Siemens Maxum II PD PA AP Service Manual page 64

Valves
4.4 Model 20 Valve
1. Using even finger pressure around edges of plunger valve body (13), push valve plunger
body against cylinder valve base (14). All six plungers should rise.
2. Release plunger valve body (13). The six plungers should drop. If plungers do not drop,
check for oil film on plungers. This can prevent plungers from dropping.
3. Apply gentle pressure to the top of each of the six plungers. If plungers drop, without
excessive pressure, the valve is operating normally and does not require additional
disassembly. If plungers stick or are sluggish in their operation, they must either be
thoroughly cleaned with a recommended cleaning solution, repaired, or the entire actuator
must be replaced.
4. Remove all connections from the valve and remove the entire valve from the oven. While
removing the valve, hold it upright to prevent plungers from falling out.
Additional work should be on a clean workspace.
5. Turn actuator on its side. Remove the three screws (16) which secure the plunger valve
body (13) to the cylinder valve base (14).
Note
When performing the following step, DO NOT allow actuator plungers to fall from plunger
valve body (13).
6. With plunger valve body (13) in the horizontal position, remove it from the cylinder base
(14). Carefully remove all six plungers (6).
Note
Perform EITHER step 7 or step 8 to remove the actuator piston from the cylinder base.
7. Place cylinder valve base (14) in upright position. Insert a 6-32 hex threaded standoff screw
into the center-threaded hole and pull to remove air loaded piston (12) and spring-loaded
piston (15).
Note
In the following step, DO NOT use more than 30 psig (210 kPa) of air pressure when using
this method.
Alternate method for removing actuator piston.
8.
Carefully apply 10 psig (70 kPa) air pressure on bottom port of cylinder valve base (14).
This extends the pistons allowing them to be pulled out of cylinder valve base by hand.
9. Inspect actuator cylinder walls and the three Belleville washers (20). These components
must be clean and show no evidence of damage. If necessary, clean parts or replace them.
10.Separate the upper air loaded piston (12) and lower spring loaded piston (15). Inspect
pistons (12 and 15), silicone O-rings (18 and 19) and finger loaded valve spring (12c). These
components must be clean and show no evidence of damage. If necessary, clean parts or
replace them.
64
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001