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

Rolling Element Bearings and Lubrications 531
Figure 20*2. Temperature vs. viscosity relationships for various lube oil grades.
Note that centrifugal pumps are typically lubricated with ISO grades 32 through
100,
a low shear rate to the lubricant. This low temperature aids an operating
bearing to establish a temperature equilibrium, even if a lubricant is applied
having a slightly higher viscosity than the application demands.
Higher fluid friction increases the temperature of the lubricant until the
viscosity is reduced to the proper level. It should be noted, however, that
short-fibered greases may lead to "false brinelling" damage in applications
subject to vibration without equipment rotation.
Greases generally are applied where oils cannot be used, for example,
in places where sealing does not exist or is inadequate, dirty environments,
in inaccessible locations, in places where oil dripping or splashing
cannot be tolerated, and often, where "sealed-for-life" lubrication is desired.
Greases are fine dispersions of oil-insoluble thickening agents—usually
soap-—in a fluid lubricant such as a mineral oil. When a bearing lubricated
with grease starts to move, the grease structure (created by the
thickening agent) is affected by the shearing action, and lubrication is
provided by the oil component of the grease. As the bearing slows to a