Download Corrosion Training – design part 1

Corrosion Training
CP Designed – Part 1
Galvanic Anodes (current requirement
testing), Insulators, Test stations,
Coatings
Learning Over View

Part One –







Part Two –


Current requirement design
Galvanic anode design
Insulators
Coatings
Test stations
Coupons
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 system
17lb anode - remediation of WT pipelines
 17lb anode - new steel coated pipe
 9lb anode - bare main or service
 3lb anode - bare customer service
 1.5lb drive in anode – company or customer
metallic coated risers
 1.0lb 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 pipeline
Thermite welds shall be 4” apart from each
other
 Thermite welds shall be 6” away from an
adjacent weld


At 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 anode
Number of anodes = Icp/Ia

Sunde theory
Galvanic Anode – Design
(new Coated Steel Main)

Surface Area of pipeline
Diameter
 Length

Coating Effectiveness
 Current Density
 Soil 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 
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?
Keep in mind, a 6 inch diameter pipe is truly 6.625 inches
R
Length Area

3.14 • (6.625) = 1.735 • 12,000 = 20,820 sq ft
12
Need to divide the diameter by 12” to
convert to feet
New Steel Pipe Calculations –
Number of anodes

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
New Steel Pipe Calculations –
Number of anodes

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
New Steel Pipe Calculations –
Number of anodes

What is the total surface area?
New Steel Pipe Calculations –
Number of anodes

What is the total surface area?


20,820 sq ft
What is the total bare area of the
pipeline?
New Steel Pipe Calculations –
Number of anodes

What is the total surface area?


20,820 sq ft
What is the total bare area of the
pipeline?

104.1 sq ft
New Steel Pipe Calculations –
Number of anodes
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 sqft
 What is the current density?

New Steel Pipe Calculations –
Number of anodes

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.
New Steel Pipe Calculations –
Number of anodes
Whatthe
if the
wasof current
Next calculate
totalsoil
amount
veryforsandy
andpipeline
requirement
CP of the
normally
dry?density = ICP
 Total bare
area x current
 104.1 x 1mA = 104.1 mA’s

Bare Area of
pipeline
Current
density
Total amount of current
requirement
New Steel Pipe Calculations –
Number of anodes
Next calculate the total amount of current
requirement for CP of the pipeline
 Total bare area x current density = ICP
 104.1 x 3mA = 312.3 mA’s

Bare Area of
pipeline
Current
density
Total amount of current
requirement
Change current density
to a higher number,
such as 3 mA’s
New Steel Pipe Calculations –
Number of anodes
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
New Steel Pipe Calculations –
Number of anodes
The top three numbers are given based anode design,
such as shape and weight of anode.
120,000 • 1 • 1.21 = 22.3 mA
6,500 ohms cm
Input the soil resistivity to the
bottom of the equation
Anode output is
calculated
New Steel Pipe Calculations –
Number of anodes

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
Sunde Theory
Used for
banking
anodes
10 FT
spacing
5 anodes
5 anodes at
10ft apart =
4.19 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 anodes

Summary

6” WT Pipe @ 12,000 length =
5 anodes, if distributed along the line
 6 anodes, if banked at 10 feet apart

Soil resistivity of 6500 ohms cm
 Current density of 1 mA
 Coating effectiveness of 99.5%

Test Stations

Above Ground

Cott





Gerome
Tri-view flex
B-T


Large Fink
Small Fink
Curb box type
COH and CKY – Recommended use is the Triview flex for above ground use

Gerome box for any continuity or interference
bonds
Test Stations

Two wires – No. 12 Black
New
 Carrier pipe


Two wires – No. 12 White
Old/bare
 Casing

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 Feet
 Rural – 6000 Feet
 P/P - 653-3

Coatings

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 – Jeep Settings
(525) T= Voltage
(125)T= Voltage
(1250)T= Voltage
Fusion Bonded Epoxy
Powercrete
Extruded
Reference
Nace RPO274-98 = Extruded coating
Nace RPO490-95 = Epoxy coating
Powercrete Manual
Coatings – Jeep Settings
Extruded
Thickness
10mils
20mils
30mils
40mils
50mils
60mils
70mils
Epoxy
Thickness
10mils
20mils
30mils
40mils
50mils
Voltage
3953
5590
6847
7906
8839
9682
10458
Voltage
1650
2348
2876
3320
3712
Some common
Jeep voltage
settings for
common coatings
Powercrete
Thickness
45mils
75mils
Voltage
5625
9375
Coatings – Jeep settings

You maybe asked to QA or verify the
coating thickness base on the jeep
process

Check the coating thickness

DFT
Check the voltage setting of the Jeep
 Verify, the contractor or crew is creating a
holiday to verify the setting

Coatings – Jeep Process
Coatings – Jeep Process
Coatings

Three common types mostly used in the
gas industry
Extruded
 Fusion bonded epoxy (FBE)
 Powercrete

