Lubricating Oils

Abstract

The scope of this discussion has been limited to those types of service wherein considerable quantities of lubricants are used, such as in the lubrication of industrial machine bearings, automotive internal combustion engines, and turbines. The primary object of lubrication is to provide between bearing surfaces a film of a type that will permit the conversion and the use of power without large friction losses and without serious harm to the lubricated surfaces. In the case of factory machines, shafting, motors and other housed-in equipment, where the temperature of the bearing does not fluctuate excessively, this is relatively easy since it is merely necessary to provide sufficient inactive fluid of proper viscosity to support the load. In other types of service, the conditions are far more severe. For instance, in some passenger car engines in extreme cases the lubricant must function properly over a temperature range of 350 deg. Fahr. In addition to that, it must not deteriorate too rapidly at higher temperatures nor leave an excess of residue when burned. In the following paragraphs viscosity will be discussed first, since it is the primary factor in practically all cases. It will be followed by a discussion of the limitations that must be imposed on the lubricant in special cases where the conditions of service are severe.