Underwater HRT Gate Groove Inspection using ROV And Sonar Technology

  • Date :

Project Overview

Dams have various hydromechanical components and one of the key components is the gates, which help in maintaining the water storage and controlling the outflow of water as per demand. The major elements which affect the proper functioning of any such system are the condition of the Gate grooves, seal seats, sill beams etc. Any damage, misalignment, blockage or debris accumulation in these could seriously affect the functioning of the gate and in effect the storage capability and maintenance of the dam itself.

Recently, EyeROV was called upon to inspect the gate grooves for two Head Race Tunnels(HRTs) for a major high-head dam. The maintenance shaft gates were found to be leaking and the authorities needed to find out the condition of the gate seals and grooves. Advanced survey methods using  ROV were the best option as the site conditions were extremely demanding with water depths of over 100m. Furthermore, the site had exceptionally high turbidity due to fine clay as the users have agitated the region with repeated gate movement, posing further challenges for any survey/corrective actions.

Proposed Solutions

The proposed solution was to employ ROV with Imaging SONAR. EyeROV TUNA ROV (Remotely Operated Vehicle), a highly stable mini observation class ROV was chosen for the inspection of the gate grooves of the two HRTs. Laser scalar and Forward-looking imaging SONAR were used as the payloads for the inspection. The laser scalar provided a visual reference over video footage with a ruler over the monitor to calculate the size of the objects. Imaging SONAR for navigating the ROV in hazy or turbid waters and for bottom imaging.

Execution 

The major areas of concern were Gate grooves, seal seats, sill beams etc Each of these elements were systematically surveyed to get a clear visual. The survey was done by diligently piloting the TUNA ROV from the top of the groove to the bottom in vertical lines and from the left of the groove to the right of the groove in horizontal directions. The exceptional dynamic stability of the ROV platform provided high-quality visuals. These collected data were then analyzed in detail to get the results. The floor regions had ultra-fine silt making the sill beam visuals survey impossible as the dust plumes were unsettling. Here the Imaging SONAR with dual frequencies was employed to get the overall condition of the floor/sill beam regions.

Results

  • HD visuals of the gate grooves

  • Imaging SONAR survey data of the gate grooves

  • Consolidated findings in a hardcopy report as well as in a software platform for future reference

Conclusion

With this survey, the asset owners could properly identify the reason behind the improper seating of the gates inside the gate grooves. This provided the authorities with additional information and confidence to plan the next course of action.