Non-intrusive strake inspection is changing how operators approach one of the most persistent headaches in subsea integrity management. Vortex induced vibration (VIV) strakes protect risers and jumpers from fatigue, but removing and reinstating them ahead of a conventional inspection adds weeks of vessel time, introduces its own risk to the coating system, and drives up the cost of an already expensive campaign. For operators managing ageing subsea assets, that has often meant choosing between an incomplete inspection scope and an expensive coating removal exercise.
Non-intrusive subsea pipeline inspection technology is changing that equation. Tracerco's Discovery™ system uses computed tomography to see through steel, coatings, marine growth and strakes alike. The pipe wall, any internal build-up and the strakes themselves all appear on the same scan, without a single layer being stripped away.
Strakes are effective precisely because they wrap tightly around the pipe in a helical pattern, which is exactly what makes them difficult for most inspection tools to work around. Their fins extend the effective outer diameter, they vary in height and pitch from project to project. Removing them for inspection risks introducing additional concerns, as it changes the design parameters of the system while also adding time to the overall inspection campaign.
Discovery™'s ROV-deployed clamshell tool is designed with this in mind. Once the ROV delivers the tool to the pipe and the soft clamping feet centralise it, the system walks along a straight run of pipe independently. When it encounters a fin, the ROV steps in to unclamp, rotates the tool around the strake, and repositions it for the next section. The result is complete pipeline coverage, including strakes, without any need to cut, remove, or reinstate coatings.
Because coatings, wet insulation and marine growth add only shielding, not complexity, to the scan, the same tool handles concrete coated pipe, FBE coated pipe and bare steel with equal ease. Total outer diameter capability runs from 6 to 26.5 inches, with wall thickness up to around two inches depending on material density.
Tracerco’s Discovery™ non-intrusive inspection through strakes.
On a recent life extension project in the Gulf, an operator commissioned inspection at five locations along a gas export riser, each covering one metre of pipe. Discovery™ was deployed using a fast and full scan methodology: nine rapid scans at each location to check for any deviation from a healthy pipe signature, followed by one full tomographic scan to confirm the picture and take physical wall measurements.
This sampling approach, sometimes run at intervals of nine, fifteen or twenty scans depending on client preference, allows the team to move quickly through sound pipe while automatically triggering a full high resolution scan the moment a defect signature appears. On this project, that defect signature flagged significant wall loss in one section of the riser, giving the operator clear, measurable data on location and severity while the vessel was still on site.
Because it provides real-time data insights, decisions to extend scanning areas or add locations can be made on-site, preventing missing data from being discovered later.
For engineers planning life extension work, the value lies in being able to inspect a full scope, strakes, jumpers, risers, PiP, heavy insulated and bare pipe, using a single tool mobilisation. There is no separate workflow for coated versus uncoated sections, and no additional time built in for coating removal and reinstatement. Every scan also captures flow assurance data on internal build up alongside the integrity measurements, so operators receive a complete picture of pipeline condition from one inspection campaign.
For operators working through Department of Transportation (DOT) driven inspection intervals or Bureau of Safety and Environmental Enforcement (BSEE) life extension requirements, this combination of full strake coverage, real time data and dual-purpose scanning helps build a more complete, better evidenced case for continued asset operation.
Check out our latest webinar to see how Discovery™ is helping operators master flow assurance management, streamline integrity activities, and boost long-term pipeline performance.
Can Discovery inspect pipelines without removing VIV strakes?
Yes. Discovery™ CT technology scans through strakes, coatings and marine growth without requiring their removal, if the total outer diameter, including fin height, fits within the tool's clamping range.
What pipe sizes and wall thickness can be inspected?
The standard tool covers 6 to 26.5 inches total outer diameter, with wall thickness capability of roughly up to two inches depending on the material and coating involved. Smaller diameters can be accommodated with a specially adapted clamp.
Does the type of coating affect scan time or accuracy?
Coatings such as concrete or wet insulation add a small amount of shielding, which can slightly increase scan time, but they do not affect the accuracy of the results. Marine growth has no meaningful effect on inspection quality.
How does the fast and full scan method work on strake covered pipe?
A series of rapid scans checks for any deviation from a healthy pipe signature at each location. If a defect appears, the tool automatically switches to a full high-resolution scan to capture precise measurements, keeping inspection time efficient across sound sections of pipe.
Can this technology support life extension assessments for ageing subsea assets?
Yes. Because it combines integrity and flow assurance data in a single scan and delivers results in near real time, operators can use the findings to support Bureau of Safety and Environmental Enforcement (BSEE) life extension submissions or Department of Transportation (DOT) driven inspection intervals with well evidenced, location specific data.
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