As we have already had the opportunity to recall in one of our previous reflections on the subject, oil lubrication is one of the types of lubrication provided for mechanical bearings , as an alternative to grease lubrication. But in what situations is a similar type of lubrication preferable? And which oil lubrication variants can be identified?
When oil lubrication is better than grease lubrication
In general, lubricating bearings with oil may be preferred to using grease if the bearing rotation speed is quite high, or if it is necessary to remove heat generated by the bearing or coming from outside. Furthermore, it may be preferable to lubricate with oil in cases where the supports are difficult to access, or when the rolling elements are small and therefore difficult to access by grease.
Naturally, the best criterion to understand whether or not it is better to proceed with oil lubrication is to read the component manufacturer's manual: despite the benefits it can bring, it is not certain that lubricating oil is the preferred type of lubrication, taking into account as it presents some disadvantages such as, among the main ones, the request for better sealing elements and the possibility of conveniently checking the presence of lubricant.
Main types of oil lubrication
Even though we usually talk about oil lubrication as if we meant a single type, in reality lubrication can include different variants which, due to substance and purpose, may well be considered separately. Among the main ones we can certainly remember the presence of bearing oil bath lubrication , certainly the simplest and most economical solution, obtained by immersing the bearings in the oil contained inside the housing, so that they can distribute it throughout the entire bearing.
Alternatively, it is possible to note the presence of ideal circulation lubrication if you want to use small quantities of oil, with the lubricant circulating internally or externally to the bearing: in the first case, the oil will be made to flow to the bearing through special bushings which, rotating in high speed, release the oil onto rolling elements.
Other forms of lubrication with bearing oil include an injection system , in which the oil is pumped at very high pressure through a pump and released at high speed into the rolling elements through special nozzles. Furthermore, the “mist” type of lubrication is sometimes used, a particular type in which the oil is nebulized with a jet of air from a special nebulizer nozzle: for this, compressed, dry and filtered air is used, at a pressure that is slightly higher than that of the atmosphere.
With this system it is possible to obtain excellent cooling of the bearing, making it possible to create a good support with pressure – as expected – slightly higher than atmospheric pressure, which prevents the entry of foreign substances.
