Siemens Maxum II PD PA AP Service Manual page 42

Valves
4.2 Liquid Injection Valve
O-Ring Replacement
The silicone O-rings of the pneumatic drive should be regularly greased with a high-quality
lubricant such as DuPont Krytox EG2000 or equivalent (Siemens part number G87004).
Procedure
1. Carefully remove the two large O-rings (4) and the small O-ring (8) out of the valve body
(7) and control piston (3) using a small screwdriver or a needle. Only use silicone O-rings,
temperature class -40°C to 200°C.
2. Insert new O-rings in all three locations (4 & 8).
3. Apply a thin film of grease to the new O-rings and the sliding surfaces of the control cylinder
(1) and the piston guide (2 & 8).
Valve Assembly
Read the following notes before performing the assembly procedure. See the Exploded View
(Page 38) for the following procedures.
Notes
• The screw threads on the flange plate (17) must move freely. Grease if necessary.
• The diameter of the piston guide hole (8) should be 5.7 mm and be smooth. Replace the
part if there are traces of wear on the piston shaft.
• The adjustment assembly (13) must slide smoothly down inside the valve body (7).
Procedure
1. Before assembling the valve, apply a thin coat of grease (discussed in
Replacement above) to the following parts.
– Internal wall of control cylinder (1)
– Shaft of Control Piston (3)
– Piston Guide hole/small O-ring (8)
– Outside of Large O-rings (4)following reassembly of valve body (7) and piston (3)
2. Insert the piston (3) with stem (6) into the valve body (7) such that the stem does not become
greasy.
3. Drop the Belleville washer plate springs next to one another over the stem into the valve
body. Washers must be positioned in an alternating bevel up/bevel down manner (to form
a spring). See
4. Slide the adjustment assembly (13) with nut (11), counternut (12) and Teflon gasket (14)
onto the stem.
42
Liquid Injector Valve Exploded View for washer orientation.
O-Ring
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001