A properly functioning motor is essential, not just to production, but also to the safety of operatives and other staff. When motor failure is imminent, it is often preceded by high bearing temperatures. Understanding and monitoring temperature conditions not only saves time and money in the long term, but also simplifies motor repair.
Related Blog: 10 Reasons Why Motor Bearings Fail
Understanding Bearing Temperature Conditions
There is always some fluctuation in the operating temperature of bearings within motors. Individual operating temperatures depend on elements such as the application of the motor and the ambient temperature. However, as a guide, 170°F or 80°C should be considered normal. As the temperature increases from this point, so does the risk of severe failure and motor damage.
At 190°F or 90°C, temperature alarms should engage. It is important not to ignore them and to take immediate action to find and treat the cause of the temperature rise. Stopped at this point, the damage is minimal and complete breakdown can be avoided.
A complete shutdown is required if the operating temperature rises to 210°F or 100°C. Failure to action at this point can lead to significant damage, and motor repair may not be possible. The outcome, instead, is likely to be the need for an extensive motor repair or even replacement, resulting in a longer shutdown period and loss of revenue.
Potential Causes and Solutions to High Bearing Temperatures
Understanding why the temperature has increased is just as important. Failure to investigate can lead to potentially taking the wrong course of action and further motor damage.
The following are some of the most common causes of heat increase in motor bearings:
- Lubrication failure - One of the primary causes of overheating, particularly in electric motors, is lubrication failure. This results from lack of lubrication, usage of the wrong type of lubrication, over lubrication or usage of incompatible grease mixes. All of these result in inadequate viscosity to provide lubrication at normal operating temperatures. To avoid these issues, follow manufacturer’s guidance when lubricating bearings. If the problem does occur, clean the bearings, checked them for damage and correctly lubricate them before reinstalling.
- Loss of fit - While the fit of any bearing needs to be loose enough to make installation possible, too loose a fit can cause excessive wear and vibration. Left untreated there is an increased risk of further damage including bearing seizure and ring fracture. This is most commonly fixed with a slight press fit. However, ensure that the bearing’s internal clearance is not compromised or eliminated as it can also lead to increased operating temperature and potentially the failure of the bearing and the motor. It is also important to remember that the exact type of fit is determined by various factors, including the type of bearing, and the material used in the housing or shaft.
- Improper installation - As with all the components of the motor, proper installation of the bearings is essential as improper installation can cause damage to the bearing assembly. The installation process should not at any point involve the transmission of forces between bearing rings through the balls. If this occurs, the life cycle of the bearing is significantly reduced. The installation also needs to take place in a clean and contaminate free environment, with all bearings mounted squarely. Make sure to use only the correct tools and procedures during installation, and never be tempted to resort to hammering or other impact techniques to complete the installation.
- The Need for Vigilance - Whether you believe that the problem is a bell ring failure, shock stress, shaft currents or excessive ambient temperatures, quick action to assess and repair the damage will help you avoid further damage. As with anything that has moving parts, there are any number of potential things that can go wrong with bearings that result in the need for motor repair. However, staying vigilant and monitoring temperatures are the easiest ways to avoid complete shutdown of your operations regardless of the underlying problem.