Investigation of an anomalous failure of bearing on a fan within the columbus module of the ISS

Abstract

A premature failure of an Inter module Return Fan Assembly (IRFA) within the Columbus module of the
International Space Station (ISS) has been investigated to identify the root cause and the counteractions to be taken. The dismounted parts and the collected debris have been analysed using optical microscopy, Scanning Elecron Microscopy (SEM), Energy Dispersive spectroscopy (EDS) and dedicated dimensional measurements have been performed. The inspection indicated an anomalous wear of one
only of the two support bearings and in particular a strong interaction between the cage and the lands of the outer ring with consequent friction and wear, while the other parts of both the bearings were in reasonable conditions.

The analyses indicated a misalignment of one bearing this being the origin of the non-nominal load conditions that led to the premature wear of the bearing. The inspections conducted allowed the identification of the corrective actions to be implemented in order to minimize the likelihood of occurrence of the failure.