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PARADIP REFINERY PROJECT

PROJECT SPECIFICATION ACATHODIC PROTECTION PHILOSOPHY

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CONTENTS

1.0 PROJECT SCOPE .................................................................................4 2.0 REFERENCE DOCUMENTS ..................................................................4 2.1 International Standards........................................................................4 2.2 Indian Standards ..................................................................................5 2.3 Project Specifications ..........................................................................5 3.0 ABBREVIATIONS..................................................................................5 4.0 GENERAL ..............................................................................................6 5.0 MARINE JETTY ....................................................................................6 5.1 Jetty Structure .....................................................................................6 5.2 Design Life............................................................................................7 5.3 Anti-Corrosion Coatings ......................................................................7 5.4 Anode Design .......................................................................................7 5.5 Monitoring ............................................................................................8 6.0 PIPING AND PIPELINES .......................................................................8 6.1 External Surfaces (Buried Piping) ........................................................8 6.2 External Surfaces (Subsea Pipelines/Outfalls)..................................10 6.3 Internal Surfaces of Piping/Pipeline ..................................................11 7.0 AT GRADE STORAGE TANKS ..........................................................11 7.1 External Surfaces ...............................................................................11 7.2 Internal Surfaces ................................................................................13 7.3 Anti-Corrosion Coatings ....................................................................13 7.4 Cathodic Protection ...........................................................................13 7.5 Monitoring ..........................................................................................14 8.0 BURIED STORAGE TANKS/VESSELS ...............................................14 8.1 External Surfaces ...............................................................................14 8.2 Anti-Corrosion Coatings ....................................................................14 8.3 Cathodic Protection ...........................................................................14 8.4 Internal Surfaces ................................................................................15 9.0 SITE CONDITIONS .............................................................................16 10.0 TECHNICAL CONSIDERATIONS .......................................................16 11.0 CONSTRUCTION FEATURES ............................................................16 11.1 Piping ..................................................................................................16 11.2 Tanks ..................................................................................................17 11.3 Power Source .....................................................................................18

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11.4 Groundbed Design and Current Distribution ....................................18 11.5 Cabling................................................................................................20 11.6 Electrical Connections .......................................................................20 11.7 Test Points..........................................................................................20 12.0 INSTALLATION ..................................................................................20 12.1 Sacrificial Anodes ..............................................................................20 12.2 Anode Cabling ....................................................................................20 12.3 Power Source (Transformer Rectifiers).............................................21 12.4 External Impressed Current System for At Grade Storage Tanks ..21

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1.0 PROJECT SCOPE

This document describes the general strategy and specific parameters that shall beapplied to the detailed design of the corrosion control systems by cathodicprotection.

The objective of this document is to cover the minimum requirements for the pre-design survey, design, detail engineering, supply of material, installation,commissioning and start up of cathodic protection systems

The requirements in this document apply to corrosion protection of the followingareas:

1. External protection of steel buried in or in contact with soil i.e. buried metallicpiping, pipelines , buried metallic vessels and tanks, above grade tankbases.

2. Steel structures/pipelines in corrosive immersion service. The buried, wettedand wave zones of the marine jetty and the subsea pipeline/outfall.

3. Internal protection of steel in corrosive aqueous immersion service, i.e. tankscontaining corrosive water phase and seawater intake and outfall piping.

Codes, Standards, and Project Specifications are listed in Section 2.

2.0 REFERENCE DOCUMENTS

The cathodic protection philosophy shall be in accordance with the latest editions ofthe following codes, standards, and project documents:

2.1 International Standards

BSI, BS 7361: Part 1 Cathodic Protection Code of Practice for Land and MarineApplications.

ASTM B418: Standard Specification of Cast and Wrought Galvanic Zinc

AnodesNACE RP0169 Control of External Corrosion of Underground or

Submerged Metallic Piping Systems

NACE RP0286 The Electrical Isolation of Cathodically Protected Pipelines

NACE RP0285 Corrosion Control of Underground Storage Tank Systemsby Cathodic Protection

NACE RP0388 Impressed Current Cathodic Protection of InternalSubmerged Surfaces of Steel Water Storage Tanks

NACE RP0193 External Cathodic Protection of On Grade MetallicStorage Tank Bottoms

DNV RP-B401 Cathodic Protection Design

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API RP651 Cathodic Protection of aboveground Petroleum StorageTanks

2.2 Indian Standards

IS 8062 : PART 1 : 1976 Code of practice for cathodic protection of steelstructures, part 1 general principles

IS 8062 : Part II : 1976 Code of Practice for Cathodic Protection of SteelStructures - Part II : Underground Pipelines

IS 8062 : Part 4 : 1979 Code of practice for cathodic protection of steel

structures ,part 4 Galvanic protection of dockgates,caissons, piers and jetties

IS 8062 : 2006 Cathodic Protection of Buried Pipeline/Structure forTransportation of Natural Gas, Oil and Liquids - Code ofPractice

