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In some cases, significant cost savings can be realized by extending the life of a platform by retrofitting the structural members to ensure they can withstand the necessary loading. 2G Robotics was contacted about a project to extend the life of an offshore platform where bracing was required at structural nodes. Uncertainty regarding the current geometry of the platform meant that the bracing could not be fabricated based on existing information. An accurate and current assessment of the geometry at the structural nodes was required and ultimately provided using the 2G Robotics ULS-100 underwater laser scanner.

Solution

The 2G Robotics ULS-100 underwater laser scanner is ideally suited for close range, highly accurate measurements. Working with the engineering contractor 2G Robotics developed an approach to obtain a 3D model of each node. Using the 3D model generated by the ULS-100, the engineering contractor correctly sized and fabricated structural bracing, with no re-work required during fabrication or installation. The ULS-100 provided accurate data required to undertake this large capital investment project with confidence.

To capture this model, the ULS-100 was secured to the nodes at various locations and orientations focusing the majority of the scans toward the joints between beams. Sufficient overlap between adjacent scans allowed them to be merged without the need to place artificial target points that could be used to tie the scans together. Multiple scans of each node were merged using the 2G Robotics post processing software to create the final surfaces. By importing these surfaces into SolidWorks a solid model and engineering drawings of the nodes was created and provided to the engineering contractor. Using these drawings as a guide, the engineering contractor custom made each support bracket with confidence, knowing that they had accurate information about the current geometry of the structure.

Using the ULS-100 to capture the 3D models is a more time consuming process than using a 3D sonar, however, the level of detail captured with the ULS-100 is far beyond the capability of sonar systems.

Sonar and video could not provide the desired level of detail for this inspection. In particular, the engineering contractor and asset owner were impressed by the laser scanners ability to accurately determine:

• Angle of support beams in relation to one another
• Diameters of support beams
• Precise measurement of the weld sizes

Underwater Laser Scanner Applications

Inspection of seb-sea assets using the ULS-100 will provide an increased level of certainty for engineering contractors and asset owners. This technology can be applied to the inspection of a wide range of sub sea assets where measurements are required from detailed pipeline inspection to hydroelectric dam and bridge pier inspection. In all of thes2ge cases, currently, decisions must be made with a level of assumption and guess work. The ULS-100 underwater laser scanner can provide certainty when making costly construction and repair decisions. It however is impractical, due to the range limitations of the underwater laser scanner compared to sonar, to completely replace sonar and scan an entire asset with the laser system. Instead these technologies should be viewed as complimentary with sonar being used to obtain an overall understanding of the asset and laser scanning being used at specific locations of interest that have been identified in advance or through the sonar inspection. This is the approach that was used for inspection of the offshore platform where only the nodes were scanned with the laser scanner rather than the complete structure. All images used with the permission of Oceanus Co. Ltd. Busan South Korea.

The ULS-100 provides an unprecedented level of accuracy and detail to underwater measurements. If you can benefit from increased confidence through improved measurement accuracy, please contact 2G Robotics.

ULS-100 is secured to a structural node of an offshore platform and multiple scans are captured to create a complete 3D model.

Front View of offshore platform node consisting of multiple merged scans.

End View of a circular beam looking toward the node. Both the inside and outside of the node was scanned.

3D animation of merged scans visualizing the offshore platform sub-sea node scans.

In the figure above, two blue cylinders have been overlayed on the scan showing the path of two beams of the platform. The weld bead is visible between the two beams and both the width and depth of this bead is measurable.