Chromatography Forum

Our air compressor wasn't drained and we got water in our air lines. We've been blowing through these lines for several days and we've cleaned out our FID's but they still wont light.

Has anyone had this problem? Is this as huge of a problem as we think? How did you solve it if you could?

(We're all very upset)

any help appreciated.

FID is so rugged that i wouldn't be worried much. What GC are you using? Usually a small filament, heated red hot electricaly, lights the FID. If that filament is broken, then you might have to change it. You could simply use a cigarette lighter (to fire up the FID) to see if the problem is becuase of that filament or something else.

Good luck!
Suresh.

The FID is rugged, but not so rugged that you can blow water through it and expect to get good results. How serious the problem is, and how difficult to solve depends on the layout of your gas lines, and whether the water had damaged the flow controllers for the FID.

First step - check the air flow rate. If the flow controller is damaged the flow rate will be wrong.

Second - does the air going to the FID still have water vapour in it ?. Disconnect at the back of the GC, point the pipe in a safe direction and blow air through at full flow - if there is liquid water still in the lines you will probably see mist or droplets. If no mist or droplets, blow the air through some indicating silica gel or something similar for several minutes, if it changes colour you still have water vapour. In this case put a high capacity drying trap (which should be there anyway along with a hydrocarbon trap) into the line, purge the GC plumbing and try the detector.

If you get water droplets you need to check the whole air line for places where water could be trapped, anywhere that the pipe goes down and then up again, T sections and blind ends. You might need to dismantle some pipes to get the water out.

Once you have clean dry air at the right flow rate the FID should light as before - if not have a look in the forum archives where there are a host of tips and tricks.

Peter

The FID itself probably has no problem. I think you'd better check the gas controller valves (solenoid or something) in the air tube.
My first experiment with FID long ago also had this problem because I did not drain the compressor for quite a time.

Thanks for all of your help!

We've got a long day of purging water lines ahead.

Thanks again!

We had a similar problem some time ago. The water in the air line destroyed one of the pressure control valves on the instrument which had to be replaced.

GCguy

If you are using an Agilent 5890 there are restrictors in the gas box that could have been plugged. I don't think cleaning them would be effective, replace them with ones of the correct color code.
If your instrument has an EPC the water may have dammaged it. Contact the manufacturer.
I know when I solvent wash the injection ports on my 6890's I have to disconnect the solvent vent line so that no liquid gets to the EPC.

Good luck

when you finally get the problem fixed, install a moisture trap.

You just need a step by step trouble shooting guide for the repair of the pipes. Some valves should be replaced to reduce possible leakage. This way, you can also learn to fix it by your own if you can encounter the same problem the next time.