IS 12560 : 1988 Code of practice for cathodic protection of heatexchangers and condensers

IS 10028 : Part 1 : 1985 Code of Practice for Selection, Installation andMaintenance of Transformers - Part 1 : Selection

IS 10561 : 1983 Application guide for power transformers

IS 2705 : Part 1 : 1992 Current transformers: Part 1 General requirements

IS 2026 : Part 1 : 1977 Power transformers: Part 1 General

IS 10028 : Part 3 : 1981 Code of practice for selection, installation andmaintenance

IS 3639 : 1966 Specification for Fittings and Accessories for PowerTransformers of transformers: Part 3 Maintenance(superseding IS:1886)

IS 3156: Part 1 : 1992 Voltage transformers: Part 1 General requirements

13956 : 1994 Testing transformers

2.3 Project Specifications

3210-8440-SP-0008 Coating and Wrapping of Buried Pipework

3.0 ABBREVIATIONS

AC: Alternating Current

CP: Cathodic Protection

DC: Direct Current

ICCP: Impressed Current Cathodic Protection Sysytem

MMO: Mixed Metal Oxide

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ROV: Remote Operated Vehicle

T/R: Transformer Rectifier

4.0 GENERAL

Corrosion control of the items listed in this document shall be provided by thecombined application of coatings and cathodic protection.

Coating systems and type of cathodic protection shall be dependent uponapplication. Design shall be compliant with best industry practice . Hydrocarbonstorage tanks which contain a water phase shall be protected internally usingdistributed sacrificial anodes and coatings. Firewater and other tankage storingcorrosive water shall be protected with impressed current cathodic protection.Temporary cathodic protection shall be provided for tankage during hydrotest(where tanks may contain raw water for prolonged periods).

Impressed current cathodic protection systems for the external surfaces of at gradestorage tank floors shall be of the closely distributed type installed beneath the tankand within the tank ring beam foundation. Buried vessels shall also be protectedusing impressed current in combination with coatings.

Buried metallic piping shall be protected externally using the specified coatingsystem in conjunction with close distributed impressed current anode cathodicprotection. Type, location and orientation of the anode material selected shall bedetermined using available soil resistivity and geotechnical data. Temporarycathodic protection shall be provided by galvanic sacrificial anodes. Sacrificialanodes may also be used for internal protection of piping containing seawater.

The jetty shall be protected in its buried, wetted and wave zones by the applicationof a coating system of coal tar epoxy in combination with a cathodic protectionsystem of aluminium alloy sacrificial anodes. The atmospheric zone shall beprotected with a coating system of coal tar epoxy and where applicable additionalimpact resistant coatings or wraps.

5.0 MARINE JETTY

5.1 Jetty Structure

Piles shall be externally coated in the wetted, splash and atmospheric zones with aproject approved coal tar epoxy. Further protection is to be provided in the wettedand buried zones by the installation of aluminium zinc indium alloy sacrificial anodeshaving an approved chemical composition and electrochemical performance.Coating of the structures and installation of anodes shall be the responsibility of thejetty Contractor.

In the event of piles being of reinforced concrete in place of steel piles, or acombination of both, an anti-corrosion philosophy shall be developed for the rebar inthe buried, wetted and atmospheric zones of the pile for approval. Such a

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philosophy shall address the possibility of attachment of sacrificial anodes andcoating of concrete in the splash and atmospheric zones.

5.1.1 Design Life

The design life for the impressed current corrosion control systems shall be not lessthan 20 years.

5.2 Anti-Corrosion Coatings

5.2.1 Piles

All surfaces of piles in the atmospheric, wetted and submerged zones shall becoated with an approved amine adduct cured high build coal tar epoxy. Thesubstrate shall be prepared in accordance with the coating manufacturers datasheets and the coating applied without primer to a minimum dry film thickness of400 microns.

Where boat impact or wave action may act to accelerate degradation of the coal tarlayer consideration shall be given to the installation of heavy duty splash zonecoatings or wraps.

5.2.2 Deck steel work

All structural steelwork exposed to atmospheric conditions under the jetty deck ortrestleway shall be coated with an approved amine adduct cured high build coal tarepoxy. The substrate shall be prepared in accordance with the coatingmanufacturers' data sheets and the coating applied without primer to a minimum dryfilm thickness of 300 microns.

5.3 Anode Design

A system of cathodic protection shall be designed (by jetty sub-contractor) tosupplement the coating system in the wetted and buried zones. The design shall bebased upon the current densities and coating breakdown figures detailed in thereferenced codes and standards. In all cases the anode shall be cast in analuminium zinc indium alloy (bismuth containing alloys shall not be considered).

Anodes shall be installed on the pile immediately after pile installation by anapproved attachment procedure. In all cases the method of connecting the anode toprovide electrical continuity is critical and shall be reviewed fully.

