High temperature failure of natural gas feed burner pipe

The degradation of AISI 310 austenitic stainless steel pipe, which was used at high temperature in carbonaceous reducing atmosphere, was investigated in this work. In order to examine the causes of failure, various techniques including on-site investigation, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, metallography, and micro-hardness measurement were carried out. Scale separation and spallation were only observed at the internal surface of the pipe as a result of overheating service condition at the tip portion. The scale separation and spallation caused nozzle block and subsequent furnace shutdown. Growth of carbide precipitates and disintegration of alloys into dusts of coke and particles suggested carburization and metal dusting failure. It is recommended to monitor service temperature periodically at the tip portion. The service temperature should not exceed the designed value. Careful control of oxidizing/carburizing burning condition is strongly advised. Material selection is also discussed as an alternative means of failure prevention.