(a) Definition. ECDA is a four-step process that combines preassessment, indirect inspection, direct examination, and post assessment to evaluate the threat of external corrosion to the integrity of a pipeline.
(b) General requirements. An operator that uses direct assessment to assess the threat of external corrosion must follow the requirements in this section, in ASME/ANSI B31.8S (as described in section 10.3 of this Title), section 6.4, and in NACE SP 0502 (as described in section 10.3 of this Title). An operator must develop and implement a direct assessment plan that has procedures addressing preassessment, indirect inspection, direct examination, and post-assessment. If the ECDA detects pipeline coating damage, the operator must also integrate the data from the ECDA with other information from the data integration (section 255.917 of this Part) to evaluate the covered segment for the threat of third party damage, and to address the threat as required by section 255.917(e)(1) of this Part.
(1) Preassessment. In addition to the requirements in ASME/ANSI B31.8S section 6.4 and NACE SP 0502, section 3, the plan's procedures for preassessment must include:
(i) Provisions for applying more restrictive criteria when conducting ECDA for the first time on a covered segment; and
(ii) The basis on which an operator selects at least two different, but complementary indirect assessment tools to assess each ECDA Region. If an operator utilizes an indirect inspection method that is not discussed in Appendix A of NACE SP 0502, the operator must demonstrate the applicability, validation basis, equipment used, application procedure, and utilization of data for the inspection method.
(2) Indirect inspection. In addition to the requirements in ASME/ANSI B31.8S section 6.4 and NACE RP 0502, section 4, the plan's procedures for indirect examination of the ECDA regions must include:
(i) Provisions for applying more restrictive criteria when conducting ECDA for the first time on a covered segment;
(ii) Criteria for identifying and documenting those indications that must be considered for excavation and direct examination. Minimum identification criteria include the known sensitivities of assessment tools, the procedures for using each tool, and the approach to be used for decreasing the physical spacing of indirect assessment tool readings when the presence of a defect is suspected;
(iii) Criteria for defining the urgency of excavation and direct examination of each indication identified during the indirect examination. These criteria must specify how an operator will define the urgency of excavating the indication as immediate, scheduled or monitored; and
(iv) Criteria for scheduling excavation of indications for each urgency level.
(3) Direct examination. In addition to the requirements in ASME/ANSI B31.8S section 6.4 and NACE SP 0502, section 5, the plan's procedures for direct examination of indications from the indirect examination must include:
(i) Provisions for applying more restrictive criteria when conducting ECDA for the first time on a covered segment;
(ii) Criteria for deciding what action should be taken if either:
(a) Corrosion defects are discovered that exceed allowable limits (Section 5.5.2.2 of NACE SP 0502), or
(b) Root cause analysis reveals conditions for which ECDA is not suitable (Section 5.6.2 of NACE SP 0502);
(iii) Criteria and notification procedures for any changes in the ECDA Plan, including changes that affect the severity classification, the priority of direct examination, and the time frame for direct examination of indications; and
(iv) Criteria that describe how and on what basis an operator will reclassify and reprioritize any of the provisions that are specified in section 5.9 of NACE RP 0502.
(4) Post assessment and continuing evaluation. In addition to the requirements in ASME/ANSI B31.8S section 6.4 and NACE SP 0502, section 6, the plan's procedures for post assessment of the effectiveness of the ECDA process must include:
(i) Measures for evaluating the long term effectiveness of ECDA in addressing external corrosion in covered segments; and
(ii) Criteria for evaluating whether conditions discovered by direct examination of indications in each ECDA region indicate a need for reassessment of the covered segment at an interval less than that specified in section 255.939 of this Part. (See Appendix D of NACE SP 0502.)