Let's talk about insulation - not the pink kind you put in your attic, but insulation for tanks. There are many reasons to insulate field erected welded steel storage tanks. Sometimes insulation is required to keep the tank's contents cold, and sometimes it's applied to keep the product in the tank warm. In today's post, Will Connor & Chad Davis, of Mascoat, shed some light on the why and how of tank insulation, and offer some info about insulating coatings for above ground storage tanks.
A New Kid On The Insulation Scene
With the multitude of products requiring bulk storage, there are a percentage of tanks that require thermal insulation. Though thermal insulation is a necessity for these specific products, the expense of installing and maintaining it can outweigh any costs saved by decreasing energy usage or vapor loss. Due to its ability to absorb moisture, an aged insulation system may promote corrosion under insulation (CUI), and could have reduced insulating properties. CUI can significantly increase maintenance costs and lead to the need for an entirely new tank. Occasionally, these issues have led to the decision not to insulate in order to prevent future maintenance or structural concerns. Fortunately, there is an exciting technology that has industry acceptance and can solve these issues while providing thermal insulation as an easily applied coating.
Thermal insulating (or insulation) coatings came onto the market in the mid 1990’s and were mainly used in commercial and industrial applications. These were not reflective rooftop coatings or radiant barriers, which solely reflect UV rays due to their bright white color. Thermal insulating coatings are usually acrylic resins filled with ceramics and silica, among other things, creating a true thermal barrier between two environments. The market was slow to accept them, as it was hard to believe that a coating thickness 1.0-5.0 millimeters could effectively insulate and replace inches of conventional insulation, but today, there are countless applications in a wide spectrum of industries in all corners of the globe.
Most insulating coatings manufacturers will say that they are not always the perfect solution for every tank application, but can help with many of them. This article will discuss both successful and unsuccessful applications.
Insulating Coatings May Solve Pesky Insulation Challenges
Bulk storage tanks are typically very large, so there is no choice but to have them exposed to the elements. If traditionally insulated, it is very likely that moisture will make its way into the insulation and to the surface of these tanks. Due to their large surface area, it is not possible to check everywhere for signs of corrosion, so it is not uncommon to see them re-insulated every few years (depending on the amount of corrosion present.) Tanks that hold product over 320°F (160°C) may seem to be resistant to CUI due to the higher temperatures, however, that temperature is only up to the fill line. Areas above the fill line that do not reach the higher temperatures will be subject to corrosion.
The tank roof is the most difficult to insulate properly and is sometimes left un-insulated to begin with, because of the increased probability of corrosion when insulated with conventional products. The roof usually contains exhaust pipes, vents, or other types of protrusions that can eliminate the possibility of achieving a perfect seal with traditional panel systems. Also, personnel can compromise the jacketing and damage the insulation by walking on it when accessing the roof for a routine inspection. The coatings can also greatly reduce the effects of flash cooling due to a passing rainstorm.
Since insulating coatings are applied (just like paint) to the exterior of the tank, they adhere directly to the substrate or primer. This forms a seamless barrier that rain and moisture cannot penetrate, effectively negating the possibility of CUI occurring. There are no gaps, like you would have with steel jacketing or panel systems. Also, their performance is not diminished by regular foot traffic.
Location, Location, Location Matters
The geographic region in which the tank is located can affect how the coatings will perform and can be the deciding factor on whether or not to use them. Coastal areas that are humid and don’t experience harsh winters are prime candidates for insulating coatings. With high humidity and elevated ambient conditions, traditional insulation will hold moisture against the substrate and the corrosion process will progress rapidly.
In colder climates, applications must be carefully scrutinized. The combination of freezing temperatures and wind load do not bode well for a thin film coating. Though they can still adhere to the surface at low temperatures, their performance value can be reduced. Where 60 mils (1.5mm) may be sufficient in the Gulf Coast of the United States, an application may require 180 mils (4.5mm) in a climate similar to The Netherlands. Or, depending on the application, an insulating coating may not be recommended at all. It may be in their best interests to apply the coating only to the roof of the tank, while the sidewalls remain conventionally insulated because higher surface temperatures (+320°F, +160°C) keep corrosion from being an issue, or a certain thermal performance value may be required. Regardless, there must always be a heat source. Freeze protection application are usually not recommended for insulating coatings.
Some facilities are not trying to keep heat inside the tank, rather they are looking to insulate against radiant heat gain to minimize vapor loss or stabilize contents. Some newer tank farms are constructed with this in mind and have taken measures, such as floating roofs, to combat the issue. However, there are tanks in-service that are older than the new vapor recovery technology, therefore, it is still an issue for them. Fixed roof tanks depend, mainly, on being white or light-colored for UV reflection. Some insulating coatings companies have developed products that are very bright white. Combining the thermal insulation with the highly reflective color is more effective than just a white paint. Radiant heat gain applications, in most cases, require no more than 40-60 mils (1.0-1.5mm.)
With products stored at less-than-ambient temperatures, radiant heat gain can impact the storage conditions. With a product like LPG, as temperature increases, so does the vapor pressure. This makes it beneficial to use an insulating coating over a white paint, due to the fact that our products will maintain a lower temperature, yielding a lower vapor pressure.
Protecting Personnel With Insulating Coatings
Insulating coatings can easily be used for personnel protection on storage tanks. The coating can only be applied to areas that are susceptible to being touched by personnel. It is not necessary to coat any other areas, so the amount of material needed can be very low. Conventional insulation requires custom fabrication when trying to insulate next to stairways, or really anything other the sides of the tank. In an application in Pasadena, TX, one company chose to only insulate along the stair well and the bottom 7 feet of the tank. Also, if these areas were conventionally insulated, the promotion of corrosion in the smaller areas can still warrant the replacement of the insulation, or even the entire tank, in the future.
What About The Tank Roof?
As mentioned before, a large number of tank roofs remain un-insulated. Rainwater and snowmelt will undoubtedly find their way to the surface and then the corrosion process will begin. Heat rises, therefore a thermal insulating coating that can bond directly to the surface and reflect the rising heat back into the tank will conserve energy while stopping the risk of corrosion. Some companies have application examples where the customer coated the roof and even extended down the sidewalls 10’ (3m.) This not only kept the corrosion process from beginning on the fixed roof, but also limited moisture from getting behind the conventional insulation panels on the rest of the sidewalls.
Consider And Evaluate - Is A Thermal Insulation Coating Right For Your Tank?
All of the different types of thermal insulation have their strengths and weaknesses. Though thermal insulating coatings have not been around as long as more conventional forms of insulation, it has become fairly clear where they are and are not successful. The benefits yielded on the successful applications make believers out of the most resistant skeptics. By using insulating coatings in their comfort zone, you are ensuring a sustainable system that will provide a return on your investment well before any maintenance concerns arise.
For more information about field erected welded storage tanks, or to talk with us about your tank project, visit Fisher Tank Company. We'd love to help!
For more information about insulating coatings and your tank insulation needs, visit Mascoat.