Abusing compressor as a vacuum pump

Yes, it will work, but it won't pull a very deep vacuum. Probably good enough for casting though. Make sure you filter the inlet to the compressor though as any solids will destroy it pretty quickly. Change the oil after its been used as it may condense a fair amount of water vapour,which might get into the oil.

I have not seen the set-up you are proposing, not helpful I know.

how about this:

You can pick up a venturi for short money which pulls a vacuum using shop air. You need to be mindfull of leaks in your vacuum system otherwise your compressor will run constantly.

good luck, Andy

Building your own vacuum pump

Eferg

HF sells a venturi-based vac pump for $9.99 Noisy but it works.

- - Rex Burkheimer WM Automotive Fort Worth TX

Nick Müller wrote:

That's interesting, what % of air does it remove?

i

[I tried it on my compressor, but it didn't pull enough vacuum to debubblize investment. That requires enough vacuum to boil water at room temperature (about 29" Hg). The result was worse than no vacuum at all - bubbles everywhere. If all you want to do is suck on the bottom of your flasks to get the metal to flow in, you don't need as high a vacuum, so this might work for that.]

Andrew Werby

According to the box, an "ideal vacuum"!

Might be OK for evacuating vehicle cooling systems though-in fact, I have a Blue Point setup I use at work. Pulls to about 22-24 inches Hg...

I don't know, but it's sold for A/C work, so it should be able to pull a decent vacuum. Not that this is a copy of a design sold by Four Seasons and others in the mainstream A/C aftermarket. I have one I bought just to see what it was, but I've never really used it. I can testify that it's way to noisy for my tastes, probably consumes a lot of CFMs.

Do they ship to Germany? :-) Sounds strange, but I never came across a ventury pump (either water or air) here. Well, you get some, but they cost 10 times what HF wants.

Also, I guesstimate, that I get about 100l/min of "sucction", because my compressor has nominal 300l/min.

Nick

Sad. :-( OK, that for, I need more vacuum but little flow.

This was the primary intention.

Thanks for sharing your experience.

Nick

An old refrigerator or dehumidifier compressor will pull about 26" (660mm Hg) of vacuum. Two of them in tandem will get down to about

27, maybe 28 in Hg. Mine does (do) anyway, YMMV.

The HF venturi claims 28.3 in Hg at sea level. What's inside the box is just a 2" x 3" x 3/4" block of aluminum with three holes drilled in it and a couple of brass fittings. If you have a lathe and a drillpress you could make one quite easily. If you're curious, email me. I'd be glad to take mine apart, take some photos and make some measurements. Note: I'll be offline for a few days starting later this week.

I recently bought a couple vacuum pumps off ebay. One was a nice Welch 1400 pump for $140. It was used for Air Condition pump down.

I also bought a welch 1405 pump that was suppose to be freshly "rebuild" but I'm pretty sure it was just "freshly repainted" to make it look good because the oil was dirtier that dirt. It still pumps well so I kept in anyway. It went down to 40 mTorr with a crude plumbing so the pump seemed to be working. Full atm is 760 torr and it was pumping .040 torr, but it should easily do .010 torr.

The welch 1400 didn't do as well but the plumbing was even worse, so it wasn't a fair test.

Anyway there are lots of vacuum pumps FS on ebay. chuck

I would bet the rings are not designed to control oil with constant high (low?) vacuum. I would use the air pressure and a venturi setup to pull vacuum.

Thanks for your offer! Have a look in your mailbox. :-)

Nick

Another thing to consider is that mechanical vacuum pumps use a low vapor pressure mineral or a silicone based oil to keep what boils out of the lube oil from hindering the pump's progress.

Bob

Dimensioned sketch on the way.

... and received. Thanks! See PM.

Nick

Nick or Don, could you please post this info in the dropbox?

Thanks!

Is it OK if I build it in the next days and put the drawing + pics on my HP? I'm not familiar with the drop-box, also Don has the (C) for the drawing. :-)

Nick