Chromatography Forum

Hi,
I was wondering if anyone has had issues with the transfer line on an Agilent GC MS. The thread on the end in the oven seems to be getting a bit worn. Does anyone have any info on the thread pitch and type? I am planning to get hold of a die to clean up the threads.

GCguy

Restek sells a rethreading tool for this purpose - its the correct die size for that fitting.

Thanks for the reply. Do you have a part number? The only one I can find from Restek is for the injection port. I am looking for one for the transfer line which is smaller.

GCguy

Thanks for the reply. Do you have a part number? The only one I can find from Restek is for the injection port. I am looking for one for the transfer line which is smaller.

GCguy

I thought they have the same thread.

On Agilent the injection port uses the male nut and the MS interface uses a female nut. Not sure if the thread sizes are the same or not.

Hmm it looks like Restek may have dropped that part, or I got it from someone else (SiS perhaps).

The one I have says it is Hanson 10-32 NF. I have no idea what those numbers mean, sorry. The "10" is marred on the tool, so that could be anywhere from 10 to 19.

On Agilent the injection port uses the male nut and the MS interface uses a female nut. Not sure if the thread sizes are the same or not.

Now I see it in my mind. You are absolutely right.
If threads are the same, injection port male nut should fit MS interface female nut.

The one I have says it is Hanson 10-32 NF. I have no idea what those numbers mean, sorry.

10-32NF is a standard thread designation, like for nuts and bolts sold at Ace Hardware, so should be a standard die.

For something 10-32 NF, 10 is the size/diameter and 32 threads per inch, fine thread, so NF.

See http://www.amazon.com/Irwin-Hanson-HAN9 ... =10-32+die

Hi,
I was wondering if anyone has had issues with the transfer line on an Agilent GC MS. The thread on the end in the oven seems to be getting a bit worn. Does anyone have any info on the thread pitch and type? I am planning to get hold of a die to clean up the threads.

GCguy

The thread does wear and starts to leak. I have also seen a lot of cross threaded and strangely bent threads where too much pressure has been put on them. Let us know how you get on. I usually order up a new transfer line but that gets v. expensive.

CPG, that looks like the one I have, so 10-32 NF is likely the right one.

Thanks for the tips on nuts and bolts , that stuff has always been a little over my head.

Thanks for the help guys. I agree the ideal remedy would be to replace the transfer line, but we have done this in the past and it was expensive.
Interestingly the thread pitch and size seems to be the same as that for HPLC fitting. Many years ago we had a tool to rethread the end of columns that had male fittings, however that tool has been lost over the years.

Always the same, you know exactly the tool you need, just can't find it!!

GCguy

Thanks for the information on your die Yama. I am running a 5975c MSD and having the same trouble with the threads of the transfer line wearing out. It appears that some brass material from the transfer line column nut is getting deposited between two of the threads and causing difficulty with installing new columns. I used to be able to thread the column nut by hand but now I need a wrench to get it past the damaged section.

I swap columns frequently and noticed that the nut is beginning to squeak more as I tighten it on the transfer line. I have not had any trouble with leaks thankfully, but I fear It's just a matter of time until things won't seal up anymore. If worse comes to worse I will trying running a die over the marred section of the threads to clean them up. Cheaper than a new transfer line at least if it works.

Anyone have any tips on avoiding the damage in the first place? I'm generally very careful when threading the nut but I am probably over tightening it or something.

... If worse comes to worse I will trying running a die over the marred section of the threads to clean them up. Cheaper than a new transfer line at least if it works...

You'd better not wait until thread deformation or something, just rethread transfer line.

Thanks for the information on your die Yama. I am running a 5975c MSD and having the same trouble with the threads of the transfer line wearing out. It appears that some brass material from the transfer line column nut is getting deposited between two of the threads and causing difficulty with installing new columns. I used to be able to thread the column nut by hand but now I need a wrench to get it past the damaged section.

I swap columns frequently and noticed that the nut is beginning to squeak more as I tighten it on the transfer line. I have not had any trouble with leaks thankfully, but I fear It's just a matter of time until things won't seal up anymore. If worse comes to worse I will trying running a die over the marred section of the threads to clean them up. Cheaper than a new transfer line at least if it works.

Anyone have any tips on avoiding the damage in the first place? I'm generally very careful when threading the nut but I am probably over tightening it or something.

You could use one of these:

http://www.restek.com/catalog/view/3354

Use a fused silica transfer line in the MS interface then leave maybe a half meter of transfer line in the oven and use the union to join your column to it. Over time you can replace the column several times before you need to replace the transfer line into the oven which should reduce wear on the MS hardware.

The ferrules in those fittings take a few days to shrink and seal perfect, but once they do you are good to go. You will need to find a 3/16" wrench though to tighten the fitting, but otherwise they should work well. You could use a fused silica press tight, but you would need to replace it every time you changed the column and cut a little of the transfer line each time and that runs the risk of getting fragments into the MS from cutting the line.

Also, since the line makes a restriction into the mass spec, you can use it like a no-vent fitting and swap columns without completely venting the MS, just shut down the turbo pump, change lines and pump down and are back in business faster because little air or water gets into the analyzer.

Most of our operators routinely overtighten the tranfer line nut and end up distorting things a bit (often a lot, with crooked nut and the ferrule squished ito the line, leading to ferrule particles plugging you column if you are careless on the next install). Whenever I am asked to intervene, I can rethread the transfer line and get things back to normal.

It looks to me like the 5975 often displays transient air peaks when the cal gas is first looked at, inspiring much of the over tightening (I suspect this may be due to air diffusing through the septum purge). I have learned to ignore this, as the air background usually dissipates after a run or so, with maybe just a slight tightening at the nut. Sometimes is does not pay to focus excessively on the air background.