Troubleshooting
6850
6850
Released: April 2004 6850 Series Gas Chromatograph Service Procedures 267
Inlets
Split/Splitless inlet
Actual pressure is higher than the
setpoint (GC is “not ready”)
The purpose of this section is to outline a logical
procedure for troubleshooting a 6850 GC that
will not equilibrate to the setpoint pressure of
the capillary inlet system. The inlet over-
pressurizes and the actual pressure stays higher
than the setpoint. The GC cannot become "Ready
for Injection." This is a common problem in appli-
cations with high split vent flow and low inlet
pressure, as required by short 530 µM or other
wide bore capillary columns in split mode.
The 6850 GC capillary inlet system uses pres-
sure to control flow through open tubular, capil-
lary columns. The capillary column flow is not
measured directly, but is calculated from the
column dimensions, inlet and exit pressures,
temperature of the column, and carrier gas type.
The capillary inlet system can be run in two
modes of operation: split and splitless. This prob-
lem occurs more frequently in the split mode of
operation. The capillary inlet can equilibrate to
the pressure setpoint if the following conditions
are met:
1. The capillary inlet system is assembled
correctly and is leak free.
2. The EPC control module is functioning
properly.
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