Enbridge Pipelines Inc. Line 3 is an 860mm (34 inch), API 5LX Grade X52 pipeline with nominal wall thickness ranging from 7.14 mm to 12.5 mm. The Canadian portion of the Line runs from Edmonton, Alberta to Gretna, Manitoba. It was constructed between 1963 and 1969 in a series of loops designed to increase the capacity of the Enbridge system. Until 1999 the pipeline operated in a looped configuration with neighboring 24 inch and 48 inch pipelines. Line 3 downstream of Kerrobert, Saskatchewan began operating in straight 34 inch configuration in 1999 following completion of the first phase expansion project known as Terrace Expansion Project that connects the (48 inch) loops with a new (36 inch) pipeline.
In 1997, the Pipetronix (now PII) Ultrascan CD in-line inspection tool was run for 283 km from Cromer to Gretna, Manitoba, to identify long seam cracking and pipe body stress corrosion cracking. This section of the line is comprised primarily of pipe manufactured with a double submerged arc welded long seam with short sections of pipe having electric resistance welded long seams.
There were two primary objectives set forth in this inspection project. The first was to assess the integrity of this section of Line 3 and identify anomalies, which might affect the future operation of the pipeline. The second objective was to evaluate the performance of the Ultrascan CD tool and determine its potential role in the Enbridge integrity program.
A series of excavations have been conducted based upon the analysis of this data and none of the indications identified were considered to be an immediate concern to the integrity of the pipeline. Notably, two of the excavations resulted in the detection of the first two “significant” SCC colonies (based upon the CEPA definition of significant) [1] found on the Enbridge system.
This paper will focus on the tool performance requirements established by Enbridge prior to the inspection run which include specific defect type and size and defects at a maximum sensitivity of the tool. In addition, the information obtained as a result of the excavation program and onsite inspection and assessments. The information gathered, from this program were useful in better understanding the tool tolerance in detecting such defects and to better differentiate between them.
