8
7820A GC Safety Manual
Introduction
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 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.
Measuring hydrogen gas flows
When measuring gas flows on a detector using hydrogen for the detector flame
or carrier gas, measure the hydrogen flow separately. Never allow an air
stream to enter when hydrogen is present in the flow meter.
WA R N I N G
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.
WA R N I N G
Do not measure hydrogen together with air or oxygen. This can create explosive
mixtures that may be ignited by the automatic ignitor.
To avoid this hazard:
Turn the automatic ignitor off before you begin.
Always measure gases separately.
