Corrosion Training Design Part 11

Corrosion TrainingCP Designed Part 1Galvanic Anodes (current requirement testing), Insulators, Test stations, Coatings

Learning Over ViewPart One Current requirement designGalvanic anode designInsulatorsCoatingsTest stationsCouponsPart Two Rectified Systems, Solar panelsPart Three AC Design

Objective of ClassUnderstanding of design for COH and CKY with Corrosion Anodes (Galvanic) Insulators (types)Coatings (types)Test stationsIR Coupons

Galvanic Anodes Types?Magnesium anodes are used for galvanic anodes in our system17lb anode - remediation of WT pipelines17lb anode - new steel coated pipe9lb anode - bare main or service3lb anode - bare customer service1.5lb drive in anode company or customer metallic coated risers1.0lb zinc serv-a-node

Galvanic Anodes When?Any time a metallic pipeline is exposed and the surface of the pipeline is disturbed and the pipe to soil readings are below -1.000 V CSE.Any time corrosion technician has indicated on corrosion recommendationsCP mains reading below -.850 V CSE on a 2512 J.O. (annual monitoring)Cost and application evaluation performed for comparison of anodes vs. solar vs. rectified systems

Galvanic Anodes Connected?Thermite welded to the pipelineThermite welds shall be 4 apart from each otherThermite welds shall be 6 away from an adjacent weldAt any test station locations, connected by mechanical means by junction of the test station terminal

Galvanic Anodes Design?Current Requirement test Soil resistivity testDetermine the output of a 17lb HP anodeNumber of anodes = Icp/Ia Sunde theory

Galvanic Anode Design (new Coated Steel Main) Surface Area of pipelineDiameterLengthCoating EffectivenessCurrent DensitySoil Resistivity

New Steel Pipe Calculations Number of anodesFor an example First calculate the total surface area of 6 WT MP pipe at a length of 12,000 feet?Use the formula Total surface area = Diameter x Length x

New Steel Pipe Calculations Number of anodesFor an example First calculate the total surface area of 6 WT MP pipe at a length of 12,000 feet?

RLengthArea 3.14 (6.625) = 1.735 12,000 = 20,820 sq ft12Need to divide the diameter by 12 to convert to feetKeep in mind, a 6 inch diameter pipe is truly 6.625 inches

New Steel Pipe Calculations Number of anodesNext Calculate the total coating effectivenessThe coating effectiveness will decide the total bare area that the CP current will be neededKeep in mind, the CP current protects only the holiday areas of the pipelineCalculate Coating Effectiveness %99.5 % - Great98.5% to 99.5% - Good95% - FairLess than 95% - Poor

New Steel Pipe Calculations Number of anodesNext Calculate the total coating effectivenessThe coating effectiveness will decide the total bare area that the CP current will be neededKeep in mind, the CP current protects only the holiday areas of the pipelineCalculate Coating Effectiveness %99.5 % - Great (Columbias Standard used)98.5% to 99.5% - Good95% - FairLess than 95% - Poor

New Steel Pipe Calculations Number of anodesWhat is the total surface area?

New Steel Pipe Calculations Number of anodesWhat is the total surface area?20,820 sq ftWhat is the total bare area of the pipeline?

New Steel Pipe Calculations Number of anodesWhat is the total surface area?20,820 sq ftWhat is the total bare area of the pipeline?104.1 sq ft

New Steel Pipe Calculations Number of anodesNext calculate the total amount of current requirement for CP of the pipelineTotal bare area x current density = ICPWhat is the bare area?104.1 sqftWhat is the current density?

New Steel Pipe Calculations Number of anodesCurrent DensityIs considered the square of the pipeline in which will conduct currentNormally in the range 1 to 3 mASandy or Dry soil 3 mASemi-dry soil 2 mAWet soil 1 mAFor current requirement calculations, we use a higher number for higher soil resistivity for the purpose of designing a higher amount of current requirement.

