Thermo FID Flame Out

[lusi]

Hello,
I am not very familiar with the FID.
We have not used our FID for about over a year now. When we tried putting it on recently but the message OUT appears.
We recently changed the jet also. There flows appears alright my the instruments measurements. But we do not have a flow meter to verify.
However, there is no trap on the air line. I am wondering if this could be the problem.
I am looking forward to your suggestions.

[dblux_]

Hello,
I am not very familiar with the FID.
We have not used our FID for about over a year now. When we tried putting it on recently but the message OUT appears.
We recently changed the jet also. There flows appears alright my the instruments measurements. But we do not have a flow meter to verify.
However, there is no trap on the air line. I am wondering if this could be the problem.
I am looking forward to your suggestions.

Probably there is temporarily air in hydrogene line making the mixture fuel lean.
Let hydrogen flow through until air is completely removed from the line. Then ignite again.

[lusi]

Thanks dblux, but the hydrogen generator has been on for a while now. So I am thinking that there shouldn't be excess air in there. But maybe we can leak check again.

[dblux_]

Thanks dblux, but the hydrogen generator has been on for a while now. So I am thinking that there shouldn't be excess air in there. But maybe we can leak check again.

Are hydrogen and air pressures sufficient for your GC ?

What are flows of hydrogen, air and makeup ? (values in ccm/min)

[lusi]

They are set to He- 35ml/min, air - 350ml/min, make-up 30ml/min. However, during ignition I have no control of what they are. They seem to go to (He) 70 and (Air) 200 and something.

[dblux_]

They are set to He- 35ml/min, air - 350ml/min, make-up 30ml/min. However, during ignition I have no control of what they are. They seem to go to (He) 70 and (Air) 200 and something.

Flows seem quite O.K.

Check whether there is such configuration parameter as "lit offset".
At least Agilent FID let you set this parameter (default value is 2 pA).
When the FID signal drops below set value (eg. 2 pA), hydrogen flow shuts down completely and FID announces faulty condition.

You may try to find gas flows sufficient for stable FID flame.

First of all I would reduce makeup flow temporarily for example to 10 mL/min.

If it doesn't help, leaving makeup at 10 increase hydrogen flow 70 mL/min.

If it doesn't help get back with hydrogen flow to 35 mL/min and increase air flow to 700 mL/min.

Isn't your capillary column installed in jet orifice (too high), blocking hydrogen flow ?

[Peter Apps]

Hi Lusi

You need to verify that the flame really is not igniting - faults with flame out sensors are common. Hold a cool shiny surface close to the outlet of the detector - do you see condensation ? If you do the flame is burning. Some GCs have an adjustable flame-out sensor, maybe yours needs adjusting.

Peter

[Johnny Rod]

The glowplug could be a bit duff. Do as Peter says, if it isn't lit then while it's trying to light, ignitie it yourself with a lighter. If all is okay apart from the glowplug, it should light then settle down as normal.

[dblux_]

Hi Lusi

You need to verify that the flame really is not igniting - faults with flame out sensors are common.

Very good idea. In fact diagnosing should start with this test.

Some GCs have an adjustable flame-out sensor, maybe yours needs adjusting.

Peter

Agilent calls this configurable parameter "Lit offset" and as said earlier, default value is 2 pA. (I haven't the faintest idea on Thermo)
Very pure hydrogen, air and FID itself give less than 2 pA current and GC logic thinks that there is no flame. Consequence is shutting down hydrogen and air flows to FID for security reasons.

[lusi]

Thanks so much for your suggestions. However, right now we are out of carrier gas. Our shipment has been at customs for the longest while.

We may consider capping off and lighting it.

I dont see anything in the manuals about glowplugs. So I am not sure what that is in the Thermo systems.

As for the threshold it is set at 0.5pA. So I think that is pretty low.

We did pull back the column last time but it did not change. Maybe we can consider blocking off the inlet to the detector and lighting it.

What do you think?

[dblux_]

As for the threshold it is set at 0.5pA. So I think that is pretty low.

Yes. Sufficiently low.

We did pull back the column last time but it did not change. Maybe we can consider blocking off the inlet to the detector and lighting it.

What do you think?

Yes. FID will work without a column and without a carrier gas. Just remove the column and insert dummy ferrule into the column nut. Reduce makeup gas flow to make ignition easier. Keep us informed about progress.

[Yama001]

I have had this problem all week; dblux_ advice just worked for me so thanks!

I had been regarding the lit offset setting as "turn off the H2 if the signal fluctuates more than the lit off set value". I had swapped my sytem to a different column with little bleed; my signal was dropping below 2 and I could not figure out why the flame kept going out (I was thinking it was blowing itself out as the air flow ramped out).

So I had a little knowledge that turned out to be wrong . Always good to be humbled now and then.

[uzman]

Is your detector heated ?
It must be at least at 150 C , preferably over 200 C to be ignited.

[lusi]

Hello Everyone.
So we took out the column and still no continuous ignition. Before the retries I see an ON (for 1 second) and then IGNITING message.
The base temperature is 300C. I do hear a small click.
We change the compressed air. However I have no filter on this line, is it remotely possible that there is excess moisture that can lead to OUT.

Not sure what else to do really.

[Chenosuke]

Hi Lusi,

You should really have a moisture trap installed along your air line. In the interim however, if you haven't tried using the lighter to ignite yet, I've seen a technician actually blow gently on the glow plug while it was trying to ignite. Turns out the glow plug was dying, but blowing on it kept it lighting when we needed it until the new one arrived. (Remember, blow gently & dry!!!)

I hope that works. If not, you may have to get that trap installed ASAP. Also, while you're at it, it may or may not help this problem directly, but maybe it's a good idea to take the detector apart and give it a good clean. Consult your user manual for the steps to take to disassemble and clean it.

Finally, while the 0.5 lit offset value has proven more than adequate in my few years of experience, maybe you should increase the H2 flow to 45ml/min and air to 450ml/min, just to see if that helps. I had a baseline signal that was around 1 when I changed the filters and catalysis module in my Zero Air Generator last year (I was running at 35/350 then) and the flame would go out and try to reignite unsuccessfully sometimes. I didn't like how close it was to the lit offset, so I upped my flow to 45/450 and now I'm running at a baseline of 2.2 or so, which keeps the offset at a safe distance from the lit offset value.

Best of luck.

They are set to He- 35ml/min, air - 350ml/min, make-up 30ml/min. However, during ignition I have no control of what they are. They seem to go to (He) 70 and (Air) 200 and something.

One last thing Lusi, I see you have in your quote ''He'' at 35ml/min. I'm sure it must be a typo, but you do mean Hydrogen and not Helium, correct?

Chen.