Since the introduction of in-line inspection tools (ILI) more than 50 years ago, there have always been pipelines that were considered unpiggable. Typically, it is a combination of various circumstances relating to pipeline design, operating conditions, and/or characteristics of the medium that prevents a successful in-line inspection using traditional methods. Today however, solutions are available which allow the internal inspection of pipelines formerly deemed “unpiggable”. Special ILI tools can inspect these challenging or difficult to inspect pipelines.

The system introduced here is capable to measure crack depth and profile quantitatively, whereby data is collected on the way in and out, and results are visible in real time. Tethered technologies are capable of inspecting pipelines with a 6" or larger diameter, and up to 24 km in length.

This paper will explain the technologies used and the specifications achieved. Furthermore, the unique ability of the system to navigate complex pipeline geometry will be explained through a case study of a 10" offshore oil riser. During this inspection, the tethered tool safely negotiated a total accumulated bend angle of 1,188° (17 bends) whilst successfully inspecting the pipeline for wall thickness and cracks.