Introduction 1
5977B Series MSD Troubleshooting and Maintenance Manual 23
Dangers unique to GC/MSD operation
Hydrogen presents a number of dangers. Some are general, others are unique
to GC or GC/MSD operation. Dangers include, but are not limited to:
• Combustion of leaking hydrogen
• Combustion due to rapid expansion of hydrogen from a high-pressure
cylinder
• Accumulation of hydrogen in the GC oven and subsequent combustion (see
your GC documentation and the label on the top edge of the GC oven door)
• Accumulation of hydrogen in the MSD and subsequent combustion
Hydrogen accumulation in an MSD
All users should be aware of the mechanisms by which hydrogen can
accumulate (Table 4) and know what precautions to take if they know or
suspect that hydrogen has accumulated. Note that these mechanisms apply to
all mass spectrometers, including the MSD.
The MSD cannot detect leaks in inlet 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.
Tab le 4 Hydrogen accumulation mechanisms
Mechanism Results
Mass spectrometer turned off A mass spectrometer can be shut down
deliberately. It can also be shut down accidentally
by an internal or external failure. There is a safety
feature that will shutdown the flow of carrier gas in
the event of an MSD foreline pump shutdown.
However, if this feature fails, hydrogen may slowly
accumulate in the mass spectrometer.
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