Oil in Analyzer Chamber on HP 5973N

[spthom77]

Hi, I have a HP 5973N that after a screw up yesterday, now has foreline pump oil coating the chamber. For a little backstory...we have a HP 6890 with 5973 MSD plus a Varian Archon with tekmar 3000 autosampler set up. One of the motors in the archon died and I decided to swap it out with a known good unit until I can fix the bad motor. The archon uses the same H2 gas as the GC, so I needed to shut it all down. Through vacuum control, I vented the system and cooled the various zones. Once everything was cool, I shut down all the components and made my swap. Go to turn the vac pump back on to start it pumping down and its making a weird noise and I notice that the line from the pump to MSD is full of oil. I tried draining the hose by cracking the line at the pump and watched oil bubble up into the MSD. Upon opening the analyzer chamber, I found that the entire thing is coated in oil drops. I'm assuming the source and body are covered as well. I am cleaning the chamber and source with DCM. Now, will this be enough? Or will I need to pull the diff pump and associated plumbing to get the remaining oil out? Anything else I should be concerned about? Now, I realize that I vented the system wrong by trying to pull the hose off the vac pump, but I wasn't planning on messing with the vacuum portion of the system. What did I do wrong in this respect? I was under the impression that as long as I wasn't messing with vac connections and was essentially just power cycling it like I would to change tanks, I should have been good. Any help is appreciated! Thanks!

[James_Ball]

Sounds like the anti suck back valve in the rough pump is not working. When you shut down the pump, the vacuum in the chamber began to pull oil backward up through the line. Was it the Pfifer pump or just the small Edwards pump? Those small pumps seem to have more trouble with that than the larger E2M2 from the 5970,71 and 72s did.

You will need to remove the diffusion pump, because the oil in it which is glycol based is now contaminated with the oil from the rough pump. Clean it out with DCM and recharge it with the proper Santovac 5P oil. You may also have problems with the rough vacuum gauge that is attached to the side of the diffusion pump since oil could have gotten into it. If it doesn't read correctly the diffusion pump won't begin to heat up, it has to drop below 300torr to activate the diffusion pump heater.

It is good you have the diffusion pump, the oil backing up into a turbo pump would probably not be so easy to fix.

For future reference, I always put 1/8" toggle valves in each line just before each part of an instrument so that I can disconnect each of the units without needing to cut flow to the whole system. It saves a lot of down time.

[spthom77]

I was kind of surprised that there weren't any shut-offs on the gas line...and was kinda peeved that I had to power down the system in the first place. Shut-off are going to be installed prior to bringing this system back online. The rough pump is an Edwards E2M2. Is repairing the anti-suck back valve something that can be done in-house or should I send it out. I've noticed oil in the vac line before after power outages but was able to get it to drain back fairly easily. I hope to have everything cleaned out and reassembled today. thanks!

[James_Ball]

I have not rebuilt an E2M2 yet but I have found the rebuild kits online, I think they include the valve and the diagrams make it look rather simple. But then I have no problems rebuilding car engines and brake systems, so depends on your level of repair skills.

There are others here who I think have rebuilt these and might know more about how difficult it could be.

[mckrause]

If you have reasonable mechanical skills, and you can read a diagram, rebuilding an E2M2 is not all that hard. A pain in the butt, and quite dirty, but not difficult. Given that it was working previously you probably don't need a rebuild, just a good oil drain and replacement.

Getting oil out of a source is quite difficult. Even when it looks clean to you it isn't. You'll have a significant hydrocarbon background for quite a while.