Large SS vessel passivation 1

[stewbaby]

Anyone have experience with or contacts for passivating large vertical vessels, specifically a 6' ID x 110' T/T tall vessel with 321 SS overlay? Need to perform internal inspection and repairs without concern for stress corrosion formation caused by exposure to oxygen.

Typically keep an N2 blanket on vessel during outages as it has not typically been opened.

 

[unclesyd]

stewbaby,
You got me on this one. Never heard of this scenario. What state is the surface in that you would want to passivate. Normally O2 is an excellent passivator of S/S. At one time we had a lot 321 S/S vessels and tanks and this precaution was never taken even though the process media was very slightly corrosive. A vessel of your size is going to be hard to passivate with any of the normal materials used for passivation. Without your statement concerning O2 causing SCC on something as big as your vessel I would use hot air or steam and air.
As I have stated before we have never seen the benefits of passivation of S/S if it is in a corrosive media. We pursued this in the lab and with inservice tests for years.


We had plenty of SCC around but never under your stated condition. I think all would be most interested in this SCC mechanism.

 

[qualityManager]

Never done anything that large, but have rigged a sprayball type devices in top of vessel w/ recirc pump to get solution over vessel area for the designated time period. You might need several sprayballs on a column to insure coverage of the surface area.

See ASTM A-380 for solutions, temperatures, and times.

Happy New Year,
WRW

 

[WingTipHsu]

Hello, stewbaby
You can begin with any of the large stainless steel vessel purveyors (DCI, Precision Stainless, Mueller) or go directly to the contract passivation people (Hayward, Active, Oakley).

It's not a problem, the trick (as always) is to properly prep (degrease) and select the right agent (I like nitric). The Koslow company makes a tester, so simple "before and after measurements" ought to work.

Stress corrosion is independent of exposure to atmospheric oxygen. Look at a photomicrograph of stainless steel, you'll see a distinctive lamellar microcystalline lattice familiar to undergraduates. If you have a Lange's Handbook of Chemistry you can find the electrochemical series, which shows to different voltages (activities) for the exact same grade of stainless steel: one is "active" (just machined/polished) and one is "passive" (in my opinion, washed and chemically oxidized with a powerful oxidizing which happens also to remove iron-rich and other soluble constituents).

Good luck

Wing Tip Hsu

 

[stewbaby]

All, Practice mainly imployed to meet NACE standard RP-01-70 for "Protection of Austenitic Stainless Steel in Refineries Against Stress Corrosion Cracking by use of Neutralizing Solutino During Shutdown". Better safe than sorry, especially with a million dollar vessel. The spray head or "butterworth" idea QUALITYMANAGER mentions seems the way to go...just will be a much bigger setup than we have ever attempted ourselfs. Anyone have more detail on contractors that would provide such passivation service (guess they would be kin to chemical cleaning contractors).

 

[EMKWR]

Stewbaby,
passivation programmes usually are taylor made for each situation. In a lot of cases pre-tests are performed and a passivating agent is formulated. My company gives consultancy and supports before and during chemical cleaning and passivation of large vessels and boilers. Have done this a few weeks ago for a large boiler of a power plant which had a disturbed passive layer. You can contact me if you like. Maybe if you have more details we can help.

Edwin Muller
KEMA Power Generation & Sustainables
Arnhem, The Netherlands
E-mail e.f.muller@kema.nl
Internet:

http://www.kema-water.nl