Lubricants for roller bearings and plain bearings
Lubricants for roller bearings are offered as grease, oil and solid substances. In addition to actually reducing friction or reliably separating metallic surfaces through the build-up of a lubricating film, their duties also include reliable antioxidation, anticorrosion, and wear reduction. Greases consist of a base oil and a thickener, as well as additives. Solid lubricants are primarily used in extreme environmental conditions. Correctly choosing the optimum lubricant for the application conditions is as complex as the correctly choosing the design of a bearing series.
Product range
| Manufacturer | SD | HS | HT | LT | EP | Special lubricants |
|---|---|---|---|---|---|---|
| Kyodo Yushi | X | X | X | X | X | conductive |
| Klüber | X | X | X | X | X | conductive, electrically insulating, solid lubricants |
| Shell | X | X | X | X | X | solid lubricants |
| Lubcon | X | X | X | |||
| Mobil | X | |||||
| Rhenus | X | X | X | special lubricant manufacturer | ||
| Total | ||||||
| Other | X | X | X | X | Several manufacturers offer their own lubricants: FYH, NACHI, FAG, SKF |
SD: standard multigraded lubricants; HS: for high speeds HT: high temperature, LT: for low temperatures, EP: for high loads
Technical information
Simple and complex soaps
Soap grease | Properties |
|---|---|
Simple lithium soap | can be used at up to 120 °C |
Complex aluminum soap | can be used at up to 160 °C good adhesion can be broken down by hot water poor mechanical stability |
Complex barium soap | can be used at up to 150 °C water and steam resistant resistant to weak acids and bases very good corrosion protection very high pressure accommodation capacity toxicological concerns and unapproved in some countries |
Complex calcium soap | can be used at up to 150 °C water and steam resistant good corrosion protection very good pressure accommodation capacity hardens during storage time |
Complex lithium soap | can be used at up to 150 °C good water resistance good cold properties |
Complex sodium soap | can be used at up to 180 °C water resistant up to 90 °C good adhesion good corrosion protection not suitable for water vapor |
Non-soaps
Non-soaps | Properties |
|---|---|
| PTFE | solid lubricant, excellent high-temperature characteristics, preferably used in boundary and mixed friction. |
| Polyurea | suitable for high temperatures, usually in combination with ester oils |
| Silica | ceramic base of SiO2 |
| Bentonite | inorganic thickener |
| Gel |
Base oil | Properties |
|---|---|
| Mineral oil | standard base oil type |
| Ester | often used as an admixture, partly biodegradable |
| Silicone oil | caution: this substance is harmful to paint structure |
| Polyalphaolefin | synthetic oil, also food-approved |
| Polyglycol | critical in case of aluminum contact, elastomers, poor miscibility with other oils |
| Alkoxyfluoro oil | also known as PFAE, PFPE, immiscible |
Additive | Effect |
|---|---|
anticorrosion | surface-active additives barriers hostile to moisture are formed forms a protective layer on metal surfaces |
antioxidation | lubricating oils tend to oxidize (age) when exposed to heat and oxygen additives oxidize in the place of lubricants cannot prevent the aging process, but can slow it down |
antifoam | foam formation impairs lubricant characteristics lower surface tension and decrease foaming tendencies |
wear protection | extremely thin layers, whose shear strength is significantly lower than that of metals, are formed on sliding surfaces prevent metallic friction partners from being “eaten away at” EP = extreme pressure (compressive strength) AW = anti-wear (friction minimization) |
VI improvers | increase or extend the viscosity of an oil and thus improve the viscosity-temperature behavior solubility at high/low temperatures |
Consistency of greases
Determining class affiliation based on worked penetration according to ISO 2137
NLGI class | Worked penetration | Central | Gear | Plain | Roller bearings | Water | Block | |
|---|---|---|---|---|---|---|---|---|
000 | 445 to 475 | liquefied greases | X | X |
|
|
|
|
00 | 400 to 430 |
| X | X |
|
|
|
|
0 | 355 to 385 |
| X | X |
|
|
|
|
1 | 310 to 340 | soft greases | X | X |
|
|
|
|
2 | 265 to 295 |
|
|
| X | X |
|
|
3 | 220 to 250 |
|
|
| X | X |
|
|
4 | 175 to 205 |
|
|
|
| X | X |
|
5 | 130 to 160 | hard greases |
|
|
|
| X |
|
6 | 85 to 115 |
|
|
|
|
|
| X |
Data | Measurement | Meaning |
|---|---|---|
density | mass/volume | auxiliary identification value |
base oil viscosity | ISO VG | load carrying and wear behavior |
dropping point | °C | dropping behavior |
(worked) penetration | 0.1 mm | stiffness |
apparent dynamic viscosity | mPas | inner resistance of a grease |
flow pressure | Mbar/Temp. | indicator for lower service temperature |
oxidation resistance | pressure drop | indicator of aging |
water resistance | visual assessment | emulsification of the grease |
anticorrosion effect | visual assessment | corrosion protection of grease |
oil separation | % of the mass | bleeding of the grease |
Solid lubricant additives increase service life in cases of mixed friction, oscillating movements and at very high or low ambient temperatures. Preferred substances include graphite and molybdenum sulfide (MoS2).
As an alternative to this there are special roller bearings with a solid lubricant cage.
The use of lubricants in the food industry requires the selection of an approved lubricant, unless it can be ruled out that the lubricant will come into contact with the food.
The FDA (U.S. Food and Drug Administration) certifies such lubricants and awards H1 approval. The selection of possible lubricants is large and every big manufacturer has suitable products in its portfolio.
In electric motor and generator construction, there is often a risk of currents passing through the roller bearing, which can cause raceway damage and a premature failure of the roller bearing without suitable protective measures. Typical measures include:
- insulating outer ring coatings
- using ceramic balls with non-conductive greases
- using conductive lubricants
We would be happy to give you more in-depth advice here.
