ARCHIVED - Letter to TransCanada PipeLines Limited
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File OF-Fac-NOMA-T201-2011-01 01
28 October 2011
Mr. Murray Sondergard
Regulatory Services, Law & Regulatory Affairs
TransCanada PipeLines Limited
450-1st Street, S.W.
Calgary, AB T2P 5H1
Dear Mr. Sondergard:
Trans Québec & Maritimes Pipeline Inc. (TQM)
2010 Operations and Maintenance Activities
Proposed Mitigative Work for Change in Class Location
Request for Pressure Restriction to be lifted on Line 2000
On 28 September 2011, TransCanada submitted a request to the Board to lift the pressure restriction imposed in Order SG-T201-002-2011. TransCanada was of the view that based on the results of its stress corrosion cracking (SCC) investigative digs, the integrity of Line 2000 was not in question and the pipeline could be safely operated at the full licensed maximum operating pressure (MOP).
Considering the results of the investigative digs and TransCanada’s responses to NEB Information Requests (IRs), the Board believes it has sufficient information to consider TransCanada’s request to lift the pressure restriction on TQM’s Line 2000.
Views of the Board
The Board is of the view that the SCC on TQM’s Line 2000 is not an immediate threat, but may become a future threat if not found and remediated. TransCanada therefore will need to ensure future integrity of Line 2000 within class location change sites by detecting and removing all SCC susceptible locations (i.e. girth welds coated with polyethylene tape (PE)).
The Board notes TransCanada’s assertion with respect to Line 2000’s low susceptibility to SCC, but recognizes that it is contingent on factors that will not be definitively resolved until all girth welds have been investigated. One such factor is the identification of corrosion by In-Line Inspection (ILI) and thereby the indication of possible SCC where the girth welds are coated with PE tape. As a measure of protection, any leave to operate at a pressure higher than the current restricted pressure before all girth welds have been investigated should be limited to a time period that is well below any estimated time to failure. The Board believes that a suitable time period would be eight months.
In its response to NEB IRs, TransCanada states that the SCC discovered does not indicate an increased threat of SCC. The Board considers the evidence of susceptibility to SCC under tape coated girth welds as further justification for imposing a time limit on investigation and remediation actions.
Accordingly, the Board lifts the current pressure restriction and permits TransCanada to operate TQM’s Line 2000 at its full MOP (7067 kPa). As SCC has been detected on Line 2000 and mechanical damage has been identified by TransCanada as the predominant hazard at the class location change sites, the Board also directs TransCanada to implement the following integrity and damage prevention measures to enhance safety around the class location change sites:
- Provide evidence that the mechanical damage threat is currently being controlled by submitting monthly reports to the Board on the enhanced surveillance activities described in the engineering assessment until further notice.
- Immediately install above ground markers at all class location change sites on Line 2000 and Line 3000 described in the engineering assessment. Notify the Board when installation is complete.
- By 30 June 2012, eliminate all of the SCC susceptible locations of Line 2000 within class location change sites by exposing all girth welds that have not yet been excavated, removing any PE tape found, repairing if necessary and re-coating with higher performance coating such as field applied liquid epoxy. Submit results of the investigative digs once complete.
- Immediately conduct bi-weekly ground based leak detection until the activities listed in (3) are completed. Report to the Board as in (1).
As a result of the implementation of these measures, the Board is of the view that Line 2000 will be operated safely.
The Board is continuing to evaluate the suitability of TransCanada’s plan to deal with the class location change on Line 2000 and Line 3000. The Board is also continuing to assess the proposed mitigative actions described in TransCanada’s engineering assessment.
If you have any questions concerning this matter, please contact Anne-Marie Bourassa Mota, Engineer, Integrity Management Team - Gas, Operations at (403) 221-3287.
Secretary of the Board
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