Page 176 - Know and Understand Centrifugal Pumps

Bearings

ENTRANCE
FORCED LUBE
RADIAL
BEARING

EXTERNAL
LUBE BOlTLE OIL LEVEL i\
INDICATOR

Figure 11-1 ~~

bearing failure, which leads to coupling and motor failure on the power
end, and mechanical seal failure on the wet end.
Oil mist systems exist to provide continuous minute quantities of oil
fog to the rolling assembly. These systems normally employ an
additional pump, atomizer, and filter. These systems are gaining
popularity in hot applications, or with heavy thrust and radial loading.
The oil fog is sprayed into the bearing chamber with either a wet sump
or a dry sump. The wet sump method provides the bearings with a bath
(the liquid oil level) and a fog spray. See Figure 1 1-1.
The dry sump method of oil misting has no liquid oil contained in the
bearing chamber. Instead, the entire chamber is filled with the atomized
oil fog. See Figure 11-2, next page.

Both the dry sump and wet sump method of oil misting have a slight
positive pressure in the bearing housing. This prevents contaminants
and even humid air from entering the bearing chamber.

Bearing failure

Pump operators and pumping systems are plagued by unexpected
premature bearing failures. Even if the cost of the bearing is small, the

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