements. The coupon shall be of the same material as the pipe. Test stations shall be installed at the following locations: · Every 100-150 meters of pipeline/piping run and at every change of pipe direction. The test station should generally be installed above the pipeline/piping. · 2 per tank. · At all isolation joints. · At every foreign service crossing. · At road crossings. · At points of parallelism with high voltage AC. From each monitoring station two separate cables as a minimum shall be attached to the pipeline/piping. All cables shall be identified by colour coding or tags.

14.

INSTALLATION & TESTING

14.1 Cable Connections to Buried Piping and Tank Bottom Cable connections (up to and including 16 mm2) to buried piping or at grade tank bottoms for test, bond and drain cables shall be by means of drawn arc pin brazing. Negative cable connection shall be by a welded doubler plate with welded threaded stud. Pin brazing procedure and operators shall be qualified in accordance with project procedure to be developed during detail design. Cadweld or thermit welding shall not be used. Impressed current anodes cables shall be connected to positive feeder cables in above ground positive distribution boxes to enable individual anode control and monitoring by means of grid coil resistors and shunts, and shall be terminated above ground to allow for current monitoring and disconnection. Where current carrying cables run outside of the pipe trench they shall be buried in a narrow excavation and laid on a bed of soft sand. They shall be marked with cable warning tape and the route shall be marked with concrete cable markers every 30 meters (minimum) and at each point where there is a change of direction. If cables are to be laid in areas used by vehicular traffic or where earth-moving machinery is used, cabling shall be suitably protected against damage or exposure. This document is the sole property of N.I.O.C, all information contained herein may neither be reproduced, used, disclosed, transmitted nor in any way made public without permission of the owner.



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The electrical current rating of a cable shall not be exceeded for the temperature of use. Cable crosssection shall be selected to suit the condition of use.

14.2 Sacrificial Anodes The sacrificial anodes shall be inspected and tested in accordance with NACE RP0387.

14.3 Electrical Isolation Isolation joints should be tested to establish their functionality in accordance with NACE RP0286. All isolation joints should be protected from voltage transients and ac fault current by means of correctly rated and selected solid state over voltage protection devices. Total electrical isolation shall be ensured, i.e. no short circuits should be allowed to exist at pipe supports, control piping, etc.

15.

ELECTRICAL INTERFERENCE

Corrosion caused by electrical interference on buried metallic structures differs from other causes of corrosion damage in that the current, which causes the corrosion, has a source foreign to the affected structure. Usually the interfering current from a foreign source, not electrically continuous with the affected structure is drained from the soil by the affected structure. Detrimental effects of interference currents occur at locations where the currents are subsequently discharged from the affected pipeline to the earth. Types of DC interference are: · Constant current sources such as from CP rectifiers, and · Fluctuating current sources such as direct current electrified railway systems and transit systems, coal mine haulage systems and pumps, welding machines and direct current power systems. Types of AC interference are: · Short term interference caused by faults in a.c. power systems and electrified railways · Long term interference caused by inductive or conductive coupling between the pipeline and high voltage lines or electrified railways · Telluric currents.




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It is the responsibility of the detail design Contractor to ensure that that no electrical interference will occur within the plant by employing suitable corrective actions. Further information on mitigation is detailed in ISO 15589-1 and shall be evaluated during detail design.

16.

DOCUMENTATION

Detail design contractor shall develop a detailed CP design based on this document and the referenced standards. The detail design shall be documented in a detail design report, CP layout drawings, CP detail drawings, equipment datasheets, cable schedule, test post schedule and a material take off list. All documentation shall be approved by Company.

16.1 Detail Design Report The detail design report shall include, but not be limited to the following: · Design philosophy including design life, design current densities, protection levels and referenced codes, standards and documents. · Results and assessment or soil and site survey. · Definitions of systems to be applied including sizing and placements. · Evaluation of any possible electrical interferences. · List of all items to be protected including dimensions, coating system and tag numbers. · Detail calculations in accordance with Appendix A of this document.

16.2 CP Layout Drawings and Detail Drawings The layout drawings shall show placement of anodes, groundbeds, transformer rectifiers, monitoring stations, negative and positive distribution boxes and negative connection points. Neighbouring CP systems shall also be indicated. All tag numbers shall be included on the drawings. The CP detail drawings shall include block diagrams of the systems and the various connection details of CP equipment to tanks, piping and pipelines.




