Grubby pump oil - is this just water/emulsion!?

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Grubby pump oil - is this just water/emulsion!?

Postby chrismb » Sat Jan 29, 2011 2:05 pm

In my recent chamber refit I changed the oil but didn't do a self-pump of the fresh oil. I just ran the new oil - and also didn't bake the trap that sits right on top of it.

I just had a quick look at it, a 'routine' check - no concerns with the way the pump is running - and saw this brown goo where not so long ago there was nice fresh oil.

I am presuming that the oil already had soaked up its full load of water vapour when I put it in, then when it got hit with the output of the chamber and the trap I have ended up with an emulsion for oil because I didn't do a 'self-pump'.

Not sure this is very good! Or maybe it is just benign. I don't really have enough experience to know. I've left it pumping the trap for now, with ballast on. Any other comments/warnings welcome. I can change it again, but it'll be a bit of an awkward fiddle.

[Sorry for the file size - I shrank it but if I tried to upload anything but the original, it came up with an error 'cannot determine the size of the image'.]
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Re: Grubby pump oil - is this just water/emulsion!?

Postby Doug Coulter » Sat Jan 29, 2011 3:01 pm

Sure looks like an emulsion, maybe water, maybe air, and perhaps some rust. Old gunk could have been in there and now dissolved into the new oil as well. I'd run it a day or two and keep it hot, and see if it clears up (run with intake sealed off). If nothing else, you'll finally really scavenge off any crud deposits in there so next oil change will be "the last one". Some purists might get upset with the idea, but I've been known to run them in kerosene (deodorized naptha or just plain stuff as used in heaters) for a little bit between oil changes - basically some handy solvent. The solvent left in there after draining gets gone in a day or two of pumping due to its high vapor pressure after you add the new oil back in. The fact that kerosene is a fairly terrible oil itself tends to let any rust in there really polish up the insides of the pump in even a few minutes running, so it actually works better after that.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Grubby pump oil - is this just water/emulsion!?

Postby chrismb » Sat Jan 29, 2011 3:14 pm

It's pretty odd because when I first got the pump I filled it with some cheap pump oil, ran that for a bit, then refilled with the same as the current oil. I ran that for the whole of last year, and it was still quite clean. Took that out just after Christmas, put in a third lot, and this is what it is like after two weeks! I do tend to think it 'boils' down [no pun!] to me not pumping on the oil to start with.

I don' t have space in my setup for a valve between the pump and the trap, so I am going to have to keep pumping with the trap in place. The valve to the rest-of-system comes on top of the trap, so that's shut and I'll leave it run on ballast for a day.

(Still not sure if that much emulsion is good for the pump?)
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Re: Grubby pump oil - is this just water/emulsion!?

Postby Doug Coulter » Sat Jan 29, 2011 3:46 pm

Well, if it first worked, and then "just happened" it's not because of something you didn't do long ago -- there will be a close time correlation with something you did recently -- that would be where the crud is coming from. Trap, chamber, whatever. The thing is to determine perhaps what it is -- take a sample and heat it up, and see if that's air or water (more likely) in there.
Then you'll know the cure. If you ran it a lot of hours without trouble earlier, then it's something that changed since that is the trouble now. Oil does not absorb significant quantities of water just sitting out in air (or you'd not see an emulsion, but a soluble situation), but things like pumps can collect condensation in storage (and that's one reason there are so many messed up ones on ebay). Anything that is a big chunk of metal will go through internal condensation of water when stored in an uncontrolled environment, about a drop of water a day, as it stays cold while the air heats (and becomes more humid) every day. I know as I store a lot of rust-able fine machinery here (those politically incorrect lead projectile launching devices), and it's the main problem I have with them, and surplus pumps as well. Basements, garages, outbuildings -- kill things like this pretty quick. I've even had troubles "indoors" when I was sloppy about allowing day/night temperature/humidity swings.

The thing that solves it the easiest for my other storage issues is putting them in a wardrobe with a 25 watt incandescent lamp (also politically incorrect and getting hard to find!) so they stay warmer than ambient all the time.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Grubby pump oil - is this just water/emulsion!?

Postby johnf » Sat Jan 29, 2011 4:31 pm

Chris
If your system has been up at air for any time and if the trap uses molecular sieve then the sieve will absorb moisture --lots of it

run the pump blanked off without the trap and gas ballast fully open for two hours while doing this bake the trap in your domestic oven 200 -250 degrees C for the same time as your are gas ballasting --remove any orings or plastic covers etc.

PS download Irfanview (its free)and it's plugins. Its resize /resample algorythm is excellent for compressing photos
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Re: Grubby pump oil - is this just water/emulsion!?

Postby chrismb » Sat Jan 29, 2011 4:43 pm

Thanks, all. Clearly there was a lot of water that had condensed in my oil!... see below...

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Re: Grubby pump oil - is this just water/emulsion!?

Postby Doug Coulter » Sat Jan 29, 2011 4:50 pm

FWIW, I use "the Gimp" on photos (which is both free and cross-platform), and various free software to mess with video -- Kino for simple stuff.
The first thing I do for photos is scale them down to 1024x768 or so (or whatever preserves the XY ratio of the camera), which in my case gets factor 4 or better right off in bits.
Then I tweedle the compression ratio in jpeg during the save with the realtime preview until I just barely can see any artifacts of that at all -- another factor of 4 or more. You get photos that are about as good anyway (because of camera and lighting limitations) that are small and load quick. Since this is scriptable, I've thought of doing that for whole directories of photos, but I like keeping the original around and having a descriptive name for the ones I process too. The Gimp also has an excellent "levels" dialog that fixes up dynamic range and exposure pretty automatically or manually if something really wasn't lit well during the picture taking end.

I've seen pumps almost totally destroyed by storage in an outbuilding for 6 months (and been stuck with them -- "It worked fine before I sold it to you!"). You're probably lucky you didn't rust-weld the rotor. If you've got air bubbles -- you might have a stuck vane at this point, that'll do it, and it's pretty common to find along with rusty water. A lot of times you can fix that without having to buy anything (assuming you can make a new end gasket if needed).
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Grubby pump oil - is this just water/emulsion!?

Postby chrismb » Sat Jan 29, 2011 5:41 pm

This rather looks like it is *just* water vapour outgassing, Doug. With the ballast closed, no bubbles...

As John says, I have had the chamber open so many times that it is not surprising the trap has been dumping stuff it has collected into the pump, where it has condensed. Several cycles of that, and an emulsion is, clearly (or, rather opaquely..) the end result!

Of the 110 components within my vacuum chamber, about a half are plastics and the majority of the volume is mild steel. Vacuum 'contamination' is a given! Just a case of keep-on-pumpin'! I also use polycarbonate - which I recall John dreads - but I have found it OK once well outgassed. (On that note, I found a paper which studies what polycarbonate gets up to in vacuuo; it is extremely good at adsorbing water vapour and other contaminants, which it holds on to for a long time, so it gives the impression that the polycarb itself outgasses.)

It's beginning to clear up now. I'll run it for more hours tomorrow. I'll have to make sure that I run ballast from now on, whenever I begin a pump-down.

cheers...
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