Welch Vacuum 8925 Direct Drive Rotary Vane Pump - Manual (Page 20)

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6.04 Lip Seal / Gasket change
Changing the Lip Seal and Gasket for 8905
When the shaft seal in the mounting plate shows signs of excessive oil leakage, it should be replaced.
Before attempting replacement of the seal, the pump must be disconnected from the vacuum system and
from the power outlet. New lip seal (P/N 41-2988) and new gasket (P/N 61-2149B) or seal replacement
kit (Cat. No. 8905K-03) should be available before attempting repair.
1. DRAIN OIL by opening the drain plug. The pump may be tilted to remove residual oil out of
the oil case.
2. SEPARATE BASE from the pump by removing four socket head screws, 10-32x5/8.
3. SEPARATE THE PUMP FROM THE MOTOR ASSEMBLY by removing
four socket head screws #10-32x1 from the motor adapter plate. The isolator valve coil should
be slipped off by removing nut, name plate and large washer from valve projecting from the
inside of the mounting plate. Set aside the motor assembly with isolator coil placed next to it.
4. REMOVE OIL CASE from the pump by placing it on its mounting plate side and unscrew four
socket headscrews 10-32x3/4.
5. REMOVE COUPLING from the pump shaft by loosening the setscrew. Separate pump module
from then mounting plate by unscrewing three socket head screws #10-32x1/2 and three split
lock washers. Discard the gasket.
6. PUSH OUT LIP SEALS out of the wear plate with a blunt edge of a screwdriver blade.
Discard the lip seal. Older models will have lip seal installed in the mounting plate.
7. INSTALL NEW SHAFT SEAL with flat side of the seal toward the motor. Use a little oil on the
lip seal outside periphery. The seal is located 0.09 in. from the coupling end inside the bore.
Seal assembly tool 61-2172A used to install and locate the lip seal.
8. PLACE THE PUMP MODULE on a table with shaft up. Slide shaft insertion tool 61-2170A
over the shaft end and place the new gasket over the modular assembly.
9. MOISTEN THE LIP SEAL, shaft and the tool with oil prior to the assembly. Slip the mounting
plate over the shaft of the modular pump.
10. ADJUST GASKET in proper angular location and then tighten gradually the 3 screws
#10-32x1/2 with lock washers.
11. ASSEMBLE COUPLING BODY to pump shaft all the way to the shaft shoulder and
tighten the setscrew.
12. ATTACH OIL CASE to the mounting plate using four socket head screws 10-32x3/4
with 4 lock washers. Tighten screws gradually.
13. Insert two dowel pins to the mounting plate and put the coupling spider in place.
14. ATTACH MOTOR ASSEMBLY to the mounting plate using four socket head screws #10-32x1
with lock washers. Watch for wires from the isolator valve coil to be placed in groove of motor
adapter plate during assembly. After carefully fitting all parts together cross tighten the four
screws gradually.
15. ATTACH THE COIL TO ISOLATOR VALVE mechanism by first slipping on the coil
shoulder and then the coil with name plate. Tighten the coil nut (name plate should turn freely).
16. ATTACH BASE to the mounting plate by means of four socket head screws 10-32x5/8 long.
17. FILL PUMP WITH OIL, DIRECTORR® Oil (Premium or Gold) and is ready to be inspected
for its performance.