Direct Assessment ECDA Program Development
- 1. Ted Christensen, PE Direct Assessment ECDA – Program Development
- 2. Objective: 1. Why is there an ECDA plan ? 2. What are acceptable methods of an ECDA plan ? 3. Does it make a difference ?
- 3. Requirements “Pipeline Safety Improvement Act of 2002” Signed into law on December 17, 2002 The law has 25 sections “RISK ANALYSIS AND INTEGRITY MANAGEMENT PROGRAMS FOR GAS PIPELINES”
- 4. Requirements Each operator who owns or operates a gas transmission line in a high consequence area must adopt an integrity management plan that - • Identify the high consequence areas (HCA’s) • Perform risk assessment to prioritize HCA’s • Perform baseline assessment • Has integrity management plan (14 required sections)
- 5. Requirements • December 17, 2002 - Pipeline Safety Improvement Act of 2002 signed into Law • December 17, 2002 – Operators may begin base line assessment (grandfather) • January 28, 2003 – DOT issues proposed rule • December 12, 2003 – DOT issues regulation • June 17, 2004 - Operators must start base line assessment • December 17, 2004 – Operators must complete risk analysis and adopt an integrity management plan (24 months) • December 17, 2007 – Operators must complete baseline assessment for 50% of facilities, must be the highest priority (5 years) • December 17, 2012 – Operators must complete base line assessment for 100% of facilities (10 years)
- 6. Requirements There are 4 acceptable methods defined by the rule for the baseline assessment: 1. Internal inspection (ILI) 2. Pressure testing 3. Direct assessment 4. Other methods
- 7. Direct Assessment • Types of Direct Assessment • External Corrosion Direct Assessment (ECDA) • Internal Corrosion Direct Assessment (ICDA) • Stress Corrosion Direct Assessment (SCCDA)
- 8. ECDA External Corrosion Direct Assessment A four part process that combines pre- assessment, indirect inspections, direct examinations, and post assessment to evaluate the impact of external corrosion on the integrity of a pipeline
- 9. Regulation DOT 192.925 - What are the requirements for using External Corrosion Direct Assessment (ECDA)? Must follow the requirements in ASME/ANSI B31.8S - section 6.4 NACE RP 0502-2010
- 10. Regulation The operator must develop and implement a plan that has procedures addressing: (1) Preassessment (2) Indirect examinations (3) Direct examinations (4) Post assessment and continuing evaluation
- 11. The 4 required steps (1) Pre-assessment (2) Indirect examinations (3) Direct examinations (4) Post assessment and continuing evaluation
- 12. Preassessment • NACE RP 0502-2010 section 3 • ASME B31.8S section 6.4 Apply a more restrictive criteria for first time use of ECDA in HCA section Use of two different, but complimentary tools (must be listed in NACE RP 0502-2010 appendix A or the operator must prove technique)
- 13. Preassessment (cont.) NACE RP 0502-2010 Section 3 Preassessment - • Data collection (3.2) • Assessment of ECDA feasible (3.3) • Selection of indirect inspection tools (3.4) • Identification of ECDA regions (3.5) Requires - • Sufficient data collected, integrated, and analysis • Comprehensive and thorough fashion
- 14. Preassessment (Data collection) As a minimum, the pipeline operator shall include data from the following five categories, as shown in Table 1 1. Pipe-related (6) 2. Construction-related (11) 3. Soil/environment (5) 4. Corrosion Control (10) 5. Operational (11) A Total of 43 Data Elements
- 15. Preassessment (Data collection) Table 1: ECDA Data Elements (PIPE-RELATED) Data Elements Indirect Inspection Tool Selection ECDA Region definition Use and Interpretation of Results PIPE -RELATED Material (steel, cast iron, etc.) and grade ECDA not appropriate for nonferrous materials. Special considerations should be given to locations where dissimilar metals are joined. Can create local corrosion cells when exposed to the environment. Diameter May reduce detection capability of direct inspection tools. Influences CP current flow and interpretation of results Wall thickness Impacts critical defect size and remaining life predictions Year Manufactured Older pipe materials typically have lower toughness levels, which reduces critical defect size and remaining life predictions. Seam Type Locations with pre-1970 low frequency electric resistance welded (ERW0 or flash welded pipe with increased selective seam corrosion susceptibility may require separate ECDA regions. Older pipe typically has lower weld seam toughness that reduces critical defect size. Pre-1970 ERW or flash-welded pipe seams may be subjected to higher corrosion rates than the base metal. Bare pipe Limits ECDA application. Fewer available tools – See Appendix A. Segments with bare pipe in coated pipelines should be in separate ECDA regions. See ECDA methods provided in Appendix A.
