Electric motor bearing re-lubrication is a critical aspect of maintenance. As with other high speed bearing applications, it is important for re-lubrication practices to take the risks associated with over-lubrication into account while providing sufficient re-lubrication to deliver long bearing service life.
The combination of the following practices can provide a lubrication program which avoids over-lubrication and lubricant starvation:
- Add small amounts of grease at short time intervals using an automatic lubricator which provides accurate dispensing rates, independent of temperature.
- Re-lubricate when the motor is in operation.
- Always ensure that spent grease can escape the bearing housing via well maintained grease escape holes or collection traps.
- Do not use powered grease guns.
Challenges
High speed bearings of electric motors must be lubricated with care and with greater precision than lower speed bearings, mainly due to the risk of bearing damage due to over-lubrication.
The optimal method for lubricating high speed rolling element bearings is to add grease in small quantities at short time intervals, rather than in large quantities at long time intervals. The method of adding grease frequently in small quantities maintains an equilibrium of full lubrication, avoiding both lubricant starvation and over-lubrication.
Over-lubrication of high speed bearings can occur when a large quantity of grease is introduced to the bearing too quickly. The rapid addition of grease can lead to excessive churning and shearing of the grease which can result in elevated bearing temperatures, which in extreme cases can lead to bearing failure. However, even mild cases of over-lubrication can be problematic because the short term elevated bearing temperatures may cause equipment to trip due to “over-temperature” sensing and may cause rapid degradation of the grease.
The use of single point lubricators* which develop relatively low pressure (compared to a manual or battery powered grease gun) can also prevent potentially damaging high pressure grease being presented to the bearing. When grease is delivered to an electric motor bearing at high pressure the risk of grease breaching the inboard shaft seal and entering the motor windings is increased. The use of single point lubricators* can reduce this risk.
* Also commonly referred to as autolubes or SPLs
Bearing heating and possible fire hazard since it takes hours to distribute excess grease
Possible shut-off with temperature monitoring
Bearing damage due to lubrication starvation results in unscheduled machine downtimes and higher production costs
Increasing maintenance costs caused by premature wear
High accident risk
Motor shut-down when entering secured areas
Lubrication points
Lubrication points are located on the drive and non-drive end of electric motors. When relubricating, you must ensure that excess grease is discharged through the discharge openings, grease relief ports or grease traps. Bearings will overheat if grease cannot escape and / or if grease traps are filled up with used grease.
Solutions
Mount a perma lubrication system at the lubrication point. Depending on the conditions prevailing at the lubrication point, the perma lubrication system can either be mounted directly or remotely.
- Easy, quick mounting
- For lubrication points with little vibration / shocks
- For easy-to-reach, safe lubrication points
- For lubrication points with strong vibration / shocks (isolation of lubrication system)
- For lubrication points which are unsafe to access: Mounting in safe areas
- For hard-to-reach lubrication points
Any more questions?
Simply contact us by phone or email for an individual consultation on electric motors.
Advantages of automatic lubrication
Relubrication
Relubrication is generally performed when the motors are running, rather than stationary. High speed bearings should not be relubricated when they are stationary
Predictable exchange intervals
Bearing service life is extended by avoiding lubricant starvation and over-lubrication
Workplace safety
Work place safety can be improved via automating a manual work task
Reduced damage potential
The potential to cause damage to bearings and motors by the delivery of high pressure grease is reduced
