Bearing Lubrication

Bearing Lubrication Introduction:

Bearing lubrication is absolutely essential to the proper operation of all kinds of ball and roller bearings.
A proper lubricant will reduce friction and reduce or prevent metal-to-metal contact of the rolling elements with their raceways.
There are two basic types of bearing lubricants readily available: Oil and Grease.
Oil is free-flowing liquid, while grease has oil that is entrained in a thickened base.

Two Lubricants Advantages and Disadvantages:

The major advantages and disadvantages of oil and grease lubricants are as below:

Oil Lubrication:

Rolling bearings are lubricated by oil lubrication, which can achieve good cooling and cooling effects, and is especially suitable for rolling bearings with relatively high operating temperatures.
The viscosity of the lubricating oil used in rolling bearings is about 0.12 to 0.2cm/s.
If the load of the rolling bearing is high and the working temperature is high, choose a high-viscosity lubricating oil. While a rolling bearing with a fast speed is suitable for a low-viscosity lubricating oil.

The disadvantage of using oil lubrication for rolling bearings is that oil lubrication requires the bearing to maintain a good sealing condition to avoid leakage of lubricating oil.
In addition, oil lubrication requires a more complicated oil supply device, which is not as convenient as lubricating grease in operation and increases the maintenance workload of bearings.

Oil Lubrication Guide：

Grease Lubrication:

When choosing a grease for an application, several of its properties need to be considered for the expected operating conditions.
The priority of these properties is as below,
1. Required oil viscosity at temperature of the bearing.
2. Grade for the operating temperature.
3. Soap base which is best for the application.
4. Availability of EP (Extreme Pressure) additives.

How Much Grease Should Fill ?

Once the available grease filling space for the bearing is determined, the amount of grease required will be calculated as a percentage of the available grease filling space.
The correct weight is important to ensure proper lubrication of all contact surfaces. Overlubrication is just as harmful as insufficient lubrication: for example, too much grease in high-speed bearings can cause overheating or higher starting and running torques.

Generally speaking, the amount of grease in the bearing should occupy approximately 25% to 35% of the available internal space.
In some very high-speed applications, the use of lubricants can be as low as 10% to 15%.

Commonly Used Grease Characteristics Table: