Valve Operation - Siemens Maxum II PD PA AP Service Manual

Valves
4.6 Model 11 Valve
4.6.1

Valve Operation

The Model 11 valve can be applied in proc‐
ess chromatographs as a liquid or vapor
sample valve, column switching valve, or a
column backflush valve. It provides the uni‐
form sample volume, high reliability
(500,000 cycle life on clean gas), low inter‐
nal volume, and high speed (switching time
in milliseconds) required by process chro‐
matography. Plus it provides the added ben‐
efits of minimum wear (critical parts move
only thousandths of an inch for switching),
dependable reproducibility and simplified
construction for easy maintenance.
The Model 11 valve body and cap are con‐
structed so cleaning or replacement of seal‐
ing and cushion discs can be done without
removing the valve from the chromatograph
oven. Removal of three bolts allows access
to the disc with no special tools required.
The specially constructed manifold elimi‐
nates leakage of air used for valve actua‐
tion. This feature is especially beneficial
when bottled helium or nitrogen is used in
place of instrument air.
The Model 11 valve is a 6-port, two-position, air-actuated valve. The six ports are arranged in
a circular configuration.
Between each two ports is a plunger that opens or closes the passage between these two
ports. A Teflon™ disc seals, prevents process fluids from contacting other components of the
valve. Six plungers operate in two sets of three. Each set of plungers is controlled by a spring-
loaded, air-actuated piston so that one set closes three passages between ports as the other
set opens three passages between ports. Passages between ports 1 and 6, ports 5 and 4, and
ports 3 and 2 are normally closed. The other three passages between ports 1 and 2, ports 3
and 4, and ports 5 and 6 are normally open.
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Model 11 Valve, LDV Version
Maxum II Valves and Oven Components
Service Manual, 10/2018, A5E42019844001