We’ve repaired and replaced more than a few motor rotor shafts in our time, and most damages are due to improper use, general wear and tear, or lack of proper maintenance. In many instances, the same can be said to cause bearing failures in electric motors. However, sometimes it can be a bit more specific than that. We look at the most prevalent causes of bearing failures in electric motors, to assist you to avoid making these common mistakes.
Electrical erosion can not only cause bearing failure, but can also degrade the lubricant and damage the rolling elements. Electrical erosion happens when a current moves from one ring to another, through the rolling element. If energy continues to pass in this fashion, it can cause long-lasting damage to the motor and result in your bearings failing.
Metal to metal contact due to lack of lubrication
Choosing the correct lubrication and maintaining its scheduled application is very important to the smooth running of your motor. Ensuring that the lubrication between the rolling elements and raceways is thick enough, is vital to the bearings’ efficiency. Contamination of lubrication can also occur, causing the film to thin and the metal to grind against one another. If the lubrication is contaminated, the seals also need to be scrutinised to evaluate if they need replacing.
Incorrect storage and transportation
If the bearings in a motor are subject to vibration for a prolonged period, this can do serious damage. If a motor is transported without the rotor shaft secured, the strong vibrations from the vehicle can harm the bearings. It’s also crucial that the motor is not stored in an area subject to consistent vibrations, such as a workshop.
If the wrong tools and procedures are used to install a motor, this can impact its efficiency and reliability. If an untrained person attempts to install a motor’s bearings, this can result in misalignment, belt tension and imbalance. Furthermore, incorrect mounting can cause overloading. None of these mistakes bode well for the future of the bearings and can actually end up permanently damaging a brand new motor.
Ignoring minimum load requirements
If your motor does not have preloaded bearings and you notice a smearing on the rolling elements or raceways, it’s a typical sign that your bearings aren’t holding their minimum required load. This type of damage is particularly prevalent in cylindrical roller bearings, which are made to carry heavy loads.