A Bunch of Failures

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Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Sun Dec 31, 2017 11:23 pm

Yes, it starts at atmospheric pressure and then slowly drops. I generally wait until the thirty minutes is up to check the gauge after it has had sufficient time to heat up, but I'm pretty sure it gets down to near its lowest pressure immediatetly.

I had my eyes on this pump for sometime:
https://www.ebay.com/itm/EDWARDS-5-ROTA ... SwQS1aQn4L

It's a bit pricey but I'm sure I could negotiate.
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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Mon Jan 01, 2018 7:35 pm

That is a good price a working 5CFM Edwards.

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Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Mon Jan 01, 2018 9:26 pm

Oddly enough, it's supposedly on 3.75 CFM, but is rated to reach 7.5 X 10^-4 Torr. I figure that will be enough to back a diffusion pump.
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Rex Allers
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Re: A Bunch of Failures

Post by Rex Allers » Mon Jan 01, 2018 10:44 pm

Checking the specs, the 5 in E2M5 model is 5 m^3/hr pumping speed which I convert as about 3 cfm.
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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Mon Jan 01, 2018 11:05 pm

Sorry, I forgot Edwards is Euro and thus SI. Still, it is good enough for a fusor, if in good shape.

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Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
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Dennis P Brown
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Re: A Bunch of Failures

Post by Dennis P Brown » Fri Jan 05, 2018 3:33 pm

That appears to be a good pump and will certainly work with any DP as long as it gets below 50 microns; so when you say
but is rated to reach 7.5 X 10^-4 Torr. I figure that will be enough to back a diffusion pump.
So, as long as it gets under 5 microns (assuming the system has no real leaks) you will be more than fine.

No mechanical pump (even new) will really do that sub-micron - I have a very large pump, a leak proof system (and back fill with dry air), and 2-3 microns is what it can do and that is excellent for most mechanical pumps.

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Bob Reite
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Re: A Bunch of Failures

Post by Bob Reite » Sat Jan 06, 2018 3:16 am

IMHO, a mechanical pump is doing well to get into the single digit micron range.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Re: A Bunch of Failures

Post by Jackson Oswalt » Sat Jan 06, 2018 4:02 am

I knew not to expect it to reach that pressure. I learned not to expect things like that from my HVAC pump. Anyways, the Edwards pump is here now and, of course, I can't find anyone selling adapters from 1 bsp to kf25 that doesn't ship from Hong Kong.
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John Futter
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Re: A Bunch of Failures

Post by John Futter » Sat Jan 06, 2018 7:35 am

Anyone with a lathe some brass tube and a little brass plate would make one in under an hour
no oxy acetylene no prob just soft solder will do.

MAKE ONE!!!!

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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Sat Jan 06, 2018 8:36 pm

Bob and John are correct.

A used pump is doing fabulous if it easily hits 15 microns within a minute or two at the head. If it goes below 10 microns, it was well cared for or not used much in a good environment.

Where there is a will there is a way. KF Adapters can be whipped out quickly by even a novice machinist. Made in brass, they are easily soft soldered.

I have had to do this a number of times back in the 1990's as I used a lot of HVAC pumps. Some good and some not so good. The worst ever did hit 30 microns rapidly. The best was a 5 CFM yellow jacket that hit 12 microns at the head in under 40 seconds! Now, I use only belt drive pumps which on whole are no better or worse in evacuating a system but are much, much more quiet and easy on the nerves, easy to repair and replace motors.

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Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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