Retention areas around storage tanks are necessary to contain accidental leaks within the site. Diked areas must be sufficiently impervious to contain discharged product and keep the facility and the community surrounding it safe from harm. Unfortunately, this can cause a problem when torrential rains cause flooding. Rain and floodwater that collects in the retention area can sit there for an extended period depending on the severity of the storm and how long the rain continues. When this happens a string of maintenance issues will arise that can cause long-term damage that costs time and money to clean up.
How Flood Waters Reduce Insulation Efficiency and Lead to Corrosion Under Insulation (CUI)
After the water fills the area around the storage vessel, and assuming there is no leaking product, the main issue that will appear is saturated insulation. It doesn’t matter how well the jacketing is fabricated; standing water can be absorbed into the insulation material and its negative effects will begin to take hold quickly. When the water subsides the most immediate problem is that the insulation's effectiveness (i.e., insulation value) will have dropped significantly, and valuable energy will be drained from the system. Any moisture will wick throughout the insulation, and its effectiveness will decrease anywhere the moisture is present. In fact, mineral wool can hold many times its own weight in water. Corrosion under insulation (CUI) will follow soon thereafter, and it can creep throughout the system if proper remediation procedures are not taken quickly. (For background reading about CUI, see Corrosion Under Insulation: The Challenge and Need for Insulation.)
Thermal Insulating Coatings Prevent Water Ingress
All of this can lead to lost energy, maintenance concerns and safety hazards for those working and living around a plant or terminal. There is a solution to this problem, so that when the proper preventative steps are taken, wet insulation due to flood events never needs to be an issue again.
Thermal insulating coatings (TIC) are a spray-applied acrylic coating filled with ceramic and silica air-filled particles. These coatings are distinctive in the insulation industry, as they adhere directly to the primed surface and do not permit moisture intrusion. In cases of ponding water or flood prone areas as described above, a TIC will need a top coat to completely seal out moisture. This presents a unique answer to the above problem, in that they can be combined with conventional forms of insulation to create a system that is overall thermally efficient, protects personnel working on and around the vessel, and reduces future maintenance issues.
Retention basins vary in depth depending on the needs of the facility, but the high water lines on storage vessels after flood events have been noted up to 5 feet (1.5 m) in height. By applying a TIC with a top coat to the bottom 6-8 feet (1.8-2.4 m) above the chime, a company can effectively prevent saturated insulation due to flooding. With moderately custom fabrication, conventional insulation and jacketing can be installed above the insulating coating section. This combination can effectively keep moisture out of the fibrous insulation, while providing personnel protection and energy retention in the areas where flooding is an issue. After the water recedes, the coating will not hold any moisture and the negative effects described earlier will not be an issue. (For more on the benefits see our Q&A: With respect to CUI, how well do thermal insulating coatings retard the spread of corrosion?)
Thermal Insulating Coating Case Study
One company in the rainy Pacific Northwest (US) had issues with CUI due to moisture intrusion at the area just above the chime. By installing a TIC to the bottom 2 feet (0.6 m) of the tank and specially fabricating the insulation jacketing immediately above it, the company was able prevent future issues with moisture entering the insulation and causing constant maintenance worries. In fact, the maintenance supervisor said, “I thought this was a pretty slick system for addressing the issue of under insulation corrosion damage. In the past, I’ve used a coating system suitable for under insulation service. But this way, you still have a visual on the chime and you don’t have to strip off insulation to perform an inspection.”
By planning ahead or remediating damaged insulation with a long-term solution using a TIC combined with conventional forms of insulation, facilities can achieve their desired energy savings while preventing future maintenance needs and safety concerns stemming from saturated insulation surrounding storage tanks.