Fábio de Castro Marangone - Petrobras
Ediberto Bastos Tinoco - Petrobras
Julian J. Bedoya, P.E. - Stress Engineering Services
Luiz Carlos Largura Jr. - Stress Engineering Services
The objective of this study was to determine the viability of using weld overlay repair methods to reinforce coke drum material that has experienced bulging, as an alternative to traditional repair methods.
The approach taken in this project was to perform testing of the same material as coke drums using a combination of fully reversed, axial fatigue testing and bending thermo-mechanical fatigue testing on coupons. The material was taken from spool sections coming from cones that were in service at a PETROBRAS refinery. The spool sections were reinforced, provided as in kind donation, with Inconel 625 via weld overlay deposition by Welding Services Incorporated.
The potential advantage of a weld overlay reinforcement, is that it can be performed with efficiency and expected longer lasting quality compared to window replacements and can replacements. This testing has provided fatigue data at stress ranges commensurate and at higher magnitudes than typical coke drum operations. The base metal fatigue calculations from ASME Section VIII Division 3 suggest that they last only 4% of the life of Inconel 625 at a stress range of 134 ksi (923.8 MPa), and 37% at a stress range of 186 ksi (1,282 MPa).
These results show the potential of this technology. In addition, results from different testing configurations including reinforced circumferential seams, testing of weld overlay deposited directly on the cladding, and transitions from repair to base metal will be discussed.