SKF’s introduction to motor bearing lubrication

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Maintenance knowledge: Lubrication – Bearing grease lubrication
Grease is by far the most popular method for bearing lubrication. It is easy to apply and remains within the bearing housing, while also functioning as a seal to protect the bearing. Grease consists of approximately 85% oil (mineral or synthetic) and 15% soap or thickener. All soaps work in the same way; they retain the oil in a manner similar to how a sponge retains water. The oil can drain out when needed, as the bearing requires it when its internal temperature rises.

SKF Bearing Grease
The bearing should be filled with grease, leaving up to 50% of the housing space empty, so that excess grease can be expelled from the bearing during startup. Filling the bearing with grease should be one of the last steps when installing a replacement bearing, in order to maintain cleanliness and minimize contamination. A full fill is advisable in situations where the bearing operates at low speeds and overheating is not a concern.

How long will the grease last?
The lifespan of grease depends on various factors, the most important of which are operating temperature, the type of grease, operating speed, as well as environmental conditions and the sealing arrangement. Lightly loaded ball bearings may not require re-lubrication throughout their lifetime, allowing for the use of sealed or “lifetime-sealed” bearings.

Re-lubrication intervals
Determining the re-lubrication intervals for a particular application depends on many factors. The most important ones are operating conditions such as temperature, speed, and load, as well as the type and arrangement of bearings. Environmental factors can also influence the frequency of re-lubrication. In highly contaminated environments, such as those found in quarries and foundries, more frequent or even continuous lubrication may be necessary. In some applications, continuous lubrication is preferred, and this can be achieved using a centralized system or an automatic lubricator. It is important to ensure that the lubrication fittings are clean, that the right type of lubricant is used, and that the appropriate amount of lubricant is supplied. For open bearings, the best way to determine the re-lubrication interval is to use the SKF DialSet re-lubrication interval calculation program, which can be downloaded from this website. To find out the estimated lifespan of SKF bearing grease for sealed bearings, it is best to contact your local SKF representative. Download DialSet, SKF’s re-lubrication interval calculation program