Selecting the Right Coating for Insulated High-Temperature Fans
It’s common to apply an industrial coating on the external airstream to make a fan more resistant to heat, fire, particles, etc. and to protect it from corrosion. But there’s more to it than slapping on a coat of paint. There are special considerations for high-temperature fan coating, particularly when you add insulation to the mix. The choices are based entirely on the fan material of construction, namely what kind of steel is used.
Why Coatings Can Be an Issue with Insulation
When you insulate something that has high-temperature air flowing through it, the wrong kind of paint will begin to bubble up. That’s because when you wrap the insulation around the fan, the natural condensation from the heat is trapped and can have an effect similar to submersion in water. That makes certain paints bubble, negating the protective effects of the high-temperature fan coating.
Why Insulate a High-Temperature Fan
Insulation serves two purposes for industrial process fans. In this case, we use it for thermal protection in the system and environment surrounding the fan. The other reason to use insulation is for sound protection, which may or may not be necessary in this case. There are three primary types of industrial fan insulation: a removable insulation jacket, cladding (often aluminum), and a double-wall insulated housing.
The Right Coating for Your Insulated High-Temperature Fan
If you know you’ll be using insulation, or even if you might add it later, you’ll want to choose your high-temperature fan coating carefully. “Regular” coatings including enamel-, epoxy- and polyurethane-based wet paints and resin-based powder-coating are not sufficient to avoid bubbling when insulated.
In reality, the choice is between whether or not to coat the external airstream at all, depending on the material of construction. Here’s how to determine the proper treatment for the external airstream:
Use a Zinc-Rich Primer
If your fan material of construction is standard carbon steel (A-36 grade) and you know the fan will be under insulation, use a Zinc-rich primer. You’ll recognize this immediately by its distinctive green color.
Do Not Add Any Coating
Equally important, if your fan material is Corten (a carbon alloy) steel or stainless grade, it’s best not to use a coating at all. Many customers will bristle at not getting a coating on a Corten housing because it’s weathering steel (meaning it’s intended to rust) because it’s actually good for the material to rust! It’s most effective to leave the fan uncoated in this case.
Hear it from an Application Engineer
Senior Application Engineer Chet White demonstrates why there are special considerations for coating insulated high-temperature fans in this one-minute video.
When you need to specify a centrifugal fan or blower for your industrial process application, or if you need centrifugal fan or blower maintenance, repair or retrofit, reach out and connect with one of our application engineers to discuss the details of your project.
For more information on centrifugal fans, check out these additional pages:
- Industrial Fan Insulation Types & Considerations
- Industrial Finishes, Custom Coatings
- Fan Materials of Construction
- High-Temperature Fans