Motor Bearing Grease Up

Motor bearing life is assured by maintaining proper alignment and good lubrication at all times. Most of the new motor bearings are lubricated to provide 3-6 months of satisfactory service under normal operating conditions. Thereafter, re-lubrication is required. Here are some maintenance tips for re-lubricating.

Greasing Interval

Typical Greasing Interval of 460-575 Voltage/3 ph/2 poles motor
Motor Size Less than 100 HP
143T-256T frame size
125-350 HP
404TS-447TS frame size
Standard Duty: Up to 8 hours per day 8 months 8 months
Severe Duty: 24 hours per day 4 months 4 months
Note Above table is reference use only. Consult motor manufacturer for specific greasing interval.

Type of Grease, Compatible or Incompatible.

It is common for several different greases to be used in the engine room. It is important to be aware of grease compatibility. Not all greases are fully compatible with one another because different types of thickeners and oil-bases are used. A mineral oil-base grease SHOULD NOT be mixed with a synthetic oil-base grease. The table below shows commonly used greases for motor bearings, their oil-base and their thickener compatibility.

Table 1. Grease Name, Type of Oil and Thickener
Name of Grease Type of Oil-Base Type of Grease Thickener
Chevron SRI Mineral Polyurea
Exxon Unirex #2 Synthetic Lithium Complex
Exxon Polyrex Mineral Polyurea
Shell Dolium Mineral Polyurea
Citigo EP Mineral Lithium
Shell Alvania EP #2 Mineral Lithium 12-Hydroxy

Table-2 Grease Thickener Compatibility
  Aluminum Complex Barium Calcium Calcium 12 Hydroxy Calcium Complex Lithium Lithium 12 Hydroxy Lithium Complex Polyurea
Aluminum Complex   X X O X X X O X
Barium X   X O X X X X X
Calcium X X   O X O O X
Calcium 12 Hydroxy O O O   O O O X
Calcium Complex X X X   X X O O
Lithium X X O O X   O O X
Lithium-12 Hydroxy X X O X O   O X
Lithium Complex O X O O O O O   X
Polyurea X X X X O X X X  
O=Compatible   =Borderline Compatibility   X= Incompatible

Because motor manufacturers specify different types of grease for their motors, errors in mixing incompatible greases can take place easily. If a motor is being repaired in-service, shop grease may be used that the engine room does not stock.

There are several good practices you may implement in order to prevent these errors from occurring.

  1. Use color-coordinated grease guns (color sleeves are available.) and grease nipple tags.
  2. Store greases in an organized manner (location, name tag, color coding, etc…).
  3. Specify the type of grease before the motor is sent to a service shop.