Chromatography Forum

I'm working on Varian 3800 as well, when I reboot it, it always takes a very long time
(whole day) to equliberate. What's the problem with it?

When instruments re=start they usually have set points on the heated zones that are close to room temperature - so close in fact that if your room is a bit hotter than usual the heated zones cannot get to the setpoints.

Take the trouble to check default set-points and change them to what you will be using in your method.

Peter

If it's the oven that taking so long to equilibrate, it could be an electronic problem. Flapper motor on the back has failed, heater triacs are ON on the time etc. I'd do more troubleshooting

I'm working on Varian 3800 as well, when I reboot it, it always takes a very long time
(whole day) to equliberate. What's the problem with it?

Everything is ready except for rear flow/pressure, because this GC can install three columns and we only install one colume in middle. I just set front and rear injector pressure control as 0.1 psi and the front actual total flow is 10mL/min and the rear actual total flow is 25mL/min. Does anybody know what's the total flow mean? How can I solve this problem?

Total flow will be the sum flow of column, septum purge & split flows. The total flow will be influenced by several variables including carrier gas type, column length/ID, injector split setting, etc. It is calculated by the software by looking at your hardware setup.

As Peter mentioned, ensure that all heated zone setpoints are reasonable to achieve. If one of your unused injectors is set to 25C, you might not achieve "ready to run" status and the 3800 will remain in the equilibrating state. Also be sure to check unused detector makeup flow settings, if not using detectors on your GC ensure the heaters are turned off. Or turn them on and have makeup flow gases programmed accordingly. If you have gas sampling valves on your 3800, also make sure they are set to easily achievable temperature values. Once you know which specific parameter(s) are delaying the equilibration of your system, you can modify them in your acquisition method.

Good luck! The Varian 3800 GC is a great, dependable system.

I'm working on Varian 3800 as well, when I reboot it, it always takes a very long time
(whole day) to equliberate. What's the problem with it?

Everything is ready except for rear flow/pressure, because this GC can install three columns and we only install one colume in middle. I just set front and rear injector pressure control as 0.1 psi and the front actual total flow is 10mL/min and the rear actual total flow is 25mL/min. Does anybody know what's the total flow mean? How can I solve this problem?

Plug the column connections on the unused inlets, and set the pressure to 1 psi so that the controller has something to do. Set total flow to 5 ml/min or so - that gas will come out through the split vents of the unused detectors.

Peter