Best Practices For Underwater ROV Tank and Tower Inspections
Posted on March 24, 2023 by Brent Phillips
Water tank inspections are more accessible than ever with the help of underwater remotely operated vehicle (ROV) drones. From urban sprawls to rural municipalities, NACE inspectors use underwater drones to get an accurate snapshot of the internal state of a water tower or an above-ground tank.
Old Inspection Convention
Before ROVs existed or even before the technology was reasonably affordable, the old convention was to empty the tank or send in a diver. The continued practice of performing inspections by tank diving is costly for such a cumbersome and arduous process.
Despite the old inspection conventions still being practiced today, it is sunsetting and quickly being replaced by those capable of underwater drone inspections. The high-definition cameras on ROVs can provide a way to detect and record areas where protective coatings are failing, or tank repair is necessary.
ROV Inspection Practices
Water towers and storage facilities should minimize contaminants entering the water supply by design. The protocols, however, for inspecting these large vessels are intended to explore these three areas:
- Sanitation conditions
- Structural integrity
- State of the protective coating
Water tanks and storage units should protect the contents from contaminants to preserve clean drinking water. Even with established procedures, it’s vital to examine the sanitation of the tank as often as possible to take prompt action and protect the water. Sometimes, it can be challenging to determine if something has entered the tank.
But near-surface items, like insects, require immediate removal by authorized water municipality personnel. In addition, visual inspection of the external roof and side walls should be watertight, including at any access points, like the brackets connecting to the overflow pipe.
Any signs of external leaks or corrosion mean the interior of the tank needs inspection. That’s where a NACE Inspector with an underwater ROV comes into play.
In addition, ROVs can conduct interior sweeps for corrosion, condensation, and silt buildup on the following:
- Roof, walls, seams, and bottom of the vessel
- Access hatch seals
- Flange joints
Capable of returning 360 degrees of camera views, some ROVs can save video recordings to an SD memory card.
The space inside a water tower or tank varies, but no matter what, the size of the vessel is limited to the amount of water it can hold. That compact design allows ROVs to maneuver easily within tight spaces, including areas too small for divers to reach.
In addition, many ROVs come equipped with high-definition (HD) video recording capabilities. The HD resolution illuminates those tight spaces with a bright LED flood light.
State of the Protective Coating
A thorough investigation of the protective coatings on a water storage facility is a critical step in a NACE inspection. Once corrosion begins, there’s no chance it will correct itself.
Common characteristics of premature corrosion can include the following:
- Cracks in existing protective coatings
- Concrete spalling
- Raised coating, or blistering
To determine the extent and nature of corrosion, NACE inspectors use various tools to source the evidence needed to include in reporting.
Schedule Your Next NACE Inspection
Underwater ROV inspections improve on the old conventional methods of water tank inspections. The team at Cunningham Inc. discovered the benefits of ROV inspections outweigh the expense of performing outdated methodologies. By conducting ROV inspections, municipalities can:
- Eliminate the dangers associated with entering confined spaces.
- Reduce planning and complete paperwork to obtain permits.
- Water vessels no longer need to be wastefully discharged and refilled.
- Digital video footage provides for long-term reference following inspections for planning and repairs to save time and expense.
- ROV footage offers close-up detail on a tank’s internal condition.
At Cunningham Inc., their ROV capabilities can get within spaces under 9 inches in height or 12 inches in width. The digital video record documents the interior of the tank from top to bottom, including the sidewalls. The footage then gets saved to an SD memory card with 12 megapixels of image clarity.