New Steel Pipe Calculations Number of anodesNext calculate the total amount of current requirement for CP of the pipelineTotal bare area x current density = ICP104.1 x 1mA = 104.1 mAs

Current densityBare Area of pipelineTotal amount of current requirementWhat if the soil was very sandy and normally dry?

New Steel Pipe Calculations Number of anodesNext calculate the total amount of current requirement for CP of the pipelineTotal bare area x current density = ICP104.1 x 3mA = 312.3 mAs

Current densityBare Area of pipelineTotal amount of current requirementChange current density to a higher number, such as 3 mAs

New Steel Pipe Calculations Number of anodesNumber of anodes = Icp/Ia What is the total requirement for wet soil?Based on our calculations = 104.1 mAsHow many anodes needed?Have to calculate anode output next???

120,000 f y

New Steel Pipe Calculations Number of anodes120,000 1 1.216,500 ohms cm= 22.3 mAThe top three numbers are given based anode design, such as shape and weight of anode. Input the soil resistivity to the bottom of the equation Anode output is calculated

New Steel Pipe Calculations Number of anodesNow with the anode output and the total amount of current requirement is calculated, What is the total amount of anodes needed, if we decide to bank the anodes 10 feet apart?Number of anodes = Icp/Ia104.1 mA / 22.3 mA = 4.6 (round to highest number = 5 anodes)5 anodes Correct or not??????????

Need more anodes Not the correct design

Sunde TheoryUsed for banking anodes5 anodes at 10ft apart = 4.19 anodes10 FT spacing5 anodes

Single Anode Current

Reduction Factors (C)

# of Anodes in

Concentrated Bed

Anode spacing

5 Feet

10 Feet

15 Feet

20 Feet

2

1.84

1.92

1.95

1.96

3

2.45

2.70

2.79

2.85

4

3.04

3.45

3.62

3.71

5

3.59

4.19

4.43

4.56

6

4.12

4.90

5.22

5.41

7

4.65

5.60

6.00

6.22

8

5.15

6.28

6.77

7.04

9

5.67

6.96

7.54

7.87

10

6.16

7.64

8.38

8.68

Sunde Theory Calculation 5 anodes to be banked at 15 feet spacing. 4.43 22.3mA = 98.8 mA The current requirement was at 104mA therefore 5 anodes would not be enough. 6 anodes to be banked at 15 feet spacing. 5.22 22.3mA = 116.4mA The current requirement was at 104mA therefore 6 anodes would have enough output to meet cathodic protection.

New Steel Pipe Calculations Number of anodesSummary6 WT Pipe @ 12,000 length =5 anodes, if distributed along the line6 anodes, if banked at 10 feet apartSoil resistivity of 6500 ohms cmCurrent density of 1 mACoating effectiveness of 99.5%

Test StationsAbove GroundCottLarge FinkSmall FinkGeromeTri-view flexB-TCurb box type COH and CKY Recommended use is the Tri-view flex for above ground useGerome box for any continuity or interference bonds

Test StationsTwo wires No. 12 BlackNew Carrier pipeTwo wires No. 12 White Old/bareCasing

Test StationsInterference test station (bond)Two No. 8 wires (1-Company & 1-Foreign)Two No. 12 wires black (company)Two No. 12 wires white (foreign)

Test Station - Spacing'sBusiness 750 Feet Residential 1500 FeetRural 6000 FeetP/P - 653-3

CoatingsCoatings are our first line of defense against corrosion.Coatings are a high resistance barrier between the metallic structure and the surrounding electrolyte.A quality dielectric coating material can reduce costs in additional corrosion control materials such as sacrificial anodes or impressed current type cathodic protection systems.

CoatingsCathodic protection system design is based upon protecting the bare surface area of the buried/submerged metallic structure.Typically a well coated pipeline will be protected over 90% of its surface.In this case, only 10% of the pipeline surface will require cathodic protection current.

