Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

Roiling Element Bearings and Lubrications 529
Figure 20-1. Recommended lube oil change frequency as a function of bearing
bore diameter and lube oil sump capacity (courtesy of FAG Bearing Corporation,
Stamford, Connecticut).
susceptible metallic surfaces. In many instances, water can displace the
oil from the surfaces and cause rusting. Rust is particularly undesirable
in a rolling element bearing because it can seriously abrade the bearing
elements and areas pitted by rust will cause rough operation or failure of
the bearing.
Additives
High grade lubricating fluids are formulated to contain small amounts
of special chemical materials called additives. Additives are used to increase
the viscosity index, fortify oxidation resistance, improve rust protection,
provide detergent properties, increase film strength, provide extreme
pressure properties, and sometimes to lower the pour point.
General Lubricant Considerations
The proper selection of a grease or oil is extremely important in highspeed
bearing operation. Proper lubrication requires that an elastohydrodynamic
oil film be established and maintained between the bearing rotating
members. To ensure the build-up of an oil film of adequate
load-carrying capacity, the lubricating oil must possess a viscosity adequate
to withstand the given speed, load, and temperature conditions.