Chromatography Forum

I have a 7890A GC with an FID. We use a (normally) dry source of air that had an incident one weekend where the air dryer didn't work properly and allowed a significant amount of moisture to reach the FID EPC. After this, the mesured air flow from the EPC doesn't match the listed flow on the control panel.

Is there any way to recover from this issue? Any parts to replace/clean? Any calibration we can do on the EPC through the instrument?

I've found a few companies that do repairs for EPCs at around 1/3 of the price of a new EPC but if there's anything simple I can do on site, it would be a great help!

- Stephen

I believe the EPCs use a thermal conductivity reading to measure the flow, so if there is still moisture in the air supply line it will cause the reading to be off just as if you were to try to measure the flow of nitrogen when it EPC is set to be using Helium. You need to flush and dry the supply lines very well, and possibly use a moisture trap just before the instrument until you are sure the lines are completely dry(indicating moisture trap should show when it is dry).

Then recheck and see if there is a difference in measured versus reading for the air flow. If so then I believe it can be recalibrated, but I don't have the procedure for the 7890 on hand for that, but I am sure someone here probably does.

I have tried to repair those EPCs myself on several occasions - I have never been successful.

What repairs have you tried? Valve change?

The source of air we have is now dry and we have a zero air generator on it. The amount of air that's passed through it should have dried out any moisture by now.