SB--7--626 Page 15
FIGURE 12 -- IMPELLER LOBE CLEARANCES
clearance and c--c should have 1/3, maintaining mini-
mum open and closed per FIGURE 11, page 14.
RESETTING IMPELLER CLEARANCE
Impellers are held in time by timing gears, which are
secured in position on the impeller shafts by grip rings
inside the gear hubs. To reset impeller clearances
(timing) it is necessary to release the grip rings in one
of the gears. See FIGURE 13.
Grip rings are paired telescoping rings with conical
mating surfaces. These rings are telescoped under
clamping pressure so that the outer ring expands
against the bore of the gear while the inner ring
contracts on the shaft, locking them together.
To release the grip rings in one of the gears, first
remove the gear locking clamp which is held to the end
of the impeller shaft by one of the following:
6”, 7” and 8” Series “A” -- 3 Socket Head Cap
Screws
8” Series “B” and “C” -- 5 Socket Head Cap Screws
Use a gear puller to withdraw the gear about 1/8 inch
(3 mm.) , then lightly tap the side of the gear with a
mallet. This will release the grip rings inside the gear
hub so that the impeller will be free to adjust. Do not
remove the gear.
Wedge the two impellers together against the exact
amount of shims required to establish proper clearance
as determined previously. Push the gear firmly against
the bearing race on the shaft. Replace the gear locking
clamp and cap screws. Partially tighten the cap screws
with the shim stock still wedged between the impellers.
Proceed to tighten the cap screws progressively, finish-
ing with a torque wrench to obtain a torque of 45 ft. lb.
(6.22 Kg--m). Shock--load the gear locking clamp and
then retorque to 45 ft. lb. (6.22 Kg--m). Remove shim
stock and turn the impeller a couple of turns, then re-
check the clearances.
End Clearance
-- It is always good policy to check end
clearances between the impeller and gear--end head-
plate BEFORE AND AFTER DISTURBING TIMING
GEARS OR GEAR--END BEARINGS.
If end
clearance is not within tolerance, see “Bearing and
Seal Replacement,” page 17, for instructions for
making correction by re--shimming the bearing
cartridge. After completion of the work, replace gear
case and relubricate.
