AbstractA 4″ ID, 310 SS finned pipe was used as a heat exchanger between an external gas stream at 1660–1740°F and an internal gas stream at 315°F. Failure occurred through multiple circumferential cracks, which found their origin in extensive separations at the grain boundaries on the ID, penetrating as much as 0.150″ (50% of wall thickness). It was found that that the metal temperature ranged from 1200°F at the ID to in excess of 1400°F at the OD. Therefore the ID was exposed to creep stresses at a level of 35 ksi. Since at shutdown the metal could not recover, these creep stresses accumulated at each start‐up. Finally system stresses caused the remaining wall thickness to failure.Transposition of the fins from the OD to the ID, or even omission of the OD fins would lower temperatures as well as stress levels sufficiently to prevent this type