Rigors of ROV

Oct. 18, 2017
Inspecting water tanks with remotely operated vehicles

About the author: Durval Tavares is chief executive officer for Aquabotix. Tavares can can be reached at [email protected] or 508.676.1000.

Inspection-grade remotely operated vehicles safely inspect tanks and reduce risk for inspectors. 

Drive through any small town and you will see the landscape dotted with water towers. This is the culmination of our society using an incredible amount of potable water. In fact, the U.S. Geological Survey (USGS) estimates that on average, every American uses anywhere from 80 to 100 gal of water per day. 

It is therefore no surprise that water tank inspectors are in high demand to keep water running efficiently throughout cities and towns. Traditionally, this meant sending divers into water tanks to inspect community drinking water. Yet this option, apart from being a costly one, can sometimes yield tragic results, including loss of life inside the tank. Now, thanks to inspection-class remotely operated vehicles (ROVs), there is an efficient and safe alternative for potable water tank inspections.

With ROVs, onsite crews and off-site individuals can monitor inspections simultaneously.

Operating ROVs

When deploying and using ROVs to inspect water tanks, it is best to consider the following steps: 

  1. Check available power sources. Given that some water tanks are located at remote sites, external power sources may not be readily available. One beneficial feature of ROVs is that many are battery-operated. ROVs running on internal DC battery power are the vehicles of choice for water tank inspection because generators or power cords do not need to be run to the tank. 
  2. Establish points of reference. Before submerging an ROV inside the tank, determine what you want the inspection to accomplish. After that, the ROV and any accompanying equipment can be lowered into the tank. It is important to determine where obstacles may be located inside, considering entanglement is the greatest risk for ROVs. Check that video and data recording functions are working to pick up all sights in the tank. ROV inspections can be completed while the tank is in operation, meaning there is no need to drain the tank or take it offline.
  3. Track all ROV rotations. An ROV should rotate around a water tank the same number of times clockwise as it does counterclockwise. If one direction is preferred over another, the vehicle runs the risk of snagging on cables or extremities inside the tank. Tools such as turn counters avoid issues like these as they monitor how many rotations an ROV makes in either direction. 
  4. Enable live remote viewing. While onsite crews conduct water tank inspections, they usually are  not the same individuals who assess data gathered from these inspections. If off-site assessment teams need information about something happening inside the tank, the inspection crew will not know until after the fact. Through live remote viewing, both teams can interact in real time and see what is taking place inside the water tanks. For example, Aquabotix’s live remote viewing feature, designed for its Endura ROV, uses remote diagnostics to allow off-site customers to monitor multiple inspections, operations and explorations from a single platform in real time. This feature is beneficial for municipalities that outsource tank inspections to off-site companies. 
  5. Utilize sensors. Strong temperature differences between a tank’s top and bottom generally indicate a slowdown in proper water circulation. Temperature sensors on an ROV can detect these changes. Additionally, an ROV’s ultrasonic thickness gauge, a form of underwater nondestructive testing equipment, allows inspectors to check the thickness of tank walls without harming either the metal or metal coatings. This ensures the structural integrity of the infrastructure is not compromised. 
  6. Check sediment levels. To properly determine  the health of the water in a tank, check sediment levels inside. The higher they are, the greater the likelihood that bacteria exist in the tank. 
  7. Explore all angles. Thanks to features like lateral thrust and 360-degree underwater cameras, ROVs can explore weld seams and find compromised areas, including the tank ceiling. Additionally, LED lights allow the operator to better see the interior of a water tank, even those that are large in diameter. 
  8. Clean, pack up and analyze. ROVs typically are made of metal and plastic and require little cleaning. A water solution mixed with bleach can remove any bacteria on the vehicle. It is important to place specific ROVs in one type of water (i.e. potable) at a time. Once the ROV is packed up, assessment teams can analyze data from live remote viewing or on-board video recording. 

Water tank inspectors are just a few of the unsung heroes who keep our residents and country safe. At the same time, divers risk their lives every day doing a job most people do not even know exists. By relying on underwater technology like inspection-class ROVs, tank inspectors not only  can stay safer, but also ensure our water supply is continuously clean and flowing.

About the Author

Durval Tavares

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