Insulating Painted Pipes

I recommend that you challenge the project spec, ask "Why" it says this.

Maybe it was written for original installation of new pipe. It sounds like you are insulating older existing piping.

To be in compliance with the "Spec" you would need to add a lot of extra cost to the job to sand blast the paint off the "old" pipes.

U r right, I have to reject if it is not mating with our project requirement but this question is for my self knowledge only that Is there any technical problem to do insulation over polyurethane paint?

• I questioned because at site all polyurethane top coated tank has insulated then why i have to cost extra if technically there is no problem to accept the job?

Adeel Ahmad-Tecnicas KSA

"Is there any technical problem to do insulation over polyurethane paint?"

I don't know. I suggest you call a Paint vendor and ask them that question.

Then come back here and tell all of us what they said.

In order to insulate a pipe with a working temperature until 350° C you can use a product called Hot Pipe Coating -"HPC" ! Rockwool insulation with 1% of humidity will loose more than 30% of his efficiency ! With Rockwool you need 8 to 15 cm of insulation and most of the time a metal jacket . The humidity of the Rockwool will brig on metal pipes the so called "Corrosion Under Insolation " !With HPC you probably with 7 to 10 MM you can bring the outside temperature down to 50 to 60° C as heat is reflected back to the inside of the pipe!! It's easy to spray with an airless and you don't need to shutdown the heat in the pipe for the application . You can get this unique product via Superior Products Europe info@specoating.com att. Jos or Stef

solutionproviders

What are the primers, intermediate and the finish paints ?

Since you are working at a bit difficcult temperature for most of the organic and epoxy based paints, that must be the reason.

At this temperatures, these paints will peel off/ burn/decompose epxosing the pipe to corrossion.

If the organic paints are applied, with sufficient margin for this temperature then there is no trouble. Else this has to be done.

Usually on these temperatures we go for inorganics or aluminium paints.

The only real good material for that is a Novolac epoxy able to stand 232oC. it contains fiber so it is a thick paint to apply. The problem is when a shut down is done, CUI can occurs at that time. that's why you want to coat pipes or any steel that is under insulation. Normally 2 coat of Novolac epoxy (as Thermaline 450) is sufficient for a DFT of 12 to 15 mils (300µm to 375µm) the most important thing to consider is a pinholes free coating: so run a holiday test.

Hope this can help

Thanks to all i got alot of details regard to subject but i forgot to clarify some as see below,

Three coat system with insulation and cladding,

• First Coat - Inorganic Zinc Silicate - DFT 65microns
• Second Coat - Epoxy High Build Polyamide(MIO) - DFT 150microns
• Third & Final Coat - Acrylic Polyurethane (Gloss) - DFT 50microns
• Insulation Rockwool thickness - 38mm
• Cladding sheet thickness - 0.25mm

Actually most of the line insulated over inorganic / aluminium but availability of this subjected pipe was at site and construction people was hurry to install the line, so they didn't think in this way that line need to be insulated.

what is the range of temperature for above given coating system can defend to peel off/ burn and decompose?

ADEEL AHMAD (Tecnicas-KSA)