210 Split/Splitless Inlet
EPC inlet
2 of 30
Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
EPC inlet
Split mode operation
For an EPC inlet in split mode, the proportional valve, PV1, is a mass flow
controller for the total inlet flow as measured by the flow sensor, FS. V is an
on/off valve which is turned on to allow flow out of the split vent. PV2 is a
back pressure regulator controlling the inlet pressure as measured by the
pressure sensor, PS. SPR is a calibrated regulator/frit which is used to control
the septum purge flow.
Figure 210-1 EPC control split mode flow diagram. 100:1 split ratio
Pulsed split mode
For EPC inlets in this configuration, the split flow and the column pressure
(flow) are programmed up to a higher value prior to sample injection. The
Flow
limiting
frit
PV1
Proportional
valve1
Total f low
control loop
Flow
sensor
Septum holder
Pressure
sensor
Septum purge
regulator
(not adjustable)
FS
PS
SPR
Column head pressure
control loop
PV2
Proportional
Valve
V
valve 2
open
To Detector
101 mL/min
Safety shutdown mode:
Proportional valve1 closed
Proportional valve 2 open
On/off valve open
1 mL/min
104 mL/min
Septum purge
~3 mL/min (He, N
2
, AR/CH
4
)
~6 mL/min (H
2
)
Inlet vent flow (split)
100 mL/min
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