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Pump Bearings

7.3 Ball bearings

While other bearing types arc frequently used in special applications,
the modern centrifugal pump predominantly depends on the use of the
anti-friction ball bearings.
Ball Beatings comprise an inner and outer hardened steel rings
separated by a number of steel balls. The inner ring is mounted on the
pump shaft while the outer ring is fitted in the housing. The balls are
spaced around the bearing by a separator that helps to reduce the
amount of friction. These items are manufactured to extremely tight
tolerances, and it is essential that the shaft and housing must also be
held to the same level of machining tolerances during repair and
overhaul. When installing a ball bearing, great care must be taken to
ensure accuracy and cleanliness.
Ball Bearings are classified
according to the type of loading
they are required to accom-
modate. The size and class of
precision are governed by the
Anti-Friction Bearing Manu-
facturing Association (AFBMA)
and by the Annular Bearing
Engineers Committee (ABEC).
Of the five ABEC classifications
(1, 3, 5, 7 and 9), Class 1 is
standard and Class 9 is high
precision. Regardless of the
Tolerance Class or the lnternal
Clearance Class of the bearings
used, sound engineering practice
requires that the pump original
equipment manufacturer's bearing Figure 7.6. Single row deep groove ball
selection be duplicated during bearing (Reproduced with permission of SKF
repair and overhaul. USA Inc.)
Various ball bearings are used on centrifugal pumps, with the most
common being the single row, deep groove bearing. In addition to it's
ability to handle the radial load, this bearing type is designed with a
close contact between the balls and the deep continuous groove in each
ring, and is therefore capable of handling an axial thrust load in either
direction.
It is also capable of accommodating combined radial and thrust loads.
In many small pumps, both the radial bearing and the thrust bearing
will be this type of bearing. In the larger sizes, such as a typical ANSI or
AP1 pump, it will serve solely as the radial bearing.

111 m