CoatingsAs an example:100 feet of 12 diameter pipe has 314 ft2 of surface area.A vertically installed 17# high potential magnesium anode in 5000 -cm soil has a current output of 30 mA.A design current density of 2 mA/ft2 results in a current requirement for the pipe of 628 mA. With 30 mA per anode, 21 anodes are required.However, if the pipe is 90% coated, then only 10% or 31.4 ft2 is bare.At 2 mA/ft2 the current requirement is 62.8 mA.With 30 mA per anode, only 3 anodes are required!This shows the importance of having a quality coating.

CoatingsHoliday Testing (Jeeping)Test process which the operator can identify holidays (imperfections) in the coatingInvolves a high voltage power sourceInstruments can be adjusted to apply the proper voltage across the coatingDifferent thickness of coating requires different settingsElectrode is passed over the coating surfaceIf the coating resistance is low or a holiday is present, an audio signal is heard due to an electrical discharge from the electrode onto the pipe surfaceRepair of the coating is made

Coatings Jeep SettingsPowercreteFusion Bonded EpoxyExtruded

Jeeping Calculation

Reference

Nace RPO274-98 = Extruded coating

Nace RPO490-95 = Epoxy coating

Powercrete Manual

Formula for calculating the voltage setting

Extruded and Coal Tar

8.5440037453

73Coating Thickness in mil's *

10680Volts

Coatings Voltage Chart

Extruded

Formula for calculating the voltage settingThicknessVoltage

FBE Coating

6.324555320310mils3953

20mils5590

40Coating Thickness in mil's *30mils6847

40mils7906

50mils8839

3320Volts60mils9682

70mils10458

Powercrete

ThicknessVoltage

45mils5625

75mils9375

Epoxy


Powercrete Coating

10mils1650


30mils2876

6250Volts40mils3320

50mils3712

* - enter coating mil thickness to calculate V

Coating Application

Bridge Crossing

TypeThicknessJoints

Powercrete Coating40-45 milProtal 7200

Directional Boring ApplicationNote : On the Joints, maintain same thickness as the pipe for jeeping purpose. On the X-tech 2 coating, double layer any tape to achieve the 60 mil coating thickness. If color tap is used then apply the poly wrap for extra protection.

TypeThicknessJoints


Tuff Coat - Lillycad40-45 milProtal 7200

Direct Buried Application

TypeThicknessJoints

Extruded - Polyethylene - x-tech 260 milColor tape - Petrolatum/ Polyken 936

Tapecoat H35

Note : Powercrete has been found to crack under stress of bending for directional boring application. We should atempted to use Tuff coat as much as possible but powercrete is an approved method.

