PHMSA Gas Transmission (GT) Integrity Management
Time: 11/24/2014 09:04 AM

Protocol Item D.09

D.09 Dry Gas ICDA Post-Assessment

For dry gas systems, verify that the operator performs post-assessment evaluation of ICDA effectiveness and continued monitoring of covered segments where internal corrosion has been identified. [192.927(c)(4)]

  1. Verify that the operator's plan defines criteria to be applied in making key decisions (e.g., reassessment interval determination, techniques for monitoring internal corrosion) in implementing the post-assessment evaluation stage of the ICDA process. [192.927(c)(5)(i)]

  1. Verify the operator has a process for evaluating the effectiveness of ICDA as an assessment method and determining reassessment intervals. [192.927(c)(4)(i) and ASME B31.8S-2004, Appendix B2.4]
    1. Verify that if corrosion is found in areas where the pipeline inclination is greater than the estimated critical inclination, that the operator re-evaluates the critical inclination angle and additional new areas are selected for direct examination. [ASME B31.8S-2004, Appendix B2.4]
    2. Verify the operator's process determines whether a segment must be reassessed at intervals more frequently than those specified in 192.939 using the largest defect most likely to remain in the covered segment as the largest defect discovered in the ICDA segment and estimating the reassessment interval as half the time required for the largest defect to grow to critical size. Verify that this evaluation is to be carried out within one year of completion of the assessment. [192.927(c)(4)(i) and 192.939(a)(3)]
    3. Verify the operator's reassessment intervals comply with the following maximum allowed intervals in accordance with 192.939 (see Protocol F). [192.939(b)]
      1. 10 years for segments operating at SMYS levels greater than 50%
      2. 15 years for segments operating between 30 and 50% SMYS
      3. 20 years for segments operating below 30% SMYS
  1. Verify the operator continually monitors each covered segment where internal corrosion has been identified using techniques such as coupons, UT sensors or electronic probes, periodically drawing off liquids at low points and chemically analyzing them for corrosion products. [192.927(c)(4)(ii)]
    1. Verify the operator has a process to determine the frequency for monitoring and liquid analysis based on all integrity assessments results conducted in accordance with 192 Subpart O and risk factors specific to the covered segment. [192.927(c)(4)(ii) and ASME B31.8S-2004, Appendix A2.2]
    2. Verify the operator's process requires that if any evidence of corrosion products is found in the covered segment, prompt action must be taken including, as a minimum: [192.927(c)(4)(ii)]
      1. Remediate the conditions the operator finds in accordance with 192.933, and
      2. Implement one of the two following required actions: (1) Conduct excavations of covered segments at locations downstream from where the electrolyte might have entered the pipe, or (2) assess the covered segment using another integrity assessment method allowed by Subpart O.
  1. Verify that the operator's plan contains provisions for applying more restrictive criteria for the post-assessment when conducting ICDA for the first time on a covered segment [192.927(c)(5)(ii)]

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