Inadequate Lubrication & Overheating
Insufficient or degraded lubricant causing overheating, discolouration and surface damage.
Symptoms
Discolouration (blue/brown/straw heat tinting) of rings and rolling elements, smearing or scoring of surfaces, possible cage damage or seizure. The bearing runs hot and may smell of burnt grease.
Likely causes
Insufficient lubricant quantity, wrong lubricant viscosity or type for the speed/load, degraded or contaminated lubricant, or excessive speed/load beyond the lubricant's capability. Starvation causes metal-to-metal contact and rapid heat build-up.
Prevention
Use the correct lubricant grade and quantity for the speed, load and temperature. Follow relubrication intervals. Monitor running temperature. Ensure lubricant can reach all rolling elements. For high speeds, select a lubricant with the right viscosity and base oil.