Troubleshooting front inlet flow problems

The parameters are below; the flow issues start when the oven reaches 200C where the flow is half the setpoint, and the shut down occurs shortly after when the oven is around 220C.

OVEN
   Initial temp:  50 'C (On)               Maximum temp:  300 'C
   Initial time:  4.00 min                 Equilibration time:  0.50 min
   Ramps:
      #  Rate  Final temp  Final time
      1 20.00      250        6.00
      2   0.0(Off)
   Post temp:  0 'C
   Post time:  0.00 min
   Run time:  20.00 min

FRONT INLET (SPLIT/SPLITLESS)           BACK INLET (SIM DIST)
   Mode:  Split                            Pressure:  15.00 psi (On)
   Initial temp:  260 'C (On)              Gas type:  Nitrogen
   Pressure:  10.00 psi (On)
   Split ratio:  50:1
   Split flow:  115.7 mL/min
   Total flow:  120.5 mL/min
   Gas saver:  Off
   Gas type:  Nitrogen

COLUMN 1                                COLUMN 2
   Capillary Column                        Capillary Column
   Model Number:  Agilent 19091J-413       Model Number:  Agilent 19091P-Q04
   HP-5  5% Phenyl Methyl Siloxane         HP-PLOT Q
   Max temperature:  325 'C                Max temperature:  290 'C
   Nominal length:  30.0 m                 Nominal length:  30.0 m
   Nominal diameter:  320.00 um            Nominal diameter:  320.00 um
   Nominal film thickness:  0.25 um        Nominal film thickness:  20.00 um
   Mode:  constant pressure                Mode:  constant pressure
   Pressure:  10.00 psi                    Pressure:  15.00 psi
   Nominal initial flow:  2.3 mL/min       Nominal initial flow:  2.3 mL/min
   Average velocity:  38 cm/sec            Average velocity:  43 cm/sec
   Inlet:  Front Inlet                     Inlet:  Back Inlet
   Outlet:  Front Detector                 Outlet:  Back Detector
   Outlet pressure:  ambient               Outlet pressure:  ambient

FRONT DETECTOR (FID)                    BACK DETECTOR (TCD)
   Temperature:  270 'C (On)               Temperature:  250 'C (On)
   Hydrogen flow:  40.0 mL/min (On)        Reference flow:  20.0 mL/min (On)
   Air flow:  450.0 mL/min (On)            Mode:  Constant column+makeup flow
   Mode:  Constant makeup flow             Combined flow:  7.0 mL/min
   Makeup flow:  45.0 mL/min (On)          Makeup flow:  On
   Makeup Gas Type: Nitrogen               Makeup Gas Type: Nitrogen
   Flame:  On                              Filament:  On
   Electrometer:  On                       Negative polarity:  Off
   Lit offset:  2.0

valentinrusu,

I understand that the flow will decrease over the temperature ramp, the method compensates for this by adjusting the flow rate setpoint as the temperature ramp increases... the issue is that the instrument cannot reach this decreased setpoint and does a front inlet flow shutdown when it can't reach this setpoint.  I have tried also with a constant flow program and the same front inlet flow shutdown occurs as the temperature increases.

James,

The shutdown message just says "Front Inlet Flow Shutdown", and sometimes has said "Back Inlet Flow Shutdown" in addition.  The front inlet flow rate is always below the setpoint on the instrument display when it happens.  I have noticed that if I increase the split ratio at the front inlet, the temperature where the shutdown occurs is lower.  I have also tried with constant flow to see if this helps, however it does not. I notice when setting up the method, the back inlet pressure always needs to be about 5psig higher than the front inlet in order to be able to get the right flow rate.

It sounds like you have some issues with the split lines and split vent cartridges. I would suggest cleaning or replacing the lines, but more importantly, the split vent cartridges should be replaced. In one of the above posts, valentinrusu has a link for manually checking for a split vent restriction. You could start there.

James

Replacement cartridges in a two pack G1544-80530, for flushing, I have just adapted a syringe and forced solvent (your choice) through once the lines have been removed.Flushed into a beaker in a hood.  Part of the lines are copper and can be replaced if needed.

That's the interesting part as they shouldn't depend on each other, two flow channels that are separate with seperate EPC modules. You have good supply pressure to the instrument so unless there is a restricted external gas trap its interesting that you see the effects that you do.