Page 180 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

162 Major Process Equipment Maintenance and Repair

7. Draw up screws holding plates just enough so packing rings are
retained without undue deformation.
8. Fill with oil in top cup (6) until overflow cup (9) is full. Fill only
when fan is not running.
9. Occasionally, bearings can be converted to grease lubrication per
bearing manufacturer’s instructions.
10. To disassemble, reverse this procedure. Be sure to remove burr on
shaft (caused by the set screw) with a honing stone before remov-
ing the pillow block from the shaft.

Set Wheel and Shaft In Bearings

Proceed to install the wheel and shaft in the bearings. Extreme caution
must be used as the thrust collars are placed over the held (fixed) liner.
Mishandling can damage the bearing metal beyond repair. This is diffi-
cult for large bearings because the rotors are very bulky to move with
only a few mils tolerance in their final position. The technique we sug-
gest is to lower the rotor to just above the bearings and then lift the held
(fixed) bearing liner up around the shaft. As the bearing liner is much
lighter than the rotor, it is easier to guide into place between the thrust
collars. Next, fasten the bearing liner to the shaft so that the liner can be
lowered into the bearing housing. If clearance is restricted, some erectors
assemble both bearings to the shaft completely before setting the bearings
on the pedestals. If the bearings are completely assembled to the shaft, be
sure that the free end bearing is secure so it does not slide off. Set rotor in
bearings.
Arrangement 5 and 8 fans feature an overhung wheel that causes the
outboard bearing to be top loaded. Use a chainfall to pull the outboard
shaft extension so that the shaft seats tightly in the bearing. Do not
tighten the plunger screw on sleeve bearings until the shaft is seated. The
coupling alignment should follow.
On Arrangement 1 and 3 fans with a bearing on each side of the fan
housing, a small deflection of the shaft will occur due to its own weight
and that of the wheel. Level the drive-end bearing (held bearing), making
sure the fan shaft passes through the center of the housing inlets. The fan
shaft extension will then be level with the motor shaft and allow easier
coupling or V-belt drive alignment. The outboard bearing is set at a slight
angle due to the shaft deflection. The bearing surface must lie properly
against the shaft especially if a sleeve bearing is used. On all direct-con-
nected fans, the motor must be on the same horizontal centerline as the
fan shaft, except on high temperature applications, where an adjustment
is made for expansion. Refer to Figure 4-15.