Basic Maintenance: Model 50 Valve; Preventing Port To Port Leaks; Maintenance Considerations - Siemens Maxum II PD PA AP Service Manual

Valves
4.3 Model 50 Valve
4.3.1

Basic Maintenance: Model 50 Valve

The following equipment is required to repair the Model 50 valve:
● Model 50 Repair Kit: Siemens PN 2020164-001 (includes 10 diaphragms, 10 screws with
washers, and 12 Valco fittings).
● Valve Assembly Fixture: Siemens PN 2020281-001
● Torque screwdriver with Allen head bit: Siemens PN 1631005-003
Figure 4-9
4.3.2

Preventing Port to Port Leaks

Particulates introduced to the valve either from the sample or from the columns can prevent
the diaphragms from sealing against the center plate of the valve. Also, to insure proper sealing
of the diaphragms, the actuation pressure should be 25 psig higher than the carrier gas or
sample gas pressure.
To help prevent leaks, always turn the sample and carrier gas off before the actuation gas is
turned off. Without actuation gas, the Model 50 valve is in an undefined state where ALL ports
are interconnected, and the flow path of the carrier or sample cannot be controlled. Leaks in
the actuation gas lines could result in a lower actuation gas pressure which could result in port
to port leaks. The symptoms can include small peaks, repeatability problems, contaminated
columns and noise on the detector.
4.3.3

Maintenance Considerations

If customer maintenance personnel are not technically trained to repair the Model 50 valve on
site, it is recommended that the valve be returned to Siemens for service, repair, or direct
replacement.
To repair the Model 50 valve on site, the customer must have the necessary maintenance
tools and replacement parts. Recommended valve spare parts can be obtained from Siemens.
When cleaning the Model 50 valve and associated components, it is imperative that the
maintenance be performed in a clean and contaminant free facility. Components should be
placed on a lint free cloth to prevent impurities from contaminating the valve and its
components. Hands should be clean and free of contaminants. Presence of any foreign
contamination can cause additional valve problems after reinstallation.
46
Model 50 Valve
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001