Re: IPMS-USA Journal: 'Build your own vacuum chamber'
- From: Ron Smith <rwsmithjr@xxxxxxx>
- Date: Wed, 29 Mar 2006 14:52:49 -0500
Don Stauffer wrote:
How can a vacuum pump remove more than ONE atmosphere? One atmsphere = 1 Bar = 14.7 psi.
Even if the units were psi instead of atmospheres, ambient pressure is only 14.7.
Theoretically it can't but nobody is even using the correct units here. Atmospheres and bar are units of pressure, not vacuum. The cheaper pumps are rated in "inches of water" which is how many inches of water they can draw up a specific diameter tube (if you're lucky these pumps will pull the equivalnet of 25"Hg). Next come pumps rated in "inches of mercury", same idea. A theoretical "perfect vacuum" is 29.92"Hg (generally these pumps will be rated to 27-28"Hg). Then you get into the $1000 or more pumps for lab use and at about that price point you start seeing them rated in millitorr, the more you pay the closer to a "perfect" vacuum you can pull, assuming your vacuum chamber and seals can take it. To get even close to "perfect" you'll spend tens of thousands of dollars and end up a huge chamber, hardline piping and multistage pumps with turbos, cryos and ion gages.
.
- References:
- IPMS-USA Journal: 'Build your own vacuum chamber'
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- Re: IPMS-USA Journal: 'Build your own vacuum chamber'
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- Re: IPMS-USA Journal: 'Build your own vacuum chamber'
- From: Don Stauffer
- IPMS-USA Journal: 'Build your own vacuum chamber'
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