Convection Section Failure Analysis and Fitness-for-Service Assessment

摘要

“We had a failure of convection tubes in our furnace. Can we restart and continue to operaternuntil our next planned shutdown?”rnA brittle fracture failure of several HK-40 tubes in a convection section occurred in 2012. Thernfailed convection section tubes were removed and submitted for metallurgical failure analysis.rnHydrotesting was performed on the remaining tubes in the convection section to confirm thatrnadditional tubes were not substantially damaged and return the furnace to operation withoutrnfurther repairs. A failure analysis and API 579 Fitness-for-Service assessment were performed torndetermine the mode of failure and to determine the remaining life of the HK-40 tubes. Thernremaining life assessment determined the permissible existing flaw sizes in the tubes, which wouldrnnot grow to a critical flaw prior to a future shutdown date. Several shutdown dates were evaluatedrnto determine the timing of the next shutdown. This information provided the operator with arnsound basis to evaluate the business and safety risks of continued operation until long-termrnrepairs and system improvements could be implemented.