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Section 5: MAINTENANCE
5.10 General Maintenance
Welch Vacuum units are 100% oil-free. All bearings are sealed and permanently lubricated.
Lubrication should not be attempted. The units are built for duty operation just like a water
aspirator, but with the quietness, performance and durability of a diaphragm.
5.11 Diaphragm Replacement
WARNING
Do not remove the diaphragm unless you are wearing hand protection.
The steel disc inside the diaphragm may cause harmful injury
Component parts required.
1. Diaphragm & diaphragm liner.
2. Four screws for intake valve plate.
Disassembling the diaphragm & liner
1. Disconnect power.
2. Disconnect air lines and remove pump from enclosure.
3. Observe the position of the air intake and exhaust ports
before disassembly.
4. Remove six screws (1) from head, remove head, set head
with screws aside for assembly.
5. Remove four screws (2) from valve plate. Remove valve
plate and set aside for reassembly.
6. Remove diaphragm & liner and discard.
Reassembling the diaphragm & liner.
1. Wipe top of connecting rod clean with a soft clean cloth.
2. Place new diaphragm & liner on top of connecting rod.
Line up the holes in the diaphragm & liner with the screw
holes in connecting rod. Replace valve plate and line up
holes.
3. Torque valve plate screws to 20 inch-pounds using criss-
cross pattern.
Caution: To prevent damage to the pump, never apply any
sealant or lubrication to the gasket.
Head valve plate replacement.
1. Wipe inside of head clean. Install new gasket if needed, be
sure to remove any excess gasket.
2. Replace valve plate in head. Chamfer side of valve plate
should face you. Insert four new screws. Torque valve plate
screws to 22 inch-pounds.
Head screw
Valve plate screw
Valve plate
Diaphragm
Connecting
Rod Top
Gasket
Head valve plate
Valve plate screw
