KNOWLEDGE

Bearing Lubrication

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:

Lubricant Advantage Disadvantage
Oil Easy to distribute, lubes other components, less drag, easier to drain out and change.  Better for high temperature. May leak (environmental concern), then no more lubrication
Grease Remains in place, doesn’t leak out easily, improves sealing, and does not require monitoring. Requires more labor to clean out and replenish.  High temperature grease is very expensive.

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:
Recommended General R&O Lubricant
Basic Oil Refined solvent, high viscosity index mineral oil
Additive Rust inhibitors and antioxidants
Viscosity Index 80 min
Pouring Point -10℃ max.
Viscosity Grade ISO 32 to 220

 

Recommended Industrial Extreme Pressure Gear Oil
Basic Oil Refined solvent, high viscosity index mineral oil
Additive Rust inhibitor and antioxidant, extreme pressure agent (EP)
Viscosity Index 80 min
Pouring Point -10℃ max.
Viscosity Grade ISO 100, 150, 220, 320, 460

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:
Manufacture Ref Grade Base Oil Thickener Base oil viscosity
40℃ 100℃
kyodo Yushi 1 Multemp SRL Polyol ester + diester Lithium Hydroxystearate 26 5.1
2 Multemp SB-M Synthetic hydrocarbon Polyurea 47.6 8.9
3 Raremax SUPER N Mineral oil + synthetic hydrocarbon Polyurea 95.9 10.5
4 Multemp PS2 Diester + synthetic hydrocarbon Lithium soap 15.3 4.7
5 Mutemp SRH Polyol ester Lithium soap 83
6 Multemp SRM Polyol ester Lithium soap 55
7 Multemp ET-K Ether-based synthetic oil polyol ester Aromatic diuretic 95.1 12.3
Kluber 8 BQH72-102 Base oil, ester oil Polyurea 100 11
9 BEP72-82 Base oil, ester oil Polyurea 70 9.4
10 ASONIC GLY32 Base oil, ester oil Lithium-based 25 5
11 ASONIC Q74-73 Base oil, ester oil Polyurea 67.5 10
12 Isoflex LDS 18 special A Ester oil, mineral oil Lithium soap 15 3.5
13 ISOFLEX TOPAS NB 52 Synthetic ether + polyol ester Compound barium soap base 30 5.5
14 PETAMO GHY133 Mineral oil + base oil Polyurea 150 18
15 BE 41-542 Mineral oil Lithium soap 540 32
16 BE 31-502 Mineral oil Polyurea 500 31
Shell 17 AV2 Mineral oil Lithium-based 130 12.2
18 RLQ2 Mineral oil Lithium-based 75 8.3
19 RL2 Mineral oil Lithium-based 75 8
20 RL3 Mineral oil Lithium-based 75 8
Exxon Mobil 21 Polyrex EM Mineral oil Polyurea 115 12.2
22 Unirex N3 Mineral oil Lithium-based 115
23 BEACON325 Mineral oil Lithium-based 12 4
24 Unirex N2 Mineral oil Lithium-based 115
25 Mobil grease 28 Synthetic oil Micro Adhesive 29.3
Cosmo 26 EMQ2(SBR) Mineral oil Lithium-based 110.8 11.98
27 PNG Mineral oil Lithium-based 73.5 6.88
Chevron 28 SRI 2 (ISOSYN)mineral oil Polyurea 100 11
Lubcon 29 N2 Ester Polyurea 150 22
Dupont 30 Krytox240 (PFPE/PFPAE) (PTFE) 200 25
Jinzhi 31 Hangu 2 Mineral oil Lithium-based 150 12
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