Consider paint in water/treatment plant maintenance, inspection
September 23, 2020 •Corrosion CONTROLLED, Infrastructure, Water
Regularly scheduled maintenance and inspections keep water/water treatment plants running optimally and provide early detection of issues that, when resolved quickly, can prevent the need for larger, more expensive repairs.
When scheduling maintenance and inspections, system equipment and components tend to be top of mind, not paint. Although a seemingly small detail, paint can have a big impact on system performance and should be included as a line item when inspecting assets. Following are inspection tips to maximize that impact.
What should be inspected and why?
It is important to inspect paint on both the interior and exterior of tanks to identify indicators of system issues that are preventable. Look for corrosion and bubbling paint, paying special attention to check near the welds. Corrosion can occur when there is an energy imbalance on the surface of water tanks that are composed of refined and smelted steel and iron. As this energy imbalance occurs, additional energy is released as electrons attempting to correct the imbalance cause the metal to rust and return to a form of iron oxide. Uneven paint thicknesses can also allow corrosion to occur.
Thickness inconsistencies can occur around welds, for example. When paint integrity becomes compromised there, the corrosion needs to be ground away and the weld needs to be repaired. This type of repair will likely be costly and will create a longer downtime for system operation. To prevent this occurring in the first place, attention needs to be given to the mil/micron thicknesses and the vessel paint brand specified to prevent paint issues from developing. Paint issues can also lead to leaks, eliminating the ability of the tanks to hold water. This will likely result in system shutdown for repairs, meaning, the water will need to be removed, which is time consuming and costly.
When should paint inspection be done?
Inspecting the exterior paint on vessels can be done when routine tank maintenance is performed. The best time to perform an interior paint inspection is when replacing the materials inside the tank. To save time, address both interior and exterior paint issues simultaneously. If paint issues are found at some other point in time, or if a problem is detected and vessels need to be emptied, this will incur a system shut down. These repairs are often more costly than preventive measures and result in reduced production.
In-field paint advice
With new treatment systems, tanks are often constructed, blasted, and primed at a fabrication shop. The process of blasting cleans the tank surface, prepares the tank for paint, and allows paint to better adhere to the tank surface. It is strongly recommended to have tanks primed at the fabrication shop with finish painting taking place at the jobsite. If the primer coat becomes chipped enroute to the jobsite, it should be touched up before the rest of the painting is done.
Loading or filling the asset is another occasion that can impact paint integrity. If the water/water treatment system uses gravel supports, dumping materials into tanks can chip the interior paint, compromising paint thickness. Rather, place new materials into your vessel by hand or fill vessels with water first, then add the materials, allowing them to safely float to the bottom before draining the vessel of the water. Chemical and brine feeds can also affect paint. If the paint thickness has become uneven, or if the wrong protective system was chosen, chlorine additions upstream or brine used during a regeneration stage can erode the interior paint, with the potential to cause costly system damage.
Although what may seem like a simple selection, paint for water treatment systems should be chosen, applied, and maintained carefully. Taking the time up front to make smart decisions about the type of protective coating to use, can go a long way towards avoiding costly water/water treatment vessel repair down the line.
For more information on protecting assets in the water/treatment industry, sign up for a free subscription to NACE’s WaterCorr News, a triannual, digital publication covering this industry’s technologies and best practices.
Source: Originally appeared on CoatingsProMag.com, by Shannon Swanson, Marketing Communications Associate and Doug Reeves, Director of Field Services, U.S. Water.
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