Diagnostic Procedures - Siemens Maxum II PD PA AP Service Manual

Valves
4.4 Model 20 Valve
Figure 4-14
4.4.1.2

Diagnostic Procedures

Depending on the installation, the following tests can be performed with the valve mounted in
the analyzer. Other tests require the analyzer to be shut down and valve ports disconnected.
These diagnostic tests indicate specific areas of the fault or trouble.
Valve Leakage
Sample Pressures Lower Than Carrier Gas Pressure: Leakage may be from a carrier-gas port
to a sample port within the valve regardless of whether valve is actuated or deactivated. With
sample inlet flow turned off, sample outlet should be zero. Check carrier and sample gas for
leakage.
Carrier and Sample Gas Leakage: Bubbles indicate internal leakage. For a liquid carrier, check
for liquid dripping from sample outlet tube.
Sample Pressure Higher Than Carrier Gas: Leakage between ports is visually displayed on
analyzer recorder as a baseline shift when sample pressure is removed from valve.
56
3
2
1
4
5
3
4 2
6
5 6 1
BODY
CAP
Model 20 Valve Exploded View
19
12c
16
12b
17
12a
13
19
18
15
20
21
BASE
Service Manual, 10/2018, A5E42019844001
12
1. Valve Cap
2. Belleville Washers
(6 total)
3. Allen Screws (3 total)
4. Teflon Disc Seal
Diaphragm
5. Dacron Cushion
Diaphragm
6. Plungers (6 total)
12. Air Loaded (Upper)
Piston
13. Valve Plunger Body
14. Cylinder Base
15. Spring Loaded (Lower)
Piston
16. Allen Screws (3 total)
17. Belleville Washers
(6 total)
18. Inner (small) O-Ring
19. Outer (large) O-Rings
20. Large Belleville
Washers (3 total)
21. Control Port (Upper,
Middle, or Lower
depending on
14
location)
Maxum II Valves and Oven Components