septum retainer nut for 6890 GC

[smithdm]

Has anyone ever had trouble tightening down a new septum retainer nut (18740-60835)? And how do I fix this? It seems the coating is preventing it from being tightened and the inlet pressure won't stabilize.

Thanks!

[James_Ball]

Has anyone ever had trouble tightening down a new septum retainer nut (18740-60835)? And how do I fix this? It seems the coating is preventing it from being tightened and the inlet pressure won't stabilize.

Thanks!

You might try running it down once with no septa installed to clean the threads.

How tight are you trying to tighten it? For most of those, it is properly tight once the little E-Clip on top raises about a fingernail thickness above the nut. That is how I actually gauge mine, tighten until I can slip my fingernail under the clip and stop there. The septa will last much longer will less tension on them.

[smithdm]

I tried your idea, and also tried to scrape off some of the green coating on the nut. I also let the inlet cool to room temp hoping that the threading would shrink so the nut would fit. Nothing worked.

The nut did fit on another GC and a new inlet. I'm assuming now that the problem might be with the inlet on this GC.

Thanks for the quick reply!

[James_Ball]

I think Restek sells a thread tool to straighten the threads on an Agilent injection port. I can't remember the part number but you should be able to find it on their web site under the GC tools. If you can find the thread size you can also check with a hardware store and find a die the proper size and use it to straighten the threads.

[Consumer Products Guy]

Have you tried the gold inlet seal with vespel rings on each side to seal instead of the thin sealing washer Agilent sells? See Restek.

This thread fits better in the Gas Chromatography section

[01310040231]

Consumer Products Guy:

Yes, I have tried them and they are NOT as good as Agilent. The O-rings from Restek are not as good as Agilent.