Varian 3800 /1079 injector flow issues

[MarkU]

We have started seeing problems with our varian 3800 with 1079 injector being able to come to pressure or flow set-point. Can get it to stabilize if we crank up the pressure and set the split to something like 20x. I have leak checked all the carrier gas fittings that I can find.

Have done the EFC calibration routine over and over.
The septum purge calibration does not complete.

Anyone have any experience with this system ?

Thanks,
Mark

[Peter Apps]

Hi Mark

I have used a 1079 quite a bit and I did not have any serious problems with it.

To troubleshoot we need detailed symptoms - which EPC do you have, what pressures and or flows are you setting, what flows do you get out of the split and septum purge (measured with a bubble flow meter), column dimensions, is there an MS at the end of the column, what carrier gas etc etc etc

There have been some other threads on flow and pressure problems - try searching the forum as well.

Peter

[sanjay]

I think partly choke in split line .

sanjay

[MarkU]

Hi Mark

I have used a 1079 quite a bit and I did not have any serious problems with it.

To troubleshoot we need detailed symptoms - which EPC do you have, what pressures and or flows are you setting, what flows do you get out of the split and septum purge (measured with a bubble flow meter), column dimensions, is there an MS at the end of the column, what carrier gas etc etc etc

There have been some other threads on flow and pressure problems - try searching the forum as well.

Peter

The EPC is type 1
Carrier - He
Column - 30m x 0.25 DB5
Pressure - attempting to get 10 psi
No MS, a PFPD setup for sulfur
the split is set at 25 ml/min and septa purge at 3 ml/min

The septa purge calibration will not complete. I have to turn off the instrument to get out of cal mode. It is using 15.6 psi and 3 ml/min as settings. When I set pressure to 15.6 and adjust purge needle valve to ~3 (measured with flow meter) and press calibrate it will stay in that mode forever. The Save and exit button never becomes active.

I am going to try to blow out the injector gas lines with He and see if that helps.

Thanks
Mark

[Peter Apps]

Hi Mark

This sounds like an electronics or software/firmware problem, what flow (if any) do you get out of the split line ?.

Peter

[WK]

Mark U
I had a problem when the engineer changed a board for the flows on 1079 - the split line flow was very high when set low. I guess it had changed back to some previous calibration setting or default. The engineer came back and sorted it out.
WK

[MarkU]

I have got the instrument to come to ready with this setup:

30m X 0.25um DB5
20 psi with 10X split (software shows 1.6 ml column flow at 100C oven temp)
measured split flow is 15.2 ml/min

If I drop the pressure setpoint to 10psi the actual reading will go to 9.6 or so and the instrument does not come to ready.

PS
When I go into edit GC setup the split flow increases to 95-97 ml/min.

Thanks
Mark