Coating Blistering in SAGD water treatment vessels 2

[mat211743]

In our SAGD facility, vessels in water deoiling unit and water treatment unit are internally coated with Two-Component Epoxy. We are experiencing severe blistering of the coating. Some blisters are 4" in dia. Does anybody dealing any issues like this? Willing to share some knowledge?

 

[SJones]

The first question is: was the coating system performance tested for the worst case service conditions?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[TomDOT]

Sure. Immersion blisters are typically osmotic blisters of some type. The most common are salts or residual solvents. Glycols are particularly good at causing blisters. You could also have a mis-mixed layer of amine-rich epoxy that the contractor covered up with a "good" layer.

Lots of possibilities. There are failure analysis experts who specialize in paint. Cost is probably $1,000 and up. The low end is if you can take good samples and photos yourself and send them to the expert, and the cause is readily found. "And up" can also depend in large part how many lawyers are involved.

 

[mat211743]

Steve, Field trials with coated coupons are going on. Waiting for the results.

 

[SJones]

Hasn't the field trial failed then?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[TomDOT]

If the tank took 2 months to start blistering, identically coated coupons should take about 2 months to duplicate, plus sample prep time.

 

[SJones]

What I was driving at was: the coating should have been proven for service by testing BEFORE application. Testing would be along the lines of NORSOK M-501 or ISO 20340 as examples in order to avoid the 'it's the paint; no, it's the application' scenario.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[TomDOT]

Ah, yes. The paint should already be prequalified. However, you do still have "it's a bad batch of paint; no, it's the application; no, it's a bad spec"

 

[mat211743]

Thanks Steve. You know the construction issues usually end up in the hands of operating integrity folks!!. It seems the coating was not tested before hand. Now field trails are going on with different coating systems. These trails may help us to identify the suitable coating system. in the meantime there is another expansion project and the project team is looking to purchase the same piece of equipment but with better coating.As the test results are not available i wanted check with other industry guys....

TomDOT: Aren't the osmotic blisters common in relatively clean water? inside the blisters the residual salts will produce the concentrated solution and natural equilibrium shift causes water to accumulate inside the blisters. isn't it? we are dealing with produced hard water? do you still expect Osmotic blistering?

 

[mat211743]

Sorry trials..

 

[TomDOT]

Generally speaking, the cleaner the water, the lower the chance of osmotic blistering. Hard water doesn't eliminate it - the solubility of carbonates is not all that high.

Have you looked inside a blister yet? Collected blister liquid with a needle and syringe? Knowing what the paint looks like (discolored? soft? is the blister inside the coating, or behind all of the coating?) and what the liquid characteristics are helps. (pH, color, SMELL, if you dry some out on glass, is there residue? What does the residue look like?) - and compare the in-blister liquid to the vessel liquid.

Lots of paths to investigate, which is why I suggested an expert.

 

[SJones]

Get the project team to consult the paint suppliers and let them come up with test data report supporting their recommended coating system for the specific application.

http://www.jotun.com/

http://www/com/20020116.nsf/viewunid/914D460814F746B7C125707C002A3B6C/$file/Norsok+Systems+No+3.pdf

NACE Corrosion 2004, Paper 04034

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Mtcheam2]

This is a very complex issue presently on many SAGD sites. What type of vessels do you have? Are they in the water treatment plant? Most of the blistering in the coatings we see is occuring mainly from "osmotic" blistering as noted above from other responses. During fabrication, most shops do not prepare the surface to meet SSPC-SP 12 - NV1 ( NV2 or NV 3) specifcations. This specification, addresses the Non-visible standards and deals directly with Chlorides/Sulphate cleanliness and PPM allowed on the metal surface prior to coating. So during the application of the coating, the applicators meet the Blasting cleanliness ( ie SSPC-SP5, etc), however, the chlorides/sulphates may still be present in high PPM's.

Secondly, from our experience, the process water is not clean as it comes from the local ground water (usually brackish water) which contains very high concentrations of Chlorides, between 200-900 PPM, - depending on geographic area.

As for coatings, there are some very good coatings that work in the SAGD vessels, however, in the water treatment plants, there has been no coating hold up within the WAC's, SAC's or demineralized vessels. This is a very complex issue, but during the regeneration cycles, the exothermic reactions that occur during this stage are so great, the temperatures are greater than most internal coatings can handle ( 100C/212F +). The repetiveness of the regen cycle breaks down the coatings quickly, some quicker or longer than others, but they will all deteriate with time.

There are other coatings on the market that may handle the service conditions/regen cycles, but these coatings are not condusive to applying in the vessels inthe small parts within the vessels.


The solution we have found has been rubber linings.

If you can provide more information on your vessels operating conditions and type, I would be glad to discuss what has worked and not worked from our experiences. I hope this is helpful.

 

[mat211743]

Thanks Mtcheam2. Here are the process conditions in our WAC P = 1138 kPag T=93C pH=9.5 hardness 38 mg/L, TDS = 6858 mg/L, Oil = 0.2 mg/L.