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Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
Programmed Temperature Vaporization Inlet (PTV) 240
Leak testing
4. Set the pressure to 25 psi.
Scroll to Pressure and enter “25” in the “Pressure” field.
5. Wait approximately 15 seconds for equilibration.
If pressure cannot be achieved, either a very large leak is present in the
system, or the supply pressure is not high enough.
6. Turn the inlet pressure “Off.”
Press [Front Inlet] (or [Back Inlet]), scroll to the “Pressure” field,
and press [Off]. Both the flow controller and the back pressure valves
will close.
Note When the inlet pressure or flow is turned off, the safety shutdown feature,
including the audible alarm, is not functional. The inlet will not automatically
shut down. This will provide you with unlimited time to locate leaks.
7. Note the “Actual” reading on the display and monitor the pressure for
10 minutes.
You can use the stopwatch feature of the 6890 GC to monitor the time.
Press [Time] and then [Enter] to start timing, then toggle between the
time and the pressure reading with the [Time] and the [Front
Inlet]/[Back Inlet] keys.
• If there is less than 0.5 psi pressure loss, consider the system leak
tight.
• If pressure loss is much greater than 0.5 psi, there is a leak that must
be found and corrected. Note, however, that you may want to slightly
decrease the leak test time based on the internal inlet volume which
changes with the liner type used (smaller volumes = shorter
acceptable leak test times). See Correcting leaks later in this section.
8. When the system is considered leak tight, the caps may be removed, the
column reinstalled, its dimensions configured at keyboard, and the
desired pressure and flow rate set.
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