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cathodic protection on grade storage tank.pdf
- 1. Cathodic Protection Cathodic Protection forOn for On- -Grade Storage Tanks and Grade Storage Tanks and Buried Piping Buried Piping John Fitzgerald John Fitzgerald Corrpro Corrpro Freshwater Spills Symposium Freshwater Spills Symposium April 6 April 6- -8, 2004 8, 2004
- 3. • • Preserve Assets PreserveAssets • • Reduce Maintenance Costs Reduce Maintenance Costs • • Governmental Compliance Governmental Compliance • • Preserve The Environment Preserve The Environment Why is Corrosion Control Why is Corrosion Control Important? Important?
- 4. What I WillCover…. What I Will Cover…. - - Causes of Corrosion Causes of Corrosion - - SPCC/State/OPS Regulations SPCC/State/OPS Regulations - - Cathodic Protection Applications Cathodic Protection Applications - - Maintenance Requirements Maintenance Requirements
- 5. Spill Prevention Controland Spill Prevention Control and Countermeasure (SPCC) Regulation Countermeasure (SPCC) Regulation (Implementation Required by 2/18/05 ) (Implementation Required by 2/18/05 ) - - Provide buried piping that is installed or Provide buried piping that is installed or replaced after August 16th, 2002 replaced after August 16th, 2002 protective coating and protective coating and cathodic cathodic protection. protection. - - Should a section of line be exposed for any Should a section of line be exposed for any reason it must be inspected for deterioration. reason it must be inspected for deterioration. If corrosion damage is found you must take If corrosion damage is found you must take additional examination and corrective action. additional examination and corrective action. with a with a
- 6. Federal Level (Breakout Tanks) a)Relieves surges in a hazardous liquid pipeline system or b) receive and store hazardous liquid transported by a pipeline for reinjection and continued transportation by pipeline
- 7. Breakout Tank Piping(DOT) M Main Line Valve OPS Inspection Meter M Product Tank (Breakout) M
- 8. - - Approximately 25%of States now Approximately 25% of States now require require cathodic cathodic protection be installed protection be installed and maintained on new, refurbished, or and maintained on new, refurbished, or repaired tanks in contact with soil or sand repaired tanks in contact with soil or sand foundations. foundations. - - A number of other states are in the A number of other states are in the process of implementing regulations process of implementing regulations governing AST’s. governing AST’s. State Level
- 9. Terminal Tankage Main Line M Valve OPS Inspection Meter M NoOPS Inspection OPS Inspection Stops (Enforcement Policy) Loading Terminal Product Tank (Terminal) Product Tank (Terminal)
- 10. Corrosion Can beDefined as Either: Practical Tendency of a Metal to Revert to its Native State Scientific Electrochemical Degradation of Metal as a Result of a Reaction with its Environment
- 11. IRON REFINING MILLING IRONCORROSION IRON OXIDE Corrosion - A Natural Process OXIDE
- 12. 1) ANODE 2) CATHODE 3)ELECTROLYTE 4) ELECTRICAL CONNECTION Anode -600mV Cathode -550mV -575mV
- 13. Corrosion Corrosion of of Metallic MetallicStructure Structure
- 14. Anodic Area ( -) Current Flow Cathodic Area ( + ) Structure
- 18. SAND CURRENT FLOW Corrosion Cellon Tank Bottom CLAY Steel Tank Floor ANODE ANODE CATHODE CATHODE CATHODE CATHODE
- 19. DRY SAND MOIST SAND WATER Corrosion Causedby Poor Water Drainage
- 20. New Bottom (Anode) CURRENTFLOW SAND SAND New Steel Coupled to Old Steel Old Bottom (Cathode)
- 21. Galvanic Anode Cathodic Protection 4Current is obtained from a metal of a higher energy level
- 22. PRACTICAL GALVANIC SERIES MaterialPotential* Pure Magnesium -1.75 Magnesium Alloy -1.60 Zinc -1.10 Aluminum Alloy -1.00 Cadmium -0.80 Mild Steel (New) -0.70 Mild Steel (Old) -0.50 Cast Iron -0.50 Stainless Steel -0.50 to + 0.10 Copper, Brass, Bronze -0.20 Titanium -0.20 Gold +0.20 Carbon, Graphite, Coke +0.30 * Potentials With Respect to Saturated Cu-CuSO4 Electrode
- 24. Structure Magnesium Anode Current Flow Galvanic CathodicProtection on Coated Pipeline
- 25. Cathodic Protection TestStation Test Station Magnesium Anode Coated Pipe