Sheet3

MBD000271FE.bin

MBD0002CC4D.bin

MBD000255B9.bin

Coatings Jeep SettingsSome common Jeep voltage settings for common coatings

Jeeping Calculation

Reference



Powercrete Manual



8.5440037453


10680Volts


Extruded


FBE Coating

6.324555320310mils3953

20mils5590


40mils7906

50mils8839

3320Volts60mils9682

70mils10458

Powercrete

ThicknessVoltage

45mils5625

75mils9375

Epoxy


Powercrete Coating

10mils1650


30mils2876

6250Volts40mils3320

50mils3712


Coating Application

Bridge Crossing

TypeThicknessJoints



TypeThicknessJoints




TypeThicknessJoints


Tapecoat H35


Sheet3

MBD000271FE.bin

MBD0002CC4D.bin

MBD000255B9.bin

Jeeping Calculation

Reference



Powercrete Manual



8.5440037453


10680Volts


Extruded


FBE Coating

6.324555320310mils3953

20mils5590


40mils7906

50mils8839

3320Volts60mils9682

70mils10458

Powercrete

ThicknessVoltage

45mils5625

75mils9375

Epoxy


Powercrete Coating

10mils1650


30mils2876

6250Volts40mils3320

50mils3712


Coating Application

Bridge Crossing

TypeThicknessJoints



TypeThicknessJoints




TypeThicknessJoints


Tapecoat H35


Sheet3

MBD000271FE.bin

MBD0002CC4D.bin

MBD000255B9.bin

Jeeping Calculation

Reference



Powercrete Manual



8.5440037453


10680Volts


Extruded


FBE Coating

6.324555320310mils3953

20mils5590


40mils7906

50mils8839

3320Volts60mils9682

70mils10458

Powercrete

ThicknessVoltage

45mils5625

75mils9375

Epoxy


Powercrete Coating

10mils1650


30mils2876

6250Volts40mils3320

50mils3712


Coating Application

Bridge Crossing

TypeThicknessJoints



TypeThicknessJoints




TypeThicknessJoints


Tapecoat H35


Sheet3

MBD000271FE.bin

MBD0002CC4D.bin

MBD000255B9.bin

Coatings Jeep settingsYou maybe asked to QA or verify the coating thickness base on the jeep processCheck the coating thickness DFTCheck the voltage setting of the JeepVerify, the contractor or crew is creating a holiday to verify the setting

Coatings Jeep Process

CoatingsThree common types mostly used in the gas industryExtruded Fusion bonded epoxy (FBE)Powercrete

CoatingsExtruded High density polyethylene Can be supplied in different thickness up to 60 milsAsphalt or rubber butyl adhesiveNormal thickness is in the range of 10 to 15 milsUsed primarily for direct bury applicationGirth welds normally coated with cold-applied tapes

Coatings - Extruded

Coatings - ExtrudedDirect Bury - X-Tech II COH & CKY practice for direct bury design, 1st choice70 mill applicationTwo layers of 30 mills of polyethylene coating10 mills of butyl rubber mastic

Coatings - ExtrudedDesign for AC and/or DC interference currentsUse only Extruded X-TECH II coating systems

Coatings - FBEFusion Bonded EpoxySurface preparation includes sand blastingTo clean the surface and form anchor patterns for the coating to adhere or bond to the pipe surfaceSurface is acid washed to remove salt depositsSurface is washed with dionized waterPipe surface is heated to 500 degrees or hotterEpoxy powders are electro statically charged and sprayed onto the hot surface The powders melt to a liquid form and fuse to the pipe surface forming a hard shellThe applied coating normally cures within 90 seconds and then is blasted with cool water in order to facilitate handling

Coatings - FBEFBE12 15 mills of FBE first layer20 mills of FBE second layerTotal of 32 to 35 mills coatingCOH & CKY practice only use dual coats, never single layer systems, 2nd choice for direct bury

Coatings Powercrete Epoxy base Polymer ConcreteThe pipe is coated with an FBE normally with a thickness of 12 to 15 milsThe FBE is then coated with the polymer concrete coating (Powercrete) 20 mills

Coatings - PowercreteCan be applied in the fieldEach pass applies approx. 20 mils thicknessMax 125 milsPerfect for directional boringCOH and CKY recommendation for directional boring designUse for above ground design with a polyurethane outer coat

Coatings - PowercreteCOH & CKY practice a minimum of 50 mils for above ground applicationCOH & CKY practice a minimum of 50 mils for directional boring applicationCOH & CKY practice a minimum of 70 mils for rocky directional boring applications

Coatings Girth WeldsGirth WeldsFBE and Powercrete coating applicationsCOH & CKY practice two part liquid epoxy systemProtal 7200 temps at or above 50 degreesProtal 7125 temps below 50 degreesR95 temps at or above 50 degrees back up coating Surface will need to be sand blasted to a Nace 1 anchor patternThe two parts are mixedEpoxy resinEpoxy hardenerCoat the surface of the girth weld according to manufactures recommended wet film thicknessUse the same material on the holiday areas as well

Coatings Girth WeldsGirth WeldsExtruded Coatings X-Tech IIAcceptable methods Polyken 936Tape coat H35Petrolatum Tape Utility tape (PVC) on new steel applications to be usedS105 paste recommended, especially in cold climates

