Routine Maintenance: Inlets
Maintaining a split/splitless inlet
Released: March 2004 6850 Series II GC User Information page 129 of 256
5. Cap the septum purge fitting with a 1/8-inch Swagelok cap or with a capillary
column nut, a solid piece of wire (such as a metal paper clip), and a 0.5 mm id
graphite ferrule.
6. Set the oven and inlet to their normal operating temperatures.
7. Set the inlet to Split Mode.
8. Configure the column as 0 m length.
9. Make sure that the pressure at the gas supply is at least 35 psi. Enter a
pressure setpoint between 20 and 25 psi, or enter your normal operating
pressure if it is greater.
10. Set the total flow to 60 mL/min. Wait a few moments for the pressure and
flow to equilibrate. If the GC cannot reach the setpoint, there is a large
leak somewhere. See “Correcting leaks” on page 130.
11. Turn either the pressure or the flow Off. Because the septum purge and
the column fittings are capped, gas is trapped in the system and the
pressure should remain fairly constant.
12. Monitor pressure on the Control Module or ChemStation/Cerity Chemical
for 10 minutes.
• A pressure drop of 0.5 psi or less (approximately 0.05 psi/min) is
acceptable
• If the drop is greater than 0.5 psi, there is a leak that must be found
and corrected. See “Correcting leaks” on page 130.
• If the pressure rises, there is probably a leak in the in the flow
manifold across the forward pressure proportional valve. Although a
slight leak here does not cause a chromatographic problem, it may
obscure other small leaks that let air get into the system. The forward
valve can leak at 0.2 mL/min and be within specifications.
13. When the system is leak-free, restore normal connections and operating
conditions.
Septum vent
Split vent
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