Lubricants and Lubrication

The most important property of a lubricant is usually its viscosity. This chapter includes viscosity and related lubricant properties, synthetic lubricants, greases, solid lubricants, and lubricant supply methods. Lubrication supplies can be grouped into three classifications: self-contained units for supplying lubrication to individual bearings; circulating systems dedicated to a single piece of equipment such as a motor, turbine, or compressor; and centralized systems in manufacturing plants, and metalworking. The chapter illustrates how important it is to include the effect of pressure and temperature on lubricant viscosity. This is particularly crucial in elastohydrodynamic (EHL) applications where the effect of pressure on viscosity can become enormous. The chapter discusses the equation of state, which describes a relationship between the lubricant density to pressure and temperature. The density of a lubricant is necessary in performance calculations since the kinematic viscosity measured in laboratory instruments must be multiplied by density to obtain the absolute viscosity for oil-film characterization.