A simple rule for troubleshooting bearing temperatures: No more than 180 degrees Fahrenheit (82 degrees Celsius) on the housing. The bearing outer ring can be up to 20°F (11°C) hotter than the housing. The lubricant originally specified for the application was likely selected to run at lower temperatures. A temperature increase of 50°F (28°C) may cause oil viscosity to drop by 50% or more. This could be the "tipping point" for the application, causing it to go from a hot (but stable) condition, to a hotter, unstable condition where thermal runaway occurs. Eventually, it doesn't matter how much lubricant you add to the application: the oil film is too thin inside the bearing to prevent metal-to-metal contact. Friction and heat build up, which could lead to catastrophic machinery seizure.
A better procedure for "hot" bearings would be:
Catastrophic failures can have untold consequences. Contact SKF to apply our Knowledge Engineering to your application - we can help you with temperature issues in bearings. A simple call could save you time, money, and perhaps someone's life.