corrosion training cp designed – part 1 galvanic anodes (current requirement testing), insulators,...

Corrosion Training

CP Designed – Part 1Galvanic Anodes (current requirement testing), Insulators, Test stations, Coatings

Learning Over View

Part One – Current requirement design Galvanic anode design Insulators Coatings Test stations Coupons

Part Two – Rectified Systems, Solar panels

Part Three – AC Design

Objective of Class

Understanding of design for COH and CKY with Corrosion Anodes (Galvanic) Insulators (types)Coatings (types)Test stations IR 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 recommendations

CP 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 test

Determine the output of a 17lb HP anodeNumber of anodes = Icp/Ia

Sunde theory

Galvanic Anode – Design (new Coated Steel Main)

Surface Area of pipelineDiameterLength

Coating EffectivenessCurrent DensitySoil Resistivity

New Steel Pipe Calculations – Number of anodes

For 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


For an example – First calculate the total surface area of 6”

WT MP pipe at a length of 12,000 feet?

R Length Area

3.14 • (6.625) = 1.735 • 12,000 = 20,820 sq ft12

Need to divide the diameter by 12” to convert to feet

Need to divide the diameter by 12” to convert to feet

Keep in mind, a 6 inch diameter pipe is truly 6.625 inchesKeep in mind, a 6 inch diameter pipe is truly 6.625 inches

Next Calculate the total coating effectiveness The coating effectiveness will decide the total

bare area that the CP current will be needed Keep in mind, the CP current protects only the

holiday areas of the pipeline Calculate Coating Effectiveness %

99.5 % - Great 98.5% to 99.5% - Good 95% - Fair Less than 95% - Poor


Next Calculate the total coating effectiveness The coating effectiveness will decide the total

bare area that the CP current will be needed Keep in mind, the CP current protects only the

holiday areas of the pipeline Calculate Coating Effectiveness %

99.5 % - Great (Columbia’s Standard used) 98.5% to 99.5% - Good 95% - Fair Less than 95% - Poor


What is the total surface area?


What is the total surface area?20,820 sq ft

What is the total bare area of the pipeline?


What is the total surface area?20,820 sq ft

What is the total bare area of the pipeline?104.1 sq ft


Next calculate the total amount of current requirement for CP of the pipeline

Total bare area x current density = ICP

What is the bare area?104.1 sqftWhat is the current density?



Current Density Is considered the square of the pipeline in which

will conduct current Normally in the range 1 to 3 mA

Sandy or Dry soil – 3 mA Semi-dry soil – 2 mA Wet soil – 1 mA

For current requirement calculations, we use a higher number for higher soil resistivity for the purpose of designing a higher amount of current requirement.



104.1 x 1mA = 104.1 mA’s


Current density

Current density

Bare Area of pipeline


Total amount of current requirement


What if the soil was very sandy and normally dry?



104.1 x 3mA = 312.3 mA’s


Current density

Current density





Change current density to a higher number, such as 3 mA’s

Change current density to a higher number, such as 3 mA’s

Number of anodes = Icp/Ia

What is the total requirement for wet soil?Based on our calculations = 104.1 mA’s

How many anodes needed?Have to calculate anode output next???


120,000 • f • y ρ


120,000 • 1 • 1.216,500 ohms cm = 22.3 mA

The top three numbers are given based anode design, such as shape and weight of anode.

The 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

Input the soil resistivity to the bottom of the equation

Anode output is calculated

Anode output is calculated

Now 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/Ia

104.1 mA / 22.3 mA = 4.6 (round to highest number = 5 anodes)

5 anodes Correct or not??????????


Need more anodes – Not the correct design

Single Anode CurrentReduction Factors (C)

# of Anodes inConcentrated 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

Used for banking anodes

Used for banking anodes

5 anodes at 10ft apart = 4.19 anodes

10 FT spacing

5 anodes

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.

