230
Agilent 7820 GC Service
Valves
Valves are used to modify the carrier gas flow during an analysis.
Among their uses are:
Highly reproducible injections
and many others. Some examples are included in this section.
In this GC, most sampling valves are rotated by air-driven
actuators. This keeps electrical activity away from where hot
sample might leak. The air is controlled by solenoid valves
located behind the right side cover.
A manually-operated gas sampling valve is also available.
Introduction
This document does not provide instruction for first time
installation of any of the options discussed. The add-on sheets,
which accompany the various options, exist for just this purpose,
and should be referenced when performing a first time
installation.
The valves described in this manual are W-series minivalves,
manufactured by VALCO Instruments Co, Houston, Texas. The
valve body is made of Nitronic-60 nickel steel with 1/16-inch
fittings.
Proper instrument operation will prolong the life of the valve
system. Read all the accompanying information and avoid the
following operational abuses:
Exceeding the specified temperature and pressure ranges
Plugging a valve with column packing or sample precipitation
Scoring valve surfaces with column packing or particulates in
liquid or gas sample
Contaminating the system with samples (non-eluting
materials) or poor quality support gases
Because valves operate best at a constant temperature, the GC
places valves in their own heated compartment.
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