Fitness-for-Service Assessment of Externally Corroded Convection Coil Tube

During inspection of a heating coil in the convection section of a steam reformer, significant thickness loss due to external corrosion was discovered in a large number of tubes. In order to optimize the scope of repairs and ensure further safe operation, a level 3 fitness-for-service and remaining life analysis were performed in accordance with API-579. This paper will describe the fitness-for-service assessment that was performed, first using an idealized geometry, and thereafter using the actual corroded geometry of a removed tube. The procedure used to estimate the remaining life of the damaged coil will also be presented.