TM 10-4320-310-14
4-14. REPLACE DIFFUSER, IMPELLER, SHAFT SEAL, BACKHEAD AND STUB SHAFT (Continued)
NOTE
If the same Impeller assembly (4) and backhead (14) are
reassembled and no clearance change was required, make
sure the same thickness of shims (9) Is used.
5
If a new impeller assembly (4) or backhead (14) is to be installed, or if the impeller assembly clearance is to
be changed, determine shim (9) thickness required to obtain a clearance of 1/16 i 1132 inch (1.59 ± 0.79mm)
between the impeller assembly and backhead as follows:
a.
Without using shims (9), press impeller assembly (4) firmly onto stub shaft (7) and rotate impeller
assembly. If no rubbing is heard or felt between impeller assembly (4) and backhead (14), no shims
(9) are required.
b.
If rubbing occurs, remove the impeller assembly (4), add a few shim laminations, press impeller
assembly firmly onto stub shaft (7) and again rotate impeller assembly.
b.
Repeat steps a. and b. until clearance between impeller assembly (4) and backhead (14) just occurs.
c.
Then remove impeller assembly (4) and remove installed shims (9). Install key (8) into stub shaft (7)
keyway and reinstall removed shims plus an additionall/16 inch (1.59 mm) thickness of shims (9).
6
Install impeller assembly (4) and secure with impeller washer (6) and hexagon head cap screw (5). Impeller
washer beveled face is to be oriented toward the screw head. Torque hexagon head cap screw to 80 inch-
pounds.
7
Install diffuser assembly (2) in pump housing assembly (3) engaging spring pin (1) with slot in pump housing
assembly.
4-16
