164 Agilent 7890 Series Troubleshooting
7 Checking for Leaks
15
From the keypad, press [Service Mode]. Select Diagnostics >
Front or Back Inlet > Pneumatics Control > Septum Purge control.
16 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.
17 Press [Front or Back Inlet]. Scroll to Pressure and press Off/No.
18 Quickly turn off the carrier gas supply at its source, if
possible. The goal is to prevent any residual pressure from
the supply lines from leaking into the closed system and
causing a pressure rise and masking leaks. (Such leaks in
through the EPC module typically do not impact runs.) If the
setup does not include shutoff valves at the GC, or if
changing the source pressure is not practical, skip this step.
If there is a relatively large volume in the supply tubing
leading up to the GC, consider whether or not there could
have been a leak into the system when evaluating the test
results.
19 Monitor the pressure for 10 minutes. Use the timer by
pressing [Time] and [Enter].
A pressure drop of less than 0.5 psig (0.05 psi/min or less;
3.4 kPa or 0.34 kPa/min) is acceptable.
If the pressure drops much faster than the acceptable rate,
see “To Correct Leaks in the PTV Inlet”. Retest.
Note that liner size impacts pressure drop. An inlet with a
smaller volume liner does not tolerate as large a leak rate as
an inlet with a larger volume liner.
20 After the inlet passes the test, restore the GC to operating
condition.
• Restore source pressures.
• Remove any caps/plugs.
• Reinstall the column.
• Restore the correct column configuration.
• Load the operating method.
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