Noise spikes on a 6850

[AICMM]

I am working with someone who has a 6850 with an FID and it has lots of problems with noise spiking, especially when first getting warmed up after a re-start. Once it is running it still has noise spikes once in a while but much less often. Flow rates are where they need to be, chromatography is excellent, FID has no problem staying lit so everything appears to be in order. I am wondering if anyone else has seen a similar problem and what they did to try to resolve the problem.

Best regards.

AICMM

[Schmitty]

Well, I know you're pretty much an expert, but I have tried the following things on 5890s:

-Check for pieces of graphite in the jet (some people around here tighten them too much).
-Swap out the jet.
-Tap the collector with a wrench.
-Ramp up temperature of the FID for an hour or two.

I have 7890s as well, and the FID is pretty much the same, so I am assuming that the 6850 and 6890 are the same as well.

Good luck.

[chromatographer1]

I would try replacing or cleaning the jet. There may be an interior coating of phase that is breaking off into the flame. As it heats up most of the available pieces fly off and only when it is cooled down and reheated does the layer break off again.

Just a guess. I am not always right when guessing.

best wishes,

Rod