A Review of the Use of Load Indicating Studs During Assembly and Optimization of a Coke Drum BUD Joint

Bottom Un-heading Devices (BUD’s) are often installed on coke drums to facilitate remote opening and closing of the bottom of the drum pair during petroleum coke production. The BUD removes the need for personnel to manually open the drum, which is a high-risk activity and has led to many process safety incidents across the refining industry, and in some cases may offer shortened time to close the drum, resulting in increased production time. These valves are bolted to the bottom head flange and typically only removed during scheduled maintenance intervals, often exceeding five years. During service, the bolted joint must maintain integrity while being subjected to repeated thermal transients during the drum cycle. Correct design and assembly of these critical joints is essential to avoid safety risks and expensive downtime resulting from operational leaks. This paper will show how the use of load indicating studs can achieve reliable assembly, optimize scheduled re-tightening activities and provide effective ongoing joint management. Three case studies will be presented detailing how to correctly assemble and manage a typical BUD joint throughout its life cycle involving the use of load indicating studs. In each case, the joints have maintained integrity during service and allowed the plant engineers to gather reliable data to ensure effective future joint management. Load indicating studs alone cannot guarantee leak free operation and should be used in conjunction with a properly designed joint. BUD anatomy will be explored with insights into the fundamentals of reliable joint from flange geometry, gasket behavior and a review of common assembly techniques.