Within the global integrity program of Enbridge a 36/48″ dual diameter pipeline with a total length of approximately1800 km needs to be inspected for wall thickness and axial cracking in a single run. The line consists of 29 sections, each of an approximate length of 60 km. A challenging characteristic of the line is the 36″ launcher and 48″ receiver in 28 of the sections. Thus, the resulting outer diameter change is about 305mm or 33%. From an intelligent inspection perspective additional boundary conditions had to be taken into account, e.g. tight 1.5D bends and a medium with high attenuation — which is especially important for the crack inspection technology.
Pipeline operator and in-line inspection (ILI) vendor agreed on an extensive testing and qualification program including small scale tests (200 anomalies) and field verifications. Therefore, the operator witnessed pull tests of the 36/48″ UCM tool at the test facility in Stutensee, Germany during the development phase in 2012. The first inspection in an operating pipeline system, as part of the validation process, was made in July 2012 after only 12 months of development and construction. Some shortcomings of the tool concept were observed within the first inspection, which led to an unsuccessful run. Both parties worked closely together to implement some modifications to the tool. In 2012 and 2013 the modified tool was run a total of 29 times, with further runs planned for 2014.
The first excavations have been completed, and show an excellent correlation between tool performance and specification. Further excavations are scheduled for early 2014 that will provide additional feedback to assess and validate the tool. At the time of writing, the 36/48″ tool is fully validated for metal loss defects, and validated for cracks only up to 2.5mm in depth.
The authors will present in detail the development of the tool and the definition of the validation process. Mechanical and operational conditions are discussed. The predefined validation process of the tool is briefly presented and the test results are discussed in detail. Furthermore, field verification results are presented.
