Vacuum pump UNSTUCK -- and question

Thanks to Bill and Christopher.
I took the vacuum pump apart. Removed the motor, cover, and took the pump body apart from housing and removed one end of the body, exposing the rotary vane. As an aside, it had quite a bit of sludge in the pan. I realized that it was slightly rusted, not completely but just a little bit. After the disassembly, I had better access to the shaft. A generous use of a big wrench made the pump unstuck. I washed the cover to get rid of sludge, reassembled and refilled the pump.
The good news is that it pulls vacuum, not sure how deep but it pulls quite strongly on my finger when I try to close the vacuum opening with a finger. I do have a vacuum gauge (from an old broken pump), but the gauge is 1/4" NPT and the pump has a flare fitting. Maybe I will visit Ace Hardware or HD tomorrow for a fitting to put the gauge on.
The question I have is this. When the pump starts pulling a real vacuum, but before it reaches equilibrium, it makes a gurgling sound. Also, it seems that the oil became bubbly with a lot of little bubbles. I see them in the access window.
Is that normal? I am suspecting that perhaps one of the vanes (I think that they are called vanes, the little rectangular thingys that go in and out of the rotor to maintain vacuum) is stuck and does not move back and forth. Could that account for the gurgling sound?
thanks
i

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    The gurgling sound is normal until you get far enough down in pressure so you don't get noticeable bubbles with every rotation.
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    What kind of oil did you use? Real high-vacuum oil is designed to prevent outgassing. Compressor oil is *not*, nor are most other oils. There is a reason for high vacuum oil costing as much as it does.     
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    As above -- the gurgling sound is normal. With a good tight seal, and not too much volume to evacuate, the sound would be about like this:
    "GLORP, Glorp, glorp, GURGLE, Gurgle, gurgle, tick, tick tick,     murmur, murmur ... murmur"
The larger the volume to be evacuated, the longer the Glorps and Gurgles will go on, and if there are leaks, you may *never* get past the gurgle stage.
    The sounds above are from belt driven pumps. With your direct coupling, they may differ a bit, or get masked by the motor sounds.
    Enjoy,         DoN.

Yeah, what he said... I have a similar mechanical pump that I take to classrooms to demo some basic vacuum science (extiguishing a candle, boiling water at room temperature, silencing a bell, etc.) Fact is, the sound of the vacuum pump just about steals the show (well that and the gigantic marshmallows).
Go ahead and measure the vacuum, but it sounds like you fixed it. A stuck vane would actually inhibit the gurgling sound.
- Bruce
snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote in
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On Sun, 12 Feb 2006 00:33:33 -0600, Bruce Spainhower
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My pump is not that loud actually.
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Thanks Bruce. I will try to fit a gauge and a tank to this pump. I changed my mind and will not add a vacuum switch, instead I will run the pump continuously during periods when I need vacuum available. I think that restarting this pump and leaving it turned off against vacuum would create trouble, such as sucking oil into the vacuumed area etc.
After I am done using the pump, I would refill the vacuum tank with air.
i

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I am using real vacuum pump oil from McMaster.
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That's nice to know. Thanks Don.
i

As others have posted, the noise sounds normal for that type of pump. Actually, I am used to Kinney and Stokes pumps, and they both have this very loud knocking sound when they are at high vacuum, due to the lack of any air cushioning on the valves. Standing next to a large Stokes is frightening to someone not used to it, it sounds like an engine about to throw a rod!
I have the smallest Kinney for my home use, a KC-5 and really love it. I can have it running in the garage and tell when I am at a good vacuum from inside the house.
The gurgling will come back when you use the gas ballast valve (if your pump has one), but will quit and return to the knocking almost instantly if you are at a good vacuum.
Dennis

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Thanks Dennis. It seems a though the noise is indeed fully normal. What do you think about tiny bubbles in oil? I am hoping that this id due to the "break in" period when oil penetrates areas that were occupied by air (remember, I drained the pump fully), but maybe I am wrong.
i

DT wrote:
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Gas ballast, Thats the word I was looking for through this whole thread. I worked on a lot of Sargent Welch pumps at UNM and was trying to bring up the idea that maybe his was open. Getting old is hell first your memory goes, etc. :-) ...lew...

"Lew Hartswick" wrote: (clip) Getting old is hell first your memory goes, etc. :-) ^^^^^^^^^^^^^^^^ This is a true story: I was servicing machines in a shop where most of the help was female. I made the usual wisecrack, "Two things go with age. The first is memory, and the second... I can't remember." Everyone laughed, except this one quite attractive, young blonde lady. I turned to start my work again, and she got this impatient, disgusted look on her face, and said, "Well, what *is* it?"

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Some of the bubbling may be from water vapor in the oil/off the inside of the pump surfaces. Goes away when the pump is run long enough to throughly warm it up and clear that out. If you're not running it for long periods, may never go away, but won't be much of an issue.

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Thanks. I will run it for a day or so. I think that you are right about residual moisture. I would rather get rid of it.
i

Glad you fixed it. I suspect the gurgling and foaming are quite normal. My pump makes a really cool gurgling noise which is loudest when large volumes of air are being pumped. Large volumes of air passing through the pump (i.e., if you're running the pump with the inlet open) may well cause the oil to foam as the air exits through the flap valve.
If you haven't already found it, check out Sam's Vacuum FAQ. This is the bible of vacuum pumps:
http://www.repairfaq.org/sam/lasercva.htm
Best wishes,
Chris