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16.3 Equipment Datasheets The equipment datasheets shall be produced for the transformer rectifier, positive and negative distribution boxes, test stations, reference electrodes, isolation joints, anodes, over voltage protectors, polarisation cell replacements and cables.

16.4 Cable Schedule and Test Post Schedule The cable schedule shall include all cable routings, tag numbers and cable lengths. The test post schedule shall include all tag numbers, location and all cables in and out of the station including cable tag numbers.

16.5 Material Take off List A material take off list of all CP equipment required to achieve an optimum and economical design for the specified design life. This list shall be used as the basis for a purchase order of the equipment.

17.

PRE-COMMISSIONING

During detailed design a pre-commissioning test specification shall be generated which covers all aspects of tests during mechanical completion and pre-commissioning testing for tanks and buried piping. Such tests shall include: · Procedure for testing backfill under tanks. · Trial operation of anodes including individual anode loop resistance to earth immediately after completion of tank foundation and before tank plates are installed and then after the tank has been fabricated and power sources to confirm they can deliver their maximum capacity. · Measurements and testing shall also be carried out to confirm satisfactory connection of all cables and circuits. · Resistance to earth testing of all distributed groundbeds. · Calibration of permanently installed reference electrodes.




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COMMISSIONING

Onshore commissioning procedures shall be produced during detailed design for the approval of the COMPANY. The purpose of the commissioning procedure shall be used to show that the installed systems operate as specified and that the required design criteria have been met. The specification shall include as a minimum the following: · Standard forms for recording commissioning results · Procedure for disconnection of all sacrificial systems, depolarisation of the piping and measurement and recording of natural potentials · Procedure for setting the cathodic protection systems in operation and measuring ON potentials · Procedure for setting the cathodic protection parameters(potential and current) after 72 hours polarization period minimum. · Procedure for measurement of IR free potentials · Incoming/outgoing piping and pipelines with" foreign structure". · Procedure for balancing CP systems The CONTRACTOR selected for detailed design shall provide the company with a program for the commissioning of the cathodic protection systems. The CONTRACTOR selected shall prepare a commissioning report, which shall include all commissioning results. The report shall include a discussion of the results obtained giving conclusions. The report shall also show the Natural ON and instant OFF potentials at all test stations in both tabular and graphical formats.




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Appendix 1. – CATHODIC PROTECTION BASIC DESIGN CALCULATION METHODS At-Grade Tank Bottoms – Anode Wire Loop System Design Data Soil resistivity (washed sand)

500 ohm.m (maximum) 100 om.m (minimum)

MMO wire anode type

3mm diameter

MMO ribbon burial depth beneath tank base

350mm

MMO ribbon anode-to-anode spacing

1.5m typical

MMO ribbon anode current output in sand

5 A/m2 (max) to be confirmed by anode VENDOR

Circuit resistance (target)

2 ohms (max)

Rectifier voltage

50V (max)

IR loss in anode circuit

10% (max)

Surface Areas

pD 2 St (m2) = 4

Where D = tank diameter (m)

Current Requirements

It ( A) = StCD

Where CD = applied current density (A/m2)

MMO Ribbon Length Requirements (min)

Rl (m) =

It Acd

Where Acd = maximum anode current density (A/m2)




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MMO Ribbon Single Loop Resistance to Earth (Dwight)

Ranode(Ohms) =

r é æ 8D ö æ 2 D öù lnç ÷ + lnç ÷ú ê 2 2p D ë è d ø è s øû

Where

r = soil resistivity (ohm.m) D = anode loop diameter (m) d = anode wire diameter (m) s = anode burial depth (m)

MMO Ribbon Loop Resistance to Earth (all loops)

1 1 1 é ù Rtotal (Ohms) = ê + + ... RanodeN úû ë Ranode1 Ranode2

-1

Where Ranode1 = resistance of 1st anode loop Ranode2 = resistance of 2nd anode loop RanodeN = resistance of Nth anode loop

Voltage Attenuation along MMO Ribbon

IR =

R int Re xt

Where

Rint = Anode internal resistance (ohm)

Rext = Anode resistance to earth (ohm)

r a = resistivity of anode substrate

where

R int =

r a Lc (ohms) A

material (ohm.m) Lc = anode length between conductors (m) A = anode cross sectional area (m2)




