Göteborg, Sweden-- There are three ways to ensure good oil lubrication of a ball or roller bearing, says bearing manufacturer SKF. These are: supply oil directly to the bearing; supply oil in a thickened form as grease; or use SKF's Solid Oil.
Solid Oil is a polymer matrix saturated with lubricating oil. The polymer composite has a porous structure with millions of "micropores" to hold the lubricating oil. These pores are so small that the oil is retained in the material by surface tension.
Pressed into a bearing, the oil-filled polymer completely fills the bearing's internal space, encapsulating the cage and rolling elements. A very narrow gap forms around the rolling elements and raceways during the molding process, allowing the bearing components to rotate freely. This gap also encloses any free oil, for constant lubrication.
Because lubricating oil represents about 70% by weight of the Solid Oil materials, SKF claims that a bearing using Solid Oil contains as much as four times more oil than a conventional grease-lubricated bearing. This is because the bearing is completely filled, whereas a grease-lubricated bearing normally operates with approximately one-third of its free internal space filled with grease. In this respect, Solid Oil also protects the bearing as it prevents the entry of foreign particles into the bearing mechanisms.
There are other benefits to Solid Oil:
Re-lubrication is not necessary during the bearing's lifetime.
Since Solid Oil does not leak from the bearing, it suits environmentally or hygienically sensitive applications.
The polymer matrix resists most chemicals apart from light organic solvents.
SKF has identified several applications for Solid Oil, where alternative lubrication methods are not practical. In papermaking, Solid Oil protects the bearing against impurities, prevents pulp being contaminated with oil, and ultimately prevents oil from spoiling the paper at the cutting stage. In cold weather engineering applications, Solid Oil offers benefits over greases because it has lower starting torque; rolling elements do not need to overcome the stiffness of grease. In pneumatically operated couplings, solid oil is not redistributed by large centrifugal forces.