Agilent Technologies 6890 Series, Service Manual, Page: 41 / 867

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 flow
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
/
m
in
Safety shutdown mode:
Proportional valve1 closed
Proportional valve 2 open
On/off valve open
1 m
L/m
in
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