Underwater Inspections for Dams using ROV

Underwater Inspections for Dams using ROV

How important is Dam Safety?

Impact on Society

Dams are an intrinsic part of our modern power-oriented society. It has come a long way, functioning as a basic necessity in our ecosystem. Be it in the generation of electricity or irrigation they serve a great purpose.  Dams are subjected to varying temperatures, erosion, corrosion etc. And as it ages, it wears. So it is of utmost importance to guard its safety.

Dam Statistics

India ranks third globally with 5334 large dams in operation and about 411 in construction. In addition, there are several thousand smaller dams. These dams are vital for ensuring the water security of the country, and these also constitute a major responsibility in terms of asset management and safety.

What causes Dam Failures?

The main causes of dam failure are:

  • Inadequate spillway capacity,
  • Piping through the embankment, foundation or abutments,
  • Spillway design error,
  • Geological instability caused by changes to water levels during filling or poor surveying,
  • Poor maintenance, especially of outlet pipes,
  • Extreme rainfall,
  • Earthquakes
  • Human, computer or design error.

The most common cause of dam failures in India has been breaching–accounting for about  44% of cases–followed by overtopping that accounted for about 25% failures.

Why is dam maintenance difficult?

As dams are big structures, their basic attribute itself makes the Inspection process cumbersome, it is hard to reach out underwater structures like dams through conventional inspection methods employed by divers.The type of defects poses another challenge, as for different types of defects different Inspections would be needed depending on the size, shape, location and topography of the Dam.All these situations lead to increased cost for Dam Inspections, which increases the time intervals of dam inspection.

What are the alternatives?

Automation has disrupted almost all the industrial sectors where the use of robots have proved to provide better results with a high level of efficiency.Same can be applied to the inspection of underwater structures.The following are the alternatives paving way for underwater inspections previously performed by divers:

 

  • ROV (Remotely Operated Vehicle)
  • AUV (Autonomous Underwater Vehicle)
  • Underwater Crawlers

Why use an ROV?

An ROV (Remotely Operated Vehicle) is a tethered underwater vehicle or robot that is used to explore deep oceans as well as inland water bodies. It is an unmanned vehicle which will be controlled by a pilot from the control station at the surface and will be equipped with payloads such as sensors, cameras, lights, robotic arms etc. to perform various underwater operations.

It is the most suitable option to perform dam inspections for the following reasons:

  • Low risk to human life
  • Ability to work under deep water pressure for highest dams as high as 300m+
  • High Operational Endurance
  • Manoeuvrability
  • Payload options according to need
  • Easy deployment
  • Time & Cost-effective and Safe

What all conditions can ROV be employed?

ROV can be employed for activities like:

  • Concrete condition assessment using high-end cameras on the upstream wall sides on deep dams up to 200+m
  • Condition assessment and corrosion studies, damages of sluice gates, intake gates, spillway gates, trash racks etc…
  • Damages like cracks, spalling, leaching etc… size estimations of the dam wall structure
  • Alignment and condition assessment of various underwater gate guiding rails
  • Tracing the leakages and seepages through mortar joints, block joints etc…
  • Tracking the leakages in beading and adjacent concrete structures of sluice gates, “intake gates
  • Mud, slurry, silt build-up near the dam wall at river bed level
  • Erosion, scour conditions in the spillway bucket and plunge pool areas on downstream
  • Post-flood condition assessments
  • Any emergency assessment as safety clearances are minimal to nil for ROV deployment in Dam’s compared to human diving
  • Other structures like Surge tank/surge shaft, surge shaft gates etc… assessment
  • Turbine and its housing assessment without draining etc…

What kind of Dam environments – ROV is most suitable for?

  • Dams with no previous history of underwater assessments are dangerous for human divers
  • Dams with leakages/seepages etc…on wall, sluice gates, intake gates, emergency stop log gates, spillway gates etc… as these all pose serious suction hazards to divers
  • Dams infested with hazardous creatures like alligators, crocodiles, snakes etc…
  • Dams which can stop operations like power generation for a very short duration only.
  • Emergency inspections as the deployment and operational times are very less.
  • When dam draining is not an option, or costly? This is an obvious case in almost all dams across the world as water is a precious resource.
  • Post-flood or earthquake or other natural calamity initial assessments
  • Any new erection or installation projects to ensure the safe completion/installation

In India, marine robotics is an emerging technology and companies like EyeROV have provided innovative & feasible solutions to promote safe & periodic inspection of underwater infrastructures like Dams. EyeROV -TUNA is a smart and efficient micro-ROV(Remotely Operated Vehicle)/underwater drone optimally designed for the Dam sector.

Following are the solutions EyeROV have provided over the years for this industry:

  • Underwater Visual Inspection using high-quality cameras
  • Solutions to capture visuals in high turbid water
  • Side Scan SONAR Surveys
  • Bathymetry Surveys
  • Laser Technology for assessing underwater crack, damages sizes etc.
  • Solutions for custom inspection requirements
  • EVAP (EyeROV Visualisation & Analytics Platform) –  A software platform for visualising and comparing inspection data incorporated with user-friendly features.