Chemglass AF-0349 Welch Vacuum Pump User Manual
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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 the
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® Premium or Gold Oil and is ready to be inspected for its
performance.