Summary6” WT Pipe @ 12,000 length =

5 anodes, if distributed along the line6 anodes, if banked at 10 feet apart

Soil resistivity of 6500 ohms cmCurrent density of 1 mACoating effectiveness of 99.5%


Test Stations

Above Ground Cott

Large Fink Small Fink

Gerome Tri-view flex

B-T Curb box type

COH and CKY – Recommended use is the Tri-view flex for above ground use Gerome box for any continuity or interference

bonds

Test Stations

Two wires – No. 12 BlackNew Carrier pipe

Two wires – No. 12 White Old/bareCasing

Test Stations

Interference 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's

Business – 750 Feet Residential – 1500 FeetRural – 6000 FeetP/P - 653-3

Coatings 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.

Coatings

Cathodic 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.

Coatings

As an example: 100 feet of 12” diameter pipe has 314 ft2 of surface area. A vertically installed 17# high potential magnesium anode in

5000 Ω-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.

Coatings

Holiday Testing (Jeeping) Test process which the operator can identify

holidays (imperfections) in the coating Involves a high voltage power source

Instruments can be adjusted to apply the proper voltage across the coating

Different thickness’ of coating requires different settings Electrode is passed over the coating surface If 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 surface

Repair of the coating is made

Coatings

(525) T = V o lta ge

(1 2 5 )T = V o lta ge

(1250)T = V o lta ge

Powercrete

Fusion Bonded Epoxy

Extruded

ReferenceNace RPO274-98 = Extruded coatingNace RPO490-95 = Epoxy coatingPowercrete Manual

ReferenceNace RPO274-98 = Extruded coatingNace RPO490-95 = Epoxy coatingPowercrete Manual

Coatings – Jeep Settings

Extruded

Thickness

10mils20mils

30mils

40mils50mils

60mils

70mils

Voltage

8839

9682

10458

39535590

6847

7906

Epoxy

Thickness

10mils

20mils

30mils

40mils

50mils

1650

2348

2876

3320

3712

Voltage

Powercrete

Thickness

45mils75mils

Voltage

56259375

Some common Some common Jeep voltage Jeep voltage settings for settings for common coatingscommon coatings

Coatings – Jeep Settings

Coatings – Jeep settings

You 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

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

Coatings

Extruded High density polyethylene

Can be supplied in different thickness’ up to 60 mils

Asphalt or rubber butyl adhesiveNormal thickness is in the range of 10 to 15 mils

Used primarily for direct bury applicationGirth welds normally coated with cold-

applied tapes

Coatings

Coatings - Extruded

Coatings - Extruded

Direct 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 - Extruded

Design for AC and/or DC interference currentsUse only Extruded – X-TECH II coating

systems

Fusion Bonded Epoxy Surface preparation includes sand blasting

To clean the surface and form anchor patterns for the coating to adhere or bond to the pipe surface

Surface is acid washed to remove salt deposits Surface is washed with dionized water Pipe surface is heated to 500 degrees or hotter Epoxy 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 shell The applied coating normally cures within 90 seconds and

then is blasted with cool water in order to facilitate handling

Coatings - FBE

Coatings - FBE

FBE 12 – 15 mills of FBE first layer 20 mills of FBE second layer Total of 32 to 35 mills coating COH & CKY practice – only use dual coats, never

single layer systems, 2nd choice for direct bury

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 – Powercrete

Can be applied in the field Each pass applies approx.

20 mils thickness Max – 125 mils

Perfect for directional boring COH and CKY –

recommendation for directional boring design Use for above ground design

with a polyurethane outer coat

Coatings - Powercrete

COH & CKY practice – a minimum of 50 mils for above ground application

COH & CKY practice – a minimum of 50 mils for directional boring application

COH & CKY practice – a minimum of 70 mils for rocky directional boring applications

Coatings - Powercrete

Girth Welds FBE and Powercrete coating applications

COH & CKY practice – two part liquid epoxy system Protal 7200 – temp’s at or above 50 degrees Protal 7125 – temp’s below 50 degrees R95 – temp’s at or above 50 degrees – back up coating

Surface will need to be sand blasted to a Nace 1 anchor pattern

The two parts are mixed Epoxy resin Epoxy hardener

Coat the surface of the girth weld according to manufacture’s recommended wet film thickness

