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A few tips and tricks for inspection in drinkwatertanks and facilities.

01-12-2020

Watertank inspection by using an underwater ROV or underwater drone. Cities, municipalities and contractors use these underwater cameras to document the condition of the tanks and to be able to intervene quickly in case of security problems.

 

INSPECTIONS OF WATER TANKS FOR SAFE DRINKING WATER

Safe and clean drinking water may be something we take for granted here in Western-Europe, but what we don’t realise is that behind the scenes a lot of time and money goes into making sure it continues. Reservoirs, water towers and pipelines all play a major role in the water that comes out of the tap. These systems all need to be inspected regularly to make sure that no harmful bacteria make their way into our homes.

 

CONVENTIONAL WATER TANK INSPECTION

In the past, divers were required to complete inspections – but with diver safety being a major priority, regular inspection of these tanks is too expensive and not really realistic anymore. This is one of the reasons to switch to a micro ROV like the DTG3 for your inspections!

 

ROV WATER TANK INSPECTION

There is a lot involved in the inspection of water tanks for drinking water. Many different things need to be taken into account and mistakes can have major consequences for public health.

To get you started, we have listed a few things to keep in mind during your inspections.

 

HYGIENIC CONDITIONS:

The construction of water towers and water storage facilities are designed to minimise the risk of contaminants entering the water. Even with these protocols in place, it is essential to first investigate the sanitary conditions of the tank and resolve any problems as quickly as possible.

Ensure that no insects, etc. have fallen into the storage area.

The use of the grab arm can help remove objects from the tanks.

Inspect the roof and sidewalls to ensure they are watertight and have no gaps. Inspect the brackets that connect the overflow pipe to the structure to make sure that they are securely attached to both the structure and the overflow pipe and that they have not been damaged by corrosion (rust).

Using the 270-degree rotation of the camera, quick sweeps of the roof and walls of the tank can be made with ease.

rov Water Tank Inspection

  • Roofaccess hatches should be checked to ensure proper functioning and fit, that the roofs are well drained and do not tend to retain water.Checking the outside of the tank is just as important as the inside. Fortunately, looking at the outside of the tanks is quite easy while you can use our drones on the inside and stay dry outside.
  • Check whether sludge is collecting at the bottom of a tank, and how much. Deposits should be removed periodically to prevent microbial growth, minimise corrosion and prevent debris from entering the distribution system.Many tanks will develop sludge at the bottom, what is important is to ensure that the sludge does not build up to mix with the water. By using new and advanced systems on the drone, it can be ensured that the sludge remains on the bottom. This can be done even if you are hovering just above the silt, which prevents the silt from mixing with the clean water.

Camera Water Tower Inspection

Inspection of the construction:

This is where the DTG3 ROV shines. With its small dimensions, it fits into areas that are too small or too dangerous for divers to enter. The 270-degree rotating camera with LED spotlights can efficiently inspect all areas of the interior and intricate areas of the tank. Below is a short list of areas you can thoroughly inspect with the DTG3 underwater drone:

  • Inspect the entire structure for water leaks, including all hatches, risers and tower legs.

The high definition and bright LED spotlight illuminates your survey areas, even in dark water tanks. Efficiently check the integrity of the entire system, with optional thickness gauge or laser scaler.

  • Check that the anchor bolts have not corroded to drastically reduce their strength. Check that no dirt, grass or weeds have accumulated on the anchor bolts.

Internal-Water-Tank-Inspection

  • Check all welds and seams for cracks.

The laser scaler is an ideal tool for estimating the size of cracks, rust and sediment. Two lasers are positioned 25 mm apart above the camera and are displayed on your handheld controller. With these reference points, you can document the severity of cracks or rust. The difference between a 10-centimetre or 20-centimetre crack can be crucial when repairing the tank.

  • Check all bolts and rivets for corrosion and leaks.

Coating system conditions:

Examining the coating (paint and finish layer on the inside of the water tank) is an extremely important step in inspecting your water storage facility. The regulations and certification surrounding coating inspections are much more specific than general water tank inspections. Therefore, we have outlined here just a few areas that you can inspect with the underwater drones or ROVs.

  • If there is continuous rusting, approximate the percentage of the rusted area and determine the character of the areas (loose paint, spotty, general corrosion, no paint). Determine the size, nature and depth of the pits.

Another example where the camera and laser scalers come in handy. With the digital video recorder all this evidence can easily be attached to your reports.

  • Concrete structures should be inspected for signs of concrete deterioration (colour difference, crack formation, leakage, etc.).
  • Structures with a glass coating should be inspected for cracking, corrosion and other signs of coating deterioration.

Water-Tank-Coating-Inspection

 

SAFETY CONDITIONS:

With the DTG3 ROV, no overhead power supply is required, so you can perform your entire inspection from the top of the water tower if you wish. Often these water tanks are very high – your safety is extremely important.

  • Check the ladder brackets to make sure there is enough, that they are not damaged by corrosion and that they are secured to the structure as well as to the ladders.
  • Check the condition of all landings and catwalks (bridges) to ensure they are clean, have good drainage and are not damaged by corrosion.

 

SAFETY ISSUES:

Access to waterstorage structures should be restricted to authorised personnel.

  • Check that safety gates are sound and that gates and locks are in good working order, external ladders should extend at least 2.5 metres above the ground.
  • Check that all doors and access hatches are locked.

 

Why carry out a water tank inspection with an underwater drone?

Underwater robots have the potential to improve the traditional approach to water tank inspections. Our team has experienced the following benefits of using ROVs over traditional methods (deploying a dive team without underwater drones):

 

  1. The use of an ROV eliminates the risks associated with entering a confined space, which requires permits, planning and paperwork.
  2. Water tanks do not need to be drained or refilled to carry out ROV inspections.
  3. After a drone inspection, if remedial work is required, the images can be saved and used. This can help with better planning, saving time and money in the long run.
  4. ROV imagery provides the kind of detailed, close-up images needed to inspect the internal condition of a tank.
  5. Our underwater drones have enhanced features and attachments that can collect samples from the inside of a tank and measure wall thickness.

 

Easily take the drone to the top of the tower or hoist it up the side. Without the need for a generator, you can do all your inspections from the launch pad on top of the tower – or still remotely from your inspection vehicle if you prefer. The digital video recorder will document your entire dive, including depth, water temperature and course, to give directly to your client or include as documentation with your final report.

Each municipality or region may have different requirements for proper water tank inspection, we hope our blog will give you a starting point for understanding how to ensure proper and safe inspection of our water storage facilities. Whether you are a municipality, a private inspection company, someone who wants to start an inspection company, or just someone who is interested in investigating underwater drone provide unparalleled manoeuvrability and will save you time and money. All this combined with good and accurate data processing gives excellent tools for inspecting drinking water facilities.


Do you still have questions about the inspection of drinking water facilities, or about another subject? We are happy to answer your questions, and you can always reach us on Facebook and LinkedIn!

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