SS Insulation 2

[DiegoMartinez]

All,
Does anyone know if SS piping/Vessel need painting if it is to be insulated? If yes, why? Can you refer me to the relevant code?

Rgds D

 

[vpl]

I've never seen stainless steel piping being painted. What would be the purpose of painting it?

Patricia Lougheed

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[vpl]

Just to clarify, because I looked at the title after I posted:

Based on your post, I assumed your piping and/or vessel is stainless steel, not that the insulation is stainless.

Patricia Lougheed

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[kenvlach]

Under-Insulation Corrosion (UIC) is a very real problem in some environs (mostly those involving chlorides & humidity). Important to use a chloride-free insulation.
See About insulating stainless steel...
thread1135-174402

 

[kenvlach]

Lots more:

http://www.google.com/search?hl=en&...+insulation+corrosion+stainless+steel&spell=1

 

[Montemayor]

If the vessel is stainless and insulation is required (be it for Personnel Protection or Heat Conservation), I would not paint it. It goes without saying that the insulation selected is going to have to be chloride-free to avoid any possible chloride stress corrosion on the SS. If the vessel is going to be exposed to a possible chloride atmosphere, I would not trust any paint job to protect the vessel from the same chloride stress corrosion. For a chloride atmosphere, stainless is basically the wrong alloy or material of construction selection. Any small scratch or defect in the paint surface (no matter how well it is inspected beforehand after application) will potentialy spell the demise of a stainless steel process vessel - especially if it is under process stresses due to pressure / heat.

 

[SJones]

Interesting thoughts but then one has to ask why those awfully nice people at NACE go to the trouble of publishing RP0198 The Control Of Corrosion Under Thermal Insulation And Fireproofing Materials and put a table specifically for austenitic stainless steels in it.

Steve Jones
Materials & Corrosion Engineer

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

 

[kenvlach]

There are detectable levels of chloride in nearly every environment & insulating material. You simply cannot make a blanket statement concerning the use of SS, painting it or insulation. The devil is in the details.
How much chloride in atm. & insulation? Humidity range? Temp. cycling, etc.
Some epoxy paints are preferred for SS that will be insulated. Sealed cell insulation is preferred when thermal cycling may result in condensation of humidity.

 

[DiegoMartinez]

Gents,
Well, the vessel is to be installed in a normal atmosphere. Co2 media and ops pressure/ Temperature in the order of 150 Barg and 50 C accordingly.
I don't know the paint spec but I can get back to you tomorrow. However, in such a condition what is the suitable/ minimum Choloride insulation material?

Rgds,
Diego

 

[europipe]

I know a company that wraps alu foil around the ss pipe before insulation.
It's because of the influence of the salt from the sea nearby.

 

[DiegoMartinez]

Gents,
Thanks for your feedback.
Please could you tell me where is classified as chloride environment?
My application is an onshore gas plant. What about FPSO projects?

Rgds Diego

 

[dcasto]

I'm with Montemayor, If the piping is cold, then you will need to make sure the insulation is totally sealed, typically a wax compound to keep air and moisture out which will damage the insulation and make it grow huge ice blocks, not good. If it is hot, pipe insulation, moisture wont get there, including Cl in the moisture. If it is insulated for personal protection from 120 F to 200 F, unless you need the heat, do no insulate, put a screen around it.

 

[kenvlach]

"Corrosion under insulation is a very serious issue.
...
The most common corrosive ion is the chloride ion, which can be introduced through wash down water, brine, sea water, potable water or cleaning solutions. It can also originate from a range of other sources, including the insulation itself. Installations in coastal areas subject to salt water, heat, and high humidity are particularly prone to corrosion issues.
Almost all insulation products contain chloride ions. Even non-wicking thermal insulations can trap and hold chloride ions against the stainless steel surface. Fortunately, there are several specifications for corrosion control requirements.

Testing Insulations For Corrosive Properties
Three standards have evolved as the primary test methods to address stress corrosion of austenitic stainless steel:

• ASTM C795 Standard Specification for Thermal Insulation for Use in Contact with Austenitic Stainless Steel.
• MIL-I-24244 Insulation Material, with Special Corrosion, Chloride, and Fluoride Requirements. U.S. Department of Defense specification for nuclear propulsion systems.
• NRC 1.36 - Regulatory Guide for Nonmetallic Thermal Insulation for Austenitic Stainless Steel. Specification
developed by the U.S. Nuclear Regulatory Commission for the nuclear power industry.

These similar standards specify chemical properties of insulation intended for use in contact with stainless steel to minimize the possibility of stress corrosion. They quantify the maximum chloride ions permissible, as well as the minimum ratio of sodium and silicate to chloride ions.
...
A practical method of reducing potential for stress corrosion is to use an insulation such as T-12 or WR-1200, which are manufactured with sodium silicate. The basic chemistry of these industrial insulations neutralizes chlorides. IIG MinWool 1200 Pipe and Board insulation also effectively minimize corrosion potential.

Corrosion Resistant Paint
In areas of high stress corrosion potential, a recommended industry practice is to apply a protective paint or specialty coating to stainless steel prior to insulating. An industrial insulation supplier can provide appropriate materials."

Info above from the following insulation supplier:

http://www.intelligentinsulation.com/pdfs/TB1-Corrosion .pdf

Additional links:
ASTM C692-06, 'Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel.'

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/C692.htm?L+mystore+ufdp5919

ASTM C795 (cited above)

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/C795.htm?L+mystore+ufdp5919

ASTM C1617-05, 'Standard Practice for Quantitative Accelerated Laboratory Evaluation of Extraction Solutions Containing Ions Leached from Thermal Insulation on Aqueous Corrosion of Metals.'

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/C1617.htm?E+mystore

ASTM STP 880, 'Corrosion of Metals Under Thermal Insulation' Article titles & abstracts are available for free; the entire book or individual articles can be ourchased:

http://www.astm.org/cgi-bin/SoftCar...AGES/STP880.htm?L+mystore+ufdp5919+1184854364

MIL-I-24244 (cited above), now MIL-DTL-24244D:
"This specification covers asbestos-free thermal insulation, cement and adhesives, all with special corrosion, chloride and fluoride requirements"
So crucial to US security that it's a 'Controlled Distribution Document.'

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=17088

'New Industry Standards, Test Procedures and Surface Treatments Combat Corrosion Under Insulation (NACE)'

http://www.corrosionsource.com/CS2000/session04/paper0403/paper0403.htm