Agilent Technologies 7890A Troubleshooting Manual page 77

Hydrogen Shutdowns
WA R N I N G
Troubleshooting
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
is unable to reach its flow or pressure setpoint and if that
stream is configured to use hydrogen, the GC assumes that a
leak exists. It will warn you with a beep after 25 seconds,
and it will continue to beep in intervals. After about 5
minutes, the GC will shut down components to create a safe
state. The GC:
• Displays Hydrogen Safety Shutdown.
• Closes the carrier supply valve to the inlet and closes and
turns off both pressure and flow controls. When viewed,
these parameters will flash Off.
• Opens the split vent valves in the split/splitless and PTV
inlets.
• Turns off the oven heater and fan and opens the oven
flaps.
• Turns off all heaters (including any devices connected to
the auxiliary heater controls, such as valve box heaters
and transfer line heaters). When viewed, these parameters
will flash Off.
• Sounds an alarm.
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.
To recover from a hydrogen shutdown state:
1 Fix the cause of the shutdown:
• Replace the inlet septum.
• Replace the inlet O- ring.
• Check for broken column.
• Check the supply pressure.
• Check the system for leaks. See Checking for Leaks.
Power cycle the GC.
2
5
Shutdown Symptoms
77