Coatings

Extruded

High density polyethylene


Can be supplied in different thickness’ up to 60
mils
Asphalt or rubber butyl adhesive

Normal thickness is in the range of 10 to 15 mils
Used primarily for direct bury application
 Girth welds normally coated with coldapplied tapes

Coatings - Extruded
Coatings - Extruded

Direct Bury 
X-Tech II – COH & CKY practice for direct
bury design, 1st choice
70 mill application
 Two layers of 30 mills of polyethylene coating
 10 mills of butyl rubber mastic

Coatings - Extruded

Design for AC and/or DC interference
currents

Use only Extruded – X-TECH II coating
systems
Coatings - FBE

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

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
Coatings – Powercrete

Epoxy base Polymer Concrete
The pipe is coated with an FBE normally
with a thickness of 12 to 15 mils
 The 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 – Girth Welds

Girth Welds

FBE and Powercrete coating applications

COH & CKY practice – two part liquid epoxy system





Surface will need to be sand blasted to a Nace 1 anchor
pattern
The two parts are mixed




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
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 Welds

Extruded 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 – Thermite welds
No mastic…..
 Preference – especially for vacuum
systems


Acceptable methods –

Petrolatum products



Protal 7200 cartridge




Profile mastic petrolatum – Denso product (bird seed)
Top coat with the Denso Color Tape – petrolatum –
Denso product
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 contacted
 Corrosion department will inspect the
pipeline at the coating Mill using the
recommended “Hold points”

Coatings - Rock shield
In 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 - Types
Kero-Test Monolithic – Weld-in
 Bangs – Flanged – Weld-in
 Dresser bolted coupling
 Compression
 Unions
 Flanges

Insulators – When?



Tying new pipe to old pipe (coated)
Tying coated pipe to bare pipe
Domestic, large volume and GM settings



Casing from carrier pipe
Pipe from supports



Separate house lines from company lines
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.
Insulators - Tying new and old
existing Coated Pipelines

Test station installed at location
Two black wires - #12 (New)
 Two white wires - #12 (old)
 Two no. 8 wires

One wire connected to the New
 One 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

Insulators - Tying new and old
existing Coated Pipelines

If 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 Pipelines

Recommended spacing's of insulators
Business – 1500 feet
 Residential – 3000 feet
 Rural – 12000 feet

Insulators - Tying to Bare Pipe
All coated systems tying to bare systems
are to be insulated off
 Test station installed at location

Verification to be made on annual
monitoring
 Trouble shooting purpose
 Two white wires on the bare pipe
 Two black wires on the coated pipe

Insulator – Weld - In
COH & CKY practice –
always use weld-in
insulators and only the
Zunt monolithic for buried
pipelines
Monolithic 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.
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
Insulators – M&R Station
A 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 Pipe

Casing isolation – two primary functions
Prevent 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 Pipe

Casing isolation – Three primary tools used

Casing filler


Casing spacers


High dielectric material (high resistance) to displace the
electrolyte within the casing
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
Insulator – Casing & Carrier Pipe –
Casing Filling
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
Casing filler can be installed
hot or cold.
There is treatment for casings
already filled with water.
Pictures -Courtesy of Trenton co.
Insulator – Casing & Carrier Pipe Spacers
Spacers 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 boots
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.
Pipe Supports

Coated metallic pipe shall be isolated
from any bridge structure
Fiber board
 Glass mesh – insulated bridge supports

Pipe Supports

Coated metallic pipelines shall be
insulated from any supports at M&R
settings

Existing pipe may need to be lifted off the
support area to be insulated properly
Insulator – FRP’s
FRP’s –
Fiberglass
Reinforced
Plastic
Insulator – FRP’s

Primary function of FRP’s
To 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 – FRP’s
There are a variety of
types of FRP’s.
Flat FRP’s are a practical way
of physically separating two
buried structures especially in
an excavation situation.
Insulator – FRP’s
Some FRP’s 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 – FRP’s
FRP’s are an excellent material to be used on
bridge crossings or other aboveground pipe
supports.
Courtesy of Glass mesh
IR Coupons
Two no. 12 stranded wires.

Benefits of using coupons

Obtain 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
IR Coupons
The coupon needs to be of the
same material as the pipeline in
order to represent it accurately.
IR Coupons
Need to have the coupon close to
the pipeline (normally within 4”
to 12”, buried in the same native
soil as the pipeline.
IR Coupons
Best practice is to place the
coupon about mid way of the
pipeline on the side.
IR Coupons
Connect the coupon in the
test station by bonding to the
pipeline. The coupon will
receive the same cathodic
protection current as the
pipeline.
IR Coupons
The 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 Coupons
Test
Station
Bond or Switch
The blue wires
identify the lead
wires used to
electrically bond the
coupon to the pipe.
V
Connect the
voltmeter to
the noncurrent
carrying lead
wire from the
coupon.
Coated
pipeline
Coupon
IR Coupon - Measurements

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.
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