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Water Tank Internals – Impressed Current System Design Data MMO wire anode type

3mm dia (copper/titanium core)

MMO ribbon anode current output in water

50 A/m2 (max) to be confirmed by anode VENDOR

Circuit resistance

1 ohm (max)

Rectifier voltage

24V (max)


10% (max)

Surface Areas

St =

pD 2 + pDH (m2) 4

Where

D = tank diameter (m) H = High High liquid level of water


It = StCD (A)



Rl =

It (m) Acd


MMO Single Ribbon Resistance to Earth (Dwight- vertical)

R=

r é æ 8L ö ù lnç ÷ - 1 (ohms) 2pL êë è d ø úû

Where

r = soil resistivity (ohm.m) L = installed anode length (m) d = equivalent anode diameter (m) t = anode burial depth (m)




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MMO Ribbon Loop-to-Loop Interference Where

F = 1+

r [ln(0.66 N )] psR

N = number of anodes

s = anode-to-anode spacing

MMO Ribbon Loop Resistance to Earth (all loops)

Rtotal = F

R (ohms) N

Voltage Attenuation along MMO Ribbon Where

IR =

R int Re xt

Rext = Anode resistance to earth (ohm)

r a = resistivity of anode substrate material

where

R int =

Rint = Anode internal resistance (ohm)

r a Lc (ohms) A

(ohm.m)

Lc = anode length between conductors (m) A = anode cross sectional area (m2)




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Tank Internals – Sacrificial Anodes Anode Resistance for Long Flush Mounted Anode

Ra =

r 2xS

Symbol

Description

Unit

Ra

Anode resistance

Ohms

r

Fluid / Soil resistivity

ohm.m

S

Arithemetic mean of anode length & width

cm

Notes: Long defined as L ³ 4 x (anode width and thickness).

Anode Resistance for Short Flush Mounted Anode]

Ra =

Symbol

0.315 r

Description

Ra

Anode resistance

r

Fluid / Soil resistivity

A

Exposed anode surface area

A Unit Ohms Ohm.m cm2




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Anode Weight

W =

Symbol

Iav x t x 8766 Z xU

Description

Unit

W

Total anode weight for design life

Iav

Average design current over design life

Amps

t

Time

years

Z

Anode alloy capacity

A-hr/kg

U

Anode utilisation factor

NOTE 1

Kg

NOTE 1 Anode utilisation factors as given in DNV RP B401: Long slender stand-off

0.90

Long flush mounted

0.85

Short flush mounted

0.80




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Buried Piping – Impressed Current System Design Data Soil resistivity

To be confirmed during detail design

MMO anode type

Tubular

MMO anode burial depth

2 – 3 meter typically

MMO anode distance from pipe

1.5 – 3 meter typically

MMO ribbon anode-to-anode spacing

20 m typical

MMO ribbon anode current output in soil

3A/m2 in soil 50A/m2 in petroleum coke to be confirmed by anode VENDOR

Circuit resistance (target)

2 ohms (max)

Rectifier voltage

50V (max)


10% (max)

Surface Areas

pD 2 St (m2) = 4

Where D = tank diameter (m)


It ( A) = StCD



Rl (m) =

It Acd


MMO Single Anode Resistance to Earth (Dwight- vertical)




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Ra =

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r1 é æ 8 L1 ö ù r 2 é æ 8L2 ö ù lnç lnç ÷ - 1ú + ÷ - 1 (ohms) ê 2pL1 ë è d1 ø û 2pL 2 êë è d 2 ø úû

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Where

r 1 = backfill resistivity (ohm.m) d1 = anode diameter (m) (anode wire inside canister)

r 2 = soil resistivity (ohm.m) L1 = anode length inside canister (m) d2= anode diameter (m) (anode canister) L2 = anode canister length (m) MMO Ribbon Anode-to-Anode Interference Where

F = 1+

r [ln(0.66 N )] psRa

N = number of anodes s = anode-to-anode spacing

MMO Anode Resistance to Earth (all anode)

Ratotal = F

R (ohms) N

Total Resistance in system shall also take into account resistance in anode cables, positive cables to junction boxes and negative cables. Potential shift on pipe The potential shift on the pipe shall be calculated directly opposite the anode and between the anodes.


RP-1718-999-6300-5002-8

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