Understand what lies beneath the surface and receive critical decision-making data
WireScan is a laser scanning tool first developed by Hydro Québec. It produces accurate 3D scans of dam walls and gate and stoplog slots. This technology greatly improves the underwater data collected in condition assessments for the dam and hydropower industry.
Why the Technology was Developed
Hydro Québec needed to obtain higher quality data of their gate structures above and below the waterline. As a result, they designed the WireScan system to improve survey data while also developing a safer and more cost-effective solution than traditional means for underwater environments. Implementing a way to collect 3D point cloud data provides a full density survey which is not only more accurate, but it also enables them to provide improved condition assessment for better diagnostics. This data also gave Hydro Québec benchmark data for repeatable future investigations.
Upon developing WireScan and successfully using it on several of Hydro Quebec’s assets, Hydro Québec recognized that other facilities could benefit greatly from their technology. As such, WireScan’s commercialization and manufacturing RFP was distributed and upon a lengthy evaluation process, was awarded to ASI.
ASI was awarded the contract due to the company’s global reach and significant expertise in the remote inspection of underwater infrastructure.
What is WireScan?
WireScan is a laser scanning tool that produces accurate engineering-level, three-dimensional data of above and underwater vertical surfaces, such as dam walls and gate and stoplog slots. This provides dam owners with measurable and benchmark data critical for condition assessment and asset management.
The data collected using WireScan enables dam owners to identify anomalies and effectively plan for repairs. All while reducing the risk of consequential gate failure. This technology also significantly reduces risks for workers by limiting traditional manned inspections.
Traditionally divers perform inspection of gate structures prior to refurbishment projects. Divers enter the water equipped with video capability and can perform manual measurements using an inverted plumb line to conduct and capture the inspection. Although surveys can be completed with divers; sampling capabilities are limited. Visual identification of anomalies is provided as part of final reports to owners for further assessment.
How Does it Work?
Wirescan was designed for ease-of-use. It is compact and typically only requires two operators, depending on deployment set-up. If the set-up environment is ideal, i.e. from a deck, set-up would take no longer than a couple of hours. If the set-up required additional deployment solutions, such as installation of scaffolding, it would require approximately half of a day. One operator is required for data validation, the other to deploy the Wirescan. For further cost-efficiency, multiple gate slots can be measured.
This system uses a combination of plumb and guide wires, allowing the primary sensor to descend, while using lasers and cameras to measure finite details. The benefit of using this sensor is that it is accurate and capable of collecting high resolution data above and below the waterline in a single pass.
In this case, the condition and alignment of the steel gate guides were measured with an accuracy of 2 mm for the steel part of the guide and 5 mm for the concrete portion of the guide. The top of the concrete dam deck to the gate sill was measured with an accuracy of 2 mm. The data collected was processed into a digital model for subsequent review, interpretation and analysis, providing a benchmark for future inspections.
A good indication of when inspection of the gate structure is required, is when motor current is high during gate lifting. is to calculate motor current and conduct a lift test to identify any friction or concerns of interest. WireScan can be used to identify the source of gate friction (flatness and verticality defects, loss of functional clearances, etc).
Why Use WireScan?
Jammed gates and functionality issues of stop logs can create public safety issues. It can cause high water cresting (already an issue with climate change) resulting in dam failure, for example. As aging infrastructure continues to be a concern to owners, inspection for structural deformation and risk mitigation measures are highly important to identify potential hazards before they become disastrous.
Dam owners, canal operators and owners of gate structures typically conduct inspection of these structures as part of their operations and maintenance programs.
The 3D point cloud data collected by WireScan is so precise that ASI can measure the oval divot (above) at 100 mm in width, 23 mm in height, and 6 mm in depth.
WireScan in Action
ASI Marine, a division of ASI Group Ltd., was contracted to provide a gate survey at a Dam located in British Columbia. The goal of this survey was to collect highly accurate point cloud information to assess the condition and alignment of the steel gate guides and the concrete surrounding the guides. Because dewatering was not possible, ASI used remote sensing equipment which is suitable to monitor the infrastructure and conduct repeatable surveys in order to maintain the infrastructure.
ASI used WireScan to complete the survey.
ASI was able to demonstrate that it is possible to collect highly accurate point cloud data on vertical surfaces above and below water using a single piece of equipment. This will greatly improve condition assessments for the dam and hydropower industry.
ASI’s final report to the client included a point cloud, 3D model, video stills, heat map comparisons, cross sectional profiles and verticality plots.
ASI uses Hydro Québec’s WireScan technology to provide the highest resolution and accuracy for measuring assets above and below the waterline, often collected in a single pass.
FREQUENTLY ASKED QUESTIONS
What is the accuracy of WireScan?
The 3D point cloud data collected by WireScan is so precise that ASI can measure an oval divot at 100 mm in width, 23 mm in height, and 6 mm in depth.
Precision in still water : +/-1 mm
What are the limitations?
As the Wirescan uses laser scanning technology, the water must be in good visibility (1 m visibility minimum). Steady waters is also required for precision. Water current below 5 cm per second is ideal however solutions to keep the apparatus steady. Currents between 5 cm and 10 cm can be considered. To evaluate the current flow, a drop camera prior to onsite operations is recommended for particle observation.
Maximum vertical coverage : 30 m (due to cable length limitation).
Clearance to install the mechanical platform above the vertical surface is required.