I have this problem:

a 180-deg Return (ASME B16.9) of a tube heat exchanger with a thickness ander the minimun nominal (nominal - 12,5%).

I would like to verify the stability of the real thickness, which formula I have to use, the formula like that for the thickness of bending (ASME B31.1)?

Does anyone can help me?

Thanks a lot

Riccardo