COKE DRUM LIFE IMPROVEMENT - A COMBINED APPROACH

Delayed coke drums are operated under severe conditions of cyclic heating and forced cooling that apply repetitive thermal stresses to the drum walls. The variable nature of the process combined with alternative operating strategies result in a wide variety of experiences for drums of similar design. The ultimate end-of-life for coke drums results when there are unacceptable amounts of circumferential through-wall cracking due to low cycle fatigue. For the past 10 years, coke drum operators have increasingly been applying various monitoring, inspection and remediation techniques to predict and try to minimize this cracking as well as improve methods of crack repair. These various technologies have already shown benefits when applied individually, but are now available in combination to further assist operators in increasing the life of their coke drums. The individual techniques that are now being combined include laser surface profiling to measure drum distortion and bulging, strain gauging to measure drum wall stresses during the heating/quench cycle , acoustic emission testing to globally inspect the drums for ID and OD connected cracks, and improved drum construction techniques for repairing or replacing sections of coke drums. These inspection, monitoring and repair technologies are individually reviewed and their benefits when applied in combination are discussed.