Protective Coatings for Hot Water Service

[sbush]

Can anyone recommend a coating system for painting the interior of pressure vessels for hot water service at 160 - 220 deg. F. Our normal supplier (Tnemec) doesn't have a product that will go up to 220 deg. We can do baked coatings, but would prefer not to if air-dried is available. We can apply using airless or conventional. Not interested in any rubber linings or outsourced services.

S. Bush

http://www.water-eg.com

 

[Goahead]

Could Aluminum based paint systems be used? They protect steel to much higher temperatures.

http://www.welding-advisers.com/

 

[jte]

sbush-

We use products from Carboline with good results. They have too many to look at - talk to one of their distributors for a recommendation based on your specific application.

http://www.carboline.com/Products.html

jt

 

[Geof]

I believe Plasite 7156 would meet your needs. Plasite was bought by Carboline a couple of years ago, so check with them on availability & if they are going to discontinue / replace with another product.

Cure time - Dry to the touch in a couple of hours - fully cured in about a week at normal temperatures. Can also be heated for faster cure time. My old company used to pump hot air into the tanks after lining them.

Good Luck.

 

[pennpoint]

sbush

Try this company:

http://www.heresite.com/

pennpoint

 

[sbush]

Thanks to all for responding.

To goahead: Aluminum sounds like a good idea, but I've never used it in a paint system. We have a flame-spray system and we can metallize with either aluminum or zinc wire. Have you or anyone else ever tried metallizing instead of coatings or linings for hot water immersion service.

To jte & geof: Thanks, for recommending Carboline. They are currently working on our request and Plasite 7156 is one of the possible systems.

To all: Carboline has raised initial concern about coatings separation because of something known as "cold wall effect". In essence the temperature differential between the hot interior of the vessel and the cold exterior could cause separation to occur between the lining and the metal surface. One solution is to insulate the vessels but, in this case, our client doesn't want to do that.

Has anyone experienced coating separation problems cause by cold wall effect or decompression of the vessel? The working pressure in this case is 50 psi max.

S. Bush

http://www.water-eg.com

 

[Geof]

Metallizing - at the same company, we used a copper flame-spray coating (over SA-516-70 steel ) for the tubesheets of a gas-fired water heater. Vertical tubes were copper-over-steel. It seemed to work well.

It wasn't practical for our other products, however.

 

[gibson55]

Hello sbush.

I am arriving a bit late to this thread but thought I may add something to it. It's our experience that a good liquid organic coating utilizing a novolac epoxy backbone should handle your temperature requirements for the life of the vessel.

Surface prep should be SSPC-SP 10 with a 2.5-3 mils profile. The solvent-free epoxy coating I am thinking of can normally be applied in one application when using plural component equipment otherwise the resin side can be diluted up to 20% by volume with butyl acetate only then mixed with the hardener component and sprayed through an airless.

Aside from the temperature you have described a relatively mild environment. The key to long term performance will be a post-cure requirement in which you would raise the internal temperature (using heated force air) of the vessel to 10% higher than the highest anticipated operating temperature and hold that temperature for at least 2 hours but not more than 4 hours.

This hot, dry air post-cure will complete the crosslinking of the reactive components of the epoxy lining abd produce a truly impermeable dry film finish.

Cold wall effect has been referenced. With a shop application there should not be any concern however with a field coating job (but only in the right seasonal conditions) you will require to envelop the vessel and maintain the temperature outside the vessel but inside the envelope at least equal to the interior vessel temperature. This must be followed until the wet film converts to a dry film stage.

Go to

http://www.4pipelines.com

to find the coating under discussion. Once there download the data sheet entitled: KEMA 300PA.

 

[SJones]

Lots of recommendations. Make sure that they are supported with reputable test data under conditions that can be related to the proposed service.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[hbw]

Also ask the coating manufacturer and the coating applier for a list of previous projects in the same service. Get contact names and telephone numbers. Then call the previous users and ask about their service history. The coating applier skill is as important as the coating material. The coating applier must have proven history with the material specified.

Plasite 7156 and Plasite 7122 are excellent for hot water. They are hot air cured epoxy-phenolics. Heresite are typically high baked phenolic coatings that may be more expensive to install.