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Pipeline Safety: Workshop on Anomaly Assessment and Repair

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Information about this document as published in the Federal Register.

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Pipeline and Hazardous Materials Safety Administration (PHMSA), DOT.


Notice of Workshop.


Recent observations by PHMSA indicate possible inconsistencies in how natural gas transmission pipeline operators assess and repair anomalies, such as corrosion defects, and apply the results of calculations to their decision making for further action. Special permits granted by PHMSA over the past two years prescribe specific assessment and repair procedures for pipelines operating under a class location change and maximum allowable operating pressure special permit. Moreover, recent research indicating that existing methods of predicting the remaining strength of corroded pipe could provide non-conservative results (i.e., the pipe will fail at a pressure lower than that predicted) in some circumstances. Non-conservative results could be obtained even when the dimensions of pipeline anomalies are known with precision.

PHMSA is sponsoring a Workshop on Assessment and Repair of Anomalies in Pipelines to allow stakeholders of the pipeline safety community to learn about and discuss these research results, current evaluation practices, and methods to assure pipeline safety. The discussion of current evaluation practices and methods to assure pipeline safety should include: A review of safety factors used to evaluate anomalies when assessing in-line tool and excavation results, review of how outside forces and overpressure may effect anomaly stresses, how ILI tool accuracy is applied to anomaly evaluation, and how anomaly growth rates in assessments are considered.


The workshop will be held on October 22, 2008. Name badge pick-up and on-site registration will be available starting at 7:30 a.m. with the agenda taking place from 8 a.m. until approximately 5 p.m. Refer to the meeting Web site for updated agenda and times:​meetings/​Mtg55.mtg. Please note that the workshop will not be Webcast. However, presentations will be available on the meeting Web site within 30 days following the workshop.


The workshop will be held at the Gaylord National Resort and Convention Center, 201 Waterfront Street, National Harbor, MD 20745. Hotel reservations under the “United States Department of Transportation #2” room block for the night of October 21, 2008, can be made at 1-301-965-2000. A daily rate of $233 is available. The meeting room will be posted at the hotel on the days of the workshop.

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Max Kieba at 202-493-0595, or by e-mail at

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Registration: Members of the public may attend this free workshop. To help assure that adequate space is provided, all attendees are encouraged to register for the workshop at​meetings/​Mtg55.mtg. Hotel reservations must be made by contacting the hotel directly.

Comments: Members of the public may also submit written comments, either before or after the workshop. Comments should reference Docket ID PHMSA-2008-0255. Comments may be submitted in the following ways:

  • E-Gov Web Site: This site allows the public to enter comments on any Federal Register notice issued by any agency. Follow the instructions for submitting comments.
  • Fax: 1-202-493-2251.
  • Mail: Docket Management System, U.S. Department of Transportation, 1200 New Jersey Avenue, SE., Room W12-140, Washington, DC 20590.
  • Hand Delivery: Dot Docket Management System, Room W12-140, on the ground floor of the West Building, 1200 New Jersey Avenue, SE., Washington, DC between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Instructions: Identify the Docket ID at the beginning of your comments. If you submit your comments by mail, submit two copies. If you wish to receive confirmation that PHMSA has received your comments, include a self-addressed stamped postcard. Internet users may submit comments at


Comments will be posted without changes or edits to including any personal information provided. Please see the Privacy Act heading in the Regulatory Analyses and Notices section of the Supplementary Information for additional information.

Privacy Act Statement: Anyone may search the electronic form of all comments received for any of our dockets. You may review DOT's complete Privacy Act Statement in the Federal Register published April 11, 2000 (65 FR 19477).

Information on Services for Individuals with Disabilities: For information on facilities or services for individuals with disabilities, or to request special assistance at the meeting, please contact Max Kieba by October 15, 2008.

Issue Description: The current regulations contained in 49 CFR 192.485 and 192.713, allows latitude in methods used for assessing and remediating pipe with corrosion anomalies to restore the serviceability of pipe. PHMSA has found a wide variation in operators' interpretation of how to meet the requirements of pipeline safety regulations in assessing, evaluating, and remediating corrosion anomalies. PHMSA emphasizes that, while the workshop will involve issues related to Part 192, the technical discussions on research and methods are of relevance to hazardous liquid pipeline operators. For this reason, PHMSA also encourages hazardous liquid pipeline operators to attend the meeting.