Use the same material on the holiday areas as well

Coatings – Girth Welds

Girth WeldsExtruded Coatings – X-Tech II

Acceptable methods – Polyken 936 Tape coat H35 Petrolatum Tape

Utility tape (PVC) on new steel applications to be used

S105 paste recommended, especially in cold climates

Coatings – Girth Welds

Coatings – Thermite welds

No mastic….. Preference – especially for vacuum

systems Acceptable methods –

Petrolatum products Profile mastic petrolatum – Denso product (bird seed) Top coat with the Denso Color Tape – petrolatum –

Denso product Protal 7200 cartridge

Mix product on cardboard Dip brush and paint onto surface Cover with Trenton wax paper to prevent any damage

due to debri of dirt Trenton patch kits (watch cost – higher dollar)

Coatings – Transmission and/or Directional boring Applications

Corrosion FLL shall be contactedCorrosion department will inspect the

pipeline at the coating Mill using the recommended “Hold points”

In a rocky back filled situation, one In a rocky back filled situation, one should apply an outer protected should apply an outer protected shield for your pipeline coatings.shield for your pipeline coatings.

Note: On CP systems, use the Note: On CP systems, use the mesh mesh rock shield only….. As to not cause rock shield only….. As to not cause cathodic shielding with the solidscathodic shielding with the solids

Coatings - Rock shield

Insulators - Types

Kero-Test Monolithic – Weld-inBangs – Flanged – Weld-inDresser bolted couplingCompressionUnionsFlanges

Insulators – When?

Tying new pipe to old pipe (coated) Tying coated pipe to bare pipe Domestic, large volume and GM settings

Separate house lines from company lines Casing from carrier pipe Pipe from supports

Bridges M&R settings

Break a large circuit to smaller units for easier troubleshooting and management

Separate shorts with foreign lines River crossings

Insulators - Tying new and old existing Coated Pipelines

Recommended for use in galvanic systems due to limited driving potential of the magnesium anodes

Cost comparison Evaluate the cost for an insulator to be installed For 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 systems For an example, the new coated system can have a high

negative potential in reference to the old coated bare main.


Test 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 old

Bond in the test station box, if rectified system If anode system and want to cathodically protect

as a single circuit


If not bonded in the test station box, then create two facilities on WMS and two test point sheets

Recommended spacing's of insulatorsBusiness – 1500 feetResidential – 3000 feetRural – 12000 feet


Insulators - Tying to Bare Pipe

All coated systems tying to bare systems are to be insulated off

Test station installed at locationVerification to be made on annual

monitoringTrouble shooting purposeTwo white wires on the bare pipeTwo black wires on the coated pipe

Monolithic weld end Monolithic weld end insulators are an insulators are an excellent choice for excellent choice for high pressure high pressure systems where pull systems where pull out may be an issue out may be an issue with other insulated with other insulated coupling devices.coupling devices.

No field assembly required or No field assembly required or bolts,washers or sleeves that bolts,washers or sleeves that could cause an electrical short.could cause an electrical short.

Insulator – Weld - In COH & CKY practice – always use weld-in insulators and only the Zunt monolithic for buried pipelines

COH & CKY practice – always use weld-in insulators and only the Zunt monolithic for buried pipelines

Insulators - Meter settings - Types

Insulated valves Insulated Unions Insulated Meter bars Insulated Swivels Insulated Flanges

Design purpose – Domestic size meters

Insulated Valves Large volume, or GMB accounts

Insulated Unions Insulated flanges

Insulators – M&R Station

Insulated in a structure Must have a zinc grounding cell installed (DOT and

procedure requirement)

Insulated at flange @ outlet of valves Outlet valve

If need to replace flange insulators, on lower pressure end

Bypass valve

All control lines need to have insulated unions

A high dielectric strength material is A high dielectric strength material is used – fiber glass or a plastic material to used – fiber glass or a plastic material to prevent a metallic connection between prevent a metallic connection between the two flange faces.the two flange faces.

The bolt acts The bolt acts as a bypass if as a bypass if not insulated not insulated properly.properly.

