According to Rosen, the offshore in-line inspection (ILI) of the 36 inch-diameter segment of the Gulfstream pipeline will be the longest offshore ILI in the history of the United States, stretching 690 km across the Gulf of Mexico.

Previously, Rosen was the first to inspect the Langeled Pipeline System, spanning from Nyhamna, Norway, to Easington, UK, which (until late in 2011) was the world’s longest subsea pipeline at 1,172 km in length and 42–44 inches in diameter.

The Gulfstream Pipeline System – a 50-50 joint venture between Williams and Spectra Energy – is a multi-diameter pipeline that begins in Alabama and Mississippi, and crosses the Gulf of Mexico into Florida. The natural gas pipeline began construction in 2001 and became the first interstate pipeline to cross the Gulf.

The project will be completed in three phases: cleaning services, deformation assessment, and combination ILI inspection. To date, phase one – the cleaning and gauging pig inspections – has been successful, verifying that results are within the required tolerances for proceeding with the geometry ILI tool.

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The final inspection phase will include Rosen’s combination ILI tool, consisting of high-resolution magnetic-flux leakage and geometry technologies. The configuration will also include a Rosen speed-control unit, which Rosen says will stabilise the tool’s velocity during the run to ensure optimal magnetisation and data quality.

During the cleaning and gauging phase of the project, a Rosen pipeline data logger (PDL) will be used to measure and record temperature and pressure profiles, detect and locate pipe restrictions, and monitor tool behaviour. Rosen says that the additional data gained by using the PDL will be especially beneficial given the extreme offshore pipeline environment, and because it had not been previously inspected using ILI technology.