Coatings Thermite weldsNo mastic..Preference especially for vacuum systemsAcceptable methods Petrolatum productsProfile mastic petrolatum Denso product (bird seed)Top coat with the Denso Color Tape petrolatum Denso productProtal 7200 cartridge Mix product on cardboardDip brush and paint onto surfaceCover with Trenton wax paper to prevent any damage due to debri of dirtTrenton patch kits (watch cost higher dollar)

Coatings Transmission and/or Directional boring ApplicationsCorrosion FLL shall be contactedCorrosion department will inspect the pipeline at the coating Mill using the recommended Hold points

Coatings - Rock shieldIn a rocky back filled situation, one should apply an outer protected shield for your pipeline coatings.Note: On CP systems, use the mesh rock shield only.. As to not cause cathodic shielding with the solids

Insulators - TypesKero-Test Monolithic Weld-inBangs Flanged Weld-inDresser bolted couplingCompressionUnionsFlanges

Insulators When?Tying new pipe to old pipe (coated)Tying coated pipe to bare pipeDomestic, large volume and GM settingsSeparate house lines from company linesCasing from carrier pipePipe from supportsBridgesM&R settingsBreak a large circuit to smaller units for easier troubleshooting and managementSeparate shorts with foreign linesRiver crossings

Insulators - Tying new and old existing Coated PipelinesRecommended for use in galvanic systems due to limited driving potential of the magnesium anodesCost comparisonEvaluate the cost for an insulator to be installedFor example, if one insulator to separate a 100 section of new coated metallic pipe from an existing CP coated metallic anode system (older), will cost in the range 4,800.00 x 2 = 9,600.00; then it may not be cost effective to make this recommendation.Purpose to prevent a galvanic cell to be created due to the potential difference with the new coated pipeline and the old coated systemsFor an example, the new coated system can have a high negative potential in reference to the old coated bare main.

Insulators - Tying new and old existing Coated PipelinesTest station installed at locationTwo black wires - #12 (New)Two white wires - #12 (old)Two no. 8 wires One wire connected to the NewOne wire connected to the oldBond in the test station box, if rectified systemIf anode system and want to cathodically protect as a single circuit

Insulators - Tying new and old existing Coated PipelinesIf not bonded in the test station box, then create two facilities on WMS and two test point sheets

Insulators - Tying new and old existing Coated PipelinesRecommended spacing's of insulatorsBusiness 1500 feetResidential 3000 feetRural 12000 feet

Insulators - Tying to Bare PipeAll coated systems tying to bare systems are to be insulated offTest station installed at locationVerification to be made on annual monitoringTrouble shooting purposeTwo white wires on the bare pipeTwo black wires on the coated pipe

Insulator Weld - InMonolithic weld end insulators are an excellent choice for high pressure systems where pull out may be an issue with other insulated coupling devices.No field assembly required or bolts,washers or sleeves that could cause an electrical short.COH & CKY practice always use weld-in insulators and only the Zunt monolithic for buried pipelines

Insulators - Meter settings - TypesInsulated valvesInsulated UnionsInsulated Meter barsInsulated SwivelsInsulated FlangesDesign purpose Domestic size metersInsulated ValvesLarge volume, or GMB accountsInsulated Unions Insulated flanges

Insulators M&R StationInsulated in a structureMust have a zinc grounding cell installed (DOT and procedure requirement)Insulated at flange @ outlet of valvesOutlet valveIf need to replace flange insulators, on lower pressure endBypass valveAll control lines need to have insulated unions

Insulators M&R StationA high dielectric strength material is used fiber glass or a plastic material to prevent a metallic connection between the two flange faces.The bolt acts as a bypass if not insulated properly.

Insulator Casing and Carrier PipeCasing isolation two primary functionsPrevent an electrolyte from entering the casing and creating a galvanic corrosion cell.Prevent metallic contact between the carrier pipe and casing pipe.Casing isolation may remove up to two of the four parts of a corrosion cell.

