Relubrication can extend bearing unit service life under any of the following conditions:
- The bearings are exposed to high humidity or severe contamination.
- The bearings accommodate normal or heavy loads.
- The bearings operate for extended periods at high speeds or at temperatures above 55 °C (130 °F).
- The bearings are subjected to high vibration levels.
To relubricate ball bearing units that have lubrication features, the following greases can be used:
- SKF LGWA 2
- SKF LGMT 2
- SKF LGMT 3
If relubrication is needed, the relubrication intervals can be estimated by following the method explained under Estimating the relubrication interval for grease.
When relubricating, the shaft should be turned and grease should be pumped slowly until fresh grease starts to escape from the seal(s). Excessive pressure from pumping too quickly can damage the seals. When machines and equipment are used for a limited period of time, SKF recommends relubricating each bearing at the end of the operational period, i.e. immediately before being laid up.
Ball bearing units with housings made of the following materials are as standard not equipped with a grease fitting and therefore cannot be relubricated:
Relubrication feature available on request (designation suffix N).
- pressed steel
- composite for the SKF Food Line
- stainless steel
Relubrication features for cast iron housings:
- Grease fitting with a 1/4-28 SAE-LT thread. Exceptions are housings used for bearings with inch bore diameter larger than 1 in. and with designation suffix U, which are equipped with a grease fitting with a 1/8-27 NPT thread.
- The hole for the grease fitting has a 1/4-28 UNF thread, which can be changed to G 1/4, using an LAPN 1/4 UNF adapter. Exceptions are housings used for bearings with inch bore diameter larger than 1 in. and with designation suffix U, which have a 1/8-27 NPT threaded hole.
- For cast iron units comprising 5-lip seal bearings, which do not have any relubrication feature, the housing relubrication feature is plugged (designation suffix W).
SKF insert bearings are designed to facilitate relubrication. They have two lubrication holes in the outer ring as standard, one on each side, positioned 120° apart.
Bearings without lubrication holes can be supplied on request (designation suffix W).
The following insert bearings are lubricated for life and cannot be relubricated. They do not have any lubrication holes:
Bearings with grub screw locking:
- with zinc-coated rings
- made of stainless steel
- Bearings with a standard inner ring without designation suffix B
- Bearings with 5-lip seals