Agilent Technologies 5975T LTM GC/MSD, Troubleshooting And Maintenance Manual

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Chromatographic Symptoms
3
Troubleshooting and Maintenance Guide 59
Pressure Symptoms
This section describes unusual pressure readings and their
possible causes. The symptoms in this section are based on
typical pressures. At typical column flow rates (0.1 to
2.0 mL/minute), the foreline pressure will be approximately 20
to 100 m Torr. The analyzer chamber pressure will be
approximately 1 × 10
-6
to 1.4 × 10
-4
Torr. These pressures can
vary widely from instrument to instrument so it is very
important that you are familiar with the pressures that are
typical for your instrument at given carrier gas flows. Turbo
pumps are controlled according to their speed and do not have
foreline pressure gauges. The analyzer chamber pressures can
only be measured if your system is equipped with the optional
gauge controller.
Foreline pressure is too high
If the pressure you observe for a given column flow has
increased over time, check the following:
• Column (carrier gas) flow is too high
• Air leak (usually the sideplate is not pushed in or vent valve
is open)
• Foreline pump oil level is low or oil is contaminated (wet
foreline pump)
• Foreline hose is constricted
• Foreline pump is not working correctly
• Foreline pump tip seal may need to be replaced (dry foreline
pump)
Analyzer chamber pressure is too high (EI operation)
If the pressure you observe is above 1.0 × 10
-4
Torr, or if the
pressure you observe for a given column flow has increased over
time, check the following:
• Column (carrier gas) flow is too high
• Air leak
• Foreline pump is not working correctly (see Foreline
pressure is too high )
• Turbo pump is not working correctly