NACE requirements for SS316/316L

[KEC159]

Per NACE, austenitic stainless steel shall be in the solution-annealed and quenched condition and free of cold work. Does these requirement apply to Pressure Vessels? If yes, what to do with the formed ellipsoidal heads and shells while many vendors warned that solution annealing after forming will distort the head and shell.

Please help!

 

[rneill]

The NACE MR0175/ISO 15156 requirements apply to all equipment including pressure vessels. However, if you look at the tables for Austenitic Stainless Steel Materials in Part 3 of this document (e.g., Table A.2), the particular note is that the materials shall be free of cold work intended to enhance their mechanical properties. Consequently, some latitude is permitted.

I have not specifically dealt with this issue before but I believe it is common to form the heads and shells, solution anneal after forming, and then resize to correct for distortion that might occur during solution annealing. There is little you can do about the resizing but I think this is what is normally done under the premise that it is not a significant amount of cold work and it is not intended to enhance mechanical properties ? You might want to review the NACE/ISO interpretations and see if this is specifically addressed.

You might also want to review the service environment limitations of NACE MR0175/ISO 15156 Latest edition (In particular Table A-2) to see if the use of Austenitic SS is permitted in your application. The current document does have some fairly severe limitations on the use of Austenitic SS in sour service.

Keep in mind that free advise is worth exactly what you pay for it and I have not specifically dealt with this before.

 

[SJones]

Indeed, solution annealing a shell would carry a high risk of distortion and the issue of cold work is a little cloudy in ISO 15156. The flavour of the interpretations suggests that, provided the hardness criterion can be met, the deformation induced by fabrication is not considered to be deliberately enhancing mechanical properties since the original material mechanical property requirements will remain after forming. Something like an S or B condition in ASTM A276 would not meet the requirement. There was a push to state this more clearly which appears to have failed. Unfortunately, it boils down to the end user having to make the call.

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

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