Failure Analysis of Ball Bearing of Conveyor: Overusage
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TECHNICAL ARTICLE—PEER-REVIEWED
Failure Analysis of Ball Bearing of Conveyor: Overusage Urbi Pal . Piyas Palit . Prabhash Gokan . Samiran Kanrar
Submitted: 12 May 2020 / in revised form: 19 August 2020 Ó ASM International 2020
Abstract 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 (L10) 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 L10 life, for changing the bearing and scheduled ferrography checks can eliminate this type of unplanned breakdown.
Keywords Rolling contact fatigue Spalling Fatigue life Ferrography
Introduction Generally, a rolling bearing cannot rotate forever unless operating conditions are ideal, and the fatigue load limit is not reached—sooner or later material fatigue will occur. Fatigue is the result of shear stresses cyclically appearing immediately below the load-carrying surface. After some time, these stresses cause cracks, which gradually extend to the surface and fragments of material breakaway, which is known as flaking or spalling. This flaking progressively increases in extent and eventually makes the bearing unserviceable. Such an incident happened in a conveyor system in an integrated steel plant. Bearings of both drive side and non drive side of weigh feeder pulley were found failed after 4 years of service. There were a total of 48 bearings of which three bearings were found damaged. The conveyors are used to transfer coke breeze feed to the stacking yard. A pulley is used to provide tension in the system. A schematic diagram and the location of failure are shown in Fig. 1.
Experimental Procedure U. Pal (&) P. Palit P. Gokan Central Laboratories, Scientific Services Division, Tata Steel Limited, Kalinganagar, India e-mail: [email protected] S. Kanrar Mechanical Design, Tata Steel Limited, Kalinganagar, India
The failed components were collected from the plant for investiga
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