Assessment of Graphitized Carbon Steel Tubes in Fired Heater Service

摘要

Samples of carbon steel tubes were removed from the radiant section of a fired heater after 40 years operation at 950 deg F to 1000 deg F (510 deg C to 538 deg C) tube metal temperature. The tubes exhibited significant microstructural degradation in the form of advanced pearlite decomposition and graphitization (graphite nodules). However, no evidence of linking of graphite nodules was observed. This paper highlights the results of an API 579 Fitness for Service analysis using the MPC Omega creep methodology to help show that the tubes have significant remaining creep strength and are suitable for continued service, contrary to the results of an API 530 analysis.