FID continuously popping

[TimJ]

Hi there.
I am having a problem with our Ai 92 GC. When I light the FID a spark also lights at the top, which shouldn't happen, and it pops on and off repeatedly for a few minutes. Then this will suddenly happen again randomly when I am putting samples through. The flame in the base of the FID lights perfectly and doesn't go out but this continous popping at the top of the detector means I can't make any measurements.
Anyone have any ideas what the problem might be?
Thanks in advance.
Tim.

[chromatographer1]

who makes the Ai 92 GC ?

Is there a diagram of the detector available?

[TimJ]

The machine is made by Ai Cambridge Ltd, formerly Analytical Measuring Systems I think.
There is a diagram of the FID in the manual, looks like it is the ignitor filament that is continually popping.
Hope this helps.

[BG]

Hello TimJ

Have you controlled the flows of operation of the FID and particularly H2, sometimes when there is in too hight proportion compared to the air the filament tends to continuously popping........it can be a solution !

Other thing, maybe the mounting of the burner tip is defective and tight between air inlet and H2 inlet (in the FID body) is not respected.

(Sorry for my english...i'm french !!)

[BG]

Another thing......... H2 inlet is not constant, there is permanently extinction - lighting of the flame, because the burner tip is partially stopped (particles, badly assembled column...)

[chromatographer1]

The popping is apparently hydrogen gas igniting. For that to happen repeatedly, means the fire has to be extinguished, the FID senses the flameout and tries to reignite and thus the repeated popping.

The cause is as BG has noted, a leaky seal around the flame tip or around the seals within the FID body.

Dirty partially blocked eluent passages (also as BG noted ) can be the problem also, if the flame is not symmetrical but distorted it can experience a 'flameout'.

Get the FID serviced by someone who has the proper parts and the popping will go away.

Good luck.

[TimJ]

Thanks for the replies BG and chromatographer1. Do you know of a company in the UK that would service an FID?
Thanks.

[chromatographer1]

I am in Pennsylvania, USA. Sorry, don't know of anyone in the UK.

[BG]

Can not you contact "Ai Cambridge Ltd"..?
Only supplier can help you and essentially for changing parts if it's necessary.
Otherwise try to contact the principals CPG suppliers as Agilant, Varian, PE whose are based in UK , maybe they could help you !!

good luck

[Russ]

Have you already tried cleaning the detector jet? On the systems I have used this is user serviceable and generally easy to perform. A clogged jet can cause problems with the flame and resulting in the flame going out, especially during a large solvent peak. Others have mentioned this but I did not see if you have looked at it yet.