Tubes SA 268 TP 439 ferritic stainless steel. Manufacturer has to bend 180° very narrow bend 1.5 x d.
Is stress relieving post bending required? Recommended? Does anybody have experience?
Mauro

As far as Section I (Rules for the construction of Power Boilers) is concerned, Post bending stress relieving is only required for Austinitic Stainless Steel pressure parts only under the conditions of PG-19(a) & PG-19(b).
Please refer to PG-19 of Section I.
We usually check out surface cracks in tube bends by MPI for the tube materails other than austinitic stainless steels. It is a good engineering pratice. Normally, there is a chance of wrinkles that may ultimately lead to a crack in operating conditions.
Many times, we did bend at 1.5 times dia of tube for economizer bends.

Best Regards,

Nasir