Excessive bearing temperature is a common yet critical issue, often signaling impending bearing failure or underlying problems. Causes can be categorized as follows:

1. Lubrication Issues (Most Frequent Cause)

Insufficient Lubrication:

Grease desiccation or leakage due to prolonged operation without replenishment or seal failure

Underfilling during initial filling/maintenance

Incorrect grease selection:

Viscosity mismatch (too thin → centrifugal loss; too thick → poor flow)

Wrong base oil type or inadequate additives (EP, antioxidant)

Grease degradation from heat, oxidation, or shear

Over-Lubrication:

Overfilled cavity (>30%) → churning losses and friction heat

Grease types prone to thermal buildup under high shear

2. Installation & Misalignment

Improper Installation:

Impact damage during fitting (raceway/roller deformation)

Excessive interference fit → negative clearance → preload friction

Loose fit → fretting corrosion and particulate generation

Misalignment:

Shaft/motor end cover misalignment (angular/parallel deviation)

Baseplate distortion or bent shaft

Consequence: Unplanned radial/axial loads → stress concentration → friction

3. Overload & Abnormal Loads

Mechanical overload beyond design (pumps/fans/conveyors)

Excessive belt/chain tension → radial overloading

Abnormal axial thrust (e.g., unbalanced impellers) exceeding bearing capacity

Mechanical binding (rotor-stator rub, seized load)