HP GC flame Out problem
Marcus
,
I am currently using a HP GC system HP 6890 Series, with HP
ChemStation. My system has both a FID and MSD detector. I often experience
flame out problem which I don't in the past, this is especially when I
switch between the use of the detector., i,e. when I run a sample using the
FID then another with the MSD, the flame in the detector will go out and
the system hangs there until the flame come again. I have consulted the HP
guys and they told me to blow PHYSICALLY at the orifice.. it works but I
don't find it very scientific. Anyone has any suggestions?? Would
appreciate all comments. The following is the parameters I am running in:
In mL/min,
H2 flow = 35
Air flow = 300
at const. makeup
He makeup gas = 20
The inlet pressure is 100 psi. Would be please to supply more information
is necessary.!! THANK YOU GUYS !!
Leslie
Dom
>ChemStation. My system has both a FID and MSD detector. I often experience
>flame out problem which I don't in the past, this is especially when I
>switch between the use of the detector., i,e. when I run a sample using the
>FID then another with the MSD, the flame in the detector will go out and
>the system hangs there until the flame come again. I have consulted the HP
>guys and they told me to blow PHYSICALLY at the orifice.. it works but I
>don't find it very scientific. Anyone has any suggestions?? Would
>appreciate all comments. The following is the parameters I am running in:
I also have a HP 6890 with a FID, and I have MUCH trouble with the flame !
In fact I have to blow at the detector top for the flame to ignite, or it
will not. The guys from HP came many times and none was able to find out
what the f..k was wrong with this FID (but they charged me the visit, of
course). Last week, the flame started going out during runs, and I found out
that the H2 actual flow at the detector exit was much lower than the
indicated flow. I would advise you to check the flow rates with a flowmeter,
just to have an idea (I would also advise you not to buy a HP :-) )
Dominique.
Jason Ellis
problematic at times to get to light. In general when one goes out in the
middle of a run it is due to the flame not being "rich enough," but your stated
flowrates seem to indicate that you are already running a little rich in H2. I
agree with Dom in that I'd check the H2 and air flow rates with a flowmeter to
confirm that they are correct. The 10:1 ratio of air:hydrogen is generally
recommended so I might try bringing the air up to 350 or so and see if that
helps.
The other thing I'm thinking of is it may have something to do with your MSD
pulling a vacuum near the detector (??). How do you have the columns plumbed
in this GC? Is there a Y-fitting at the back end of the column that splits to
the MSD and the FID or is it some other configuration? Does the flame go out
when you make the switch between detectors or does it go out in the middle of a
run? How do you switch between detectors?
100 psi headpressure sounds awfully high, what type of column is in there?
What is the column flowrate at the FID? You dont want your column flow plus
makeup to be much more than 30 or 35 mL/min.
Best regards,
Jason Ellis
Applications Chemist
J&W Scientific, Inc.
e-mail: jas...@jandw.com
Marcus wrote:
> Hi all,
>
> ,
>
> I am currently using a HP GC system HP 6890 Series, with HP
> ChemStation. My system has both a FID and MSD detector. I often experience
> flame out problem which I don't in the past, this is especially when I
> switch between the use of the detector., i,e. when I run a sample using the
> FID then another with the MSD, the flame in the detector will go out and
> the system hangs there until the flame come again. I have consulted the HP
> guys and they told me to blow PHYSICALLY at the orifice.. it works but I
> don't find it very scientific. Anyone has any suggestions?? Would
> appreciate all comments. The following is the parameters I am running in:
>
Todd O'Connell
5890 or 6890 is the jet tip clogging. It is undetectable except by direct
examination as the total flow coming out of the column does not change. The
velocity of the gas coming out of the jet tip, however, increases tremendously
due to the small opening which blows out the flame. I've seen it get so bad
that peak retention times begin to increase as the back pressure from the jet
gets bad enough to reduce flow. Remember to examine the tip regularly and
either clean it with a syringe cleaning wire of the appropriate size or replace
the jet.
todd
Tanis Yoong
I can think of 2 possibilities.
1. I would suggest that you increase you Air flow to 400 and if possible
measure the flow to see if you are getting a flow somewhere there. From my
experience a mixture of 35 of H2 to 400 of Air usually ignite the FID easily.
2. Your FID jet could be partially clog. I have encountered a few times while
doing some installation for my customer before. I clean the FID jet and at the
same time enlarge the jet hole slightly by using a fine piece of hard wire.
This wire comes with the FID jet cleaning kit from HP.
The reason you need to blow at the FID outlet is to increase the amount of air
at the FID chamber so as to create a correct explosion mixture with H2.
Good Luck!!
Marcus
I did!! I have increased the air flow to 400 and still the flame is
still out.! Moreover, I come to discover that the GC is "Okay" when its
running a lot of samples in the morning but in the evening when I am
working, flame out is a common experience. It just went out like that. I
wonder if the GC needs to "cool down" after running many samples (abt 30 in
the morning). But couldn't rationalise this, the GC is okay again in the
next morning, so I never got to run a decent sample in the evening.
Other findings I made was : When I on the air and H2 flow, it becomes
stablised quite fast, but as long as I ignite the flame, both gases flwo go
to zero. I have already set the Lit Offset to 2 but still it couldn't get a
decent output signal.
I have a Whatman H2 generator connected to it, and sometimes the
pressure can get as high as 5.7 bar where its usually 4.7 bar. I wonder it
has anything to do with it. I have take a look at the burner head and find
its much corroded. Does it matters? I will try to change it today and see if
it improves..
Thanks for all contributions!!!
Cheerios!
Marcus
Tanis Yoong <y...@pacific.net.sg> wrote in message
news:377A63EE...@pacific.net.sg...
Tanis Yoong
If the GC is working fine in the morning but have problem igniting in the
evening, then I suggest you look some where else for the problem. Because from
what I understood, there is nothing wrong with your gc.
Another thing is, if the FID flame is ignited, it should remain on unless either
the H2 or Air or both are turn off, or there is a sudden surge of pressure from
the carrier gas if you are using a valve system. Anyway, your FID does not
require to rest even if it ran100 samples.
If you still have no luck, go back to the old way by blowing into the FID outlet
during ignition cycle. But once you have the flame on, increase your h2 to 40
and Air to 450.
May the Force be with you...
4th_Doctor
Varian 3100. It turned out to be a bit uncombustible
matter built up in the flame tip. It would move about in
the gas flow and occasionally act as a check valve. Flow
would be blocked just long enough to cause a flame out.
Another possiblity is the flow regulation on your gas
generator. If it is happening at night, perhaps your
geneator is under less load and the flow to your GC is
proportionaly increased.
Good luck
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