Siemens Maxum II PD PA AP Service Manual page 58

Valves
4.4 Model 20 Valve
1. Inspect the valve cap Teflon® base seal disc diaphragm (4) and the Dacron® disc cushion
diaphragm (5) for dirt, contamination or breaks.
Regardless of whether damage or contamination is evident, discard old seal and cushion,
and replace them with new component(s).
Note
If Teflon® sealing disc and Dacron® cushion disc are brittle or dirty, but not ruptured, or
they are ruptured but clean, visually inspect the rest of the valve. If it is clean and in good
order, it is possible to continue with this procedure.
If ruptured discs appear to have caused contamination of the valve, it will need to be
disassembled in order to be cleaned. It is recommended that the valve be returned to
Siemens for service.
Note
All valve fittings and tubing must be clean and valve diaphragms inspected for cleanliness,
catalyst or polymer buildup. Valve cap or plunger valve body faces should be wiped clean
using hexane, acetone or methanol and a lint free cloth.
2. Prepare a large syringe with a Tygon® tubing adapter installed. Fill syringe with a
recommended cleaning solvent.
3. An ultrasonic cleaner filled with a recommended cleaning solvent is recommended for
cleaning all components. Solvent must not leave any residue on evaporation.
Clean valve cap while it is disassembled.
After cleaning of cap, using syringe, flush solvent through each port in the valve cap.
4. Position the Dacron® cushion disc diaphragm (5) between the three alignment pins on the
plunger valve body (13).
5. Using tweezers, hold Teflon® seal disc diaphragm (4) by its edges. Before installing disc,
remove lint, dust and oils by sliding disk between your index and middle fingers.
6. Install Teflon® seal disc diaphragm (4) over the Dacron® diaphragm disc cushion (5).
7. Align valve cap (1) over the valve body three-plunger guide pins (13). Port 1 must be placed
toward the upper control port.
8. Lower valve cap (1) over plunger valve body plunger guide pins (13) then install valve cap
(1) onto the plunger valve body.
9. Install, but DO NOT securely tighten, the three Allen screws (3) each with two Belleville
lock washers (2).
Note
To assure proper tightness in the following two steps, it is recommended to use the torque
wrench available from Siemens, PN 1631005-002, which can be adjusted over the range
of torque measurements listed below.
58
NOTICE
When reassembling the valve cap, always install a new Teflon® Seal Disc diaphragm (4)
and Dacron® Cushion Disc (5). DO NOT install the previously used Seal and/or Cushion
Disc.
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001