Chemglass AF-0349 Welch Vacuum Pump User Manual
Page 21
21
Changing the Lip Seal and Gasket for 8907, 8912 and 8917
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 61-6042) and new gasket (P/N 41-0643) or seal replacement kit (Cat. No. 8917K-03)
should be available before attempting repair.
1.
DRAIN OIL by turning the valve handle counterclockwise in the horizontal position. The pump may be
tilted to remove residual oil from the oil case.
2.
REMOVE THE HANDLE of the pump by removing 2 M8 screws.
3.
REMOVE THE TOP AND SIDE COVER, The top cover (located under the handle) and Side Panels
can now be removed by removing two size M3 screws from each.
4.
REMOVE THE BASE by removing four M8 screws. Wipe up any oil in the base. If the Dip Pad
is saturated with oil, replace it.
5.
REMOVE THE ELECTRICAL BOX The Electrical Box Cover is removed by unscrewing four
Philips-head screws.
6.
DISCONNECT the green quick disconnect located in the electrical box.
7.
DISCONNECT MOTOR, Motor can be disconnected by removing four motor mounting screws.
8.
REMOVE THE COUPLING from the pump shaft (1 set screw)
9.
REMOVE THE THREE SCREWS attaching lip seal housing.
CAUTION
Don’t lose the woodruff key that sits in the key slot of the coupling;
it can drop out. If the key has any burrs (caused by previous
tightening of the coupling screws), sand it smooth.
NOTE: If the lip seal gasket (under the lip seal in the lip seal housing) looks intact, there may be no need to
replace it.
IMPORTANT: Note the position of the arrow and “UP” on the housing surface. After you replace the Lip
Seal, be sure the arrow on this coupling again points in the same direction (so that other components will be
properly aligned).
10.
REPLACE THE LIP SEAL
a) Place the lip seal housing in a vise (place a rag against the surfaces to protect against scratching). Gently
hammer a screwdriver against the lip seal at opposite sides until it pops out.
b) Before inserting the new lip seal, use your finger to add a thin coating of pump oil around its periphery.
c) Place the new lip seal in the coupling. It is essential that it be positioned perfectly flat on the bottom inner
flange. For best results, use a hand press. Place the coupling upright with the new seal on the hand press.
Then place a block of wood or metal having a very flat surface on top of the Lip Seal. Turn the hand press
lever until the Lip Seal is seated.
d) To be sure the seal is completely seated, use a round tool having a slightly smaller diameter than the seal
to hammer the seal completely down to the bottom.
e) As for the lip seal gasket, even if you decide it’s not necessary to replace it, clean the coupling surfaces
that the gasket rests on.