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- 27. • Typically limitedto new piping, that has a good quality coating and electrical isolation. • If the particular location is lacking any of the above, an impresses current system may be warranted. Galvanic Anodes
- 28. Anode Cathode Water /Sediment Fuel Product Internal Corrosion
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- 32. Conventional CP Systemsfor Conventional CP Systems for AST’s AST’s - - Shallow (Distributed) Anodes Shallow (Distributed) Anodes - - Deep Anode Deep Anode Groundbed Groundbed
- 33. Impressed Current TransformerRectifier Unit Impressed Current Transformer Rectifier Unit
- 34. Rectifier Anode Groundbed ( - )( + ) Pipeline (Structure) Current Flow Impressed Current System
- 35. Tank Tank Anode Splice Typical Depth 20’ ShallowAnodes Rectifier (-) (+)
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- 39. ABOVEGROUND STORAGE TANK CATHODICPROTECTION 3”∅ PVC 20% Exposure Anode Material Anode Tube 10’ Typical Test/Access Station Grade Aboveground Storage Tank
- 40. New/Refurbished AST Bottoms withor without Secondary Containment
- 41. Secondary Containment 4 EnvironmentalProtection 4 Minimize Liability 4 State and Local Regulations
- 42. New Tank Constructionwith Liner New Tank Construction with Liner
- 43. Anode ReferenceCell Placement Anode Reference Cell Placement in High Resistance Sand in High Resistance Sand
- 45. Liner Floor Anode Conduit CP Installation onDouble Bottom Tank CP Installation on Double Bottom Tank
- 46. New Floor Installationon Existing AST New Floor Installation on Existing AST
- 47. CP Installation on CPInstallation on Rebottomed Rebottomed Tank Tank
- 48. Installation of CPSystem on Lifted AST Installation of CP System on Installation of CP System on Lifted AST Lifted AST
- 49. Maintenance of Cathodic Maintenanceof Cathodic Protection Systems Protection Systems - - Conduct Annual Testing Conduct Annual Testing - - Meet NACE Criteria/Standards Meet NACE Criteria/Standards - - Conduct Bi Conduct Bi- -Monthly Rectifier Monthly Rectifier Checks Checks - - NACE Qualified Technicians NACE Qualified Technicians
- 50. NACE Cathodic ProtectionCriteria • -850mV or more negative with current applied • -850mV “Instant off” • -100mV shift between “Instant off” and “Native”
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- 52. Tank Rim Potential Measurements PortableReference Cell Soil (+) ? ? ? ? - -850mV 850mV
- 53. Rim 25' Center55' Rim On -1411 -698 -404 -601 -1455 Off -902 -664 -402 -578 -911 Reference Cell Bullseye® Monitoring Tube Test / Access Station boveground torage Tank ade 3’ Typical Potentials (mV)
- 54. Test Station Structure Stray Current MonitoringTest Station Stray Current Monitoring Test Station
- 55. Computerized Potential LoggingSurvey Reference Cells Pipeline Test Station Backpack Computer Unit Chainer/Wire Dispenser Counter
- 56. Monitoring • Record voltsand amps s • Compare values to target setting • Conduct annual cp survey by NACE engineer • Maintain cp records every 30-60 day
- 57. Bi Bi- -Monthly Rectifier Check MonthlyRectifier Check
- 58. Visual Check ofVolts/Amps Visual Check of Volts/Amps
- 59. Record Keeping Record Keeping - -Provides History Provides History - - Computer Records/Data Collection Computer Records/Data Collection Remote Monitoring Remote Monitoring Hand Held Computers Hand Held Computers Close Interval Surveys Close Interval Surveys Data Printouts Data Printouts Flagging of Problem Areas Flagging of Problem Areas Prioritize Action Items Prioritize Action Items - - As Built Drawings As Built Drawings - - Store Data Records for Life Store Data Records for Life
- 60. System Characteristics Galvanic Impressed 8Noexternal power 8 External power required 8Fixed driving voltage 8 Voltage can be varied 8Limited current 8 Current can be varied 8Small current requirements 8 High current requirements 8Used in lower resistivity 8 Used in almost any environment resistivity environment 8 Usually negligible 8 Must consider interference interference with other structures
- 61. Recommended Practices API-651 -Cathodic Protection of Aboveground Petroleum Storage Tanks: “Galvanic anodes method is not practical for protection of large bare structures.” NACE RP0193-01 - External Cathodic Protection of On-Grade Metallic Storage Tanks: “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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