ASSESSMENT OF COKE DRUM BULGE DEFORMATION USING ONLINE THERMAL DATA TO DETERMINE OPTIMAL WELD OVERLAY REPAIR DESIGN

Studies [1-11] have shown bulging in coke drums occurs due to several factors. One of which, are large thermal gradients that occur during the drum operating cycle. A thermocouple array comprising of 126 temperature indicators, spanning 1.7 m (5.5 ft) high, full circumference, was installed onto a coke drum at the location of a significant bulge in order to monitor the drum skin temperature distribution over a thirty-day period (total of 14 drum cycles). This paper presents the findings of this thermal study, exploring the nature of the hot and cold spots seen during the quench phase and maps out the resulting deformations and plastic strains local to the drum bulge. A reinforcing weld overlay repair is selected after using finite element analysis (FEA) to optimise weld coverage, placement (internal surface ID vs external surface OD), number of weld overlay passes and final thickness. The weld overlay effectiveness was found to be primarily based on the axial extent of overlay applied and not significantly affected by the thickness of the overlay.