Oxidation failure of radiant heater tubes

Abstract

A radiant heater tube with a burner installed inside designed to transfer the heat generated by the burner from the outside of the tube by radiation. Accordingly, the tube metal must endure a high temperature of approximately 900-1000 degrees C. The radiant tube was manufactured by centrifugal casting with high Ni-Cr alloy steel. In this study, a failure analysis of a radiant heater tube was performed by careful visual inspection of the tube cracks, metallographic observation of the near crack region and chemical analysis of tube metal and oxide scales. It is argued that the principal cause of the cracking is progressive oxidation of the tube metal beneath cracked thick oxide scales attached to the inside of the tube. The oxide scales are generated by abnormally high operating temperatures which can be verified by the aged microstructure and internal void formation. (C) 1999 Elsevier Science Ltd. All rights reserved.