PHMSA Gas Transmission (GT) Integrity Management
Time: 12/21/2014 09:53 AM

Protocol Item D.07

D.07 Dry Gas ICDA Pre-Assessment, Region Identification and Use of Model

For dry gas systems, verify that the operator gathers, integrates and analyzes data and information to accomplish pre-assessment objectives and identify ICDA Regions. [192.927(c)(1), 192.927(c)(2), ASME B31.8S-2004, Section 6.4.2, ASME B31.8S-2004, Appendix A2 and ASME B31.8S-2004, Appendix B2]

  1. Verify that the operator's plan defines criteria to be applied in making key decisions (e.g., region identification, feasibility determinations) in implementing the pre-assessment stage of the ICDA process. [192.927(c)(5)(i)]

  1. Verify that the operator collects, as a minimum, the following data and information:
    1. All data elements listed in ASME B31.8S-2004, Appendix A2 [192.927(c)(1)(i)]
    2. Information needed to support use of a model to identify areas where internal corrosion is most likely, including locations of all 1) gas input and withdrawal points, 2) low points such as sags, drips, inclines, valves, manifolds, dead-legs, and traps, 3) elevation profile in sufficient detail for angles of inclination to be calculated, and 4) the range of expected gas velocities within the pipeline; [192.927(c)(1)(ii)]
    3. Operating experience data that would indicate historic upsets in gas conditions, locations where these upsets have occurred, and potential damage resulting from these upset conditions [192.927(c)(1)(iii)]
    4. Information where cleaning pigs may not have been used or where cleaning pigs may deposit electrolytes. [192.927(c)(1)(iv)]
  1. Verify that the operator integrates the data collected and uses the integrated data analysis to evaluate and document the following:
    1. Feasibility of performing ICDA on its pipe segments [192.927(c)(1)]
    2. Identification of all ICDA Regions and the location of each region. [192.927(c)(1) & (2)]
    3. Support use of a model to identify the locations along the pipe segment where electrolyte may accumulate [192.927(c)(1)]
    4. Identify areas within the covered segment where liquids may be potentially entrained. [192.927(c)(1)]
  1. Verify the operator's plan uses the model in GRI 02-0057 ICDA of Gas Transmission Pipelines- Methodology (or equivalent acceptable model) to define critical pipe angle of inclination above which water film cannot be transported by the gas, and that the model considers, as a minimum: [192.927(c)(2)]
    1. Changes in pipe diameter, [192.927(c)(2)]
    2. Locations where gas enters a line, [192.927(c)(2)]
    3. Locations down stream of gas draw-offs. [192.927(c)(2)]
    4. Other conditions that may result in changes in gas velocity. [192.927(c)(2) and GRI 02-0057]
  1. Verify that the operator's plan contains provisions for applying more restrictive criteria for pre-assessment and region identification when conducting ICDA for the first time on a covered segment. [192.927(c)(5)(ii)]

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