Location: UK Sector, North Sea
Water Depth: NA (Top-side)
Heavy corrosion was revealed on a top-side 34-inch steel riser when the insulation covering two top-side sections of a steel riser was removed for an inspection. The riser (post-cleaning) is shown in Figure 1. Physical and ultra-sonic measurements of corrosion depths were attempted, but precise values could not be obtained due to the shape of the riser.
Figure 1: Corroded riser section
A grid was drawn on the riser before Welaptega took a set of digital still images to produce a 3D model of the corroded surface. Geometric analysis was performed on the model to determine the extent of material loss, using the surrounding uncorroded surface as a baseline for comparison. Figure 2 shows part of the 3D model in two different views.
Figure 2: 3D surface of corroded riser
A cylinder of best fit was aligned with the 3D model to perform a comparion between the corroded riser surface and a riser having the shape of a nominal 34-inch cylinder. The result of the comparison is shown below in Figure 3. High points are shown in blue and low points in red.
Figure 3: Surface Elevation Map of Corroded Riser
The greatest depth of material loss was measured to be 13.9mm. The client was provided with the 3D model in step file format (*.stp) to be used for finite element analysis, in addition to a report detailing measurement results.
