Microscopic examination of a fan blade supporting system premature fractured

A local company generates electricity via combined cycle power plant using natural gas. After the steam turbine, the in-line working fluid needs to be liquefied by a condenser. A water cooling system which is comprised of a fan cooling tower is used. The tower is consisted of series of cooling fans. The fans are comprised of blades which are supported onto a hub by “U” shaped holders. These pieces frequently brake down disturbing the normal operation of the unit. The paper refers to the microscopic examination of the failed parts. Historical data was collected, the pieces were macroscopic examined, hardness measurements were carried out and chemical analysis was performed. The study involved a detailed examination of the microstructures and fracture morphologies of the specimens derived from the failed parts. Conclusions are presented related to the fracture mechanism and the type of fractures respectively. All of the blade holders on this analysis were totally break by low cycle fatigue. Usages of impropriate material, as well as design deficiency of the holders, are considered to be the main causes for the failure.