CP-3800 GC Operator’s Manual
103
Pneumatic
Options for
Valved
Systems
Valves may be installed with independent pneumatics or in series with a
liquid injector such as a 1041 or 1079. If a valve is installed in series with an
injector then it will share the pneumatic system of that injector.
If the valve is used in series with a 1041 or 1061 injector, the pneumatic
system is type 3 EFC. This type of EFC operates is a flow controller with a
flow range of 0 - 100 mL/min settable from the 3800 keyboard. Press the
Flow /Pressure key and select from the menu of available EFC options. The
only user settable parameter with the type 3 EFC is the desired column flow
rate.
The recommended pneumatic system for valved systems is type 4 EFC.
This type of EFC is equivalent to a pressure regulator and flow controller in
parallel. The pressure regulator is used to maintain column flow rate and the
flow controller is used to overcome pressure upsets when valves are
switched. The following is an example of a type 4 EFC method used with a
3800 equipped with a gas sampling valve and a largebore (0.53 mm ID)
capillary column. There are two separate type 4 method screens, one for
control of the pressure and one controlling the flow. The pressure can be
programmed to keep the column flow constant during the run. On page 2,
the flow is maintained at 30 mL/min during the run but is ramped to 500
mL/min at the point of injection when the gas sampling valve is switched
(time 0.00 min). This sudden pulse of carrier gas quickly restores the
operating pressure of the system and minimizes detector baseline upset.
After one minute the flow reverts to 30 mL/min. Any other valve switches
during the run would be accompanied with similar flow ramps.
ACTIVE
METHOD
EDIT
METHOD
CTRL
RUN
TIME
END
TIME
Method 1
Method 1
0.00
20.00
Col Press (psi): 10 Column Flow (mL/min): 15
Linear Vel (cm/sec): 10 Total Flow (mL/min): 30
FRONT EFC TYPE 4, Page 1 of 2
Step
Pressure (psi)
Rate (psi/min) Hold (min) Total(min)
Initial
10
-
2.00
2.00
1
15
0.5
5.00
17.00
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