It is intended that each pile shall be protected by appropriate selection of anode ofsufficient size and weight to meet start, mean and end of life current demands. Theanode shall also have sufficient weight of alloy to meet the life requirements basedupon mean current demand. Anode weight, geometry, and quantity selection shallbe in accordance with the requirements of DnV RP-B401 (Cathodic ProtectionDesign) with respect to anode resistance, driving potential, and all other criteria.Anodes shall be of either bracelet, trapezoidal or cylindrical geometry.

Where interconnected and welded steel work guarantees electrical continuity for a

group of piles these shall be protected by smaller numbers of larger and heavieranodes. These larger anodes shall be placed on an individual pile, or number ofindividual piles within the group, to reduce the overall quantities of anodes required

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on the jetty. In these circumstances monitoring facilities shall be provided todemonstrate adequate current distribution.

Establishing continuity by cable bonding shall not be considered.

5.4 Monitoring

5.4.1 Potential Monitoring

Monitoring the effectiveness of the cathodic protection system shall be by potentialmeasurements. A number of permanently installed zinc reference cells shall beinstalled. Such monitoring devices shall be placed at points on the structure which

are representative of the overall system. These shall include shallowest anddeepest water and where anode concentrations change as in the case of electricallycontinuous pile groups.

5.4.2 Monitoring of Welding

Stray currents generated by welding shall be considered and any likely detrimentaleffects avoided by design or inspection of correct return path cable connectionduring the construction phase.

5.4.3 Protection Potential Range

The minimum potential value for protection of steel in seawater shall be taken as0.80 volt negative with respect to a silver/silver chloride electrode. This value is the

lower limit for steel in aerobic conditions and should be shifted a further 100mv inthe negative direction if anaerobic conditions are known to exist in the buried zones.

6.0 PIPING AND PIPELINES

6.1 External Surfaces (Buried Piping)

Paradip refinery will have a number of buried pipelines serving for raw water ,hydrocarbon export and marketing . All buried metallic piping and pipelines withinthe refinery (with the exception of pipe in culverts unless sand filled) shall beexternally protected from corrosion by the application of coatings and cathodicprotection. Maximum design temperatures and environmental conditions shall be

addressed during detailed design and coatings and cathodic protection currentdensity requirements addressed accordingly

6.1.1 Anti-Corrosion Coatings

All buried pipelines and piping shall be externally coated with one of the systemsdetailed in the coating specification which have been selected to meet therequirements of the operating conditions and environment in which they are to beburied.

Field joint coating shall be carried out with a system compatible with the parentcoating.

6.1.2 Cathodic Protection (Permanent)

Cathodic protection system design for the external coated and buried surfaces ofpipelines and piping shall be carried out at detailed design stage in accordance withthe relevant codes and standards with recognition of the service conditions and

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coating types. Use of impressed current close distributed anode systems isenvisaged in general for unit areas. However, deep well anodes shall be providedfor underground piping in offsite areas and in uncongested areas surrounding theunits.

Current densities shall be selected to produce the required potential shifts andanode distribution considered to provide the most uniform current dissipation.

To allow the system to be designed a comprehensive list of all buried metallic pipingshall be required at the design stage.

6.1.3 Cathodic Protection (Temporary)

In addition to provision of permanent cathodic protection, temporary cathodicprotection shall be applied in order to mitigate corrosion between installation andsuch time as the permanent system can be commissioned. Nominal design life ofthe temporary system shall be one year unless otherwise stated in the designreport.

Temporary systems shall either be dedicated sacrificial (zinc or magnesium), orimpressed current, utilising cross bonds to existing systems such that current can bebled onto the new lines.

6.1.4 Electrical IsolationIsolation of underground in plant piping from electrically continuous plant shallgenerally not be considered to limit the risk of sparking across flanges duringmaintenance operation. Where electrical isolation is used, it shall be limited to thoseplaces where a excessive current drain shall result in the requirement for a greatlyincreased output from the cathodic protection system. These locations shall beidentified during detailed design.

6.1.5 Effect of Cathodic Protection on Reinforcing Steel

The effect of cathodic protection on the corrosion rates of steel within concretefoundations, plant earth grid, and other structures shall be considered andallowances made for current losses. Generally in the case of refinery and other

congested plant situations it is advantageous to use uncoated reinforcing steel sothat interaction between individual sections is kept to a minimum.

6.1.6 Monitoring

Monitoring of the effectiveness of the pipeline cathodic protection systems shall beby potential measurement using portable test equipment. Test stations shall beinstalled at regular intervals along the pipe routes . Where pipelines which aresubject to cathodic protection are beneath paved areas, test access points shall beincorporated.


The value of protection potential for piping used shall be -0.85 volts, or morenegative, measured in the IR free condition. This value is the lower limit for steel inaerobic soils and should be shifted a further 100mv in the negative direction ifanaerobic conditions are known to exist.