- 16. Preassessment (Data collection) • If there is insufficient data for a ECDA region, and you cannot support the preassessment step, ECDA shall not be used for that segment • Much of the data needed for the ECDA preassessment step is also used in the risk assessment phase of a pipeline integrity management program
- 17. Preassessment (Assessment of ECDA feasible) The following conditions may make it difficult to apply ECDA • Coatings that cause electrical shielding • Backfill with significant rock content or rock ledges • Pavement, frozen ground and reinforced concrete • Adjacent buried metallic structures • Inaccessible areas If indirect inspection methods are not practical, the ECDA process may not be applied.
- 18. Preassessment (Selection of indirect inspection tools) • DOT 192.925 (b) (1) (ii) “If an operator utilizes an indirect inspection method that is not discussed in appendix A of NACE RP0502-2010, the operator must demonstrate the applicability, validation basis, equipment used, application procedure, and utilization of the data for the inspection method”
- 19. Preassessment (Selection of indirect inspection tools) Selection of Indirect Inspection Tools Minimum of two indirect inspection tools • Detect corrosion activity and/or coating holidays • Endeavor to use complimentary tools • The strength of one tool compensates for the limitations of the other tool • Table 2: ECDA Tool Selection Matrix • Appendix A: Indirect Inspection Methods
- 20. Preassessment (Selection of indirect inspection tools) NACE RP0502-2010 appendix A Indirect Inspection methods • Close -interval surveys (CIS) • AC current attenuation surveys • DCVG and ACVG surveys • Pearson surveys • Cell-to-cell surveys
- 21. Preassessment (Selection of indirect inspection tools) • Table 2: ECDA Tool Selection Matrix (Partial)
- 22. Preassessment (Identification of ECDA regions) An ECDA region is a portion of a pipeline segment that has • Similar physical characteristics • Similar corrosion history • Expected corrosion conditions • Uses the same indirect inspection tools
- 23. Preassessment (Identification of ECDA regions) • Table 1 - ECDA Data Elements and Table 2 - ECDA Tool Selection Matrix may be used as guidance in establishing ECDA regions • The definitions of ECDA regions may be modified based on the results of the indirect and direct inspection steps • A single ECDA region does NOT have to be contiguous (either side of a river)
- 24. Preassessment (Summary) • Data is gathered and reviewed (More information may be needed) • Establish if ECDA is appropriate (Could be used for some HCA segments but not for others) • Indirect inspection tools are identified (Different tools for different HCA segments) • Regions are identified (Regions may change after indirect and direct examination) Document your data, data sources, assumptions and decision making process
- 25. The 4 required steps (1) Preassessment (2) Indirect examinations (3) Direct examinations (4) Post assessment and continuing evaluation
- 26. Indirect examinations NACE RP0502-2010 Section 4 To define the severity of coating faults, other anomalies and areas at which corrosion activity may have occurred or may be occurring 1. Requires the use of at least two inspection tools over the entire length of the ECDA region 2. Align and compare the data from the two inspection tools 3. May require more than two inspection tools in a ECDA region
- 27. Indirect examinations • The boundaries of the ECDA region should be clearly marked • When ECDA is applied for the first time, consider spot checking, repeating inspections or other means to ensure consistent data • The distance selected must be such that the inspection tool can detect and locate corrosion activity • The indirect inspections should be conducted as close together as in time as practical (Change of season, installation or abandonment of facilities) • GPS shots should be taken on above ground locations (even if outside of region)
- 28. Indirect examinations After the indirect inspection data is taken, indications shall be identified and aligned for comparison • Must define criteria for identifying indications • Coated lines: Should be sufficient to locate coating faults regardless of corrosion activity at the fault • Poorly coated or bare lines: Should be sufficient to locate anodic regions • Must consider spatial errors
- 30. Indirect examinations After identifying and aligning indications, a classification system must be defined and applied • Classification is the process of estimating the likelihood of corrosion activity at each indication under typical year-round conditions • Severe - highest likelihood of corrosion • Moderate - possible corrosion activity • Minor - inactive or lowest likelihood of corrosion
- 31. Indirect examinations • The criteria for classifying the severity • capabilities of the indirect inspection tool • unique conditions within the ECDA region • When ECDA is used for the first time • Make the classification system as stringent as possible • When it cannot be determined whether corrosions is active, an indication should be considered severe
- 32. Indirect examinations • Table 3: Example Severity Classification Tool/Environment Minor Moderate Severe CIS, aerated moist soil Small dips with on and off potentials above CP criteria Medium dips or off potentials below CP criteria Large dips or on and off potentials bellow CP criteria DCVG survey, similar conditions Low voltage drop: cathodic conditions at indications when CP is on and off Medium voltage drop and/or neutral conditions at indications when CP is off High voltage drop and/or anodic conditions when CP is on or off ACVG or Pearson survey, similar conditions Low voltage drop Medium voltage drop High voltage drop Electromagnetic Low signal loss Medium signal loss High signal loss AC current attenuation survey Small increase in attenuation per unit length Medium increase in attenuation per unit length Large increase in attenuation per unit length
- 33. Indirect examinations If two or more indirect inspection tools indicate a significant different set of locations at which corrosion activity may exist- • Explained by the inherent capabilities of tools? • Specific and localized pipeline features? or • Preliminary direct examinations • Additional indirect examinations
- 34. Indirect examinations • If discrepancies cannot be resolved • ECDA feasibility should be reassessed • For initial ECDA applications, any location at which discrepancies cannot be resolved, the location shall be categorized as severe
- 35. Indirect examinations • After discrepancies have been resolved, the results of the indirect examination shall be compared with the results of the preassessment and prior history of each ECDA region • If the results are not consistent • Reassess ECDA feasibility • Reassess ECDA region definition
- 36. Indirect examinations •NOTE: 192.933 (b) states - ...to determine that the condition presents a potential threat to the integrity of the pipeline…..An operator must promptly, but no later than 180 days after conducting an integrity assessment, obtain sufficient information about the condition to make that determination.
