Vacuum pump UNSTUCK -- and question

- I
- Ignoramus1088
  
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posted
16 years ago

Sun, Feb 12, 2006 4:49 AM

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

- D
- DoN. Nichols
  
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posted
16 years ago

Sun, Feb 12, 2006 6:03 AM

According to Ignoramus1088 :

The gurgling sound is normal until you get far enough down in pressure so you don't get noticeable bubbles with every rotation.

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.

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.

- B
- Bruce Spainhower
  
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posted
16 years ago

Sun, Feb 12, 2006 6:33 AM

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 news:43137$43eecfb9$48f4e632 $ snipped-for-privacy@msgid.meganewsservers.com:
[snip]

- I
- Ignoramus8228
  
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posted
16 years ago

Sun, Feb 12, 2006 11:48 AM

I am using real vacuum pump oil from McMaster.

That's nice to know. Thanks Don.
i

- I
- Ignoramus8228
  
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posted
16 years ago

Sun, Feb 12, 2006 2:26 PM

My pump is not that loud actually.

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

- D
- DT
  
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posted
16 years ago

Sun, Feb 12, 2006 2:39 PM

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

- I
- Ignoramus8228
  
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posted
16 years ago

Sun, Feb 12, 2006 2:45 PM

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

- E
- Ecnerwal
  
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posted
16 years ago

Sun, Feb 12, 2006 4:08 PM

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.

- C
- Christopher Tidy
  
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posted
16 years ago

Sun, Feb 12, 2006 4:19 PM

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:

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Best wishes,
Chris

- I
- Ignoramus8228
  
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posted
16 years ago

Sun, Feb 12, 2006 4:47 PM

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

- L
- Lew Hartswick
  
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posted
16 years ago

Sun, Feb 12, 2006 4:50 PM

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...

- L
- Leo Lichtman
  
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posted
16 years ago

Sun, Feb 12, 2006 7:50 PM

"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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