Code Requirements for section of shell replacement of A-286C to A516-70

[mechengr12]

I have a 50% caustic storage tank designed per API650 that has a Ni repad on ID for a steam tube. The weld of theB162 Nickel plate to the A283C plate failed and the shell has buckled and there is some signs of Caustic SCC. I would like to have a tombstone shape cutout and replace the CS shell with A516-70 versus A283C due to available material. There are some differences of material properties. I was wondering what sort of documentation or recalculations might be required by API 653 for this change out and if anyone would heed against it.

Further, if anyone has experience or input on preventing preferential corrosion on the Ni to CS weld please let me know.

 

[metengr]

Read API 653.