Investigation of causes of fan shaft failure

Energy efficiency of thermal power plants depends on the vital plant elements’ reliability levels. In order to preserve high level of energy efficiency, the vital elements’ operational capability is continually monitored via observing the working temperature, vibration and noise levels. Yet, however, in spite of this, and usually due to inadequate maintenance, inadequate assembly, errors in the design or manufacturing processes, or due to accidents, abrupt failures of the plant’s vital elements can occur. An example for this is the volumetric destruction of the fresh air fan shaft due to melting of the shaft at the shaft’s stationary support. In addition to shaft destruction, the fan bearing and wheel blades have undergone destruction as well. This breakdown has occurred in the course of continual monitoring of the bearing service temperature and vibrations levels. Former studies, aimed at determining the breakdown causes, were based on the detailed examination of the damaged elements’ materials and detailed analysis of the bearing setting arrangement. Considering the fact that the shaft stationary support was realized by means of a double-pressed joint, a thorough analysis has been made in this paper of the pressed joint operational capability in the boundary service conditions, in order to determine the extent to which the pressed joint participated in the breakdown.