Electric motor bearings regularly experience high levels of stress when driving heavy loads. This makes them one of the most critical components you need to take care of to keep your motor running smoothly and consistently.
In this article, we'll go over the main reasons why they fail and how to replace them when they do fail so that you can take both preventative and proactive action to maintain your electric motor bearings and operational productivity.
Why Do Bearings Fail?
Electric motor bearings support the motor's spinning shaft during operation, absorbing large radial forces and enabling surfaces to remain in contact while moving at high speed. Despite what they must endure, adequately maintained bearings could last many years before reaching the end of their service life. Several preventable factors accelerate wear and tear and lead to premature bearing failure.
Excessive Torque and Speed
Suppose your motor is operated outside its rated limits for speed or torque or a bearing is fitted that is not properly rated for the motor. In that case, the internal friction in the bearing will overcome the cooling ability of the lubrication. Thus, the bearing will experience overheating, damage, and vibration that ends in failure. To prevent this, make a thorough assessment of your requirements before purchasing a motor or bearing. Pay special attention to radial forces and cyclic or shock loads, as these place exceptionally high stress on the bearing.
Inadequate maintenance and protection can cause a bearing to degrade very quickly. If it's not greased-for-life, you must regrease bearings periodically according to the schedule. You must pay special attention to the lubrication type and amount indicated by the manufacturer. It's also essential to do everything you can to keep contaminants out, including dust, moisture, or anything else which can cause pitting or corrosion of the inner surfaces. Proper seals and shaft slingers should be fitted to your motor where necessary, and bearings or motors that are not in use should be stored away in a clean, dry, and vibration-free environment.
Incorrect installation or removal of bearings can cause misalignment of new bearings, resulting in focused stress areas that may cause it to fail immediately on start-up or not too far down the road. When removing old bearings, avoid using excessive force as you can damage the shaft or bearing housing and make it difficult to align a new one properly. If you use the wrong tools or techniques during installation, you can damage and deform the case or rolling elements of the new bearing.
We'll cover in-depth the right way to replace bearings later on in the article, but first, let's take a look at what you need to consider when a bearing failure occurs.
Replace or Repair?
One thing you may be wondering when facing a motor replacement is whether it would be more cost-effective to have it repaired by a local shop instead. Especially if you see the signs of damage – such as increased noise, vibration, or excessive heat – but the bearings haven't completely failed, this might be an option.
Typically, it’s not worthwhile to repair bearings on small motors, especially if they're standard type and relatively inexpensive. If you have medium to larger motors with a particular type of bearing that is costly to replace, you may want to contact your local repair shop about the option of having it professionally repaired.
Ordering a Replacement Bearing
To order a replacement bearing for your electric motor, first find the part number. This is usually visible if the surface has not become worn or corroded. If you have the parts number, especially if the bearing failed prematurely, double-check that it's the right one for the motor and the intended application.
If you can't find the part number, we can help you with that. We stock a wide range of motor bearings for all motor sizes and types, and you can get in touch with us with the details of your motor to quickly find the right one.
Replacing A Bearing
Replacing an electric motor bearing is not a complicated task, but it's also not trivial. You run the risk of damaging the motor or the new bearing. You may end up saving more time and money by having the bearing replaced by a specialist. But if you want to do this task yourself, here are the key steps and things to look out for.
Before you start, make sure that the motor has no connection to power and there's no chance of an accidental contact while the maintenance work is completed. Wear appropriate PPE, and make sure you have enough time allotted for the job so that you're not in a rush.
Removing the Old Bearing
Removing an old bearing can be a tedious job, especially when it has been in service for many years, and surface corrosion keeps it firmly attached to the shaft.
The best approach is to use a bearing puller. There are several different types; common ones use two or three jaws clamped around the bearing to create an evenly distributed force and minimize friction resistance. While some pullers feature hydraulic assistance, it's not usually necessary for small to medium motors. Using such tools requires extra care to prevent damage to the motor shaft and minimize personal safety risks.
Cutting the bearing off with power tools should be avoided, as there is a high risk of damaging your valuable motor. If you're having difficulty removing it, it's far less risky to have it done by a specialist instead.
Before installing the new bearing, examine the old one for signs of the cause of the failure, such as corrosion damage or the presence of water or grit particles in the lubrication. If the problem is not found and the appropriate action isn't taken to correct it, the new bearing may well experience a similar fate.
Clean the Shaft
Ensure the entire length of the motor shaft that the new bearing will traverse is perfectly clean and smooth, free from corrosion, moisture, and particles of dust or other contaminants. Remove gouges or burrs to prevent damage to the bearing ring as it slides over.
If you need to clean the shaft, a scotch-Brite pad or similar product is preferable to sandpaper, as it won't leave small grit particles behind.
Heating the Bearing
Bearings are designed to fit precisely, with tolerances in the ten-thousandths of an inch; getting it onto the shaft can be difficult. One way to make the process easier is to heat the bearing to expand it and/or cool the motor shaft to shrink it. This can be the difference between an easy job and a difficult one.
We recommend you heat the bearing using a proper induction heater with a demagnetization cycle designed for the job. This enables you to avoid overheating the bearing and potentially damaging the lubrication inside. You should avoid risky shortcut methods such as torches, pizza ovens, or oil baths, as the temperature in these methods is difficult to track and control.
Installing the New Bearing
Install new bearings with a proper bearing installation kit, which contains the necessary tools such as a dead-blow hammer and impact sleeve that help you avoid damage to the bearing and motor shaft.
In most cases, the new bearing should go on without too much difficulty. Take your time and avoid using brute force if you encounter resistance. Instead, check for irregularities on the motor shaft, and make sure the bearing is the right size and heated sufficiently.
If the bearing is designed to be a very tight fit, using an arbor press is an alternative method, but make sure you have correctly squared and blocked the bearing so that it's not deformed or misaligned when force is applied.
Once you have the bearing fitted, reassemble the motor and run it without a load to check for any vibration, noise, or other signs that the new bearing isn't installed correctly.
Electric motor bearings endure a lot of stress, but when properly selected, installed, and maintained, they will give you many years of effective service. If you need to replace a bearing on your motor, take a look at our range of bearings to suit all kinds of motors, or get in touch with us today, and we'll help you find the right one.