Greases for Gear Boxes
The different principles of gear box lubrication
1. Sump lubrication
In this one or more gears dip into a sump comparable to the oil sump. Entrained excess grease is thrown off again and flows back to the housing wall in the sump, where it is available for lubrication again.
2. Adhesive lubrication
With this principle, the grease used is much more consistent and adheres to the gears. Excess grease is not thrown off, but only pushed out of the lubrication point and remains in the immediate vicinity of this. In this case, constructive measures should be taken so that the grease can be returned to the lubrication point during standstill or vibration and this does not deplete in the long term.
3. Relubrication via central lubrication system
Here, the grease needed for lubrication is transported from a central reservoir to the individual lubrication points. Excess grease is thrown off, as in sump lubrication, but is lost here and is no longer available for lubrication.
If the principle used is that the metal working medium can penetrate into the gear, then the grease must be resistant to these media and also provide good corrosion protection.
The gear oils are selected according to the respective requirements regarding the speed and load of the gearbox. At higher speeds greases with low base oil viscosities are used. With decreasing speed or increasing load, grease with correspondingly higher base oil viscosity is used.
The use of greases with an unmatched, too high base oil viscosity can lead to excessive self-heating. If the viscosity of the base oil is too high, the internal resistance that the grease opposes to the movement is too high, and the resulting losses lead to excessive heating of the system. If the viscosity is too low, the separating effect of the lubricating film is too low, and metallic friction also causes heat and wear.
FUCHS understands the different applications and their requirements like no other lubricant and grease manufacturer. Test our know-how and our experience - it pays off for you!