Selection of coating system to prevent CUI 1

[srijey]

Has it been proven that carbon steel surface needs coating system to prevent CUI. I understand there are various factors that control the CUI, coating system alone cannot prevent. The new API RP 583 does not address selection of coating system. It's easy to say that one need to select a right coating system based on the full understanding of CUI, but, my basic question is what is the percent of success on carbon steel surface coating aginst CUI. This is just to alleviate my reservation against coating to protect CUI on carbon steel.

 

[hokie66]

I might have an opinion if I knew what CUI stands for. Hate acronyms, or abbreviations, whatever this is.

 

[SJones]

CUI = corrosion under insulation

Consult NACE SP0198 and API RP 581, Part 2, Section 17.

Steve Jones
Materials & Corrosion Engineer

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

 

[hokie66]

Steve,
Is there a reason for the bold italics? Now that I know what CUI means, I have no opinion to offer the OP.

 

[SJones]

Yes - so that I can see my replies more clearly within the threads. I was advising the OP to consult the NACE and API documents.

Steve Jones
Materials & Corrosion Engineer

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

 

[srijey]

Thank you Steve. API 581 Part2 Section 17 helps in identifying the CUI extent of damage. We had CS pipes operating in the range of 100 to 170 C without coating for decades without CUI. NACE SP 0198 suggests coating system for all CS pipes - 45 to 650 C under insulation. This is very similar to age old concept of painting steel structures - Generally away from seashore areas, no painting is necessary on steel structures to protect against corrosion is the finding after 70s. My question for insulated CS piping and equipment operates below 170 C: Has it been accepted practice in industry to opt for coating on such assets to protect under CUI? Seems like medical statistics - surveys conducted by Universities. I'm working in oil & gas and we're attempting to review our practice on coating of CS pipes and equipment. When I enquired with few other corporate giants, opinion varied. Hope you understand my dilemma (to quote or not to).

 

[SJones]

As a final offering, try reviewing European Federation Of Corrosion Publication No 55.

Steve Jones
Materials & Corrosion Engineer

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

 

[srijey]

EFC 55 European Federation of Corrosion Publications seems to be a key player in the upcoming API 583! Thank you Steve; I'll wait for some response from operators who introduced of late such measures on CS assets.

 

[hokie66]

Steve,
If we all did that, you would lose the advantage. It just looks rude to me...shouting.

 

[srijey]

Yea, unfortunately, facial expressions are not seen here. It actually shows gratitude for your prompt, to the point response. I'm searching for the experience of operating units on CS assets within the 150 C range and how they decide coat or not to coat. As I said before, we did not follow NACE guidelines for coating the CS assets and did not see any CUI. When we develop the standards we refer to these NACE and API standards, but then originally we did not specify coating for insulated assets. Again the new microporous and silica aerogel insulations are hydrophobic. In the new version of our standard, we tend to debate over this coating on such insulation. The result is posting of this query. I hear your shouting and I politely smile over the disadvantage of not able to show my expression of appreciation. Thank you again Steve.

 

[hokie66]

srijey,
You can show your appreciation to other posters in two ways. You can click at the bottom left of the post, where it says that you thank the poster. You can also use the "Emotions" button to the left of the "Submit Post" bar.

 

[SJones]

THIS IS SHOUTING

Steve Jones
Materials & Corrosion Engineer

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

 

[SJones]

For the benefit of hokie, I'll keep this one in the same old, shade of grey text.

The decision to paint, or not, should be based on the corrosion risk assessment. You are building a case for low probability of CUI occurrence. Now consider the consequences of a leak or rupture if it occurs, followed by how much inspection would be incurred in trying to find the CUI before a leak or rupture. Of course, painting does not provide immunity, but it can help with the probability. So, as you can see, it is very difficult to advise whether to paint or not because we can't perform the risk assessment.

Steve Jones
Materials & Corrosion Engineer

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

 

[TomDOT]

Hour-long free webinar discussing coatings for CUI prevention:

http://www.paintsquare.com/webinars/?fuseaction=archive&action=view&webinarID=95

 

[sentjoh]

Dear Gentleman

We seem to forget the “I” in CUI and underestimate the influence of proper insulation design.

The NACE emphasizes on coatings and clearly favours TCA for heavy duty environments. My issue with the NACE SP0198 is that it doesn’t focus enough on the influence of insulation. We all know that wet saturated insulation creates the unwanted electrolyte, so my point is to engineer a fit-for-purpose insulations systems that allows water/moisture to drain or evaporate. There are several well documented standards which describe the use of drainplugs, aircavities, non-contact insulation or the use wicking materials. Any coating whether it’s zinc, silicate coating or even TSA are subject to the QA/QC regime and the quality level of application. Also the equipment design e.g. chamfer all sharp edges, drain holes in vacuum rings, protrusions etc. have a big influence whether a coating will meet it’s expected lifecycle. The EFC 55 CUI guideline, which is currently under review for an update, has a multi disciplinary approach which also covers a RBI method. Lets remember that CUI like any other unwantend corrosion is a organisation issue which is primary an asset-owners responsibility.

Regards
Johan

http://www.linkedin.com/in/johansentjens

 

[darthsoilsguy2]

Most of the CUI i've seen has been due to failure of the sheathing to keep the rain out. i suppose this usually goes down when the product temperatures goes up, but evaporation takes energy.

 

[srijey]

Thank you for providing valuable answers. Can I conclude that the short answer to my original question 'How successful the current industry practice on not coating the CS surfaces with insulation (microporous or flex aerogel) operating below 150 C?' is - Larger number of corporations do not coat the insulated (hydrophobic) surface below 150 C? This is because the integrity (loss of adhesiveness or flaw) of the coating is questionable. Alternatively, wait for the new release of EFC 55.