144 Agilent 7890 Series Troubleshooting
7 Checking for Leaks
To Check for Leaks in a Multimode Inlet
This procedures describes how to check for and fix leaks in the
Multimode inlet. Follow the procedures below based on the
inlet’s symptoms.
Cannot Reach Pressure Setpoint
If the Multimode EPC inlet does not reach its pressure setpoint,
the GC will be “Not Ready.” Pressing [Status] indicates the front
(or back) inlet pressure is not ready. The GC will shut down in
approximately 5.5 minutes if the inlet cannot pressurize and
control.
If you have recently performed maintenance, first check for
leaks on any fittings/parts you handled.
1 Verify sufficient gas supply pressure delivered to the GC (see
the GC, GC/MS, and ALS Site Preparation Guide), and verify
no leaks in the gas supply (see To Check for External Leaks).
The inlet requires 70 kPa (10 psi) above the highest pressure
used in the method.
• 120 psi maximum for 0–100 psi inlet
• 170 psi maximum for 0–150 psi inlet
2 Check the total flow setting. Total flow must be high enough
to maintain inlet pressure throughout the run. Wide bore
columns require higher flow rates. Typically 50 mL/min is
sufficient. To increase total flow:
• Increase split ratio if in split mode
• Increase the purge flow for splitless mode
3 Put your thumb (or a septum) over the split vent exhaust. If
the inlet pressure begins to rise to the setpoint, call Agilent
for service. If the pressure remains low, continue with the
next step.
4 Perform the inlet leak check. See “To Perform an Inlet Leak
Check”. The total flow provides an indication of the
magnitude of the leak. Monitor the total flow while
checking/tightening fittings:
• Septum nut
• Column
• Split vent trap/O-rings
• Liner/O-rings
• Split vent line connection to the inlet body
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