SB--7--627 Page 17
maining part (1/3) will be set between points c--c.
Blowers originally timed for rotation in either direction
are retimed by dividing the total clearance evenly
between points 0--0 and c--c.
RESETTING IMPELLER CLEARANCE
Impellers are held in time by gears which are bolted to
a timing hub, which in turn is secured to the serrated
impeller shaft by a locknut. The timing gear can be
rotated in relation to the hub by loosening the cap
screws. Because the cap screw holes in the gear are
oversized, the gear will rotate -- within limits -- when the
screws are loosened.
Refer to FIGURE 9, page 15, for the following
instructions.
1.
Remove the gear case.
2.
To retime, remove the cap screws (G) and
washers (H), loosen the locknut (J) and the lock
washer (K) in one gear only.
3.
Wedge the two impellers together against the
exact amount of shim stock required to establish
proper clearances as calculated in “Determining
Proper Impeller Clearances,” page 16.
4.
Secure the gear in the new position with cap
screws and washers (always reverse washers (H)
when replacing) but do not tighten.
5.
Rotate impellers by hand.
6.
Recheck clearances. If proper timing has been
re--established, tighten cap screws with a torque
wrench. Refer to FIGURE 11, page 16, for correct
torque values.
7.
Tighten lock washer and locknut.
8.
Obtain a piece of pipe of sufficient diameter to fit
over the locknut and rest against the gear. Shock
load the gear by striking the pipe with a sledge
hammer, the retighten locknut.
Repeat this
procedure several times until all gear end com-
ponents are drawn together and locknut is tight.
9.
Check the end clearance before and after any
work has been performed.
End Clearance
-- To check the gear end clearance, the
locknut (J) (FIGURE 9, page 15) must be tight.
Torque Requirements
Gear End Shaft Assembly
Blower
Ft. Lbs.
Nm
Size
Torque
Torque
10
30
41
12
50
68
14
50
68
16
115
155
18
115
155
20
225
304
22
330
446
FIGURE 13 -- TORQUE REQUIREMENTS -- GEAR END
SHAFT ASSEMBLY
1.
Remove two diametrically opposed timing bolts
(G) and replace with long jack screws.
2.
Tighten these against the bearing cartridge only
enough to remove the axial play from the bearing.
3.
Check the clearance inside the machine between
the end of the impeller and the gear headplate. If
the end clearance is less than that shown in the
accompanying table, loosen the bearing cartridge
(see “Bearing and Seal Replacement,” page 20)
and delete shims as required. Increase shims to
reduce the clearance.
4.
After completion of the work, replace the gear
case and relubricate.
Follow Blower Startup Checklist on
page 12 after every shutdown.
Shaft Replacement
-- One piece 4140 forged steel
shafts are slip fitted through the impellers and bolted to
them at the gear end. This advanced shaft design
allows the diameter to be increased in the critical area
between the impeller and gears without decreasing
impeller strength with an enlarged bore, and avoids the
use of the drive impeller to transmit power. By using a
larger shaft at the gear end, torsional deflection of the
shafts between timing gears and impellers is greatly
reduced; therefore, increased pressure and horse-
power ratings can be allowed with safety. The shafts
can be removed from the impellers without removing
