Failure Analysis of Ball Bearing of Conveyor: Overusage

Rolling bearings are machine elements found in a wide field of applications. They are reliable even under the toughest conditions. When bearings fail to meet their expected life, the consequences are increased down time, loss of revenue and missed delivery. Hence, it is important to know the bearing theoretical fatigue life. However, unfortunately, it sometimes happens that a bearing does not attain its calculated rating life. There may be many reasons for this—heavier loading than has been anticipated, inadequate or unsuitable lubrication, careless handling, ineffective sealing, improper mounting and improper clearance. This article describes the failure of a conveyor bearing in rolling contact fatigue. The investigation consists of visual observation, chemical analysis, characterization of microstructures using optical microscopes and hardness test. The study also calculates the bearing fatigue life (L 10 ) under these operating conditions. Surface-initiated rolling contact fatigue, leading to spalling, is a life-limiting failure mode in bearings. Ferrography test, discussed in this paper, indicates fatigue spalling. Analysis suggested that the conveyor bearing failed near its calculated fatigue life and the failure occurred in rolling contact fatigue. Periodic schedule, after calculating L 10 life, for changing the bearing and scheduled ferrography checks can eliminate this type of unplanned breakdown.