Aging coke drums and their connected overhead piping in delayed coking units experience fatigue cracks which most commonly occur at the skirt junction and high stress pipe welds.
This paper presents 2-case studies of this new cost-effective repair methodology with fatigue resistant design upgrade. The first case study applies to coke drum weld build-up solid skirt crack repair and the second for overhead vapor line weld crack repair.
This paper presents new field repair methodology which could also improve long term fatigue resistance. It also suggests optimizing the thermal operation & thermal gradients of coke drums for further reliability improvement.
Based on FEA, successful field execution and our experience, these case studies demonstrate a long term improvement in reliability and fatigue life of the order of 2.5 to 3 or higher especially if combined with thermal operation optimization.