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Excess overprotection should not be allowed to occur. The most negative valuepermissible shall be taken as - 1.2 volts instantaneous off. However due to thecomplicated nature of the finished plant, and the influence on potential levelscreated by the combination of materials found in plant and refinery locations, someflexibility in the figures given shall be required.

The 100mV polarisation decay test method may also be used to determine thatadequate protection has been achieved.

All potential readings are to be measured with respect to a copper/copper sulphatereference electrode.

6.2 External Surfaces (Subsea Pipelines/Outfalls)

Where pipelines are installed subsea they shall be externally coated as a primarymeans of corrosion control. In addition to the anti-corrosion coating pipelines shallbe weight coated to provide seabed stability and primary coating protection fromimpact damage. In all cases the pipelines shall also be provided with a system ofcathodic protection.


External coating of subsea pipelines in all cases shall be by means of glass mattreinforced coal tar enamel. Field joints shall be made using cold applied hightemperature tape and hot applied mastic fill.

In the landfall section where there may be a transition from subsea to undergroundto atmospheric conditions consideration shall be given to specialised coatingrequirements.

6.2.2 Cathodic Protection

Cathodic protection system design for the external wetted surfaces of subseapipelines shall be sacrificial in nature utilising bracelet anodes of the aluminium zincindium alloy type (bismuth containing alloys shall not be considered).

The cathodic protection shall be designed taking into consideration the temperatureat the steel and anode surface induced by the product or media contained within thepipeline and influenced by seabed conditions, depth of burial, rock dumping etc.

Selection of anode geometry and spacing shall be made at detailed design stage inaccordance with the relevant codes and standards with recognition of the serviceconditions and coating types. Current densities shall be selected to produce therequired potential shifts and anode distribution considered to provide the mostuniform current dissipation.

6.2.3 Electrical Isolation

Electrical isolation of subsea pipelines is only required at their point of landfall. Theexact location and type of any isolation shall be determined during the detaileddesign phase.

6.2.4 Monitoring

Monitoring of subsea pipeline cathodic protection performance shall be considered.Where possible by divers or ROv whichever applicable.

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6.3 Internal Surfaces of Piping/Pipeline

Where ferrous pipelines or piping carry corrosive (untreated) water they shall beinternally lined. Application of internal CP shall be addressed on a case by casebasis during detailed design.

CP system selection shall be carried out at detailed design stage in accordance withthe relevant codes and standards with recognition of the service conditions andcoating types. Current densities shall be selected to produce the required potentialshifts and anode distribution considered to provide the most uniform currentdissipation.

In all cases where anodes are installed the preferred method shall be by boltedfixing.


Internal coating of seawater intake piping shall comply with the referenced projectspecification.

Field joint coating shall be carried out with a system compatible with the parentcoating. Where flanged pipe joints are used coating of the flange faces is required.


Generally electrical isolation by means of flange insulation kits and monolithic

isolation joints shall be avoided. However where it is required to limit currentdistribution due consideration shall be given to limiting current leakage through theelectrolytic path by ensuring correct selection of the non metallic components of theisolation devices.

6.3.3 Monitoring

As the pipeline and piping are sealed systems when operating it shall not bepossible to monitor the cathodic protection systems in operation. However the primecorrosion control method in each case shall be the high integrity coating systemsupplemented by sacrificial anodes. The anodes shall be installed to polarise anybare steel which may be exposed at coating holidays, or which may develop inservice, and shall provide allowance for any increase in coating conductivity which

may occur over the system life. Potential monitoring shall therefore not be providedand system serviceability checks shall be confined to observation of anodedepletion rates made during shutdowns, or by designing the system such that theanodes are retrievable and replaceable in service.

7.0 AT GRADE STORAGE TANKS

7.1 External Surfaces

The external surfaces of the bases of at grade storage tanks where constructed ona ring beam are required to be cathodically protected. To improve currentdistribution and to decrease current demand the underside of tank plates (carbonsteel only) shall be coated before laying. This shall be achieved using a coal tarepoxy coating material applied directly over a prepared substrate without primer, asdetailed in the project coating specification.

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Cathodic protection system design for the external coated surfaces of at gradestorage tanks bases shall be by impressed current cathodic protection. Where tanksare constructed on concrete foundations or where thermally insulated cathodicprotection shall not be considered.

The actual nature and anode distribution of the impressed current systems shall beaddressed at time of detailed design but shall be a closely distributed MMO wiresanode, mesh or grid system constructed within the tank foundation and sittingdirectly beneath the tank floor plates.

Detailed design shall be in accordance with the relevant codes and standards andshall take recognition of service conditions likely to be encountered. Currentdensities shall be selected to produce the required potential shifts and anodespositioned to provide the best distribution of protection current.


