WRONG LUBRICANT

Lastly, it’s important to choose the right lubricant—not all greases are the same and using the wrong type can lead to premature bearing failure. Ask your supplier about a grease that is specifically designed for electric motors, which is different from multipurpose extreme purpose (EP) grease.

Furthermore, be cautious when switching greases as not all are compatible with each other due to variances in thickeners such as polyurea, lithium, or calcium. Try to use the same grease or compatible substitute throughout the life of the bearing.

Pillow Blocks UCP X SERIES Bearing (Medium -Duty)

DEVELOPING A PREVENTIVE MAINTENANCE PLAN

Now that you’re aware of common bearing failure root causes, it’s time to put together a comprehensive preventive maintenance plan. By considering the following, you can actively reduce bearing failure and uphold the integrity of your equipment.

DETERMINE GREASE VOLUME

Grease volume control has been a long-standing problem for the industry, and simply following OEM recommendations may not be enough to solve this problem. If you are using a grease gun, there is a simple equation to determine the maximum volume of grease to be added. The formula is:

G = 0.114 x D x B

Where G = the amount of grease in ounces, D = the bearing outside diameter in inches and B = the bearing width in inches.

Once the volume is found, it must be converted into shots, or pumps of the grease gun. The average value is approximately 18 shots per ounce for most manual guns, but grease gun output can vary by a factor of 10, so be sure to calibrate each gun. Noria’s online grease calculator can help in determining this number.

With that said, it’s still difficult to achieve the right volume with a manual method in comparison to an automatic single-point lubricator. One like the OnTrak system uses bearing feedback to get grease volume right, every time. Not to mention this device operates automatically, saving you time and resources.

ESTABLISH REGREASE INTERVALS

There are several ways to determine the optimal regrease interval. The best thing to do is to choose an interval that is dependent less on time and more on the condition of the bearing. This is going to require condition monitoring equipment. By measuring the bearing’s grease levels and condition, you can accurately pinpoint the moment you need to regrease the bearing (or have the monitoring equipment regrease your bearings automatically.)

Ultrasonic instrumentation is one of the best tools available to dial in the optimum relubrication frequency. A conservative approach is to use a frequency generation method as a starting point and continuously refine that value based on feedback from the ultrasonic equipment. For greater efficiency (and time-saving), invest in an ultrasonic device equipped with a single-point lubricator for automated lubrication.

FIND THE RIGHT GREASE

Establishing the correct interval and volume means nothing if you don’t have the right grease. When searching for a lube type and manufacturer or supplier, there are several things to consider. The following is a list of qualities of a good electric motor grease:

• Good channeling characteristics
• Excellent resistance to high-temperature oxidation
• Good low-temperature torque characteristics
• Good anti-wear performance (but not EP)
• NLGI Grades 2 to 3
• Base oil viscosity of an ISO VG 100 to 150 or more specifically 90 to 120 cSt at 40°C
• High dropping point, 400°F minimum
• Low oil bleed characteristics, per D1742 or D6184

Polyurea grease is popular with many bearing and motor manufacturers. A significant proportion of equipment manufacturers also specify some type of polyurea grease in their electric-powered machinery. A polyurea-based grease is an excellent grease for electric motors; however, this thickener is incompatible with most other thickeners. Some manufacturers don’t recommend mixing one brand of polyurea with another.

BOTTOM LINE

These considerations are just the foundation of a proper preventive maintenance plan for your electric motors. There are several other steps to take such as developing a task list for upkeep and maintenance and conducting training on the various condition monitoring technologies. With all these factors in mind, you can effectively prolong the life of your electric motors, saving time and money along the way.