8 7890A GC Safety Manual
Introduction
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 offending channel and any associated channels (such as septum
purge) are set off.
• The split valves in the split/splitless and PTV inlets open.
• The oven (heater and fan) turns off.
• The small heated zones are turned off.
• An alarm tone sounds.
To recover from this state, fix the cause of the shutdown (tank valve
closed, serious leak, others). Turn the instrument off, then back on.
The GC cannot always detect leaks in inlet and/or detector gas streams. For this
reason, it is vital that column fittings should always be either connected to a
column, or have a cap or plug installed. The H
2
streams must be configured for
hydrogen so that the GC is aware of hydrogen use.
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