Insulators – M&R Station

Casing 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.

Insulator – Casing and Carrier Pipe

Casing isolation – Three primary tools used Casing filler

High dielectric material (high resistance) to displace the electrolyte within the casing

Casing spacers Insulating material to prevent metallic contact between the

casing pipe and the carrier pipe

Casing seals Physical seal used to seal the ends of the casing in order

to prevent an electrolyte from entering the casing

Insulators – Casing & Carrier Pipe

Petrolatum 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 Filling

Pictures -Courtesy of Trenton co.

Casing filler can be installed hot or cold.

Casing filler can be installed hot or cold.

There is treatment for casings already filled with water.

There is treatment for casings already filled with water.

Insulator – Casing & Carrier Pipe – Casing Filling

Spacers are made from a dielectric Spacers are made from a dielectric material, hard polymer (plastic).material, hard polymer (plastic). A A spacers primary function is to spacers primary function is to prevent the metallic contact prevent the metallic contact between the casing pipe and the between the casing pipe and the carrier pipe.carrier pipe.

Insulator – Casing & Carrier Pipe - Spacers

Seals 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.

Insulators – Casing and Carrier Pipe – Link Seals & Rubber boots

Pipe Supports

Coated metallic pipe shall be isolated from any bridge structureFiber boardGlass mesh – insulated bridge supports

Pipe Supports

Coated 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

FRP’s – Fiberglass Reinforced Plastic

Insulator – FRP’s

Primary function of FRP’sTo 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.


There are a variety of There are a variety of types of FRP’s.types of FRP’s.

Flat FRP’s are a practical way Flat FRP’s are a practical way of physically separating two of physically separating two buried structures especially in buried structures especially in an excavation situation.an excavation situation.


Some FRP’s are attached to the structure with Some FRP’s are attached to the structure with an epoxy adhesive sealant, this helps mitigate an epoxy adhesive sealant, this helps mitigate crevice corrosion from taking place between crevice corrosion from taking place between the FRP and the pipeline.the FRP and the pipeline.

Another type of installation involves applying Another type of installation involves applying a petrolatum tape material between the FRP a petrolatum tape material between the FRP and the pipeline to mitigate crevice corrosion.and the pipeline to mitigate crevice corrosion.


FRP’s are an excellent material to be used on FRP’s are an excellent material to be used on bridge crossings or other aboveground pipe bridge crossings or other aboveground pipe supports.supports.

Courtesy of Glass mesh


Benefits 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 in2

Two no. 12 stranded wires.

IR Coupons

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

IR Coupons

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

IR Coupons

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

IR Coupons

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

IR Coupons

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

IR Coupons

V

Bond or Switch

The 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 pipeline

Coupon

Test StationIR Coupons

Coupon 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 pipeline’s IR-drop free potential readings.

IR Coupon - Measurements

Material Summary

Test stations – Above ground

Tri-view Flex Gerome for multiple wire connections such as bonds

Anodes Connected in the test station box Get soil resistivity in designing Use anode calculation spread sheet

17lb – CP remediation and new coated steel pipeline 9lb – Bare pipe – leak repairs 3lb – customer service lines 1.5lb – drive in anodes – isolated metallic coated risers

Material Summary

Insulators Below ground – Zunt Monolithic Weld-in Above ground – M&R – flange insulated kits Insulation made inside a building (M&R)

Zinc grounding cell installed Always place a test station at insulation Always insulate casings and fill

Material Summary

Coatings Powercrete – 50 mil – directional boring Powercrete – 70 mil – rocky directional boring Powercrete – 50 mil – bridge crossings and/or any

exposures 10 mils of polyurethane top coat

FBE – only use dual coat applications of 32 to 35 mils Extruded used primarily as direct bury applications

Use for stray current surroundings AC or DC

All coating applications transmission class Inspected at the coating mill

corrosion training cp designed – part 1 galvanic anodes (current requirement testing), insulators,...

Documents

galvanic anodes design

galvanic anodes types

comparison of anodes

magnesium anodes

total coating effectiveness

hp anode number of anodes

cp current

node slide