Page 177 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Positive Displacement and Dynamic Blowers 159

it down tight to its foundation. During the final alignment proce'dure, this
support leg will be securely fastened.

Set Bearing Base

Next, put the pedestals in place, maintaining approximate correct ele-
vation to the center of the bearing. The held-fixed bearing should be set
level. Use flat shims under the soleplates to level. Because the pedestals,
tops of soleplates, and bearings are machined to exact tolerances, they
will set in position at the correct level if the foundation was prepared to
the design drawings. Because a foundation occasionally may vary
slightly from the fan base or may settle, some fan erectors add 1/16 in.
shims between the pedestal and bearing. These shims are added because
dropping the level of the bearing is virtually impossible later if an error is
found or a change in center height is required. The shims should have an
adequate area to carry the weight of the parts and should be slotted to
clear the bearing bolts for easy installation or removal.

Wheel and Shaft lnstallatlon
Remove the shaft from the box with a nylon or rope sling. Do Not Lif?
by Bearing Journal Surfaces. As shaft rests in saddles in the shipping
box, slings can be placed underneath the shaft easily while the shaft is
still in the box. Remove the shaft preservative with solvent and coat the
journal area with clean oil using a clean applicator.

Note

Do nor touch the cleaned journal surface with bare hands since perspi-
ration can cause discoloration and pitting.
On double width wheels, clean the space between the hubs carefully
and remove all foreign objects that could fall onto the shaft as the wheel
is turned. Clean the bore of the wheel hubs with suitable solvent and lu-
bricate to ease entrance of the shaft.
Turn set screws in to check that they are long enough to hold the wheel
to the shaft. Now: turn the set screws out so the shaft will clear. If three
set screw holes appear in the hub, use only two-one over the key, and
the second leading the key in the direction of rotation. Be sure to support
the shaft for lifting with two rope slings, one near the middle to carry the
weight with the second sling balancing the shaft. Be sure that the rotation
arrow on the housing corresponds to the rotation arrow on the wheel and
that the shaft thrust collars are on the drive end. For proper wheel instal-
lation, compare blade shapes as shown in Figure 4-9 with wheel rotation.
In the case of dual drive, the held-end bearing should be determined be-