Electrical isolation by means of flange insulation kits and monolithic isolation jointsat above ground storage tanks shall be avoided. This approach shall limit the risk ofoverall system interaction and the potential for sparking across flanged joints duringmaintenance operations.

7.1.3 Effect on Steel and Electrical Grounding Material (uninsulated copper or steel)

The effect of cathodic protection on the corrosion rates of steel within concretefoundations and other structures shall be considered and allowances made forcurrent losses as appropriate. Generally in the case of refinery and other congestedplant situations it is advantageous to use uncoated reinforcing steel so thatinteraction between individual sections is kept to a minimum. Depending upon theanode type and distribution used the reinforcing steel and electrical grounding maybe made deliberately continuous with the tank to ensure interaction and acceleratedcorrosion of either one is avoided. Details showing ringbeam reinforcement barcontinuity bonding with the tank shell shall be shown on Civils foundation drawingsas appropriate.

7.1.4 Monitoring

Monitoring of the effectiveness of the cathodic protection systems shall be bypotential measurement using permanent reference electrodes installed atconstruction beneath the tank floor. Electrodes shall be placed as close as possibleto the tank floor to remove as much of the volt drop in the path as is possible.Numbers and distribution of electrodes shall be detailed on individual tankfoundation drawings 3210-8310-SP-0008.

Further monitoring facilities shall be provided at the tank periphery in the form of testcell access tubes penetrating the tank foundation. These access points shall beused in conjunction with portable monitoring equipment.


The value of protection potential for steel used shall be -0.85 volts, or morenegative, measured in the IR free condition. This value is the lower limit for steel in

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aerobic soils and should be shifted a further 100mv in the negative direction ifanaerobic conditions are known to exist.

Excess overprotection should not be allowed to occur. The most negative valuepermissible shall be taken as -1.2 volts instantaneous off. However due to thecomplicated nature of the finished plant, and the influence on potential levelscreated by the combination of materials found in plant and refinery locations, someflexibility in the figures given shall be required.

The 100mv polarisation decay test method may also be used to determine thatadequate protection has been achieved.


7.2 Internal Surfaces

Where storage tanks contain corrosive (untreated) water or potable water, or wherewater ingress is anticipated (e.g. floating roof tanks) they shall be protected bymeans of coatings and cathodic protection. Operating temperatures and conductivityof waters contained within each tank shall be addressed on a case by case basisduring detailed design and coatings and cathodic protection current densitiesaddressed accordingly.

Temporary sacrificial protection for tanks shall also be provided for tankage during

hydrotest, (where tanks may contain raw water for prolonged periods).


All tankage shall be internally lined where a water phase is expected as detailed inthe referenced project coating specification. The extent of the coated area shall bedetailed in the tank data sheets.

7.4 Cathodic Protection

Cathodic protection systems designed for the internal wetted surfaces of tankageshall be of the manually controlled impressed current type for water storage tanks

and the sacrificial type utilising Aluminium-Indium-Zinc alloy anodes (bismuthcontaining alloys shall not be considered) for floating roof tanks. Anode typeselection and distribution shall be shall be made at detailed design stage inaccordance with the relevant codes and standards with recognition of the serviceconditions and coating types. Current densities shall be selected to produce therequired potential shifts and anode distribution considered to provide the mostuniform current dissipation.

Temporary sacrificial protection shall also be provided (where tanks shall containraw, or seawater for prolonged periods during hydrotest).

In all cases where sacrificial anodes are installed the preferred method shall bebolted fixing.

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7.5 Monitoring

Monitoring of the effectiveness of the cathodic protection systems installed instorage tanks which are water filled shall be by potential shift. The Systems shall bemanually controlled and monitored using low ion sealed Ag/AgCl referenceelectrodes.

Where sacrificial anodes are to be designed for internal protection of hydrocarbonproduct storage tanks containing a water phase no monitoring shall be provided.

8.0 BURIED STORAGE TANKS/VESSELS

8.1 External Surfaces

The external surfaces of buried storage tanks/vessels shall be coated or wrappedand cathodically protected.


The external surfaces of all buried storage tanks shall be coated with either a coaltar epoxy system or primed and tape wrapped using a cold applied mastic backedtape, unless elevated temperature service properties are specified.

8.3 Cathodic Protection

Cathodic protection system design for the external coated surfaces of buriedstorage tanks/vessels shall be means of impressed current close distributed anodesystems. Anode distribution shall be addressed at time of detailed design. Detaileddesign shall be in accordance with the relevant codes and standards and shall takerecognition of the service conditions likely to be encountered. Current densitiesshall be selected to produce the required potential shifts and anodes positioned toprovide the best distribution of protection current.


Electrical isolation by means of or monolithic isolation joints may be considered sothat each buried tank has a robust system of cathodic protection.

