Selecting the appropriate grease is a highly detrimental factor when it comes to protecting the equipment from failure. It also prevents premature bearing failure on part of the equipment. The appropriate grease selection also plays a major role in acquiring higher reliability and efficient operating life of a bearing.
Lubricants such as mineral and synthetic oils are sometimes used with rolling bearings that are exposed to extreme weather conditions or radiation. Most of the bearing manufacturers recommend using of greases to ensure a good operating life of the equipment.
The characteristics of grease mainly depend on three properties, namely, base oil, type and viscosity along with the thickeners and additives that are used.
Let us now discuss in detail what each of them is used for.
Base Oil Viscosity – it is mainly responsible for the formation of the lubricant’s film. Oils can be either mineral or synthetic. While choosing synthetic oils, it is important to differentiate according to the type as there are several distinct characteristics of it.
The thickeners used generally include components such as metal soaps or metal complex soaps. Also nowadays organic thickeners also called as polymer thickeners are becoming very popular.
Additives are generally found in all types of greases. Additives can affect oil and there are additives that can affect metal surfaces and bearings.
Selecting the right grease for a rolling bearing includes considering a number of factors such as bearing type, temperature, operating speed and load. Other important factors include sealing, shock and vibration, mounting position and the environmental regulations.
Bearing Type should have to be differentiated between point contact and line contact. Rolling bears sometimes requires anti-wear additives with a consistency. Also the bearing speed should be suitable to the grease’s speed parameter. This entirely depends on the type of thickener used, the base oil and the proportion of base oil. The grease’s speed parameter requires minimum operating time and is also based on the bearing type used. Generally, for rolling bearings that rotate at high speed, greases with high speed parameters should be used. On the other hand greases with low speed parameter must be used for rolling bearings that rotate at lower speeds.
The temperature range of grease must be a match for the possible operating temperatures of the rolling bearing. The operating temperature again depends on a number of factors such as type and proportion of thickener, type and proportion of base oil, production quality and production process. The stability of the silicone grease is also a determining factor of the production quality.
For the load ratio, greases must have anti wear additives and higher base oil viscosity. Additives have a layer of protection onto the metal surfaces ultimately giving wear protection.