Connect with us to discuss your needs. Phone number. I am a Existing customer New Customer. How can we help? I consent to ExxonMobil processing my personal data to send me information about promotions, offers, and upcoming events, including any related processing for purposes of providing me this information. Send to a colleague. Chris Decker, Americas Products Technical Advisor, ExxonMobil Research and Engineering The primary functions of an electric motor bearing grease are to: Reduce friction and wear Protect bearings against corrosion Act as a seal to prevent entry of contaminants Grease is frequently used to lubricate electric motor bearings because of its simplicity of application and unique characteristics.
When determining the proper grease for your application, consider: Viscosity: Oil viscosity should be appropriate for the load and speed of the application at operating temperature.
Electric motor bearing lubrication guide Keep your electric motors and your operation running smoothly by following best practices in grease lubrication. Only grease bearings for vehicles with unsealed locks or hub units. Just like any other metal component of your vehicle, the bearings will give some telltale signs that they need to be replaced.
You may start to hear a rhythmic thumping noise that sounds like a card that's stuck on the spokes of a rotating wheel. The noise gets louder the more the bearings wear out. Dropping point refers to the temperature at which the grease changes from its semi-solid state to a liquid state. For open bearings, this time period can be minimized by applying the required quantity of grease distributed evenly on both sides of the bearing during assembly.
Spacers between adjacent bearings can also reduce the running-in period. Super-precision bearings can typically operate with a minimum quantity of lubricant when properly run-in, enabling the lowest frictional moment and operating temperature to be achieved. Grease that collects on each side of the bearing acts as a reservoir, enabling oil to bleed into the raceway to provide effective lubrication for a long time. Running-in can be done in several ways. Wherever possible and regardless of the procedure chosen, running-in should involve operating the bearing in both a clockwise and counter-clockwise direction.
This standard running-in procedure is time-consuming. For a medium- to high-speed spindle, each stage can take anywhere from 30 minutes to 2 hours before the temperature stabilizes. The total time for the running-in procedure can be 8 to 10 hours diagram 3. An alternative to the standard running-in procedure reduces the number of stages and shortens the overall running-in time.
The main steps can be summarized as follows:. Although each stage may have to be repeated several times, each cycle is just a few minutes long. The total time for this running-in procedure is substantially less than for the standard procedure. Selecting grease. In rolling bearing applications, three consistency grades are recommended: The most common greases, used in normal bearing applications, have an NLGI grade of 2. Low consistency rolling bearing greases, classified as NLGI 1 greases, are preferred for low ambient temperatures and oscillating applications.
NLGI 3 greases are recommended for large bearings, vertical shaft arrangements, high ambient temperatures or the presence of vibration. Check additional requirements In some applications, operating conditions may put additional requirements on the grease, requiring it to have unique characteristics. The following recommendations are provided as guidelines: For superior resistance to water wash-out, consider grease with a calcium thickener over a lithium thickener.
For good rust protection, select an appropriate additive. If there are high vibration levels, choose grease with a high mechanical stability. Initial grease fill. The grease is characterized by: high-speed capability excellent resistance to ageing very good rust inhibiting properties The technical specifications of the grease are listed in table 1.
Applying grease. Grease service life and relubrication intervals. Running-in of grease lubricated bearings. The time required to stabilize the operating temperature depends on the following factors: the type of grease the initial grease fill how the grease is applied to the bearings the number and arrangement of bearings in a set the available space for excess grease to accumulate on either side of the bearing the running-in procedure Super-precision bearings can typically operate with a minimum quantity of lubricant when properly run-in, enabling the lowest frictional moment and operating temperature to be achieved.
Standard running-in procedure The most common running-in procedure can be summarized as follows: Select a low start-up speed and a relatively small speed increment. SKF recommends setting the machine with limit switches that stop the spindle if the temperature rise exceeds the set limit. Start operation at the selected start-up speed. Monitor the temperature rise by taking measurements at the bearing outer ring position, and wait for the temperature to stabilize.
If the temperature reaches the limit, stop the spindle and allow the bearing to cool. Repeat the process at the same speed and run the spindle until the temperature stabilizes below the limit. Once the bearing temperature has stabilized, continue to run the spindle for an additional 10 to 15 minutes. Then, increase the speed by one increment and repeat step 4.
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