The Grease Life Factor concept for ball bearings

Bearing fatigue life is calculated using a so called basic rating life equation L10=CPp where the operating load is translated into an equivalent load P and divided by the bearing capacity. This makes it possible to test the bearing capacity C under an arbitrary load and therefore on almost any test rig. For grease life such a concept does not exist. Grease life is specified by a number of hours running on standardized test rigs and conditions. A similar concept as for bearing life is introduced in this paper for lubricating grease, called the ‘Grease Life Factor’ (GLF) concept. It is based on a grease life model for axially loaded grease lubricated ball bearings and makes it possible, similar to bearing life, to quantify the life properties of a grease using ‘any’ grease life test rig. It also implies that there is no longer a need to specify grease life for standardized test rigs. The validity is illustrated with test data obtained from the most widely used test methodologies: FE9 and R0F.