Electrically driven pumps associated with buried tanks mean that there is apossibility of electrical connection to local or networked grounding systems. In suchsituations installation of solid state DCl. blocking devices (solid state polarisationcells) may be considered to prevent cathodic protection current loss and early orpremature depletion of anode material. Use of solid state DCl. blocking devices shallonly be appropriate where motor is mounted above ground and is isolatedelectrically from the ground (e.g. MOVs).

Where motor and pump are directly mounted on ground, conventional solid earthingshall be used and DCl. blocking devices need not to be provided.

8.3.2 Monitoring

Monitoring of the effectiveness of the cathodic protection systems shall be bypotential measurement using permanent reference electrodes installed at time ofconstruction at selected locations. Electrodes shall be placed as close as possible tothe buried vessel to remove as much of the volt drop in the soil path as is possible.

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Numbers and distribution of electrodes shall be dependent upon tank size andproduct temperature and shall be fully defined during detailed design.

Further monitoring facilities shall be provided at the surface directly above the tankto allow the use of portable equipment.


The value of protection potential for steel used shall be -0.85 volts, or morenegative, measured in the IR free condition. This value is the lower limit for steel inaerobic soils.

Excess overprotection should not be allowed to occur. The most negative valuepermissible shall be taken as -1.2 volts instantaneous off. However due to thecomplicated nature of the finished plant, and the influence on potential levelscreated by the combination of materials found in plant and refinery locations, someflexibility in the figures given may be required.

The 100mV polarisation decay test method may also be utilised to determine thatadequate protection potentials have been achieved.


8.4 Internal Surfaces

All tanks/vessels shall be internally lined where a water phase is expected asdetailed in the referenced project coating specification.

Maximum design temperatures and conductivity of waters contained within eachtank shall be addressed on a case by case basis during detailed design and coatingand cathodic protection current densities requirements addressed accordingly.


All tankage shall be internally lined where a water phase is expected to be presentwith one of the systems detailed in the referenced project coating specification.


Cathodic protection systems designed for the internal wetted surfaces of buriedtankage shall be of the sacrificial type utilising aluminium indium zinc alloy anodes(bismuth containing alloys shall not be considered). Anode types and distributionshall be shall be made at detailed design stage in accordance with the relevantcodes and standards with recognition of the service conditions and coating types.Current densities shall be selected to produce the required potential shifts andanode distribution considered to provide the most uniform current dissipation.

In all cases where sacrificial anodes are installed the preferred method shall be bybolted fixing.

8.4.3 Monitoring

Monitoring of the effectiveness of the impressed current cathodic protection systemsshall by potential shift. However the choice of permanent or portable systems ofpotential monitoring shall be made during detailed design based on product type,water conductivity, chloride content, temperature and intended use.

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Where sacrificial anodes are to be designed for internal protection of hydro-carbonproduct buried storage tanks containing a water phase no monitoring shall beprovided. However all systems shall be designed for a minimum life commensuratewith inspection and maintenance schedules.

9.0 SITE CONDITIONS

To establish the soil corrosivity and its suitability for the construction of systems ofcathodic protection a soil and geotechnical survey to determine its resistivity shall berequired.

A review and audit of existing cathodic protection facilities shall also be carried outto establish functionality or otherwise of existing systems.

Additionally the conductivity and make up of waters to be contained within alltankage shall also be required for design purposes. The water make up datarequired should as a minimum should contain T.D.S., Conductivity, pH and chloridecontent. Both these subjects shall be addressed during the detailed design phase.

10.0 TECHNICAL CONSIDERATIONS

The cathodic protection system is to be designed to deliver and distribute sufficient

current to every point on the structures required to be protected such that the criteriafor protection are substantially and adequately fulfilled and the system meets thespecified design life.

The cathodic protection systems shall be of sufficient magnitude and capacity toguarantee the delivery to every point, of a minimum pipelines-to-soil potential valueof at least -0.850 volts measured between the pipelines and a copper/coppersulphate reference electrode (Cu/CuSO4) contacting the soil. Normally, this voltageshould be measured with the protective current applied This 0.850 V criterionincludes the voltage drop across the steel/soil interface.

It is the Contractors responsibility to survey/investigate whether existing cathodicprotection systems are in the same vicinity or not. In this case the Contractor is

requested to study the interferences effect from/on the new cathodic protectionsystems and clearly state it in a separate clause in his proposal and detailed designreport. Also, its the Contractors responsibility to investigate possible sources ofdetrimental DC stray current and include proposals in the design on how to mitigatethe effect of such stray current.

11.0 CONSTRUCTION FEATURES

11.1 Piping/Pipelines

All buried piping and pipelines shall be installed to a depth determined by others,subject to design consideration. At points where lines pass beneath foreign lines,

depth of burial shall be greater.

At road crossings the pipe shall be coated. Cathodic protection at road crossingsshall be supplemented with sacrificial packaged magnesium anodes. Depending on

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the size of the road crossing and the diameter of the pipe/pipes in questionmagnesium anode sacrificial CP systems shall be designed to protect these areas.

