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Introduction
1
5977 Series MSD Operation Manual
21
Table 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 shut down the flow
of carrier gas in the event of an MSD foreline pump shut
down. However, if this feature fails, hydrogen may slowly
accumulate in the mass spectrometer.
Mass spectrometer automated
shutoff valves closed
Some mass spectrometers are equipped with automated
diffusion pump shutoff valves. In these instruments,
deliberate operator action or various failures can cause the
shutoff valves to close. Shutoff valve closure does not shut
off the flow of carrier gas. As a result, hydrogen may slowly
accumulate in the mass spectrometer.
Mass spectrometer manual shutoff
valves closed
Some mass spectrometers are equipped with manual
diffusion pump shutoff valves. In these instruments, the
operator can close the shutoff valves. Closing the shutoff
valves does not shut off the flow of carrier gas. As a result,
hydrogen may slowly accumulate in the mass spectrometer.
GC off
A GC can be shut down deliberately. It can also be shut
down accidentally by an internal or external failure.
Different GCs react in different ways. If a 7890 Series GC
equipped with Electronic Pressure Control (EPC) is shut off,
the EPC stops the flow of carrier gas. If a GC’s carrier flow is
not
under EPC control, the flow increases to its maximum.
This flow may be more than some mass spectrometers can
pump away, resulting in the accumulation of hydrogen in
the mass spectrometer. If the mass spectrometer is shut off
at the same time, the accumulation can be fairly rapid.
Power failure
If the power fails, both the GC and mass spectrometer shut
down. The carrier gas, however, is not necessarily shut
down. As described previously, in some GCs, a power failure
may cause the carrier gas flow to be set to maximum. As a
result, hydrogen may accumulate in the mass spectrometer.
Содержание G7035A
Страница 1: ...Agilent Technologies Agilent 5977 Series MSD Operation Manual ...
Страница 30: ...30 5977 Series MSD Operation Manual 1 Introduction ...
Страница 88: ...88 5977 Series MSD Operation Manual 3 Operating in Electron Ionization EI Mode ...
Страница 112: ...112 5977 Series MSD Operation Manual 4 Operating in Chemical Ionization CI Mode Figure 18 PCI autotune report ...
Страница 114: ...114 5977 Series MSD Operation Manual 4 Operating in Chemical Ionization CI Mode Figure 19 NCI autotune ...
Страница 170: ...170 5977 Series MSD Operation Manual 6 CI Maintenance ...
Страница 171: ......
Страница 172: ... G3870 90003 G3870 90003 Agilent Technologies Agilent Technologies Inc Printed in USA February 2013 ...