- 37. Indirect examinations (Summary) • Mark regions and conduct surveys • Align and compare results • Define classification system • Must be as stringent as practical if ECDA is used for the first time • Compare results • May need to do a preliminary direct exam • ECDA may not be feasible • If using ECDA for first time, unresolved discrepancies must be classified as severe • Must be consistent with pre-assessment and region definitions
- 38. The 4 required steps (1) Preassessment (2) Indirect examinations (3) Direct examinations (4) Post assessment and continuing evaluation
- 39. Direct examinations NACE RP0502-2010 Section 5 The objectives of the Direct Examination Step is to determine which indications from the indirect inspections are most severe and collect data to assess corrosion activity
- 40. Direct examinations • The six phases involved • Prioritization of indication found during the indirect inspections • Excavation and data collection at areas where corrosion activity is most likely • Measurements of coating damage and corrosion defects • Evaluation of remaining strength • Root cause analysis • A process evaluation
- 41. Direct examinations (Prioritization) Table 4: Example Prioritization of Indirect Inspection Indications Immediate Action Required Scheduled Action Required Stable for Monitoring • Severe indications in close proximity regardless of prior corrosion • Individual severe indications or groups of moderate indications in regions of moderate prior corrosion • Moderate indications in locations in regions of severe prior corrosion • All remaining sever indications; • All remaining moderate indications in regions of moderate prior corrosion • Groups of minor indications in regions of severe prior corrosion • All remaining indications
- 42. Direct examinations • DOT 192.993 (c) Schedule for evaluation and remediation • Must follow schedule in ASME B31.8S Section 7 Figure 4 • Based on MAOP Above 50%/ Above 30% but not exceeding 50% / Not exceeding 30% • Table is Pf/MAOP vs Response Time (years)
- 43. Direct examinations (Measurements) • Excavations based on the priority categories • Define minimum requirements for consistent data collection • NACE RP 0502-2002 Appendix A/B/C contains typical data measurements and related activities • Gather information on • Environment soils/water/MIC • Coating type/condition/thickness/adhesion • Corrosion product/defects/measurements
- 44. Direct examinations (Remaining strength) • Evaluate or calculate the remaining strength at locations where corrosion defects are found • ASME B31G • RSTRENG • DNV Standard RP-F101
- 45. Direct examinations (Root cause analysis) • Must identify any root cause of all significant corrosion • If a root cause is uncovered for which ECDA is not well suited, an alternative method of assessing the integrity should be considered • Shielding by disbonded coatings • biological corrosion
- 46. Direct examinations (Process evaluation) The purpose is to evaluate the criteria used to categorize the repair criteria and severity criteria • If existing corrosion is less severe than prioritized, you may modify the criteria and then reprioritize all indications • If existing corrosion is more severe than prioritized, you must modify the criteria and reprioritize all indications • Any indication for which a comparable direct examination measurement shows more serious conditions than the indirect inspection data, indications shall be moved to a more severe category
- 47. Direct examinations (Summary) • Prioritization of indication • Excavation and data collection • Measurements of coating damage and corrosion defects • Evaluation of remaining strength • Root cause analysis • A process evaluation
- 48. The 4 required Steps (1) Preassessment (2) Indirect examinations (3) Direct examinations (4) Post assessment and continuing evaluation
- 49. Post assessment and continuing evaluation NACE RP0502-2010 Section 6 The objective of the Post-Assessment Step is to define reassessment intervals and assess the overall effectiveness of the ECDA process
- 50. Post assessment and continuing evaluation Reassessment intervals based on • All immediate indications have been addressed during direct examination • All monitored indications are expected to experience insignificant growth • Remaining life calculations • Must not exceed DOT 192.939
- 51. Post assessment and continuing evaluation DOT 192.939 • Pipelines operating at or above 50% SMYS • Direct Assessment every 10 years • Confirmatory Direct Assessment every 7 years • Pipelines operating at or above 30% SMYS, up to 50% SMYS • Direct Assessment every 15 years • Confirmatory Direct Assessment every 7 years • Pipelines operating below 30% SMYS • Direct Assessment every 25 years • Confirmatory Direct Assessment every 7 years