Transmission pipelines often operate at high pressures. Pipeline design requirements assure that pipe has Start Printed Page 55594sufficient strength to contain these high pressures and to provide an additional safety margin. Pipeline in-service can become degraded due to time independent and time dependent threats. Time dependent threats include corrosion and other defects which can grow over time and, if allowed to continue unchecked, may reduce the pipe wall thickness to the point of failure. Time independent threats include excavation damage, which are one-time events that may damage the pipeline's protective coating, or the pipe itself (e.g., dent, gouge, crack, or puncture). The defects caused by time dependent or independent threats can reduce the safety margin for retaining the pipeline operating pressure.

Pipeline operators predominantly use one of three accepted methods to calculate the remaining strength of pipelines containing metal loss anomalies: (1) B31G, (2) Modified B31G, and (3) RSTRENG. These methods consider the length and depth of anomalies (i.e., areas of metal loss) and produce estimates of the pressure at which the pipe will fail. Pipeline operators are required to use these estimates to (1) determine whether pipeline pressure must be reduced to provide an additional safety margin, and (2) determine the urgency with which anomalies must be investigated, evaluated, and repaired.

In practice, many anomalies are often identified by inspection of the pipeline using in-line inspection (ILI) tools. These tools provide estimates of the length and depth of anomalies that are used in calculating remaining pipeline strength. The dimensions estimated using ILI tools are subject to uncertainty because of variables that affect the accuracy in determining wall thickness and length.

Recent research sponsored by PHMSA and industry, evaluated the accuracy of the methods currently used to calculate the remaining strength of corroded pipelines. The evaluation used data from historical and recent bench tests in which pipe with known defects (some with real corrosion defects and some with intentionally machined defects) were pressurized to failure. The defect size and pipe characteristics were used to calculate a predicted failure pressure using each of the analytical methods being evaluated. The failure pressure predicted by each method was compared to the empirical failure pressure determined during the test to identify if the predicted failure pressure was conservative or non-conservative. This work involved using the analytical methods to calculate the remaining strength of pipe containing defects whose dimensions could be measured with a high degree of precision. In some cases, the pipe failed at pressures lower than those predicted (i.e., the predicted failure pressure was non-conservative). This occurred most often for deep anomalies (e.g., >60% wall loss) in high-strength pipe (e.g., grade API 5L X-52 and above). All of the accepted methods for calculating remaining pipe strength were found to produce non-conservative estimates of failure pressure in some instances.

The workshop will allow the review and discussion of appropriate repair criteria for evaluating anomalies to meet regulatory code requirements for the permanent field repair of imperfections and damages. The workshop is also intended to allow representatives of the pipeline industry, regulatory agencies, the public, and other stakeholders to discuss the implications of research results and the potential need for regulatory changes or modification of industry standards.

Preliminary Workshop Agenda

The workshop will include:

(1) Overview of recent research results,

(2) Perspective of industry and regulators on the implications of the research results, and

(3) Discussion of issues related to reliable application of methods for predicting failure pressure of pipe with metal loss defects, including:

a. Treatment of ILI tool accuracy,

b. Consideration of anomaly growth rates.

c. Appropriate repair criteria.

Refer to the meeting Web site for a more detailed agenda:​meetings/​Mtg55.mtg.

PHMSA publishes requirements for the assessment and repair of anomalies discovered by ILI tools or direct measurement in 49 CFR Part 192 for gas pipelines and Part 195 for hazardous liquids pipelines. PHMSA also publishes other anomaly assessment and repair requirements for pipelines under special permit for class location and alternative MAOP which vary from and are more stringent than the requirements contained in regulations. PHMSA plans to discuss assessment and repair requirements including the application of factors of safety, ILI tool tolerance, and corrosion growth rates. PHMSA will consider the discussion at the workshop and comments submitted to the docket in determining whether changes to regulatory requirements for anomaly assessment and repair are needed in light of the new research results and, if so, what those changes should be.

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Issued in Washington, DC on September 19, 2008.

William H. Gute,

Deputy Associate Administrator for Pipeline Safety.

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[FR Doc. E8-22602 Filed 9-24-08; 8:45 am]