Page 183 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Positive Displacment and Dynamic Blowers 165

6. If the gland cannot be loosened further, take out one row of pack-
ing. Replace the gland, finger tightening the bolts. Run the fan for a
few hours until you can take up on the gland. Coat the row of pack-
ing removed earlier with light oil and then replace.
7. Periodically inspect the stuffing box and replace packing as neces-
sary.

Install Drive
Install the fan before the drive because installation is easier and align-
ment is simplified. Read the drive manufacturer's instructions before in-
stalling the drive.

Installing Coupllngs
If the fan incorporates gear couplings and if either coupling half has
not been mounted on its shaft, the following procedure can be used:

1. Place coupling covers or sleeves over shaft ends.
2. Insert keys.
3. Install hubs on shaft with faces flush with shaft ends. If the hubs do
not go on when tapped lightly with a soft lead hammer, expand
them by heating not over 300°F in oil or oven.
4. Set the motor on its magnetic center. This is marked on many mo-
tors. The magnetic center must be known to properly adjust the
clearance between the face of the hubs. If the driver is a sleeve-
bearing motor, its magnetic center must be found before aligning
the coupling to prevent the motor side of the coupling from moving
against the fan coupling. To find the axial movement of the motor
shaft:

a. Run motor and mark a line on the shaft; this is the magnetic cen-
ter.
b. Push the shaft as far as it will go into the motor housing. Mark
line on shaft at housing. Then pull the shaft out as far as possible
and scribe another line. Half the distance between the two marks
is the mechanical center.

Notes: (1) F'lexible disc couplings may be available. Install per manufac-
turer 's instructions.
(2) Finding the magnetic center is not necessary on ball bearing
motors as their thrust bearings prevent movement. Axially soft
couplings must be used on dual drive units where there is ther-