Gorman-Rupp Pumps 12B20-B 1340494 and up - Manual (Page 33)

10 SERIES OM-00588
MAINTENANCE & REPAIR PAGE E - 10
Impeller Installation and Adjustment
Inspect the impeller, and replace it if cracked or
badly worn. Install the same thickness of impeller
shims (5) as previously removed and screw the im­
peller onto the shaft until tight.
A clearance of .020 to .040 inch (0,51 to 1,02 mm)
between the impeller and the seal plate is neces­
sary for maximum pump efficiency. Measure this
clearance and add or remove impeller shims until
this clearance is reached.
NOTE
Be sure the seal plate is tight against the pedestal
while measuring this clearance.
Install the bottle oiler and piping (59, 60 and 61).
Install the air vent and piping (6,7 and 8).
Pump Casing Installation
Remove the hardware temporarily securing the
seal plate to the pedestal. Install the same thick­
ness of pump casing gaskets (31) as previously re­
moved and secure the pump casing (1) to the seal
plate and pedestal with the nuts (30). Do not fully
tighten the nuts at this time.
NOTE
The back cover assembly must be in place to adjust
the impeller face clearance.
A clearance of .008 to .015 inch (0,20 to 0,38 mm)
between the impeller and the wear plate (34) is also
recommended for maximum pump efficiency. Set
this clearance by adding or removing gaskets in
the pump casing gasket set (36) until the impeller
scrapes against the wear plate when the shaft is
turned by hand. After the impeller scrapes, add ap­
proximately .008 inch (0,20 mm) of gaskets.
After the face clearance has been set, tighten the
nuts (30) securing the pump casing to the pedes­
tal.
Back Cover Installation
If the wear plate (34) was removed for replace­
ment, secure it to the back cover assembly (38) us­
ing the attaching hardware (35 and 36). The wear
plate must be concentric to prevent binding when
the back cover assembly is installed.
Clean any scale or debris from the contacting sur­
faces on the pump casing that might prevent a
good seal with the back cover.
NOTE
To ease future disassembly, apply a film of grease
or `Never‐Seez' on the back cover shoulder, or any
surface that contacts the pump casing. This action
will reduce rust and scale build‐up.
Replace the back cover gasket (37) and slide the
back cover assembly into the pump casing.
Secure the back cover assembly by installing the
clamp bar (44) and tightening the clamp bar screw
(43). Do not over‐tighten the clamp bar screw; it
should be just tight enough to seal the back cover
shoulder.
Check for scraping or binding between the impel­
ler and wear plate and correct any that exists be­
fore putting the pump back into service.
Suction Check Valve Installation
Inspect the check valve components and replace
as required. Subassemble the check valve weights
(51 and 52) and check valve gasket (48) using the
attaching hardware (49 and 50).
Position the check valve assembly (47) against the
face of the suction flange with the large weight to­
ward the inside of the pump casing. Secure the
check valve assembly and suction flange to the
pump casing with the hardware (45 and 46).
Check the operation of the check valve to ensure
proper seating and free movement.
Final Pump Assembly
Secure the pump to the base with the previously re­
moved hardware. Be sure to reinstall any leveling
shims used under the pump casing or pedestal