Prevent Disasters With Tank Inspections

Prevent Disasters With Tank Inspections

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You’ve read about it in the news. A storage tank ruptures or leaks and the results are not good — a waterway is contaminated, a community water system is put at risk, an expensive repair or replacement takes a huge chunk out of the budget. Maybe a lawsuit down the road. 

Water and wastewater treatment plant managers can prevent tank issues by maintaining a rigorous tank maintenance program that includes periodic tank cleanings and inspections. 

Water tanks

For potable water tanks, the Illinois EPA (one of many agencies advising on storage tank issues) suggests that a typical tank should be inspected regularly — at least once every five years, “or more often, depending on local conditions” such as highly corrosive environments. Cleaning and repairs should be based on the findings of the inspections; the Illinois EPA recommends additional inspections between maintenance intervals. 

Operators can perform tank inspections by draining the tank and manually inspecting the interior for cracks, leaks or suspicious areas. Another method gaining popularity is using divers inside the tank, or remotely operated vehicles. Whichever method you select, the Illinois EPA reminds us, the water must be tested according to AWWA C652 if the tank is used to store drinking water, and the tank must be disinfected with chlorine before being put back into service.

Generally, a permit is not required for inspection or repainting of a potable water storage tank, but utilities should check with their state regulatory authority to see if a permit is needed if alternations are going to be made to the tank structure itself. 

Chemical tanks

Polyethylene tank manufacturer PolyProcessing has some good tips on maintaining tanks that contain corrosive chemicals. The company strongly recommends annual chemical storage tank inspections. “Even if the polyethylene tank is relatively new, a routine and careful visual inspection is suggested,” the company says. 

The company advises that once the tank is empty, any remaining chemicals should be neutralized and the exterior and interior surfaces should be cleaned, and then closely examined for cracking, crazing, and brittle appearance. Pay special attention to areas around fittings and in corners; don’t forget areas that do not come in contact with the chemical contents but could be affected by fumes. Also, use the opportunity to inspect vents and fume scrubbers. 

Now let’s go back to using ROVs or commercial divers to examine and clean a water tank. 

James Cross Jr., manager at Water Treatment Inspection Services, a division of Cross Marine Projects in American Fork, Utah, says these techniques are ideal when a community has only one tank or for other reasons can’t afford to take a tank offline. 

His company provides both ROV and commercial diving services, but prefers to use divers for a number of reasons. “There’s often sediment on the tank bottom,” Cross says. “Divers — in completely contained suits — can clean the sediment using a special vacuum system, and provide a close inspection of the tank surface.” An ROV, on the other hand, can only take pictures he points out. 

He says ROVs might be suitable where the tank represents some sort of safety hazard for divers. “In that case, we might do an ROV inspection first,” Cross says.

Cross — whose company has been doing tank work for more than 38 years in the Utah-Colorado-Idaho area — says cost depends on tank size, ease of access and the amount of sediment that needs to be removed.



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