Proper lubrication of bearings

The purpose of the lubricant is to prevent direct contact between the rolling elements, the rails and the cage, thus ensuring minimum friction and wear.

The purpose of the lubricant is to prevent direct contact between the rolling elements, the rails and the cage, thus ensuring minimum friction and wear. In addition, the lubricant also provides surface protection against corrosion. At the same time, grease is often used to improve sealing, but for oil, for example, to remove heat from the bearing seat.

Which lubricant and which lubrication procedure can be considered for a particular bearing assembly depends on the operating conditions, but it can also be predefined depending on the lubrication of the adjacent parts of the machine. Environmental influences such as dust, water spray, condensed water formation, aggressive media and shaft positions (horizontal or vertical shafts) also play an important role. In addition, care must be taken on the compatibility of the lubricant and the material from which the bearing cage is made. The permissible operating temperatures (measured on the outer surface of the outer bearing ring) for cages made of polyamide 6.6 are between 100°C and 120°C, depending on the lubricant used.

Lubrication with grease

Bearings that are not sealed must be supplied with grease during installation. Time and manner depends on the type of bearing, as well as the housing design.

For demountable bearings, such as roller or conical bearings, grease the parts of the bearing with grease in the order of their assembly. After installing the first ring, first grease with the grease of the empty space created after it. Lightly lubricate the rails in the case of rings without a roller coil to prevent damage when assembling the bearing. After installing the bearing ring with the roller wrap, fill the empty space between the rollers with grease.

SKF offers a wide selection of quality bearing greases

Fill non-adjustable bearings with grease from both sides. With adjustable bearings, the outer ring can be rotated after mounting on the shaft and lubricate the intermediate spaces of the exposed rolling crown. Only when the grease can no longer be applied evenly after the mounting of the bearing, the bearing must be applied beforehand.

In cases where the bearing housing is divided, first attach the bearing to the shaft and fill it with grease on both sides. Then insert the bearing with a shaft into the chassis and fill in the empty space in the housing with the required amount of grease.

In the case of unoccupied housings and non-detachable bearings, first grease the grease with empty space for the bearings. After mounting a normally non-greasy bearing, lubricate it from the open side of the housing. The mounting of the bearing through the lubricating grooves and the holes in the inner or outer ring is particularly easy when suitable lubrication options are provided in the housing or shaft. Finally fill in the empty space in front of the bed with the grease, as far as necessary.

Re-lubrication

When re-lubricating the bearing, observe the maintenance instructions from the machine manufacturer. Carefully wipe grease before re-lubrication. If the bearing housing is not equipped with lubricants, remove the top or side cover, remove the used grease and replace it with the fresh grease of the selected type, or appropriate grease from the SKF program. Hand lubrication pumps are available for grease lubrication.

Amount of grease

In particular, replace the grease directly with a new grease. The amount of grease required depends on the size of the bearing. If you do not have any lubrication data available, you can determine the required quantity using the following equation:

G = 0.005 x D x B
with

G – amount of grease (g)

D – outer diameter of the bearing (mm)

B – total width or height of the bearing (mm)

SKF greases

It is known what impact the lifetime of the bearing has on the lubricants. Due to this, SKF, in addition to the sealing technique, also pays great attention to the development of grease for rolling bearing assemblies. The result of this development is more than 15 types of SKF greases for a wide range of uses, which are listed in the SKF Fat Catalogue.