An Investigation of Shaft Failure on Induced Draft Fan in A Steam Power Plant

Abstract

A failure phenomenon on induced draft fan (IDF) shaft became a crucial attention in Power Plant with capacity 350 MW because the failure is catastrophic without early warning information. Also, the failures on the IDF shaft occurred in a short period within two months. This paper reported an investigation and evaluation of the root cause of the failure by vibration data monitoring and material analysis. The objective of the investigation and evaluation is to identify the main root cause and specific symptoms of IDF shaft failure. According to the data collection and analysis result, each phenomenon indicated an identical vibration pattern, however, the duration of each step is different. A series of tests of shaft samples was carried out to get comprehensive information, such as chemical composition test, tensile test, hardness test, microstructural examination (SEM), and fractography examination. The shaft repair procedure was also evaluated. The results were showed that multi initial of micro-scratch and martensitic embrittlement played an important role in the shaft failure. Micro-scratch triggered high-stress concentration on shaft surface. Martensitic embrittlement was found on weld metal and heat-affected zone.