cathodic protection on grade storage tank.pdf

pipe line protection

1. Cathodic Protection Cathodic Protection
for On 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 Preserve Assets
•• 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 Will Cover…. 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 Control and 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
No OPS
Inspection
OPS Inspection Stops
(Enforcement Policy)
Loading
Terminal
Product
Tank
( Terminal)
Product
Tank
( Terminal)

10. Corrosion Can be Defined 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
IRON CORROSION 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 ofof Metallic Metallic Structure Structure

14. Anodic Area
( -)
Current Flow
Cathodic Area
( + )
Structure

18. SAND
CURRENT FLOW
Corrosion Cell on Tank
Bottom
CLAY
Steel Tank Floor
ANODE ANODE
CATHODE CATHODE
CATHODE CATHODE

19. DRY
SAND
MOIST SAND
WATER
Corrosion Caused by
Poor Water Drainage

20. New Bottom (Anode)
CURRENT FLOW
SAND
SAND
New Steel Coupled to Old Steel
Old Bottom (Cathode)

21. Galvanic Anode
Cathodic Protection
4 Current is obtained
from a metal of a higher
energy level

22. PRACTICAL GALVANIC SERIES Material Potential*
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-CuSO
4
Electrode

24. Structure
Magnesium
Anode
Current Flow
Galvanic Cathodic Protection on
Coated Pipeline

25. Cathodic Protection Test Station
Test
Station
Magnesium Anode
Coated Pipe

26. FLANGE INSULATION KIT
INSULATING UNIONS

27. • Typically limited to 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

29. Internal Corrosion

31. Coating
Anode
Bolt
Tank Bottom

32. Conventional CP Systems for Conventional CP Systems for
AST’s AST’s
--Shallow (Distributed) Anodes Shallow (Distributed) Anodes
--Deep Anode Deep Anode Groundbed Groundbed

33. Impressed Current Transformer Rectifier 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’
Shallow Anodes
Rectifier
(-) (+)

36. Shallow Anodes
Tank
Rectifier
(-)
(+)
Anode

37. Anodes
Junction
Box
Rectifier
-
+

38. Directional Boring Under
Existing AST

39. ABOVEGROUND STORAGE TANK
CATHODIC PROTECTION
3”∅ PVC 20%
Exposure
Anode Material
Anode Tube
10’
Typical
Test/Access Station
Grade
Aboveground
Storage Tank

40. New/Refurbished AST
Bottoms with or without
Secondary Containment

41. Secondary Containment 4 Environmental Protection
4 Minimize Liability
4 State and Local Regulations

42. New Tank Construction with Liner New Tank Construction with Liner

43. Anode & Reference Cell Placement Anode & Reference Cell Placement
in High Resistance Sand in High Resistance Sand

45. Liner
Floor
Anode
Conduit
CP Installation on Double Bottom Tank CP Installation on Double Bottom Tank

46. New Floor Installation on Existing AST New Floor Installation on Existing AST

47. CP Installation on CP Installation on Rebottomed Rebottomed Tank Tank

48. Installation of CP System on
Lifted AST
Installation of CP System on Installation of CP System on
Lifted AST Lifted AST

49. Maintenance of Cathodic Maintenance of 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 Protection Criteria • -850mV or more negative with current
applied
• -850mV “Instant off”
• -100mV shift between “Instant off” and
“Native”

51. Annual Cathodic Protection Survey

52. Tank
Rim Potential Measurements
Portable Reference Cell
Soil
(+)
?? ??
--850mV 850mV

53. Rim 25' Center 55' Rim
On -1411 -698 -404 -601 -1455
Off
-902 -664 -402 -578 -911
Reference Cell
Bullseye
®
Monitoring
Tube
Test / Access
Station
boveground torage Tank
a
de
3’
Typical Potentials (mV)

54. Test
Station
Structure
Stray Current Monitoring Test Station Stray Current Monitoring Test Station

55. Computerized Potential Logging Survey
Reference Cells
Pipeline
Test
Station
Backpack Computer Unit
Chainer/Wire Dispenser & Counter

56. Monitoring
• Record volts and amps s
• Compare values to target setting
• Conduct annual cp survey by NACE engineer
• Maintain cp records
every 30-60 day

57. BiBi--Monthly Rectifier Check Monthly Rectifier Check

58. Visual Check of Volts/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
8No external 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.”

62. Questions Questions
… …