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Author: Subject: how to produce .1 Pa vacuum
soma
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[*] posted on 26-5-2018 at 02:18
how to produce .1 Pa vacuum


I've got 2 pumps that can get down to at least 1 torr. Wondering how much vacuum I could get if I connect them together.
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XeonTheMGPony
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[*] posted on 26-5-2018 at 05:01


1 Torr, you have dead space depending on pump type, with out vapor diffusion or turbomolecular pump you can't get much deeper then say 25millitore
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weilawei
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[*] posted on 26-5-2018 at 08:55


My rotary vane pump will pull down to 6 mTorr on fresh oil and seals. Average is 13-17 mTorr in a closed system, 4.3 Torr if I'm pulling air into about a 2L system.
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Tsjerk
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[*] posted on 26-5-2018 at 09:15


The most important question is how much gas volume you are displacing. Every volume / time has it's own best solutuon
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soma
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[*] posted on 27-5-2018 at 03:23


I guess I need a better vacuum gauge. I've got a rotary vane (Welsh 1450) that's rated at .001 torr.

Any suggestions for the best gauge for this?
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zed
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[*] posted on 1-6-2018 at 12:53


Seems to me, there used to be pumps that could be coupled up in-series.

Produce a very high vacuum that way.

I don't remember the type of pumps though.

Is this true?
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Ubya
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[*] posted on 1-6-2018 at 14:44


Quote: Originally posted by zed  
Seems to me, there used to be pumps that could be coupled up in-series.

Produce a very high vacuum that way.

I don't remember the type of pumps though.

Is this true?


turbomolecular pumps and diffusion pumps need to be put in series with a roughing pump to work, so yes putting pumps in series can achieve much deeper vacuum





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SWIM
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[*] posted on 1-6-2018 at 15:52


Regular diaphragm pumps are often built with multiple pumps in series in the same casing to get higher vacuums, but it's often like 1 gives you 50 Torr, 2 gives you 10, four gives you 1.

Serious diminishing returns.

Doing this with separate independently driven pumps would probably require synchronization, or at least some sort of plenum chambers between the pumps to avoid their working against each other. (for reciprocating pumps at least)

For low pressures, a Mcleod gauge is great if you don't mind having a mercury filled piece of equipment around.
They're for pressures below 10 Torr, and go down to very low pressures.

And they never need calibration!



[Edited on 2-6-2018 by SWIM]





Do you want red P?
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XeonTheMGPony
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[*] posted on 1-6-2018 at 16:58


Supco V46 digital micron gauge, I had mine tested and it went clean to the bottom on a turbo molecular pump system for doing laser tubes, guy was surprised at how accurate it was.
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weilawei
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[*] posted on 2-6-2018 at 08:37


Does yours leak? I looked it up on Amazon and the reviews almost invariably slammed it for that.
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XeonTheMGPony
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[*] posted on 3-6-2018 at 06:54


If you're asking me no it doesn't leak at all, most fail to maintain their equipment! Long as you clean them and lubricate the rubber they stay solid for a very long time. Just do not draw gas through them (Allot do this and it does damage them and throw readings off)
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