FID Problem

[moecat]

I have a 6890 FID detector refusing to light.

I started having a problem with it staying lit, so I removed the jet and determined it was clogged. After sonication, cleaning with a wire, flushing with DI water and MeOH, it now doesn't lit at all.

Glow plug gets hot....air and H2 flows appear to come up on attempted ignition....but it doesn't light. I would be very surprised if I damaged the jet as I was pretty gentle with its cleaning.

Any ideas? What to try next?

Thanks

[wrighty]

try gently blowing over the detector to give it a kick start as we had an older detector with lighting problems.

[Peter Apps]

Twice in the past few months we have had FID flames refuse to burn just after an air cylinder was changed. Putting a fresh cylinder on and purging the lines got them going again. Probable diagnosis - mis-filled cylinder ?

If you have changed air cylinders, try another one.

Peter

[chromatographer1]

just to be sure, manually measure the gas flows so you KNOW you are getting the proper amount of air and hydrogen to your jet.

Double check is always a good idea.

best wishes,

Rod

[moecat]

try gently blowing over the detector to give it a kick start as we had an older detector with lighting problems.

This worked!

[Tim_van_Dyke]

try gently blowing over the detector to give it a kick start as we had an older detector with lighting problems.

This worked!

I knew it!

[AICMM]

While I am happy the problem is solved, this is the stuff of urban legends and it just pains me. Why did it work?! There has to be a more fundamental reason or else we are all going to have some black box explaining to do. Gee Mr. Auditor, I don't know why but blowing on the detector a certain way makes it work. I'm laughing while I write that since I can picture the scene in my minds eye.

Flow rates, temperatures, air reduction valve on the Agilent, something.....??

Best regards.

[chromatographer1]

Matthew,

If he had used a match the FID would have fired as well.

The igniter is off to the side of the FID channel and if the gases are well focused and do not pass within range of the heated coil in concentrations that will ignite, well..................... hold the button down as long as you can. It won't fire.

Disrupting the established flow pattern and getting the 'fire' to the fuel or rather the fuel to the fire, can have a happy ending.

Old detectors sometimes require a match too.

No urban legend. Just old Boy Scouts never die, they just slowly flicker out.

best wishes,

Rod

[wrighty]

Its a valid point about the auditor but i've never met an auditor that wants to know how the system works. Sure there is problem with the FID because it wont light automatically but it doesnt mean that the instrument is dead.

the most importnat thing to show is that however the system is started (ie auto ignition, helping hand etc.) that it does not produce erroneous results.

As long as the system passes calibration/ system suitability- however you monitor the systems performance- there is no immediate problem.

As chromatographer1 points out, its just down to old age. if the instrument is serviced then this problem is likely to be highlighted ny them (although i learned this blowing trick from our service engineer so it cant be that important )

[Peter Apps]

Having to blow on a detector to get it to light is not a problem in itself, but it might be a symptom of a problem with gas flow control - and that might affect detector response. Check the gas and air flows to the detector with a bubble flow meter rather than the readings on the GC front panel. The air flow during ignition needs to be half or less of its flow during operation.

Peter

[DR]

Fortunately, the details of getting the FID lit are seldom among a method's suitability criteria.

[Rick]

1-Check if your jet is o.k.....correctly tighten, no plug
2-Check if your column is correctly install to detector...it is not impossible that your column is so high in jet and block H2
3-Verify if Make-up, Air and H2 flow are o.k. (400ml/min for air, 40ml for make-up and 40ml/min for H2)