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Corrosion Control/Cathodic Protection Corrosion Control/Cathodic Protection for Aboveground Storage Tanksfor Aboveground Storage Tanks
Presented by:Presented by:James T. James T. Lary Lary Corrpro Companies, inc.Corrpro Companies, inc.1090 Enterprise Drive1090 Enterprise DriveMedina, Ohio 44256Medina, Ohio 44256jlaryjlary@@corrprocorrpro.com .com 330330--723723--5082 5082
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•• Preserve AssetsPreserve Assets•• Reduce Maintenance CostsReduce Maintenance Costs•• Reduce Inspection CostReduce Inspection Cost•• Company/Government RequirementCompany/Government Requirement•• Preserve The EnvironmentPreserve The Environment
Why is Corrosion Control Why is Corrosion Control Important?Important?
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IRON OXIDE REFINING MILLING
STEEL CORROSION IRON OXIDE
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CORRPROCOMPANIES INC
CorrosionCorrosion ofof MetallicMetallic StructureStructure
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Anodic Area-600mV
Cathodic Area-550mV
SAND
CURRENT FLOW
External Corrosion of
Tank Bottom
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SANDCURRENT FLOW
Corrosion Cell Caused by Foreign Material in Sand Cushion
CLAY
Steel Tank Floor
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DRY SAND
MOIST SAND
WATER
Corrosion Caused byPoor Water Drainage
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New Bottom (Anode)
CURRENT FLOW
SAND
SAND
New Steel Coupled to Old Steel
Old Bottom (Cathode)
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Liner
Floor
AnodeConduit
CP Installation on Double Bottom TankCP Installation on Double Bottom Tank
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Structure (Cathode)
Magnesium Anode
Galvanic Cathodic Protection
CORRPROC O M P A N I E S I N C
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Recommended PracticesAPI-651 - Cathodic Protection of Aboveground Petroleum
Storage Tanks:
“Galvanic anodes method is not practical for protection of large bare structures.”
NACE RP0193-2001 - External Cathodic Protection of On-Grade Carbon Steel Storage Tank Bottoms:
“Galvanic protection systems can be applied to tank bottoms where the metallic surface area exposed to the electrolyte can be minimized through the application of a dielectric coating or the area is small due to the tank size or configuration.”
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(+)(-)
Return
Rectifier
Anode
CURRENT FLOW
Impressed Current Cathodic Protection
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Shallow Anodes
Tank
Rectifier
(-)(+)
Anode
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TankTank
Anode
Splice
Typical Depth 20’
Shallow Anodes
Rectifier
(-)(+)
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Anodes
Junction Box
Rectifier
-+
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Deep Anode
Tank
(+)
(-)
RectifierTank
Tank Tank
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MFLMFL FloorFloorInspectionInspection
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Cathodic Protection Monitoring
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Tank
Rim Potential Measurements
Portable Reference Cell
Soil
(+)
????
--850mV850mV
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Directional Boring Under Existing AST
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2” ∅ PVC
Grade
Aboveground
Storage Tank
3’ Typical
Test/Access Station
Monitoring
Tube REFERENCE CELL MONITORING TUBEREFERENCE CELL MONITORING TUBE
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Rim 25' Center 55' RimOn -1411 -698 -404 -601 -1455Off -902 -664 -402 -578 -911
Reference Cell
Bullseye®
Monitoring Tube
Test / AccessStation
bovegroundtorage Tank
ade
3’Typical
Potentials (mV)
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ABOVEGROUND STORAGE TANK
CATHODIC PROTECTION
3”∅ PVC 20% Exposure
Anode MaterialAnode Tube
10’ Typical
Test/Access Station
Grade
Aboveground
Storage Tank
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Tank Bottom
Slotted Pipe
Coke Breeze
Anode Material Centered in
Coke Breeze
Native Earth
TYPICAL ANODE INSTALLATION
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Computer Guided HorizontallyBored Anode System
Tank
Rectifier
(+)
(-)
Anode Splice Box
Anode Pipe
Monitoring
Pipe
Anode Pipe
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Leak Detection Monitoring Station
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CP Applications for ReCP Applications for Re--bottomed or bottomed or New TanksNew Tanks
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New Floor Installation on Existing ASTNew Floor Installation on Existing AST
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CP Installation on CP Installation on RebottomedRebottomed TankTank
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Above Ground
Storage Tank Bottoms
with or without
Secondary Containment
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Secondary Containment
4 Environmental Protection
4 Minimize Liability
4 State and Local Regulations
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New Tank Construction with Liner New Tank Construction with Liner
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Anode & Reference Cell PlacementAnode & Reference Cell Placementin High Resistance Sandin High Resistance Sand
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RingwallRingwall Conduit for CP WiringConduit for CP Wiring
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Floor Plate InstallationFloor Plate Installation
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Installation of CP System on Lifted AST
Installation of CP System on Installation of CP System on Lifted ASTLifted AST
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System Energization
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Rectifier
Anode Groundbed
( - ) ( + )
Pipeline(Structure)
Current Flow
Impressed Current System
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Inspection of CP SystemInspection of CP System
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Remote Monitoring of CPRemote Monitoring of CP
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Anode Cathode
Water / Sediment
Fuel Product
Internal Corrosion
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Internal Corrosion
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CoatingAnode
Bolt
Tank Bottom
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Recommended Practices
API-651 - Cathodic Protection of Aboveground Petroleum Storage Tanks:
NACE RP0193-2001 - External Cathodic Protection of On-Grade Carbon Steel Tank Bottoms:
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Pipeline Inspection Tool
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Presented by:
James T. LaryCorrpro Companies, Inc.World Headquarters1090 Enterprise DriveMedina, Ohio 44256Phone: 330-723-5082Fax: 330-723-0694Email [email protected]