Page 4 - Olipes Industrial Maintenance

Electric motors

The parts to be lubricated in an electric motor are the drive shaft support bearings
(occasionally friction bushings). These in general withstand low to medium loads and rotate
at medium to high revolutions. For this application we recommend the use of greases with
high anti-wear properties, high resistance to oil separation by centrifugation and a suitable
speed factor.

RECOMMENDATIONS:
It is important to prevent the grease from coming into contact with the motor winding at all times.
Motors equipped with sealed bearings are lubricated with long-lasting synthetic greases and do
not need to be regreased.
The following factors need to be taken into account when selecting the correct grease to be used:
• the rotation speed (RPM)
• the torque at low temperature
• the loads and vibrations to which they might be subjected
• the service temperature
In order to determine the amount of grease in the bearing, we recommend:
• 1/2 to 2/3 of the free space in the bearing when the speed of the same at full performance
is less than 50% of its speed limit
• 1/3 to 1/2 when the speed of the bearing is above 50% of its speed limit
The amount of grease to be used in the bearing may also be determined using the following
equation:
Amount of grease (g) = outer diameter of the bearing (mm) x width of the bearing (mm) x 0.005

The bearing bracket, in addition to keeping it in its place and protecting it
from the outside, also serves as a grease tank. The following guideline may
be used to calculate the amount of grease required to fill this tank: fill 30% to
50% of the tank.
Less grease at greater speeds (30% for very high speeds and 50% for
low speeds, including up to 75% for very low speeds with no regreasing,
particularly in aggressive environments).
The relubrication frequency or period for small and medium electric motors
operating in a continuous manner is around once a year, reducing the
relubrication period by around half for each 10ºC above the recommended
nominal temperature (generally 60ºC).
We recommend using the engine maintenance manual and the following
equation in order to calculate the ideal relubrication time (in hours):

Period (hours) = {[14,000,000/((shaft rpm)(Di in mm) )] - (4 x Di in mm)} x F x F x F
1/2
R T C
F R : Correction factor in accordance with the type of bearing: 1.0 for swing or thrust bearings, 5.0 for
roller bearings and 10.0 for ball bearings
F T : Correction factor by temperature: 1.0 for temperatures lower than 70º C. Divide by 2 for each 10ºC
of temperature above 70º C.
F C : Correction factor by contamination: from 0.1 to 1.0 depending on the level of contamination. (in
normal conditions value 1.0)
Lubricating with oil

Forced circulation motor bushings

MAXIFLUID VG & MAXIFLUID HLP (22 -46)
Low-viscosity oils with anti-wear additives (AW)
DIN 51524/2 HLP ISO 6743/4 HM

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