Characterisation of errors during strengthen off processing furnace tubes status

Reformer tubes normally used in the refining, petrochemical and fertilizer industries are manufactured by the centrifugal casting process and heat-resistant austenitic alloys such as HK -40, HP-40, and HP – Niobium modified materials. The cost optimization of industrial plants maintenance by preventing non-scheduled outages or extending service life-time is increasingly important. Reformer units are critical to many processes in refining and chemical plants. Life management is ordinarily dominated by the service capability of the radiant catalyst tubes. Their lives are limited by creep, driven by a combination of internal pressure stress and through-wall thermal stresses generated by operational transients. Although the service life may be estimated making use of theoretical models, due to the degradation process complexity, still it is necessary to characterize the materials of concern by NDT methods. Non-destructive testing (NDT) plays an essential role on maintenance program to assure operation of industrial plants. For the purpose of NDT methods, creep damage first develops voids, coalesced voids, and then micro cracks and macro cracks, which may evolve to rupture, accelerated by service conditions. Detection of creep damage in its first stages by NDT is a difficult task due to the coarse structure of the centrifugal cast austenitic tube material and the subtle changes produced by voids. The current condition either can be measured by some destructive or nondestructive test method or calculated using an analytical model or statistical model, such as the TUBELIFE computer program. TUBELIFE is a probabilistic tube life assessment software package offered by Magnetische Pruefanlagen GmbH in Germany, US Thermal Technology Inc, and Hainsco in Saudi Arabia. The program analyses data gathered from nondestructive testing techniques to produce a statistical rather than deterministic analysis of the reformer. A custom software program TUBELIFE and inspection technology (eddy current, laser OD measurement) as well as metallographic analysis off errors are outlined in the papers discussion.