Several Case Histories of Generator Rotor Fan Failures and Methods of Repair

Generators require cooling typically provided by one or two shaft driven rotating fans. These fans see large operating stresses due to rotational forces, shrink fit pressures, axial thrust forces, and thermal stress. Over time, fatigue cracks can develop in either the fan blade or root area, potentially leading to a catastrophic failure. Failure of a rotating fan inside a generator will cause extensive damage. The stored rotational energy in a fan that lets loose will typically destroy the stator winding, sometimes damage the stator core, and cause other damage to rotor components such as retaining rings, the rotor winding and possibly, even the rotor forging. This paper will be useful to power plant owners who have to maintain plant equipment and prevent failures of that equipment. A good understanding of the possible failure modes associated with rotating fans will enhance the emphasis on conducting good inspections of this equipment.