Material in 5973 MSD chamber - pump oil?

[MMJ88]

Hi all,

I'm running a 5973N MSD. It's connected to an Edwards 1.5 pump. Last week I did vent the MS and change the pump oil, but all went as expected. Today, I wanted to clean the ion source (I wasn't getting the sensitivity I wanted), so I vented like normal and went about cleaning the source. When I went to reinstall the source though, I noticed that the diagonal oval vents at the bottom of the chamber have some stuff on them. It looks like pump oil. I don't know what happened - there haven't been any unexpected events (power outages, etc.), not to mention this pump is supposed to have some "anti-suckback" functionality, or something like that.

I also noticed that the outside of the mass spec assembly (the outer cylinder, I think Agilent calls it the "radiator") was dark with what looked like carbon deposit. It wipes off with a kimwipe with methanol. I don't know if this is related, but I thought I would mention it.

I haven't noticed any problems - it's been tuning fine and everything before this. So I'm really wondering what's going on here. For the moment, I'm avoiding pumping down and turning the heaters on, because if this just happened I don't want to get it on the actual quads, which are much more difficult to clean.

Any insight?

Much appreciated.

[Yama001]

I tend to see this quite a bit in our diffusion pump 5973s - I think this is diffusion pump oil rather than rough pump oil. I have heard the horror stories for 25 years about oil contamination, but even the sloppiest analyzers I have seen have always recovered with no issue. Perhaps I have just been lucky, but it has been a pretty long streak.

[tima]

OK Matty,

I see you posted this before I could. Thats why I came here. Anyway, I wanted to know the answer as well. The black soot that deposited on your quadrupole housing or radiator as you named it is the first time I have ever seen it.

My suspicion is its from the rough pump. When you changed the rough pump oil how dirty or dark was it? Did it smell burnt? When we looked at your rough pump a couple of weeks ago I do remember the level was rather low and it appeared to be very dark.

Maybe the oil got so low and so hot that it was burnt and created a bit of soot. Thats what I think. Did you replace the oil with the correct stuff? If you didn't could it be the rough pump oil you used. Just some thought.

Timothy

[James_Ball]

I have never seen the soot deposits, but I have often seen clear oil droplets on the slots above the oil diffusion pump on a 5973. Used to end up with the oil on the back of the analyzer plate on the 5971-72 models right around the multiplier that I always had to clean off when I did maintenance on those. Make sure the fluid is not over filled in the diffusion pump and that the fan is working and not clogged with dust to keep the refluxing oil lower in the pump tower. The cooler your room temperature the less you will see of the oil in the analyzer and the better your ultimate vacuum will be. On my original 5971 I could tell what time of day a sample ran during the summer by the percent recovery of my internal standards, ones run at night were higher because the vacuum would be better when the building was cool.

I never liked the EM1.5 that much(though much better than the Pfeiffer ones), always seem to run very hot, especially if you keep them stuffed up under the back of the analyzer like they are designed to be placed. I always preferred an E2M2 when possible, or at least a longer vacuum hose and having the pump sit on the floor below the instrument. I run the instruments for volatiles purge and trap analysis so I also have a molecular sieve trap attached to the pump inlet to keep excess moisture out of the oil, which also help capture any rough pump oil if it happens to back stream.

[MMJ88]

Thanks for the tips. It looks like it's running fine. Vacuum around 60mTorr, tunes fine, h2o/nitrogen below 2%.

This setup does have a longer vacuum line that runs down to the Edwards pump on the floor.

[LCbob]

As suggested black soot could be from the charring of the diff pump oil especially if the level is low / or the too hot switch is playing up. I spent many an hour last week trying to separate diffusion pump parts after the switch had failed and the oil literally burnt to a black sticky mass. Amazing what you can achieve with a rubber mallet and a large screw driver.....

[BCBC]

I wondered how to clean the residue, black crud, off diffusion pump parts. Use a mallet and screw driver?

[James_Ball]

I wondered how to clean the residue, black crud, off diffusion pump parts. Use a mallet and screw driver?

I have sonicated in Methylene Chloride and used sand paper to clean them up before. For the removable parts that is. Put Methylene Chloride into the body and let it soak should loosen up the deposits also.