Where sleeved road crossings are used, the carrier pipe shall be insulated from thesleeve pipe. The insulators shall act to distribute the weight of the pipe in the sleevein a manner that shall ensure no over stressing and to prevent contact betweencarrier and sleeve.

11.2 Tanks

11.2.1 External

All at-grade storage tanks shall have dedicated CP systems.

All at grade tank base plates shall be coated on the external side with a projectapproved coal tar epoxy system before lay and welding. This shall result in areduced current collecting surface, providing a lower corrosion rate, decreasedcurrent demand from the CP system and improved current distribution over theexternal surface of the tank.

CP of the tank bases shall be achieved utilising an impressed current closedistributed anode system installed within the ring beam foundation.

The tanks shall be constructed on a sand foundation without the use of a bitumen orasphaltic layer. The tank foundation shall comprise of 500mm of sand backfill to

support the tank floor and a reinforced concrete ring beam to support the tank wall.For design purposes, the sand backfill resistivity has been taken as 500 m at startof life and 150 m at end of life. For cathodic protection, the anode system shall beplaced within the ring beam and permanent reference electrodes shall be installedwithin the foundation at a maximum distance from the tank floor of 300mm. Allanode supply cables shall exit through the ring beam in conduits and shall terminatein junction boxes fixed to the external surface of the ring beam. All junction boxes(except those for water tanks) shall be suitable for installation in a zone 1 area,temperature class T3, gas group IIB. To accommodate the anode power andreference electrode cables, four conduits through the ring beam are provided. Thelocation and quantities of reference electrodes shall be detailed on the tankfoundation drawings in the detailed design stage.

Further monitoring facilities shall be provided at the tank periphery in the form of testcell access tubes penetrating the tank foundation. These access points shall beused in conjunction with portable monitoring equipment.

In addition to the installation of permanent reference electrodes, and access points,further monitoring shall be facilitated by installation beneath the tank base of aslotted watering/access tube through which portable reference electrodes may bepassed in order to map the potential profile of the tank base.

Depending upon the rating of each CP system, single or multiple junction boxesshall be required. Reference electrode cables shall exit through the ring beam in thesame manner as the power supply cables. However, anode and reference cables

shall not share the same conduits.Cathode connections in hazardous locations shall be made directly to the tankswithin enhanced safety connection points. These connection points shall be pre-

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installed by the tank fabricator. In all cases where there is an external and internalimpressed current CP system, two connection points shall be installed, one each forexternal and internal systems. Where the diameter of any single tank is 50 metres orgreater two connection points shall be provided for the external system.

The enhanced safety connection point shall be detailed in the detailed design stage.

All cables shall be installed in accordance with Project Specifications and Drawingsfor the electrical installation of cables.

11.2.2 Internal

The impressed current CP Systems for protection of the internal surfaces of tanksshall be of the suspended anode type. Anodes shall be suspended from the roofand anchored at the floor to prevent anode movement during filling and emptying.The systems shall be manually controlled and monitored using low ion sealedAg/AgCl reference electrodes (minimum of two per tank). The internal surfaces ofthe water tanks shall be coated with an amine adduct cured epoxy coating system.In all cases the resistivity of the product shall be taken as 400 m .

The anode material for the internal ICCP systems shall be either mixed metal oxide,platinum coated titanium or platinized indium.

Sacrificial CP system required for tanks where a water phase may be expected shallcomprise of aluminium indium zinc alloy anodes fixed to the tank floor. The

quantities of anodes required per tank shall be calculated during the detailed designstage.

Where internal sacrificial CP systems are required on the tank floor, the tankfabricator shall fabricate and install up-stands (brackets) for the sacrificial anodes.These shall also be coated as a part of the tank floor and first shell course, afterhydrotesting. In order that the CP systems may work it is essential that the front andback faces of the up-stands are ground to bright metal before the anodes areinstalled.

11.3 Power Source

Transformer rectifiers shall comply with the requirements of the Standards listed in

section 3 of this document.The direct current power supply for the impressed current system shall be providedby T/Rs located within the plant. The voltage/current rating of transformer rectifiersshall be rationalised to reduce the number of different rectifiers sizes. The maximumrated voltage for all T/Rs shall be 50V. Where possible, T/Rs shall be located innon-hazardous areas.

11.4 Groundbed Design and Current Distribut ion

11.4.1 Piping/pipelines

Buried metallic piping shall be protected using an external coating system inconjunction with impressed current cathodic protection.

Cathodic protection shall be achieved by use of a close distributed anode system,placed locally to the pipe, utilising either discrete (e.g. canistered) or linear (e.g.

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wire) anodes. This system shall ensure that protective current can be applied incongested piping areas where shielding or lack of isolation may be a problem.

