In underwater inspection, there is a need for sensors that can determine the structure of an asset. Usually represented as a 3D digital point cloud, these measurements are used for engineering calculations, maintenance planning, and ROV localization. The most prevalent technology in this field is sonar, and high frequency multi-beam sonar systems are capable of capturing complete 3D digital point-cloud representations of underwater environments. There are however physical limitations to the resolution capability of these technologies for understanding small yet important features of structures such as cracks and erosion in concrete structures or welds and dents in metallic marine infrastructure. Underwater laser scanners are not affected by the same physical principles as sonar and have the ability to capture details of underwater assets that were previously unobtainable.
Underwater laser scanners provide several clear advantages over sonar systems at relatively short ranges. The measurement resolution is multiple orders of magnitude higher, enabling very dense point clouds and laser systems are not affected by confined spaces prone to acoustic echoes. To demonstrate the difference between the capability of sonar and laser for measuring underwater, a cinder block wall was constructed with target features including missing blocks and offset blocks. The wall was scanned with both the 2G Robotics ULS-100 underwater laser scanner and a mechanically scanning 3D sonar using a 2.25Mhz head. The point cloud data for the two methods has been overlaid, with laser scanner data in red and black, and sonar data in green.
Using this point cloud data, a solid model of the damaged section can be created by importing the scan data into a CAD software. In this example the damaged underwater pipe section scan data was imported into SolidWorks.
Numerical strength and flow analysis can be performed on the underwater pipe section allowing engineers to understand the current status of the asset to a very high degree. By providing this level of asset understanding, costly highly conservative assumptions can be avoided while ensuring continued safe operation of the asset.
Finite Element Analysis of the pipe section can be performed to understand the stress distribution within the damaged section. Computational Fluid Dynamics flow analysis can be performed to understand the flow characteristics and hydraulic losses experienced through this section.