Installing the GC 1
Agilent 7890B Installation 35
Set source gas pressures
The pressure set at a tank regulator depends on these factors:
• The inlet pressure needed to achieve the highest column flow
rate required by your method.
The pressure/flow relationship depends on the column or
device involved. The best way to address this is to begin at a
moderate pressure level and adjust upward as needed.
• A pressure difference of about 170 kPa (25 psi) across flow
controlling devices enables them to work properly.
• The pressure limit of the weakest part of the supply system.
Swagelok fittings and copper tubing are more than adequate
for the highest pressures used in gas chromatography.
We recommend a maximum continuous operating pressure
of 1170 kPa (170 psi) to avoid excessive wear and leaks.
Traps are often the weakest part of the system. They should
be labeled, either on the trap itself or in accompanying
literature, with a maximum operating pressure. Source
pressure must not exceed the lowest maximum operating
pressure in the supply system.
Table 5 suggests starting values of source pressure.
Tabl e 5 Suggested starting pressures
Gas Use Source pressure
Carrier Packed column 410 kPa (60 psi)
Capillary columns 550 kPa (80 psi)
Air for FID, FPD Detectors 550 kPa (80 psi)
Hydrogen Detectors 410 kPa (60 psi)
Makeup gas Detectors 410 kPa (60 psi)
TCD Reference TCD 410 kPa (60 psi)
Air for valve actuators Valves 345 kPa (50 psi)
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