Root Cause Failure Analysis of a 9Cr-1Mo tube in the CCR Unit of an Oil Refinery

A severe local failure of a 9Cr-1Mo heater tube in the Continuous Catalytic Reformer (CCR) unit of an oil refinery, below the skin thermocouple shield junction, has been investigated. For this, the optical microscope and scanning electron microscope (SEM) were carried out for microstructural observation, and the micro-hardness measurements were performed for metallurgical evaluation. In addition, the elemental composition of the failed surface was studied by using EDAX analysis. Based on the results, "carburization" and, "metal dusting" were identified as two damage mechanisms in this case. The microstructural evaluation showed metallurgical phase transformation which is in agreement with micro-hardness results.