- 52. Post assessment and continuing evaluation Remaining life calculations • If no corrosion defects are found, no remaining life calculations are needed, the remaining life can be taken as the same for a new pipeline • The maximum remaining flaw size shall be taken as the same size as the most severe indication • Root cause shows most severe indication is unique, use next most severe indication • Substitute based on more sophisticated method • Use values and methods provided in Appendix D in the absence of measured corrosion rate data
- 53. Post assessment and continuing evaluation Remaining Life = C x SM x t/GR • C = Calibration factor of 0.85 • SM = Safety margin = Failure pressure ratio minus MAOP ratio, • Failure pressure ratio = calculated failure pressure / yield pressure • MAOP ratio = MAOP / yield pressure • t = nominal wall thickness (mm or in) • GR = Growth Rate 0.4 mm/y (16mpy)
- 54. Post assessment and continuing evaluation Remaining life example: • 20 inch OD / .375 wt / x-52 / fp = 1700 psig • Yield = (2 x wt x SMYS)/OD = (2 x .375 x 52,000) / 20 = 1950 psig • MAOP = Yield x CF = 1950 x .50 = 975 psig • Failure pressure ratio = fp/yield = 1700/1950 = .872 • MAOP ratio = MAOP/yield = 975/1950 = .500 • Safety margin = .875 - .500 = .375 • t/GR = .375/.016 = 23.44 years RL = 0.85 x 0.375 x 23.44 years = 7.47 years
- 55. Post assessment and continuing evaluation • When corrosion defects are found during the direct examinations, the maximum reassessment interval for each ECDA region shall be taken as one-half the calculated remaining life • Different ECDA regions may have different reassessment intervals based on variations in expected growth rates between ECDA regions
- 56. Post assessment and continuing evaluation Assessment of ECDA effectiveness • At least one additional direct assessment location at a randomly selected location shall be conducted to provide additional conformation that the ECDA process is working • For initial ECDA applications, at least two additional direct exams will be performed • One which is classified as scheduled (monitor) • One in location where no indication exist
- 57. Post assessment and continuing evaluation Activity for which feedback should be considered 1. Identification and classification of indirect inspection results 2. Data collected from direct examinations 3. Remaining strength analysis 4. Root cause analysis 5. Remediation activities 6. In-process evaluation 7. Direct examinations used for process validation 8. Criteria for monitoring long term ECDA effectiveness 9. Scheduled monitoring and period reassessment
- 58. Records NACE RP0502-2010 Section 7 The ECDA records that document in a clear, concise, workable manner all 4 steps in the ECDA process
- 59. ECDA Process Summary • Pre-assessment • Data / ECDA feasibility / Selection of tools / identification of regions • Indirect examinations • Conduct surveys / align and compare results / define classification system / compare results • Direct examinations • Prioritization / data collection / remaining strength / root cause analysis / process evaluation • Post assessment and continuing evaluation • Remaining life / re-assessment / effectiveness / improvement
- 60. Common Question Does ECDA really work? YES, BUT….. • It will not work in all HCA segments • The results of the indirect inspections may lead you to utilize IIL or pressure testing • All four steps in the ECDA process must be completed thoroughly and documented
- 61. Areas of Concern • Coatings that shield • Tapes / extruded poly • Field joints - cold and hot applied tapes / heat shrink sleeves • Deep pipelines - HDD • Poorly coated pipelines - number of indications • Casings • Remaining life calculations - 16 mils/year • Surface conditions - pavement • Sacrificial Anodes - On/Off CIS / Coating fault indications
- 62. Summary Documentation, Documentation, Documentation Detail procedures Share information Expect to revise your procedures ECDA is only one part of your company’s Pipeline Integrity Management Program
- 63. Resources • Federal Register December 15, 2003 Vol. 68, No. 240. Docket No. RSPA-00-7666 DOT Subpart O Pipeline Integrity Management 192.901 - 192.947 • NACE Standard PR0502-2010 Pipeline External Corrosion Direct Assessment Methodology • ASME/ANSI B31.8S Managing System Integrity Of Gas Pipelines
- 64. Conclusion •Why is the an ECDA plan ? •What are acceptable methods of an ECDA plan ? •Does it make a difference ?
- 65. Thank You! QUESTIONS ? Ted Christensen, PE Mercer Technical Services 816-820-2898