Page 301 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

1. Remove all nicks and burrs from the housing and bearing shell.
2. Be sure that journal and thrust faces are free of nicks and high
spots. These spots can be removed using a fine hone and polishing
with crocus cloth.
3. Obtain the proper bearing contact as described previously.
4. After the bearings are fitted and the lower halves are installed in the
housing, check the radial clearance using plastic gauge material
available in most supply stores. Check thrust clearance by moving
shaft axially in both directions while an indicator pointer is posi-
tioned against the shaft. In many cases it may be necessary to use a
small hydraulic jack to move the large gears axially to check the
clearance.

Roiling Element Bearing Maintenance

Probably a majority of the gear units in factory operations use rolling
element bearings to support the gear rotors and absorb the external and
internal loads associated with gear drives. These bearings are extremely
reliable and give long trouble-free service if they are not abused and are
properly installed and maintained. The two primary disadvantages of
rolling element bearings are that they are very seldom furnished split for
ease of installation and they cannot easily be repaired or manufactured in
local repair shops.
Volume 3 of this series contains excellent data on the causes of bearing
failure and describes proper failure analysis. Many factors can contribute
to bearing failures in gears; however, most rolling element bearing fail-
ures can be attributed to one or more of the following causes: defective
bearing seats; misalignment; faulty mounting practice; incorrect fits; in-
adequate lubrication; ineffective sealing; vibration, and electric current.
Rolling element bearings should be inspected if practical for damage
that could indicate incipient failure. However, as bearing inspection is
not usually practical since the gear unit must be disassembled, special
attention should be focused during routine maintenance and inspection on
factors that can contribute to premature bearing failure such as the pres-
ence of dirt in oil, oil condition and quantity, vibration, and electrical
current.

Defective Bearing Seats on Shafts and/or in Housings
For bearings to have long trouble-free life, the thin inner and outer
rings must be mounted on shafts or in housings that are as geometrically