Since electric motors are essential to keep your production, packaging, or assembly line moving forward, electric motor maintenance should be the top priority of any predictive maintenance schedule.
Yet, a recent EPRI (Electric Power Research Institute) study found that 95% of electric motors fail prematurely. Typically, these failures aren’t the result of a design, manufacturing flaw, or even an improper installation. Instead, EPRI found that lubrication issues are responsible for more than half of all reported engine failures.
Preventative maintenance should be straightforward, with the correct lubricant and a maintenance schedule. So why do 95% of motors experience premature failure?
Electric Motor Failures
Today’s electric motors feature anti-friction, grease-lubricated, rolling-element bearings for improved performance and longevity. But EPRI found that nearly 60% of all bearing failures could be traced back to one or more of these four key points.
Incorrect lubricant – always follow the manufacturer’s recommendations for the type of grease for all service and maintenance needs. Most manufacturers recommend polyurea grease for bearings and electric motors, not EP (Extreme Purpose) grease, designed for slower-speed bearings. The additives used in EP grease can corrode the copper windings inside your electric motor.
Grease incompatibility – Not all greases are compatible due to the thickener agents used, such as lithium, polyurea, or calcium. Even if two different lubricants use the same thickener agent, other additives could affect the seal performance or bearing lifecycle. Never mix different greases, and should you have to change brands or formulas, remove all the old grease from the motor completely before refilling.
Too much grease – overfilling the motor’s grease capacity can be as detrimental as a lack of lubrication. With the grease gun’s high pressure (15,000 psi on a manual version), a filled grease cavity will quickly push the excess grease past the seal and inner bearing cap. The extra grease can make its way into the motor windings and insulation.
Lubrication starvation – typically occurs for three specific reasons.
The most common is an extended or irregular preventative maintenance schedule. For example, check lubricant levels regularly to keep bearings and motors working at peak performance.
Another problem is incomplete greasing or improper bearing installation during the motor’s original installation.
And the third is that excessive heat has caused the oil to separate from the thickener base of the grease.
Lubrication contamination – occurs when dust, dirt, or debris makes its way into the lubrication system. Contamination can quickly thin the grease, resulting in metal-to-metal contact that can create particles that increase contamination.
Insufficient grease between the races and rolling elements will incur metal-to-metal contact, premature or excessive wear, and higher operating temperatures for your electric motor.
Eliminate Electric Motor Failures
Predictive or preventative maintenance is the best way to eliminate or minimize electric motor failures.
Setting up a preventative maintenance plan can be done with a simple spreadsheet, or you can choose from several different PM software programs, depending on your specific needs.
Whichever option you choose, be sure to include the following:
- Installation date
- Catalog or part number
- Location
- Horsepower
- Bearing type/size for inboard and outboard motor ends
- Operating RPM/temperature
- Required grease or lubrication material
- Service dates
Centralizing your predictive maintenance plan and records will streamline your maintenance processes to save time and money while reducing production downtime from motor failures.
Use the Right Electric Motor Grease
While most manufacturers’ guidelines include grease requirements and recommendations, if you don’t have these documents, here are some basic guidelines for selecting a good quality grease for your electric motors.
- Base oil viscosity of an ISO VG 100 to 150 or, more specifically, 90 to 120 cSt at 40°C
- NLGI Grades 2 to 3
- Highdropping point, 400°F minimum
- Low oil bleed characteristics, per D1742 or D6184
- Good channeling characteristics
- Excellent resistance to high-temperature oxidation
- Good low-temperature torque characteristics
- Good anti-wear performance (but don’t use EP)
Establish a Lubrication Process
Improper or haphazard lubrication will negatively impact the performance and longevity of your electric motor. Therefore, establishing a uniform lubricating process should include the following considerations.
- Clean the areas around the fill and relief fittings to minimize potential dust or dirt contamination.
- Double-check that the grease gun contains the correct grease for the component.
- Remove the drain plug or grease relief valve and set it aside.
- Using a predetermined amount, add the grease slowly to minimize internal pressure build-up in the cavity.
- Monitor the relief port. The old grease should get purged out as new grease gets pumped in. If no purge is visible, check for passages blocked by old, hardened grease.
- If the motor is out of service when regreased, run the motor to bring the bearing up to operating temperature to allow for any thermal expansion. The drain plug should be left out during the warm-up process.
- Allow the motor to run at operating temperature for a short period to expel any extra grease.
- After purging excess grease, clean the area before reinstalling the drain plug or relief valve.
- Repeat the process for each grease lubrication point on your electric motors.
If you still have questions about the proper grease for your electric motor maintenance needs, our team of engine lubrication experts is just a phone call or email away.