1 / 89

Corrosion Training

Corrosion Training. CP Designed – Part 1 Galvanic 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 –

bozica
Télécharger la présentation

Corrosion Training

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. 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

  3. Objective of Class • Understanding of design for COH and CKY with Corrosion • Anodes (Galvanic) • Insulators (types) • Coatings (types) • Test stations • IR Coupons

  4. 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

  5. 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

  6. 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

  7. Galvanic Anodes – Design? • Current Requirement test • Soil resistivity test • Determine the output of a 17lb HP anode • Number of anodes = Icp/Ia • Sunde theory

  8. Galvanic Anode – Design (new Coated Steel Main) • Surface Area of pipeline • Diameter • Length • Coating Effectiveness • Current Density • Soil Resistivity

  9. 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 

  10. 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

  11. 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

  12. 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

  13. New Steel Pipe Calculations – Number of anodes • What is the total surface area?

  14. 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?

  15. 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

  16. 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?

  17. 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.

  18. New Steel Pipe Calculations – Number of anodes What if the soil was very sandy and normally dry? • Next calculate the total amount of current requirement for CP of the pipeline • Total bare area x current density = ICP • 104.1 x 1mA = 104.1 mA’s Bare Area of pipeline Current density Total amount of current requirement

  19. 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

  20. 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

  21. 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 Anode output is calculated Input the soil resistivity to the bottom of the equation

  22. 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

  23. Sunde Theory Used for banking anodes 10 FT spacing 5 anodes 5 anodes at 10ft apart = 4.19 anodes

  24. 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.

  25. 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%

  26. 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

  27. Test Stations • Two wires – No. 12 Black • New • Carrier pipe • Two wires – No. 12 White • Old/bare • Casing

  28. 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)

  29. Test Station - Spacing's • Business – 750 Feet • Residential – 1500 Feet • Rural – 6000 Feet • P/P - 653-3

  30. 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.

  31. 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.

  32. 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.

  33. 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

  34. Coatings – Jeep Settings Fusion Bonded Epoxy Powercrete Extruded

  35. Coatings – Jeep Settings Some common Jeep voltage settings for common coatings

  36. 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

  37. Coatings – Jeep Process

  38. Coatings – Jeep Process

  39. Coatings • Three common types mostly used in the gas industry • Extruded • Fusion bonded epoxy (FBE) • Powercrete

  40. 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 cold-applied tapes

  41. Coatings - Extruded

  42. 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

  43. Coatings - Extruded • Design for AC and/or DC interference currents • Use only Extruded – X-TECH II coating systems

  44. 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

  45. 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

  46. 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

  47. 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

  48. 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

  49. Coatings – Girth Welds • 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

  50. 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

More Related