How to Properly Lubricate Bearings in Electric Motors
You should lubricate bearings in electric motors according to the manufacturer's directions because lubrication deteriorates, leaks away, or becomes contaminated through oxidation. Depending on the operating conditions of your electric motor, lubrication may be required more or less than other motors with which you are familiar. The intervals at which you should lubricate bearings in electric motors is also dependent upon the temperature at which your machinery is operating; the continuity of service; the quantity of grease in the bearing's housing; the size and speed of the bearing; the vibration generated during operation; the exposure to contaminates such as fumes and fine dust; the effectiveness of the bearing's seals; and the lubricant's suitability to the purpose for which it is being used.
The kind of lubricant that you use is just as important as its purpose. Will it thin out at high temperatures and leak out of the housing? Will it become so thick that it causes serious vibrations? The lubricant's purpose is to reduce friction, prevent wear and tear on the bearings, protect against corrosion, and help seal out contaminants. The lubricant that you choose should be based on a viscosity that will hold during operating temperatures for the load and speed of the application for which it is purposed.
Consistency is also a factor since the lubricant must be able to spread to all areas requiring lubrication. The lubricant must also be resistant to oxidation in order to extend the life of the bearings running at both high temperatures and speeds. Lubricants with extreme pressure additives should not be used unless otherwise recommended. EP additives can shorten the life of the lubricant. A lubricant or grease with a dropping point of 500°F or higher is recommended for applications that reach temperatures of these extremes to prevent the oil and the thickener from which the grease is made from separating. A final consideration is shear stability in which the lubricant will soften no more than 1 to 1.5 NLGI. This will prevent aging grease from leaking out of the bearing.
Other tips to properly lubricate bearings in electric motors:
- Always refer to the manufacturer's instructions for the correct grease to use. The OEM may have included a specific brand and/or type of grease recommended for your specific electric motor.
- Lubricate bearings at appropriate intervals: If lubrication is recommended every eight hours <em>and</em> while the motor is hot, then you should schedule the lubrication to be performed at the end of or between every shift.
- Use the correct amount of grease or lubricant. There is such a thing as "too much" and it can be harmful to the motor itself. If not immediately, then eventually you will have downtime for the machine that is dependent on this electric motor.
- Always start by purging the old grease. The old lubricant may have become too thin or too thick, oxidized, and contaminated by particulate matter in the air. You don't want to leave behind any lubricant that may contain grit or metallic particles that will ultimately destroy the bearings.
Like an oil change for your car's motor, you can expect properly lubricated bearings to extend the life of your electric motors.