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Installing the GC
Step 3. Set the Gas Pressures and Purge the System
Set source pressures
44
The pressure set at a tank regulator depends on these factors:
• The pressure needed to achieve the highest flow rate you
intend to use.
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 0.2 MPa (25 psi) across flow
controlling devices to enable 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
1.2 MPa (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 7
suggests starting values of source pressure.
Table 7
Suggested starting pressures
Gas
Carrier
Air for FID
Hydrogen
Air for valve actuators
Use
Packed column
Capillary columns
Detectors
Detectors
Valves
Source pressure
0.40 MPa (60 psi)
0.55 MPa (80 psi)
0.55 MPa (80 psi)
0.40 MPa (60 psi)
0.14 MPa (20 psi)
Getting Started
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