Questions about the suitability of spray foam for insulating a large tank
Q: What is the service / design life
A: The foam will last indefinitely as long as it is properly coated and protected from UV exposure. We need to just ensure we allow for the appropriate thickness of coating and then we can achieve the required 10year maintenance interval
Q: Is there a warranty period on the installation
A: Our standard warranty period is 1year on the installation
Q: How long would it take to apply
A: would need to look into this a bit further but if you allowed 4 weeks then that should be close (weather dependant…)
Q: The current proposal is to repaint the tank with a 3 coat system along the lines of Akzo Nobel Interzinc 52 Primer / Interplus 1180 and Interthane 990 (acrylic polyurethane) final coat. Would the foam adhere to this paint system?
A: The foam would adhere to the proposed system but I think that the final proposed coat is not necessary. This is just a finish product and I don’t believe it is integral in the corrosion protection? If not, I recommend eliminating the suggested top coat to save a few dollars?
Q: My boss says he has seen urethane foam attacked by cockatoos in the past. Is this still an issue these days.
A: Yes, this can be an issue but a bit of an unknown as to whether it will occur or not. Certainly a white finish seems to reduce this from happening. I have also suggested that we can spray an elastomer finish over the foam that will provide a hard barrier over the foam and stop this from occurring.
As mentioned above, I have revised the specification to eliminate the cockatoo issue and would recommend the following:
1. Spray apply 50mm average foam thickness to the external walls of the tank
2. Spray apply around 1.5mm coating of MPL-11 protective coating (not colour stable)
3. Spray apply two coats of Staingard 7000 in white tint for longterm colourfast and additional hardcoat protection
I believe the above would provide for an extremely tough and hardwearing application that will stand up to the rigours.
As also mentioned, I do understand the clients concern with regards to corrosion under insulation. This becomes a factor when water is able to be trapped between the substrate and the insulation. This will not be a factor in a sprayed foam application of this sort. Firstly, the foam and coating forms a completely waterproof and seamless layer of protection around the tank so water is not able to get between the foam and the tank. Secondly, there is no risk of water vapour drive causing water vapour to move through the foam and condense at the foam/steel interface as the overall drive is from the tank outwards due to the ‘warm side’ being the metal skin of the tank.