FID ignition issues

[Julieke]

Hi all,

I am in the process of replacing a 0.25mm column with a 0.32mm one in my FID. Since I installed the new one yesterday, the detector is having some ignition issues. When I first tried to restart it, it failed (the H2 flow was reading 50ml/min at that point, above the 40 set value). With the H2 and O2 flows off (kept the make up on by mistake), I noticed that the H2 flow was still high (above 30ml/min), which made me think that the jet was blocked. With all flows off on the FID but carrier at 0.5ml/min, the H2 actual flow displays around 0.3-0.4ml/min.The FID had been running without any issues until I swapped the columns yesterday.

Wondered whether I had installed the column too far or whether the wider ID was the issue but I have tried today to switch back to a 0.25mm and still seeing the issue. Now the FID made the popping sound a few times in a row, came on and switched off again. It looks like a flow issue but don't know whether it is due to jet or my poor installation. I am waiting for some cleaning supplies, as well as a new jet but wondered whether anybody would have any ideas of what could cause this?

GC7890A
Flows: H2: 40ml/min; O2: 400ml/min; make-up: 25ml/min
Optimised capillary fitting-installed column by inserting it until it bottoms out, then retract by ~1mm.

Many thanks.

[awolte]

Hi,

I not really familiar with the Agilent GC but did you changed the column parameters in the settings from .25 to .32?

best regards

[Julieke]

Thanks for the reply-yes, I had changed the column type in the settings but still had troubles.

[Consumer Products Guy]

First thing I would do is remove the collector and make sure that the jet itself is clean, no crap in its opening. We'd run a cleaning wire through the jet.

[cjm]

Is your carrier gas He or H2? 0.5 mL/min seems very low, even for helium. Is this a 30m column? Is your makeup gas N2? Air or H2 as your makeup would cause problems with the flame. FID popping suggests to me there's a flow problem, and I'd bet your fuel to air ratio is off. By O2 at 400 mL/min, I assume you are referring to air and not bottled oxygen.

[Julieke]

Thanks to all for the replies. I am waiting for a cleaning wire to arrive and am planning on doing some cleaning on the jet.
cjm-carrier is He, I am planning on using it at a higher flow but had reduced it down for investigations. Both 0.25 and 0.32mm columns are 30m. Sorry-yes meant air at 400ml/min not O2. Make-up is N2.

I have not got a very extensive practice of installing columns but have done it a few times in the FID without having issues. Could uninstalling the previous column have dislodged some impurities that are causing my flows to be off?

[Consumer Products Guy]

I have not got a very extensive practice of installing columns but have done it a few times in the FID without having issues. Could uninstalling the previous column have dislodged some impurities that are causing my flows to be off?

Or a piece of column has broken off. Or a piece got jammed with the previous installation.

We inserted gently until the column end touched, then pulled back like 2mm and tightened the nut. We generally used finger-tight knurled nuts from Agilent.

[cjm]

What temperature is the detector when you try and light it? One of our older 6890s can be problematic and requires holding a lit lighter over the castle assembly while turning the makeup gas off and slowly turning it back on until the flame catches. The detector in our case has to be >250C for it to light at all.

[Julieke]

It is on at 300°C. It was working fine before I replaced the column, which makes me think that it is something that I did rather than a fault with the actual detector. I had installed it the way Consumer Products Guy suggested but I can't rule out doing something wrong at some point. I am planning on cleaning though and installing a new jet if that still does not work.

[rb6banjo]

It's a weird thing but it sort of makes sense and it works for me. One of my Agilent service reps taught me this trick almost 30 years ago. When the glow plug comes on, gently blow air (I use my mouth) over the opening of the FID chimney toward the glow plug. Like you're blowing air over the end of a soda/beer bottle to make a musical note. I have 2 FID's in my possession that will only light this way. They won't light if I merely download a method and walk away. It's a good trick!

[Consumer Products Guy]

It's a weird thing but it sort of makes sense and it works for me. One of my Agilent service reps taught me this trick almost 30 years ago. When the glow plug comes on, gently blow air (I use my mouth) over the opening of the FID chimney toward the glow plug. It's a good trick!

I learned this too, from my supervisor, I believe, on our HP 5830A in 1975 !!!

Yes, over the years as we moved on to 5890 and 6890 GCs, some did need this to ignite.

For the youngsters, in those days one pushed a button to get the ignitor to glow for lighting. And sometimes a lit or glowing wooden stick (like a thin throat depressor stick) was used.

[ATAlR]

installed column by inserting it until it bottoms out, then retract by ~1mm

You have to retract by 6 mm, with only 1 mm clearance you would push column to far when tighten. Try without column with blank nut

[James_Ball]

It's a weird thing but it sort of makes sense and it works for me. One of my Agilent service reps taught me this trick almost 30 years ago. When the glow plug comes on, gently blow air (I use my mouth) over the opening of the FID chimney toward the glow plug. It's a good trick!

I learned this too, from my supervisor, I believe, on our HP 5830A in 1975 !!!

Yes, over the years as we moved on to 5890 and 6890 GCs, some did need this to ignite.

For the youngsters, in those days one pushed a button to get the ignitor to glow for lighting. And sometimes a lit or glowing wooden stick (like a thin throat depressor stick) was used.

When I first started we used the striker like used to light propane torches, or a butane lighter, whichever was handy, because we didn't have a glowplug in it. It was a Varian 1400 GC I believe, the one that the front door opened to cool down.

We also kept a small beaker by the instrument to place just above the chimney to look for condensation to make sure the flame was lit, a shiny wrench would also work.

[Consumer Products Guy]

We also kept a small beaker by the instrument to place just above the chimney to look for condensation to make sure the flame was lit, a shiny wrench would also work.

Yes. And yes.

[benhutcherson]

For the youngsters, in those days one pushed a button to get the ignitor to glow for lighting. And sometimes a lit or glowing wooden stick (like a thin throat depressor stick) was used.

I'm 31, and the only self-lighting GC I've been around was a 6890 where I once did a summer internship-only one person was allowed to touch that instrument.

All of my experience with more modern GCs-6890s, 7820s, 7890s, a few Varians, has been GC-MS.

I learned GC on a 5890/5971 that also had an FID, and now have one 5890 FID/NPD at work along with another 5890 FID/5971 that I service in my own instrument business.

I also work a decent amount with SRI/Buck instruments, both in my own business and in my day job. Those do have to be manually lit, although they're a fair bit simpler than something like a 5890-they use a ceramic bar that basically lasts forever unless you physically damage it, and also don't "pop" when they light. I learned to light 5890s by turning all the gases off on the front panel, turning the air on 1-2 turns, then holding the ignitor while slowly turning up the H2. Once I hear it pop and confirm it lit with a wrench/beaker/whatever else smooth and shiny is handy I slowly bring the other gases up to their stops. The SRIs never need a gas adjustment-you just be sure the internal compressor is on and that you have H2 is flowing.

And yes, I've used lighters before also-I generally use a long Bic grill lighter, although I've used other types as needed. Most recently, I had a glow plug go out on the 5890 at work and had to do that.