Chromatography Forum

Hi,
I have just removed a liner from my GC and I guess I had tightened it down too much.
When removed it had a helical crack all the way down the liner - but was intact.
Result - since they usually crush and fragment.

That's because it's Friday the 11th, not the 13th.

Peter

I have removed broken liners from instruments to find that there is much more glass sitting at the bottom of the chamber that could be accounted for by a single liner!!

GCguy

When I first started in the lab I had a co-worker come to me with a problem that he could not get his inlet to seal on an Hewlett Packard GC/MS (5995). I started looking at the gold seals and noticed the indention did not go completely around, it had a small missing part. Later he told me he had a liner get stuck in the inlet and he had taken the adapter and seal off the bottom and hit it with a wrench to break it loose. Seems in doing so he also dented the sealing surface at the bottom of the inlet.

On Agilent systems, the septum goes in the recessed portion and the nut goes on but only until the snap ring lifts off of the surface of nut. That's basically all done with your fingers. In 20+ years of doing this, I've never had a leak and I've always done it that way. You don't have to put a wrench to it to seal the inlet from the top.

Wow! Torquing it down so hard that the liner cracked. That's amazing.

I agilent recommends tightening the septa nut 1/2-3/4 of a turn or so past the point the snap ring stops turning with the nut. As for the liner I just do fairly snug. You shouldn't have to put any real muscle into it. My 6890 has the flip top system though my 5890 uses the standard stuff.

http://www.chem.agilent.com/Library/pos ... 0Inlet.pdf

I had a customer use the wrong ferrules on an agilent GC last month. They had tightened the column inlet nut sooo tight the graphite had ridden up into the gooseneck liner and formed a seal. Result blocked inlet until the liner was removed, very confusing until I notice the graphite. That was a new one.

On Agilent systems, the septum goes in the recessed portion and the nut goes on but only until the snap ring lifts off of the surface of nut. That's basically all done with your fingers. In 20+ years of doing this, I've never had a leak and I've always done it that way. You don't have to put a wrench to it to seal the inlet from the top.

Wow! Torquing it down so hard that the liner cracked. That's amazing.

It's not the septum nut which breaks liner when overtightened - it's insert retainer nut.

You're right. I typed before I thought it through.

In that case, for my old systems I make sure that the regulators are trying to pressurize the inlet and only tighten that inlet retainer nut until I make a seal against the o-ring. I then add about 1/8 of a turn past that. Just enough to make it snug.

I agilent recommends tightening the septa nut 1/2-3/4 of a turn or so past the point the snap ring stops turning with the nut. As for the liner I just do fairly snug. You shouldn't have to put any real muscle into it. My 6890 has the flip top system though my 5890 uses the standard stuff.

http://www.chem.agilent.com/Library/pos ... 0Inlet.pdf

For the septum nut I always just tighten it until I can slide my thumbnail under the clip, fingerprint facing upwards. That gives the septum plenty of pressure to seal and not so much that it cores it out quickly. It was a trick shown me by an Agilent service rep long ago.