Is it just a sleeve, or is there any weld ?
Well, you should calculate the moment at the sleeve location, and check both pipe sections (the big and the small) for that moment.
That would be conservative, since at the location where both pipes work together the combined section is more...
I am new to the forum, forgive my errors please.
Is anybody familiar with the fatigue design criteria of pressure vessels, according to ASME 8 ?
Thank you,
Padarusca.