Siemens Maxum II PD PA AP Service Manual page 52

Valves
4.3 Model 50 Valve
9. Carefully remove the placement disc without moving the diaphragm. Inspect the diaphragm
for proper alignment. If the diaphragm is not in the center of the plate, repeat the placement
procedure using the placement disc.
10.Place the middle plate on the valve taking care to use the correct holes. Check the
alignment mark on the side of the plate. It should align with the mark on the bottom plate.
If not, the middle plate is upside down and must be removed, turned over, and reinstalled
correctly.
11.Position the placement disc on the center plate and set the diaphragm in place.
12.Carefully remove the placement disc without moving the diaphragm. Inspect the diaphragm
for proper alignment. If the diaphragm is not in the center of the plate, repeat the placement
procedure using the placement disc.
13.Place the top plate on the valve, verifying alignment using the alignment marks.
14.Install the 5 screws and washers finger tight.
Tighten the screws down evenly following the 'Torque Sequence' in the above drawing.
Use a torque wrench with a 2.5mm hex bit to 6 to 8 inch-pounds of torque. (It is
recommended to use the torque wrench available from Siemens, PN 1631005-003, which
is calibrated at 7.2 inch pounds). Remove the assembled valve from the valve fixture.
15.Reinstall the valve in the oven. Use the same torque wrench with a 2.5mm hex bit to 6 to
8 inch-pounds of torque to tighten the mounting screws. Connect all tubing following the
fitting manufacture's recommendations as noted below.
16.Connect all tubing following the fitting manufacture's recommendations as noted below.
Note
Over tightening the fittings can cause the center plate to bulge at the fitting site. This bulge
will cause the valve to leak.
17.Turn the valve gas on at the block valve. Then turn on the carrier gas.
18.Power up the analyzer and enable the heaters.
19.Check for leaks at the fittings and between the plates in both the off and on valve states.
20.Verify valve operation by running chromatograms. Understand how the chromatogram will
change if the valve is not working properly by knowing what the chromatogram looks like
when the valve is working and what changes when the valve fails in different conditions.
Figure 4-13
52
Tools for Model 50 Valve Assembly
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001