Insulators Casing & Carrier PipeCasing isolation Three primary tools usedCasing fillerHigh dielectric material (high resistance) to displace the electrolyte within the casingCasing spacersInsulating material to prevent metallic contact between the casing pipe and the carrier pipeCasing sealsPhysical seal used to seal the ends of the casing in order to prevent an electrolyte from entering the casing

Insulator Casing & Carrier Pipe Casing FillingPetrolatum based material that has a high dielectric strength.Displaces the surrounding electrolyte in the casing around the carrier pipe.Prevents water from entering the casing and displaces the existing water.Environmentally safe non-hazardous.

Insulator Casing & Carrier Pipe Casing FillingPictures -Courtesy of Trenton co.Casing filler can be installed hot or cold.There is treatment for casings already filled with water.

Insulator Casing & Carrier Pipe - SpacersSpacers are made from a dielectric material, hard polymer (plastic). A spacers primary function is to prevent the metallic contact between the casing pipe and the carrier pipe.

Insulators Casing and Carrier Pipe Link Seals & Rubber bootsSeals the ends of the casing around the carrier pipe.Keeps the casing filler inside the casing.Prevents water or other elements from entering the casing and creating a galvanic cell.

Pipe SupportsCoated metallic pipe shall be isolated from any bridge structureFiber boardGlass mesh insulated bridge supports

Pipe SupportsCoated metallic pipelines shall be insulated from any supports at M&R settingsExisting pipe may need to be lifted off the support area to be insulated properly

Insulator FRPsFRPs Fiberglass Reinforced Plastic

Insulator FRPsPrimary function of FRPsTo prevent an electrical connection between the structure intended for cathodic protection and foreign metallic structures.Separates the anode from the cathode by electrically isolating the two structures.Reduces the required amount of corrosion materials to be used.

Insulator FRPsThere are a variety of types of FRPs.Flat FRPs are a practical way of physically separating two buried structures especially in an excavation situation.

Insulator FRPsSome FRPs are attached to the structure with an epoxy adhesive sealant, this helps mitigate crevice corrosion from taking place between the FRP and the pipeline.Another type of installation involves applying a petrolatum tape material between the FRP and the pipeline to mitigate crevice corrosion.

Insulator FRPsFRPs are an excellent material to be used on bridge crossings or other aboveground pipe supports.Courtesy of Glass mesh

IR CouponsBenefits of using couponsObtain IR drop free potentials Especially on systems that the current source can not be interrupted.AC measurements such as AC current density calculations.Surface area = 1.34 in2Two no. 12 stranded wires.

IR CouponsThe coupon needs to be of the same material as the pipeline in order to represent it accurately.

IR CouponsNeed to have the coupon close to the pipeline (normally within 4 to 12, buried in the same native soil as the pipeline.

IR CouponsBest practice is to place the coupon about mid way of the pipeline on the side.

IR CouponsConnect the coupon in the test station by bonding to the pipeline. The coupon will receive the same cathodic protection current as the pipeline.

IR CouponsThe coupon represents a holiday area of the pipeline. The cathodic protection system (CP) protects the holiday areas of the pipeline, by bonding the coupon to the pipeline, the CP will polarize the coupon as well. We can remove the IR drop and find the true polarization on the pipeline by separating the connections and taking an instant-off structure-to-electrolyte potential measurement.

IR CouponsVBond or SwitchThe blue wires identify the lead wires used to electrically bond the coupon to the pipe.Connect the voltmeter to the non-current carrying lead wire from the coupon.Coated pipelineCouponTest Station

IR Coupon - MeasurementsCoupon measurements:Allow the coupon to polarize by electrically bonding the coupon to the structure in the test station.Disconnect or interrupt the coupon from the structure.Obtain structure-to-electrolyte potential measurements of the coupon, current applied and momentarily interrupted.The potential readings will be IR-drop free and will represent the pipelines IR-drop free potential readings.

