Routine Maintenance: Inlets
Maintaining a cool on-column inlet
Released: March 2004 6850 Series II GC User Information page 182 of 256
1. Load the SERVICE method or reset the inlet and oven temperatures to
OFF. Let the heated zones cool to room temperature. Also, make sure that:
• If you have entered parameters that you do not want to lose, store
them as a method
• If the detector is on, turn it off
2. Turn the inlet pressure off at the source.
3. Remove the column, if one is installed, and plug the column fitting with the
column nut with a no-hole ferrule installed.
4. Remove the old septum and replace it with a new one. For instructions,
see page 175.
5. Make sure the carrier gas source pressure is at least 35 psi.
6. Cap the septum purge vent with a 1/8-inch Swagelok cap.
7. Using a control module or data system, set the oven temperature to its
normal operating temperature.
8. Set the inlet to normal operating temperature.
Enter a pressure to 25 psi, or enter your normal operating pressure if it is
higher. Make sure that the pressure at the initial gas supply is at least
10 psi higher than the inlet pressure. If pressure cannot be achieved, either
there is a large leak or the gas supply pressure is too low.
9. Wait a few minutes for the GC to equilibrate after the system has reached
the pressure. The pressure may exceed the setpoint briefly during
equilibration.
10. Turn either the pressure or the flow off. Because the column and septum
purge fittings are capped, gas is trapped in the system and the pressure
should remain fairly constant.
11. Monitor the pressure for 10 minutes.
• A pressure drop of 1.0 psi (0.1 psi/min) or less is acceptable.
If the pressure drop is much greater than 1.0 psi, go to the next section,
“Correcting leaks” on page 183
Septum purge vent
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