One way to ensure the health of a water storage tank is to conduct regular inspections. No fabricated and installed system can continue to operate without problems unless these procedures are carried out. Many states have an established set of regulations for the annual inspection of water tanks. The American Water Works Association (AWWA) recommends inspections occur at least once every three to five years.
Atmospheric welded or bolted above ground storage tanks constructed to API standards require regular API-653 inspection services. Inspectors conduct assessments of the tank bottom, foundation, roof, shell courses, and ancillary equipment. They then notify about necessary and suggested repairs to ensure a tank’s continued service and safety.
The design and construction of storage tanks has evolved over the years. Changes were largely driven by environmental and building regulations of the tank fabrication industry. Today, tank engineers have to consider how a tank structure reacts to abnormal environmental factors and conditions. Tank design has also become site-specific. Considerations include things like high winds, soil type, and snow loads in the area of concern.
There are several reasons a tank’s coating could break down. For instance, a bullet hole in the tank walls can lead to coating failure and to the development of rust and corrosion. Colder climates can force the formation of ice inside the tank itself. This will damage the lining and internal sidewall of the tank.
In cold weather, water should be allowed to circulate within the tank. This can help minimize ice buildup and prevent the liquid from freezing over. All coatings should be inspected regularly to maintain the tank’s integrity and ensure it can continue to provide safe storage.
Necessity of Inspections
Different types of problems can develop depending on the tank’s type. Contamination is a common issue. It can develop from sanitation-related issues, if roof vents on tanks don’t have screens or hatch lifts are left open and unprotected. When these holes exist, birds, animals, and insects can accidentally enter a tank.
Deterioration of cover plates and gaskets can also lead to the formation of gaps within a tank. They allow droppings from rats, birds, and other animals that initially land on the roof to get washed into the space below the roof.
A tank in good condition may have to undergo a full comprehensive inspection once every five years. However, with an old tank, or with one showing signs of deterioration, inspections should be conducted more often.
Types of Inspections
Tanks can be inspected in one of two ways. It can be drained, which means the tank cannot be used for an entire week. While the tank is out of service, it is examined, cleaned, disinfected, and repaired, if necessary.
Filled up water tanks can be inspected with divers or remotely operated vehicles. This process usually takes only a few hours. The diver or the vehicle records a video in real time, exploring the inside of the tank. Any recognizable deficiency is addressed before they turn into more pressing problems.
Regular inspections can extend the lifetime of a storage tank. They can slow down the deterioration of coating systems and improve the quality of the stored liquid.