Water storage tanks are everywhere. Drive through any small town and you’ll see water towers dotting the landscape. Fly above any city and you’ll see water tanks on top of every skyscraper. We use an incredible amount of potable water. In fact, the US Geological Survey (USGS) estimates that on average, every American uses between 80-100 gallons of water per day, and an estimated 86% of the US population has access to public water. With so much infrastructure dedicated to providing a safe and constant supply of municipal water, it should come as no surprise that water tank inspectors are in high demand to keep our cities and towns running. Traditionally this meant sending divers for a dunk in your drinking water, however, inspection-class remotely operated vehicles (ROVs) are a great (and safe) alternative for potable water tank inspections.
Inspecting Water Tanks with ROVs:
When it comes time to clean, inspect or repair a water tank, it can be accomplished in two ways: with or without water. Tank inspectors and plant supervisors often prefer inspections and repairs to be completed while the tank is still full and operational. Draining a water tank is expensive, time consuming and wasteful. Draining also comes with the added risk of causing stress damage to the water tank, and leaves residents and businesses without water.
To do their job, tank inspectors must climb to the top of a water tower with all of their gear in tow, suit up in dive gear, and then squeeze down a port hole barely big enough to fit through to reach the subject of interest: our water. It’s easy to see why packing a small, portable ROV to drop into the tank can often be an easier and safer alternative. ROVs that run on internal DC battery power are the vehicles of choice for water tank inspection, because it means no generators or power cords need to be run to the top of the tank.
A live video feed is critical to quickly inspecting and documenting potential problems within a potable water tank. Problem areas such as welded seams, bolts, pipes, and gaskets can be checked for signs of corrosion. Lateral thrusters on an ROV allow an operator to move sideways along a horizontal seam or row of bolts for a thorough inspection. An ultrasonic thickness gauge, a form of underwater non-destructive testing equipment (NDT) is often mounted to an ROV, allowing an inspector to check the thickness of tank walls without harming the metal or metal coatings. Routine inspections and preventative maintenance are important steps to providing uninterrupted water service to nearby residents and businesses.
All water tanks will naturally collect sediment over time. As this sediment builds up, it must be periodically cleaned, similar to the bottom of a pool. This often involves sending a diver into the depths of a dark water tank with a large vacuum hose. The high intensity lights and high resolution camera on an ROV provide a good look at the bottom of the tank before and during sediment removal. Some underwater robots are even designed to aid in the cleaning process directly, further reducing the risks involved with prolonged dives.
Water tank inspectors are just a few of the unsung heroes who keep our country running. They risk their lives every day doing a job most people don’t even know exists. By using inspection-class ROVs, tank inspectors can stay a little bit safer while keeping our water clean and flowing.