Analysis and redesign of failed jacket in a petrochemical reactor

The root cause of repeated water leaks due to cracking in a circumferential weld of the heating jacket of a petrochemical reactor was traced to cyclic steam pressure, not accounted for in the design. Fractographic and metallographic analyses of the jacket base and weld materials revealed widely open cracks, initiation and propagation being due to larger than allowable cyclic stresses. There were no indications of environment induced cracking, neither creep nor stress corrosion cracking. Appendix 2 of API RP 579 was used to verify alternative designs for the substitution of the heating jacket. Due to time restraints, the substituted part had to be built with a lower strength steel. Reconstruction was successfully done using an austenitic SA 316L stainless steel.