Frequently Asked Questions (FAQs)

The following are the most frequently asked questions about VR Potable Water Tank and In-Ground Reservoir Inspections:

1. Does the reservoir/tank owner need to do anything in preparation for the inspection?

NO! As opposed to dry or diver inspections, there is no preparation required by the reservoir/tank owner for a Scantron Tank Rover inspection. Unlike diver inspections, the tank stays on-line and full of water. You do not need to isolate the tank, which means no valve turning, pumping or loss of pressure. There is no need for follow-up bacteria testing or disinfecting.

2. Is there any possibility of water contamination by the ROV?

NO! The Scantron Tank Rover unit is constructed of inert high-density plastics. Even the critical thruster bearing seals have been filled with a food grade glycerin. The unit is disinfected before every inspection in accordance with AWWA C652 using a 200ppm+ chlorine solution on all components that enter the water. Unlike with divers there is no concern over medical records or discharged breathing air into the water.

3. How much detail can be viewed through the video camera?

The Scantron Tank Rover is equipped with a 12:1 macro zoom video camera, which allows the inspector to zoom in and clearly view surface features as small as 1/32 inch. The power wire-cleaning tool cleans off all surface debris, corrosion products and failed coating, permitting the inspector to see pits, cracks and weld corrosion.

4. Can still photographs be provided of the internal inspection?

YES! ScanTron is able to digitally capture any individual frame of the color video and print those frames in high quality full color. The stills are equal to a 35mm camera photo and are provided in the written report. A full explanation of the inspection video is included.

5. Has the ROV inspection ever been directly compared with dry and diver inspections?

YES! The level of detail and surface coverage of the Scantron Tank Rover was equal to the diver method, but the Scantron Tank Rover caused much less turbidity than the diver. There is no danger to human life because the ROV can stay immersed for several hours.

6. Can the ROV view larger sections of the internal surfaces?

YES! When tanks are dark due to surface staining they absorb light. When the tanks are dark they are difficult for both the divers and ROVs to get wide shots. The Scantron Tank Rover carries three high intensity halogen lamps as opposed to one or two normally carried by divers. This extra light allows for better wide views even in the darkest tanks. The Scantron Tank Rover is equipped with a 1-lux camera that can operate in natural light.

7. How does the ROV inspector assess metal loss and pitting?

The Scantron Tank Rover is equipped with a powerful wire brush-cleaning tool for removing surface corrosion. This device can fully expose all metal pits and weld defects. The inspector can use a pit gauge to accurately evaluate the size and depth of these pits. Ultrasonic method of inspection is also used.

8. Can sediment depth be measured?

YES! We simply attach a ruler that is viewed by the video camera and the Scantron Tank Rover in the sediment for a measurement. As well, the type of sediment can be determined by its color, for example: manganese, lime, and floc).

9. What are the qualifications of the ROV inspector?

Our personnel are all highly qualified tank inspectors. Qualifications include various methods of inspection. They have the support backing of a chief inspector that has NACE coating inspector qualifications and over 12 years of tank inspection experience. The background of our inspections includes protective coatings inspection, catholic protection systems non-destructive metal testing, and paint sampling and tank erection.

10. Can the ROV operator inspect the tank floor?

The Scantron Tank Rover camera rotates down 120 degrees, allowing for direct inspection of the tank floor. If the floor has sediment on it we can use a crawler mounted pump vacuum system with “pan-and-tilt” video system to safely remove bottom sediment and inspect the bottom.

11. Are there any tests called for in the AWWA D101 Tank Inspection Procedure that cannot be performed with the ROV?

The Scantron Tank Rover can perform all of the critical inspection elements required in the AWWA standard. Ultrasonic thickness measurements and other testing can be performed. Adhesion testing is per ASTM 3359 and is not performed by the ROV because we do not recommend damaging the interior coatings. Divers cannot perform this test in accordance with the ASTM procedure. We do not do this test because we never recommend spot prep and top coatings on the interior. Adhesion measurements are done to assess a coating’s ability to accept additional costs of paint. This is routinely done on the exterior but never done on the interior.

12. Other tasks using ROV that may be possible.

Anything the client requires, we will confirm the feasibility of performing (example: retrieval, sampling, testing, etc.).
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