Material SummaryTest stations Above ground Tri-view FlexGerome for multiple wire connections such as bondsAnodes Connected in the test station boxGet soil resistivity in designingUse anode calculation spread sheet 17lb CP remediation and new coated steel pipeline9lb Bare pipe leak repairs3lb customer service lines1.5lb drive in anodes isolated metallic coated risers

Material SummaryInsulatorsBelow ground Zunt Monolithic Weld-inAbove ground M&R flange insulated kitsInsulation made inside a building (M&R) Zinc grounding cell installedAlways place a test station at insulationAlways insulate casings and fill

Material SummaryCoatingsPowercrete 50 mil directional boringPowercrete 70 mil rocky directional boringPowercrete 50 mil bridge crossings and/or any exposures10 mils of polyurethane top coatFBE only use dual coat applications of 32 to 35 milsExtruded used primarily as direct bury applicationsUse for stray current surroundingsAC or DCAll coating applications transmission classInspected at the coating mill

Girth welds can be coated with a two part liquid epoxy, need to apply enough thickness to allow the jeeping to pass from the pipe surface pass the girth weld without adjusting the voltage setting.Girth welds can be coated with a two part liquid epoxy, need to apply enough thickness to allow the jeeping to pass from the pipe surface pass the girth weld without adjusting the voltage setting.This is not a coating but a impact aid for the coating to prevent chipping or damage from rocksFailure contributes are normally due to over heating the polymer material separating the two ends. The operator should be able to touch the center of the device with out being burnt during a welding operation. If the device at the center location is hot to touch, apply wet rags to cool. Recommend to test the insulator before installation and after, this may tell the reason why the insulator has failed, was it due to manufacture defect or the welding operation.Make a note, if using one insulated washer on the flange face, if the flange is going to be buried, you need to make sure the washer is on the correct side in order to protect the bolt and nut of the flange. The washer should be on the same side of the non protected side. You can order the insulating kits for existing above ground systems, for new or replacement flange insulators. Most times, you can replace one bolt at a time with an insulated sleeve and washer, and not separate the flanges to achieve isolation between the two; saves cost from rerouting gas flow or shutting down the system.The carrier pipe would become cathodically shielded by the casing. One needs to eliminate the electrolyte inside the casing to prevent the carrier pipe becoming anodic to the the casing, this will lead to corrosion over time then eventually leakage occurs.If you have a shorted casing that can not be removed, casing filler is a DOT option. You can cathodically protect the carrier pipe by supplying a non-corrosive environment inside the casing then you must protect both the carrier and the casing pipe together as a single unit.Hot casing filler - Pumped at 80 to 100 degrees, pumped directly into the casing by heated tankersCold casing filler pumped at 50 degrees, gel like, normally 55 gallon drums PRE-CON is a liquid casing water conditioner for pipeline casings. It consists of "wetting" and filming agents, vapor phase inhibitors, alkaline media additives and anti-bacterial conditioners

Separates the metallic contact between the casing and the carrier pipeYou need to seal the ends before pumping the casing filler into the casingFRPs are made of a fiberglass material, a high di-electric material, to prevent a conductive path between the anode and the cathode.If a connection between the two structures exist then any cathodic protection system applied to one structure will try to protect the other as well and require more current. The design of the system will change requiring more anodes or material.FRPs can be used above and below ground. The flat boards can be sized by cutting the board to the desire dimensions.Best practice apply a coating between the FRP and the pipeline, petrolatum tape works great in this application.You do not want the pipe to short out with the bridge or other metallic structures due to a corrosion cell will form.AC coupons will be covered in the AC interference class in the intermediate section later on.You dont want to shield the coupon or the coupon too close to the surface of the pipeline, at the same time, you want the same environment as the pipe as possible.Pictures illustrates the wire configuration of connecting the coupon and testing with a volt meter & copper-copper sulfate half cell. The bond can be a mechanical switch or a bonding bar that can be disconnected very quickly.Normally disconnection is made by some type of a switching device set up in the test station box. The coupon normally has two wires connected, one for the bond and the second wire for connecting the volt meter. When the switch is thrown to an open status, then the disconnection is made, the reading can be obtain instantly with the volt meter and half cell already connected to other connecting wire.

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Corrosion Training Design Part 11