The Valve Box; Heating The Valves - Agilent Technologies 6890 Series Operating Manual

Valve Control
The 6890 Series Gas Chromatograph (the GC) holds up to four valves in a heated
valve box on top of the oven.
The valve box is the preferred location because it is a stable temperature zone,
isolated from the column oven.

The valve box

Instrument rear
EPC pneumatics
Valve blocks
Detectors
Valve box,
cover removed
Figure 29 The valve box

Heating the valves

The valve box contains two heated blocks, each with two valve mounting
locations (shaded). The middle hole on each block is used to pass tubing into
the column oven.
If two valves are used, mount them on the same block. This allows them to be
heated using only one control channel (Aux 1 or Aux 2, depending on how the
heaters are wired). With more than two valves, both Aux 1 and Aux 2 must be
used for heating the two blocks. Set them at the same temperature.
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