Welch Vacuum 8925 Direct Drive Rotary Vane Pump - 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 mounting screws.
8. REMOVE THE COUPLING from the pump shaft (1 set screw)
9. REMOVE THE THREE SCREWS attaching lip seal housing.
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.
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).