Coating options for large carbon steel tank

[Jimmy D.]

Hello,

I'm new to this forum. My plant has two 14' dia x 16 ft tall carbon steel jacketed evaporators that have corroded and eroded on the interior surface. The evaporators are over 40 years old and are agitated. The jacket area is used to heat the evaporator ingredients with 50 psig saturated steam. The interior of the vessel is rated for full vacuum to about 15 psig so these vessels are constructed like pressure vessels. It seems the bldg was constructed around the tanks therefore their replacement would be extremely expensive. I'm looking for coating options that would give the approximate corrosion resistance of a typical stainless steel. The interior ingredients are solids suspended in water with some solvent. For process reasons we can't use any technologies that would create a potential void space behind the coating (like cladding).

What are my options?

Regards,
Jimmy D.

[djewell]

Where do you want to apply the coating? On the inside of the evaporator tanks or the inside of the jacket? How easy is it to gain access to the inside of the tanks?

[Jimmy D.]

(11-12-2010 10:16 PM)djewell Wrote:  Where do you want to apply the coating? On the inside of the evaporator tanks or the inside of the jacket? How easy is it to gain access to the inside of the tanks?

Coating needs to be applied to the interior of the tank. There is a manway on the top of the vessel so access is by ladder. It is a confined space as defined by industry standards.

Jimmy

[kschewe]

I would spray the tank with nickel. or nickel chrome. I would use wirearc process, with tafa 75b, 444mxc or metco 8400 etc. The tank will have to be cleaned and grit blasted with 90 grit or coarser. My concern would be for the saftey of the worker doing this job in the confined space. Wire arc sprays cool but lots of smoke. The smoke will have to be exhaused somehow and the operator will have to be protected with a fresh air suit.

[MichiganMan]

Field applications like this one have a lot of challenges, and very few companies have the capability to execute them. With some more information you may be able to get a solution though.

You mention that for process reasons you cannot have a "void" behind the coating. Can you define that a little more clearly?

Arcspray would be effective in lining the tank, but would leave porosity and (I'm assuming) necessitate a sealer suitable for immersion application.

We need to identify temps, pressures and chemistries in order to identify suitable sealers. In addition the "solids" that are suspended by agitation could use more clarity as well. Fibrous solids represent different challenges from nano particulate carbide (for instance). Do you have a % solids that is fairly constant? Particle size? What are the physical characteristics of the solids (hardness, behavioral tendencies like clumping, etc.)?

kschewe is right that dust/smoke control will be an issue. I cannot stress enough that this is a safety issue, not only for the application crew, but there may be an explosion or fire potential as well, so make sure it is well thought out.

Sounds like a nice application to save your company big dollars.

[Jimmy D.]

(11-18-2010 08:19 PM)MichiganMan Wrote:  You mention that for process reasons you cannot have a "void" behind the coating. Can you define that a little more clearly?

What I mean is we can't have a space where the product being processed inside the tank could be trapped (as in cladding or rubber lining). A treatment that bonds to the surface in such a way that is avoided would be ok.

To answer your other questions in general, this is a simple solids suspension application using water and small solid particles in the range of 0.010" in diameter up to 0.070". The slurry density varies greatly depending on the recipe.

Can you recommend vendors who can help me with this application. I'm unfamilair with this area of the industry. Of couse safety is the primary concern and we would not pursue an option where the worker could not be protected.

Regards,
Jim

[MichiganMan]

What is your location? If you are in the contiguous 48 of the US then I'd be happy to help. This sounds like a tremendous opportunity to me. If you aren't in the US, then I have limited knowledge of sources, but do know some folks that may be able to help dependent upon what country you are in.

Full and fair disclosure: Since I am clearly an interested party and don't want to come off as selling on the forums it may be worth looking into the Internaltional Thermal Spray Society for sources too. I'm guessing that others here may be able to identify sources as well and I'd encourage them to make suggestions, because finding field contractors in this business is often quite difficult.

[Jimmy D.]

I'm located in the Florida panhandle. Please send me your contact info or website.

Thanks,
Jim

[Grider.j]

(11-22-2010 05:35 PM)Jimmy D. Wrote:  I'm located in the Florida panhandle. Please send me your contact info or website.

Thanks,
Jim

You can get information for this project at Enerfab.com. We are currently doing something similar to what you are describing.
Regards, Jack

[ives]

Well, now that you are intending to spray your inner tank, the best thing that you can go with is certainly nickel as kschewe suggested. But make sure that you clean the tank very well and also then you have to grit blast it! Be warned! This is very risky!