During operation, a bearing temperature rise may indicate which of the following conditions?

• A. Lubrication deficiency, misalignment, overloading, or contamination.
• B. Normal operation and ambient temperature variations.
• C. Only lubrication deficiency.
• D. Only overloading.

Answer: (A)

A rise in bearing temperature during operation is a sign that something is causing extra friction or degrading the lubrication. The best explanation is that the heat can come from lubrication deficiency, misalignment, overloading, or contamination. If the lubricant isn’t providing a proper film, metal-to-metal contact increases and more heat is generated. Misalignment or improper mounting leads to uneven contact and binding, which also raises friction and temperature. Overloading pushes the bearing beyond its design load, increasing contact stress and heat generation. Contamination introduces dirt or particles that damage the lubricant film and create abrasive wear, further increasing friction and heat. Normal operation and typical ambient variations shouldn’t cause a sustained abnormal rise, and restricting the cause to only one factor misses other common sources.