Inspection of CUI ( Corrosion Under Insulation) 1

[ak1965]

Dear Forum,

1. What is the best method suggested and available for inspection of Corrosion under insulation in a petrochemcial Complex?

2.An area of driers (Hydro Carbon Driers) (working pressure 40 kg/cm2) and associated piping is subjected to a temperature variation between 15 deg c to 200 deg c in every 36 hours due to regeneration of drier beds. Do you think that CUI in this area would be more accelerated? if yes , what are the reasons for it?

 

[SJones]

1. The best method will be the one that has the highest probability of detection at the lowest cost. You can choose from several inspection methods and whether you have to take the insulation off or not: pulsed eddy current, long range ET, visual examination are three examples.

2. API Publication 581 (2000 version) will help you assess what may happen during temperature cycling. A look at European Federation Of Corrosion Publication 55 would also help. The periods at elevated temperature may be beneficial in removing moisture from the substrate surface but if it degrades the coating system then it will not be good for the normal temperature operation.

Steve Jones
Materials & Corrosion Engineer

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

 

[stanweld]

Many US Refiners are using digital radiography when insulation cannot be removed.

 

[ak1965]

Thanks Sjones and StanWeld,

To me digital radiography ......cost matters boss....! also ti could be a potetnial hazard, transportability would also be a problem....!!

Visual inspection appeals to me the most....of course i will loose the insulation .....but that is already very old.....!!

Infrared thermography could be one option but that is also ruled out because my plant is situated in ariany zone....so erroneous readings can not be ruled out....!!

My next query....the piping i am referring to undergoes a thermal cycle....15 deg c to 220 degc every 36 hrs...!

sweating...to.....dry Heating....on CS piping....which kind of insulation should be used to protect this service from Moisture ingress....??

 

[rustbuster]

ak1965,

It sounds to me, by the age of the insulation that this system would be a very high candidate for CUI. All of the methods listed are usefell.

Conventional profile radiograhy at areas where water can trap could also be considered.

The best method is visual inspection with isulation removal. (Sounds like the insulation could use replacing anyway.

There are alot of paint and coatings systems that could be applied which would increase overall confidence.

I would do a risk assessment, to me you already have a high likelihood of damage, if the conesquense of failure is also high, I would lobby for visual inspection and re-furbishment.

Good luck, let us know how you make out...

 

[ak1965]

Thanks rustbuster.....

We are on the job....would let the forum know the outcome.....!!

We are aligining RBI practices also very soon.....!

 

[sentjoh]

AK1965
CUI problems are as old as the way to Rome.
RBI seems to be the latest fashion but is only a method it you have a documented maintenance program for insulation. For instance if some steps on, and damages insulation you immediately fix this. Also a lot of companies (ExxonMobil) claim to have so many exceptions to the rule that they’ve left the RBI methods and complete strip vessels or piping. Engineering the right insulation system is however important. In your case I would advice Rockwool and a finish either GRP (Glassfibre Reinforced Plastic) or traditional Alu sheeting. If you choose alu sheeting, I strongly advice you to consider installing it with an air cavity (non-contact insulation) like described in DIN 4140 or EFC WP13 and WP15 guidelines. If you choose to insulate flanges create a drain/leak detection by using a Flangebelt. If you need to inspect under insulation install a VIP (Vessel Inspection lug) plug. And if you don’t want install insulation without aircavities at least use a thorough drainage like f.i. PMU drainplug. These products can be found on the Temati website

http://www.temati.com/corrossion-under-insulation-cui.aspx.

Just contact me if you wish further smart and simple solutions

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

 

[Lennie2611]

There is s device on the market thatbtells you where and when you have water under insulation so you can do something about it before corrosion starts ... root cause detection.

http://www.H2Obvious.com

 

[sentjoh]

Do you have any experience with this? As Temati we sell a PMU drainplug

http://www.temati.com/files/Downloads/TDS/UK/Algemeen/TDS-PMU.pdf

, which is a little bit based on the same principal, but without the electrical parts. And my experience so far is that conservatisms are our biggest enemy. Even thought it’s a rather cheap product and very easy to install. I had a look at there web site. Although its very well documented and tested, I see no references from big companies.

 

[MJCronin]

Suggest re posting in another forum..???

"Corrosion Engineering " perhaps ????