Confirmatory Direct Assessment (CDA)

1. Confirmatory Direct Assessment(CDA) NACE International Houston, Texas June 23, 2004 John S. Zurcher

2. Confirmatory DA • Only for External or Internal Corrosion Threats • An intermediate assessment technique • Verifies the original assumptions - especially corrosion rates • Validate the ongoing practices to maintain integrity • Verify same or shorter assessment intervals • Does not replace DA, ILI, or Hydrotesting as a “full” integrity technique • Only for on-shore, buried ferrous pipelines • A legal requirement in Dec. 17, 2002 PipelineSafety Act

3. Confirmatory Direct Assessment • Confirmatory Direct Assessment ( CDA ) Comments • The methodology will add value to baseline and other assessments thereby further enhancing pipeline integrity • The CDA process elements will follow the present DA process elements • The CDA methodology will be incorporated in the ASME B31.8S code as an appendix • Research efforts may be required to fill any gaps encountered during the development of CDA • CDA does not appear to be an appropriate methodology for SCC, time independent threats, or stable threats

4. Confirmatory Direct Assessment • Confirmatory Direct Assessment Process • CDA is supported by the Natural Gas Pipeline Industry • CDA process will follow the DA process with the following steps: • Pre-assessment and integration of data • Indirect examination using one tool • Direct examination to measure metal loss • Post-assessment to validate the CDA process • CDA is appropriate for the internal and external corrosion threats as an intermediate inspection methodology following In-Line Inspection, Pressure Testing and Direct Assessment • CDA is consistent with ASME B31.8S requirements

5. CDA for Integrity Validation • Integrity “established” by initial methods: • Hydrostatic Testing • ECDA for CP performance • ILI tools for wall loss • New technology • CDA confirms prior assumptions and field actions • Mandatory test point surveys give an overview, not detailed picture, of the CP system • Check that earlier fixes to CP still working • Monitor Gas Quality (e.g., ICDA CDA)

6. Corrosion Rate Projection Check if Corrosion Rate is Faster, Same, or Slower

7. CDA and Other Assessment Techniques • Hydrotesting, ECDA, and ILI all provide different information • Original assessment interval (half-life) is a function of: • defect size left behind and corrosion rate • All assessment tools require corrosion rate estimates: • ILI gives wall losses, with locations, but no or very poor CP/Coating performance • ECDA gives CP/Coating performance, but wall loss is a sampling based on the excavations performed • Hydro-testing estimates the largest defect remaining, and provides no CP/Coating performance

8. CDA Overview • CDA Follows the standard four DA steps: • Requires only one indirect inspection • Less than RP0502 or RP0104 • e.g., CIS only • If no severe indications are observed in the indirect inspection step - then there is an option to skip the direct inspection step • Must dig one excavation in the Post-assessment to validate the CDA process • There is an ASME draft proposal pending to allow CDA to extend the assessment interval if there is sufficient information on corrosion rates and the remaining defects “left behind”

9. CDA Flow Diagram

10. CDA on ILI – External Corrosion • Pre-assessment: • Choose one inspection tool from RP0502 (e.g. CIS, PCM, DCVG, etc.) • Indirect Inspection: • Inspect and integrate with ILI for dig priority • Direct Inspection • No severe indications then skip excavations • Moderate indications may need “root cause” mitigation especially for any large ILI indications

11. CDA on ILI – External Corrosion • Post-Assessment • If corrosion rates are faster than predicted, then one must shorten interval or conduct (?) second inspection which converts CDA to a full ECDA • If corrosion rate is same or slower – then the original assessment remains the same (unchanged) • ASME draft has verbiage “If corrosion rate is much slower than original assessment, then establish engineering case to extend the interval (not past the maximum in Table 3 of ASME B 31.8S)

12. CDA on ECDA – External Corrosion • Pre-assessment: • Choose a tool which worked well before • Indirect Inspection: • Re-inspect and compare with original inspection for changes • Direct Inspection: • If no “Severe” indications - then skip excavations • “Moderate” indications may need “root cause” mitigation • Post-Assessment: • If corrosion rates are faster than predicted, then • one must shorten interval or conduct (?) second inspection which converts CDA to a full ECDA • Same or slower than original interval stands

13. CDA on Hydrotest – External Corrosion • Pre-assessment: • Choose a tool which worked well before • Indirect Inspection: • Re-inspect and compare with original inspection for changes • Direct Inspection: • If no “Severe” indications - then skip excavations • “Moderate” indications may need “root cause” mitigation • Post-Assessment: • If corrosion rates are faster than predicted, then • one must shorten interval or conduct (?) second inspection which converts CDA to a full ECDA • Same or slower then original interval stands

14. CDA on ILI – Internal Corrosion • Pre-assessment: • Are there any known “upsets” (i.e., injection of water into the line) since last integrity assessment • Review all gas quality monitoring done since last assessment • Indirect Inspection: • Integrate flow modeling and elevations with ILI data to prioritize the dig sites • Direct Inspection: • If no “Severe” indications - then skip excavations • “Moderate” indications may need “root cause” mitigation especially for any large ILI indications • May consider monitoring with coupons or other technology to act as direct inspection

15. CDA on ILI – Internal Corrosion • Post-Assessment • If corrosion rates are faster than predicted, then one must shorten interval or perform full ICDA to restart clock • Same or slower then original interval stands

16. CDA on ICDA – Internal Corrosion • Pre-assessment: • Same method from earlier RP0104 • Gas monitoring to assess electrolyte input • Look for changes in flow and direction • Indirect Inspection: • Revisit old dig priority and monitored sites • New sites set as severe, moderate, or minor • Direct Inspection: • No severe indications then skip excavations • Coupon monitoring, etc. may substitute for direct exam • “Moderate” indications may need “root cause” mitigation

17. CDA on ICDA – Internal Corrosion • Post-Assessment: • If corrosion rates are faster than predicted, then one must shorten interval or perform full ICDA to restart clock • Same or slower then original interval stands

18. CDA on Hydrotest – Internal Corrosion • Pre-assessment: • Monitor gas quality • Use RP0104 to collect information • Indirect Inspection: Conduct flow modeling and prioritize sites • no comparison for seeing change • Direct Inspection: • No severe indications then skip excavations • Coupon monitoring, etc. may substitute for direct exam • “Moderate” indications may need “root cause” mitigation

19. CDA on Hydrotest – Internal Corrosion • Post-Assessment • If corrosion rates are faster than predicted, then • one must shorten interval or perform full ICDA to restart clock • Same or slower then original interval stands

20. SCC and CDA • There is no CDA for SCC • Hydrotesting is often @ < 5 year intervals • Third round before 5 years is exceeded • ILI (SCC detection) for gas is unreliable • SCCDA is still under discussion • ASME has opted to wait until the NACE standard provides a generally accepted methodology