To ensure that a fully functional cathodic protection system is installed and thatshorting does not occur, electrical isolation shall not be applied. Electrical continuitybetween all buried items shall ensure that there are no locations where underprotection occurs. However, a fully bonded cathodic protection system shall result incurrent drain to earthing, rebar, foundations etc, which shall be considered atdetailed design.

The anode-to-pipe spacing and anode-to-anode spacing (for discrete anode

systems) shall depend primarily upon the pipe diameter, pipe coating and soilresistivity.

Dedicated transformer rectifier units shall be provided for buried piping systems,with each unit feeding multiple positive distribution boxes which marshal anodeheader cables.

Provision shall be made to control the individual anode circuit currents via resistorsinstalled within the positive distribution boxes. Wherever possible, positivedistribution boxes shall be sited adjacent to transformer rectifiers in non-hazardousareas.

All cables outside the anode trench shall run on cable racks. If any cables are

required to be underground they shall be buried to a depth of least 1m and shall berun in PVC conduit with electrical warning tape in the ditch above the conduit. Aboveground concrete cable markers shall be installed every 30m and at each change ofdirection.

Test facilities shall be installed at selected locations along the buried piping in orderto allow routine testing of the performance of the installed system. Referenceelectrodes shall be installed at all test facilities. Reference electrodes shall be of theAg/AgCl type.

Temporary Protection shall be provided for buried metallic piping. Supplementarypackaged magnesium anodes shall be used at road crossings and valve pits. Zincshall meet the technical requirements of ASTM B418-80 Type II. All magnesium

alloy shall be of the high potential type. Anode alloys shall conform to an approvedchemical composition. All packaged anodes shall be surrounded with a lowresistivity chemical backfill of bentonite, gypsum and sodium sulphate the wholebeing contained within a cotton bag. Linear anodes shall be buried directly in soil.

Where more than two discrete anodes are installed as a group, individual anodeleads shall be connected to a header cable with the use of a resin encapsulatedsplice kit.

Cable connections to the pipe shall be thermic welded or attached by means ofdrawn arc pin brazing methods in accordance with the relevant projectspecifications.

It should be noted that the quantities and locations of sacrificial anodes may bemodified during the installation in order to maximise the efficiency of the CP system.

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11.4.2 Tanks (Impressed Current Systems)

All tanks shall be installed with permanent reference electrodes to provide protectiondata during operation.

11.5 Cabling

Current carrying cables routed outside of pipe trenches/cable trays shall be buried ina narrow excavation in accordance with project electrical installation details.

The electrical current rating of a cable shall not be exceeded for the temperature ofuse. Cable cross-section and external extrusion coating shall be selected to suit the

condition of use at the Jamnagar site and electrical specifications and standards.

11.6 Electrical Connections

The cable and all connections, e.g. bolted, thermic welded, or pin brazed are critical.The studs used for cable connection shall be cut down to the nut after brazing orwelding, in order to facilitate the correct application of a coating repair system.Complete electrical isolation between the cable/splice/connection and theenvironment is essential, water ingress or soil contact must not occur. Cables shallbe installed in accordance with project drawings and specifications.

When pipe anti-corrosion coating is to be removed to facilitate electricalconnections, the coating shall be fully restored afterwards to an approved

procedure. All connection to pipe and structures shall be profiled and tape wrappedafter installation. All DC negative connections to piping/tank walls shall be madewith a crimped lug, which shall be attached to the tank wall via a bolted connection.

11.7 Test Points

11.7.1 Piping

The piping cathodic protection systems are intended to enhance the corrosionprotection provided by the piping coating. The installation of monitoring facilities isrequired at maximum 100m intervals along each piping run. Where hard standing isencountered, monitoring tubes shall be installed for portable reference electrodeaccess.

12.0 INSTALLATION

12.1 Sacrificial Anodes

Packaged magnesium anodes must not be installed by suspending them by theircable tails. A system shall be employed such that the anodes shall be placedwithout strain being placed on the anode/cable connection.

Pre-packaged magnesium anodes and linear anodes shall be installed as per typicalinstallation drawings given in the detailed design stage. All cable connections shallbe thermic welded or pin brazed, and the joint area shall be profiled and tapewrapped in accordance with project specifications.

12.2 Anode Cabling

All Anode Cabling shall be 100% holiday free when checked with a holiday detectorset at 7,500 volts DC. Cables that do not meet the dielectric test shall be rejected.

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All cabling shall be installed in cable trays above grade or in trenches and markedwith cable markers.

12.3 Power Source (Transformer Rectifiers)

Transformer rectifiers, shall be installed on a concrete plinth in accordance with therelevant standards listed in section 3.

Installation of all T/Rs shall be carried out by an approved corrosion engineeringContractor.

12.4 External Impressed Current System for At Grade Storage Tanks

External impressed current systems shall be located directly under the tank plateand within the foundation. All anode materials shall be within the Vendors specifieddimensions and shall be inspected for defects prior to sand filling.

All electrical connections shall be inspected after installation.

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