Twin City Bearing Problems - ES-53 - Manual

Generally speaking, Twin City Fan & Blower uses three
types of bearings:
1. Ball bearing with set screw lock
2. Spherical roller bearings with set screw lock
3. Spherical roller bearings with adapter lock/taper lock
feature to attach them to the shaft
Ball Bearing
These are self-aligning bearings and should present no
alignment problems with one exception: i.e., on
Sealmaster bearings there is a pin beneath the grease
fitting which prevents the bearings outer race from rotat-
ing. Should this pin jam, the bearing loses its alignment
feature.
Common failure causes are (1) set screws loosening
and shaft turning within the bearing, and (2) crowned
bearing supports. Loosen one bolt and measure clear-
ance between pillow block and support. Add shim to
compensate.
Spherical Roller Bearings
With Set Screw Lock
The self-aligning characteristic of these bearings are
inherent in the spherical roller design. The closer that
these bearings are to perfect alignment, the cooler they
will operate.
Common failure causes are the same as with ball
bearings, mainly set screws loosening and crowned
bearing supports.
Spherical Roller Bearings
With Adapter Lock
Again, the self-aligning feature is inherent in the spheri-
cal design. Good alignment results in a cooler operating
bearing. The faster the bearing operates the more critical
this becomes.
Common causes of failure are improper installation
practice. Removing too much clearance from the bearing
can result in preloading the bearing, resulting in prema-
ture failure; and removing not enough can result in the
shaft rotating within the bearing. Properly tightened, this
method of attaching a bearing to a shaft is second only
to a press fit. Crowned bearing supports can also pre-
load these bearings and should be checked by loosen-
ing one side of the bearing and checking for clearance.
Lubrication
The major cause of bearing failure is contamination of
grease, insufficient grease, or incompatibility of grease.
If a fan is to be stored for any length of time at the
job site, the bearings immediately should be filled with
grease while rotating the shaft and then the bearings
should be regreased and rotated monthly. This will pre-
vent moisture, which condenses within the bearing, from
corroding the raceways. Most greases used on fan pil-
low blocks are lithium base. Use the greases shown on
the bearing decal. Do not mix the bases without com-
pletely purging out the initial grease.
Initially, follow the lubrication instruction on the side
of the fan. The frequency of lubrication should be
adjusted depending on the condition of the old grease
being purged. This is the responsibility of the user. If
the grease is dirty, the lubrication frequency should be
more often.
a. Noise — If a bearing is increasing in noise intensity
and/or vibration, it will probably result in failure.
b. Temperature — If a bearing temperature begins to
gradually rise, it will generally result in failure. A bear-
ing can operate up to 200 degrees and operate
satisfactorily if the temperature remains constant and
the bearing receives adequate lubrication. Remember
that a roller bearing under the same load and speed
will be somewhat more noisy and run warmer than a
ball bearing. This is normal.
Rough handling and/or dropping a fan can result in
brinelling the bearing. This appears as a clicking noise
at first, then gradually worsens until failure.
When replacing a bearing, always align the bearings
first, then bolt the pillow blocks to their support, rotate
the shaft, fasten the bearings to it. If the bearing is
fastened to the shaft first, tightening the pillow block
bolts may bind the shaft and preload the bearings.
ES-53
April 1998
Bearing Problems
Twin ciTy fan & blower | www.Tcf.com
5959 Trenton Lane N | Minneapolis, MN 55442 | Phone: 763-551-7600 | Fax: 763-551-7601