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Flow and Pressure Control
Hydrogen shutdown
Hydrogen shutdown
Hydrogen gas may be used as a carrier or as fuel for some detectors. When mixed
with air, hydrogen can form explosive mixtures.
The GC monitors inlet and auxiliary gas streams. If a stream shuts down because
it is unable to reach its flow or pressure setpoint and if that stream is configured
to use hydrogen, the GC assumes that a leak has occurred and declares a
hydrogen safety shutdown. The effects are:
• The carrier supply valve to the inlet closes and both pressure and flow
controls are turned off.
• The split valves in the split/splitless and PTV inlets open.
• The oven heater and fan turn off. The flaps at the rear open fully.
• The small heated zones are turned off.
To recover from this state, fix the cause of the shutdown (tank valve closed,
serious leak, others). Turn the instrument off, then back on.
WARNING The GC cannot detect leaks in the detector gas streams. For this reason, it is
vital that the column fittings of the FID, NPD, and any other detectors that use
hydrogen always be connected to a column or have a cap or plug installed and
that hydrogen streams be configured so that the GC is aware of them.
Column shutdown
If the carrier gas source shuts down, the oven heater turns off to avoid column
damage from heat without carrier gas. The flaps at the rear open halfway.
To recover from this state, fix the cause of the shutdown (tank valve closed,
serious leak, others). Turn the oven and the offending inlet or auxiliary channel
back on.
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