Innovative submersible-drone technology is helping CTL simplify the process of structure inspections in challenging underwater settings.
At CTL, we’re often called upon to inspect concrete structures. Durable, strong, and versatile, concrete is used in everything from bridges to dams to domed stadiums. It’s been around since the ancient Romans used it to build the Appian Way and the Colosseum.
But concrete does not last forever. Over the years it develops cracks and other evidence that it needs to be repaired or replaced. Concrete inspections help identify weak points to prevent catastrophic failure of concrete structures.
Inspecting concrete is rarely easy because it’s so difficult to access. Reinforced concrete in a skyscraper is hidden behind walls and flooring, for instance. In the foundation of a bridge, it’s surrounded by water.
Concrete inspections in municipal water tanks
Another common underwater concrete challenge is inspecting water tanks for municipal water systems. Recently, CTL concrete inspection experts were hired for a project at the Richard Miller Water Treatment Plant in Cincinnati. Part of the job requires inspecting a 105-year-old concrete water tank.
In the past, professional divers could have been hired to inspect the water tank’s walls for signs of deterioration , cracks, leaks, and other structural risks. It’s a highly demanding job that requires the divers to also know about concrete. Divers would also need to be carefully sanitized to prevent them from contaminating the drinking water in the tank.
But we now have an innovative way to simplify this process—by deploying a submersible remote-operated vehicle, or ROV. It works on the same principle as an aerial drone: High-definition cameras are attached to allow photography at ranges that usually aren’t available with traditional processes.
Why drones are so attractive
Aerial drones present an excellent option because they can hover and maneuver at low altitudes of a few hundred feet. Normally, a helicopter would have to be chartered to perform this kind of work.
ROVs essentially take all these benefits underwater. We’ve purchased a compact, specialized ROV with a high-definition camera that can sweep 270 degrees and rotate 360 degrees.
This allows the ROV to maneuver into any position a human diver could get into—and many more because it is so compact and versatile. And thanks to the high-definition camera, we can see everything a diver sees without facing the inherent risks of sending people underwater with heavy dive gear to perform the inspection.
Most submersible ROVs are big and bulky, but the model we’ve chosen is small and compact. It’s 12.8 inches wide, 10.2 inches tall and 11 inches long, and weighs just 18.7 pounds before any attachments are added.
What we look for in a submersible ROV
These are some of the key features that attracted us to the ROV we purchased from Deep Trekker:
- High-definition camera that works well in low-light situations
- LCD viewing pad to see what the cameras are recording
- 150-foot tether
- High-efficiency LED lights
- 6-8 hours of battery life on 1.5-hour charge
- Rated at depths to 150 feet
- Travels up to 2.5 knots
- Wide range of attachments and custom add-ons
The controller is much like a video game device with joysticks that move the camera and the ROV to get into precise positions. It’s easy to learn and doesn’t take long to master the controls.
Limits of submersibles in concrete inspections
Some underwater concrete structures will be covered with marine life or degraded to an extent that the camera in an ROV would have a difficult time revealing underlying problems.
In those kinds of situations, there may be no choice but to send dive teams down to perform the inspections. Ultimately, concrete inspections are the work of well-trained, experienced engineers who can spot the subtle signs of concrete damage and recommend possible solutions.
Submersible ROVs give us one more tool to inspect concrete, but it will always be our people who deliver the results our clients require.